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qemu/block/io.c
Nir Soffer d05ae948cc Consider discard option when writing zeros 
When opening an image with discard=off, we punch hole in the image when
writing zeroes, making the image sparse. This breaks users that want to
ensure that writes cannot fail with ENOSPACE by using fully allocated
images[1].

bdrv_co_pwrite_zeroes() correctly disables BDRV_REQ_MAY_UNMAP if we
opened the child without discard=unmap or discard=on. But we don't go
through this function when accessing the top node. Move the check down
to bdrv_co_do_pwrite_zeroes() which seems to be used in all code paths.

This change implements the documented behavior, punching holes only when
opening the image with discard=on or discard=unmap. This may not be the
best default but can improve it later.

The test depends on a file system supporting discard, deallocating the
entire file when punching hole with the length of the entire file.
Tested with xfs, ext4, and tmpfs.

[1] https://lists.nongnu.org/archive/html/qemu-discuss/2024-06/msg00003.html

Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-id: 20240628202058.1964986-3-nsoffer@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2024-07-11 11:06:36 +02:00

3756 lines
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/*
* Block layer I/O functions
*
* Copyright (c) 2003 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "trace.h"
#include "sysemu/block-backend.h"
#include "block/aio-wait.h"
#include "block/blockjob.h"
#include "block/blockjob_int.h"
#include "block/block_int.h"
#include "block/coroutines.h"
#include "block/dirty-bitmap.h"
#include "block/write-threshold.h"
#include "qemu/cutils.h"
#include "qemu/memalign.h"
#include "qapi/error.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "sysemu/replay.h"
/* Maximum bounce buffer for copy-on-read and write zeroes, in bytes */
#define MAX_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS)
static void coroutine_fn GRAPH_RDLOCK
bdrv_parent_cb_resize(BlockDriverState *bs);
static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int64_t bytes, BdrvRequestFlags flags);
static void GRAPH_RDLOCK
bdrv_parent_drained_begin(BlockDriverState *bs, BdrvChild *ignore)
{
BdrvChild *c, *next;
IO_OR_GS_CODE();
assert_bdrv_graph_readable();
QLIST_FOREACH_SAFE(c, &bs->parents, next_parent, next) {
if (c == ignore) {
continue;
}
bdrv_parent_drained_begin_single(c);
}
}
void bdrv_parent_drained_end_single(BdrvChild *c)
{
GLOBAL_STATE_CODE();
assert(c->quiesced_parent);
c->quiesced_parent = false;
if (c->klass->drained_end) {
c->klass->drained_end(c);
}
}
static void GRAPH_RDLOCK
bdrv_parent_drained_end(BlockDriverState *bs, BdrvChild *ignore)
{
BdrvChild *c;
IO_OR_GS_CODE();
assert_bdrv_graph_readable();
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c == ignore) {
continue;
}
bdrv_parent_drained_end_single(c);
}
}
bool bdrv_parent_drained_poll_single(BdrvChild *c)
{
IO_OR_GS_CODE();
if (c->klass->drained_poll) {
return c->klass->drained_poll(c);
}
return false;
}
static bool GRAPH_RDLOCK
bdrv_parent_drained_poll(BlockDriverState *bs, BdrvChild *ignore,
bool ignore_bds_parents)
{
BdrvChild *c, *next;
bool busy = false;
IO_OR_GS_CODE();
assert_bdrv_graph_readable();
QLIST_FOREACH_SAFE(c, &bs->parents, next_parent, next) {
if (c == ignore || (ignore_bds_parents && c->klass->parent_is_bds)) {
continue;
}
busy |= bdrv_parent_drained_poll_single(c);
}
return busy;
}
void bdrv_parent_drained_begin_single(BdrvChild *c)
{
GLOBAL_STATE_CODE();
assert(!c->quiesced_parent);
c->quiesced_parent = true;
if (c->klass->drained_begin) {
/* called with rdlock taken, but it doesn't really need it. */
c->klass->drained_begin(c);
}
}
static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
{
dst->pdiscard_alignment = MAX(dst->pdiscard_alignment,
src->pdiscard_alignment);
dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
dst->max_hw_transfer = MIN_NON_ZERO(dst->max_hw_transfer,
src->max_hw_transfer);
dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
src->opt_mem_alignment);
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
src->min_mem_alignment);
dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
dst->max_hw_iov = MIN_NON_ZERO(dst->max_hw_iov, src->max_hw_iov);
}
typedef struct BdrvRefreshLimitsState {
BlockDriverState *bs;
BlockLimits old_bl;
} BdrvRefreshLimitsState;
static void bdrv_refresh_limits_abort(void *opaque)
{
BdrvRefreshLimitsState *s = opaque;
s->bs->bl = s->old_bl;
}
static TransactionActionDrv bdrv_refresh_limits_drv = {
.abort = bdrv_refresh_limits_abort,
.clean = g_free,
};
/* @tran is allowed to be NULL, in this case no rollback is possible. */
void bdrv_refresh_limits(BlockDriverState *bs, Transaction *tran, Error **errp)
{
ERRP_GUARD();
BlockDriver *drv = bs->drv;
BdrvChild *c;
bool have_limits;
GLOBAL_STATE_CODE();
if (tran) {
BdrvRefreshLimitsState *s = g_new(BdrvRefreshLimitsState, 1);
*s = (BdrvRefreshLimitsState) {
.bs = bs,
.old_bl = bs->bl,
};
tran_add(tran, &bdrv_refresh_limits_drv, s);
}
memset(&bs->bl, 0, sizeof(bs->bl));
if (!drv) {
return;
}
/* Default alignment based on whether driver has byte interface */
bs->bl.request_alignment = (drv->bdrv_co_preadv ||
drv->bdrv_aio_preadv ||
drv->bdrv_co_preadv_part) ? 1 : 512;
/* Take some limits from the children as a default */
have_limits = false;
QLIST_FOREACH(c, &bs->children, next) {
if (c->role & (BDRV_CHILD_DATA | BDRV_CHILD_FILTERED | BDRV_CHILD_COW))
{
bdrv_merge_limits(&bs->bl, &c->bs->bl);
have_limits = true;
}
if (c->role & BDRV_CHILD_FILTERED) {
bs->bl.has_variable_length |= c->bs->bl.has_variable_length;
}
}
if (!have_limits) {
bs->bl.min_mem_alignment = 512;
bs->bl.opt_mem_alignment = qemu_real_host_page_size();
/* Safe default since most protocols use readv()/writev()/etc */
bs->bl.max_iov = IOV_MAX;
}
/* Then let the driver override it */
if (drv->bdrv_refresh_limits) {
drv->bdrv_refresh_limits(bs, errp);
if (*errp) {
return;
}
}
if (bs->bl.request_alignment > BDRV_MAX_ALIGNMENT) {
error_setg(errp, "Driver requires too large request alignment");
}
}
/**
* The copy-on-read flag is actually a reference count so multiple users may
* use the feature without worrying about clobbering its previous state.
* Copy-on-read stays enabled until all users have called to disable it.
*/
void bdrv_enable_copy_on_read(BlockDriverState *bs)
{
IO_CODE();
qatomic_inc(&bs->copy_on_read);
}
void bdrv_disable_copy_on_read(BlockDriverState *bs)
{
int old = qatomic_fetch_dec(&bs->copy_on_read);
IO_CODE();
assert(old >= 1);
}
typedef struct {
Coroutine *co;
BlockDriverState *bs;
bool done;
bool begin;
bool poll;
BdrvChild *parent;
} BdrvCoDrainData;
/* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */
bool bdrv_drain_poll(BlockDriverState *bs, BdrvChild *ignore_parent,
bool ignore_bds_parents)
{
GLOBAL_STATE_CODE();
if (bdrv_parent_drained_poll(bs, ignore_parent, ignore_bds_parents)) {
return true;
}
if (qatomic_read(&bs->in_flight)) {
return true;
}
return false;
}
static bool bdrv_drain_poll_top_level(BlockDriverState *bs,
BdrvChild *ignore_parent)
{
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
return bdrv_drain_poll(bs, ignore_parent, false);
}
static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
bool poll);
static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent);
static void bdrv_co_drain_bh_cb(void *opaque)
{
BdrvCoDrainData *data = opaque;
Coroutine *co = data->co;
BlockDriverState *bs = data->bs;
if (bs) {
bdrv_dec_in_flight(bs);
if (data->begin) {
bdrv_do_drained_begin(bs, data->parent, data->poll);
} else {
assert(!data->poll);
bdrv_do_drained_end(bs, data->parent);
}
} else {
assert(data->begin);
bdrv_drain_all_begin();
}
data->done = true;
aio_co_wake(co);
}
static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
bool begin,
BdrvChild *parent,
bool poll)
{
BdrvCoDrainData data;
Coroutine *self = qemu_coroutine_self();
/* Calling bdrv_drain() from a BH ensures the current coroutine yields and
* other coroutines run if they were queued by aio_co_enter(). */
assert(qemu_in_coroutine());
data = (BdrvCoDrainData) {
.co = self,
.bs = bs,
.done = false,
.begin = begin,
.parent = parent,
.poll = poll,
};
if (bs) {
bdrv_inc_in_flight(bs);
}
replay_bh_schedule_oneshot_event(qemu_get_aio_context(),
bdrv_co_drain_bh_cb, &data);
qemu_coroutine_yield();
/* If we are resumed from some other event (such as an aio completion or a
* timer callback), it is a bug in the caller that should be fixed. */
assert(data.done);
}
static void bdrv_do_drained_begin(BlockDriverState *bs, BdrvChild *parent,
bool poll)
{
IO_OR_GS_CODE();
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(bs, true, parent, poll);
return;
}
GLOBAL_STATE_CODE();
/* Stop things in parent-to-child order */
if (qatomic_fetch_inc(&bs->quiesce_counter) == 0) {
GRAPH_RDLOCK_GUARD_MAINLOOP();
bdrv_parent_drained_begin(bs, parent);
if (bs->drv && bs->drv->bdrv_drain_begin) {
bs->drv->bdrv_drain_begin(bs);
}
}
/*
* Wait for drained requests to finish.
*
* Calling BDRV_POLL_WHILE() only once for the top-level node is okay: The
* call is needed so things in this AioContext can make progress even
* though we don't return to the main AioContext loop - this automatically
* includes other nodes in the same AioContext and therefore all child
* nodes.
*/
if (poll) {
BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));
}
}
void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, BdrvChild *parent)
{
bdrv_do_drained_begin(bs, parent, false);
}
void coroutine_mixed_fn
bdrv_drained_begin(BlockDriverState *bs)
{
IO_OR_GS_CODE();
bdrv_do_drained_begin(bs, NULL, true);
}
/**
* This function does not poll, nor must any of its recursively called
* functions.
*/
static void bdrv_do_drained_end(BlockDriverState *bs, BdrvChild *parent)
{
int old_quiesce_counter;
IO_OR_GS_CODE();
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(bs, false, parent, false);
return;
}
/* At this point, we should be always running in the main loop. */
GLOBAL_STATE_CODE();
assert(bs->quiesce_counter > 0);
GLOBAL_STATE_CODE();
/* Re-enable things in child-to-parent order */
old_quiesce_counter = qatomic_fetch_dec(&bs->quiesce_counter);
if (old_quiesce_counter == 1) {
GRAPH_RDLOCK_GUARD_MAINLOOP();
if (bs->drv && bs->drv->bdrv_drain_end) {
bs->drv->bdrv_drain_end(bs);
}
bdrv_parent_drained_end(bs, parent);
}
}
void bdrv_drained_end(BlockDriverState *bs)
{
IO_OR_GS_CODE();
bdrv_do_drained_end(bs, NULL);
}
void bdrv_drain(BlockDriverState *bs)
{
IO_OR_GS_CODE();
bdrv_drained_begin(bs);
bdrv_drained_end(bs);
}
static void bdrv_drain_assert_idle(BlockDriverState *bs)
{
BdrvChild *child, *next;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
assert(qatomic_read(&bs->in_flight) == 0);
QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
bdrv_drain_assert_idle(child->bs);
}
}
unsigned int bdrv_drain_all_count = 0;
static bool bdrv_drain_all_poll(void)
{
BlockDriverState *bs = NULL;
bool result = false;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
/*
* bdrv_drain_poll() can't make changes to the graph and we hold the BQL,
* so iterating bdrv_next_all_states() is safe.
*/
while ((bs = bdrv_next_all_states(bs))) {
result |= bdrv_drain_poll(bs, NULL, true);
}
return result;
}
/*
* Wait for pending requests to complete across all BlockDriverStates
*
* This function does not flush data to disk, use bdrv_flush_all() for that
* after calling this function.
*
* This pauses all block jobs and disables external clients. It must
* be paired with bdrv_drain_all_end().
*
* NOTE: no new block jobs or BlockDriverStates can be created between
* the bdrv_drain_all_begin() and bdrv_drain_all_end() calls.
*/
void bdrv_drain_all_begin_nopoll(void)
{
BlockDriverState *bs = NULL;
GLOBAL_STATE_CODE();
/*
* bdrv queue is managed by record/replay,
* waiting for finishing the I/O requests may
* be infinite
*/
if (replay_events_enabled()) {
return;
}
/* AIO_WAIT_WHILE() with a NULL context can only be called from the main
* loop AioContext, so make sure we're in the main context. */
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
assert(bdrv_drain_all_count < INT_MAX);
bdrv_drain_all_count++;
/* Quiesce all nodes, without polling in-flight requests yet. The graph
* cannot change during this loop. */
while ((bs = bdrv_next_all_states(bs))) {
bdrv_do_drained_begin(bs, NULL, false);
}
}
void coroutine_mixed_fn bdrv_drain_all_begin(void)
{
BlockDriverState *bs = NULL;
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(NULL, true, NULL, true);
return;
}
/*
* bdrv queue is managed by record/replay,
* waiting for finishing the I/O requests may
* be infinite
*/
if (replay_events_enabled()) {
return;
}
bdrv_drain_all_begin_nopoll();
/* Now poll the in-flight requests */
AIO_WAIT_WHILE_UNLOCKED(NULL, bdrv_drain_all_poll());
while ((bs = bdrv_next_all_states(bs))) {
bdrv_drain_assert_idle(bs);
}
}
void bdrv_drain_all_end_quiesce(BlockDriverState *bs)
{
GLOBAL_STATE_CODE();
g_assert(bs->quiesce_counter > 0);
g_assert(!bs->refcnt);
while (bs->quiesce_counter) {
bdrv_do_drained_end(bs, NULL);
}
}
void bdrv_drain_all_end(void)
{
BlockDriverState *bs = NULL;
GLOBAL_STATE_CODE();
/*
* bdrv queue is managed by record/replay,
* waiting for finishing the I/O requests may
* be endless
*/
if (replay_events_enabled()) {
return;
}
while ((bs = bdrv_next_all_states(bs))) {
bdrv_do_drained_end(bs, NULL);
}
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
assert(bdrv_drain_all_count > 0);
bdrv_drain_all_count--;
}
void bdrv_drain_all(void)
{
GLOBAL_STATE_CODE();
bdrv_drain_all_begin();
bdrv_drain_all_end();
}
/**
* Remove an active request from the tracked requests list
*
* This function should be called when a tracked request is completing.
*/
static void coroutine_fn tracked_request_end(BdrvTrackedRequest *req)
{
if (req->serialising) {
qatomic_dec(&req->bs->serialising_in_flight);
}
qemu_mutex_lock(&req->bs->reqs_lock);
QLIST_REMOVE(req, list);
qemu_mutex_unlock(&req->bs->reqs_lock);
/*
* At this point qemu_co_queue_wait(&req->wait_queue, ...) won't be called
* anymore because the request has been removed from the list, so it's safe
* to restart the queue outside reqs_lock to minimize the critical section.
*/
qemu_co_queue_restart_all(&req->wait_queue);
}
/**
* Add an active request to the tracked requests list
*/
static void coroutine_fn tracked_request_begin(BdrvTrackedRequest *req,
BlockDriverState *bs,
int64_t offset,
int64_t bytes,
enum BdrvTrackedRequestType type)
{
bdrv_check_request(offset, bytes, &error_abort);
*req = (BdrvTrackedRequest){
.bs = bs,
.offset = offset,
.bytes = bytes,
.type = type,
.co = qemu_coroutine_self(),
.serialising = false,
.overlap_offset = offset,
.overlap_bytes = bytes,
};
qemu_co_queue_init(&req->wait_queue);
qemu_mutex_lock(&bs->reqs_lock);
QLIST_INSERT_HEAD(&bs->tracked_requests, req, list);
qemu_mutex_unlock(&bs->reqs_lock);
}
static bool tracked_request_overlaps(BdrvTrackedRequest *req,
int64_t offset, int64_t bytes)
{
bdrv_check_request(offset, bytes, &error_abort);
/* aaaa bbbb */
if (offset >= req->overlap_offset + req->overlap_bytes) {
return false;
}
/* bbbb aaaa */
if (req->overlap_offset >= offset + bytes) {
return false;
}
return true;
}
/* Called with self->bs->reqs_lock held */
static coroutine_fn BdrvTrackedRequest *
bdrv_find_conflicting_request(BdrvTrackedRequest *self)
{
BdrvTrackedRequest *req;
QLIST_FOREACH(req, &self->bs->tracked_requests, list) {
if (req == self || (!req->serialising && !self->serialising)) {
continue;
}
if (tracked_request_overlaps(req, self->overlap_offset,
self->overlap_bytes))
{
/*
* Hitting this means there was a reentrant request, for
* example, a block driver issuing nested requests. This must
* never happen since it means deadlock.
*/
assert(qemu_coroutine_self() != req->co);
/*
* If the request is already (indirectly) waiting for us, or
* will wait for us as soon as it wakes up, then just go on
* (instead of producing a deadlock in the former case).
*/
if (!req->waiting_for) {
return req;
}
}
}
return NULL;
}
/* Called with self->bs->reqs_lock held */
static void coroutine_fn
bdrv_wait_serialising_requests_locked(BdrvTrackedRequest *self)
{
BdrvTrackedRequest *req;
while ((req = bdrv_find_conflicting_request(self))) {
self->waiting_for = req;
qemu_co_queue_wait(&req->wait_queue, &self->bs->reqs_lock);
self->waiting_for = NULL;
}
}
/* Called with req->bs->reqs_lock held */
static void tracked_request_set_serialising(BdrvTrackedRequest *req,
uint64_t align)
{
int64_t overlap_offset = req->offset & ~(align - 1);
int64_t overlap_bytes =
ROUND_UP(req->offset + req->bytes, align) - overlap_offset;
bdrv_check_request(req->offset, req->bytes, &error_abort);
if (!req->serialising) {
qatomic_inc(&req->bs->serialising_in_flight);
req->serialising = true;
}
req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
}
/**
* Return the tracked request on @bs for the current coroutine, or
* NULL if there is none.
*/
BdrvTrackedRequest *coroutine_fn bdrv_co_get_self_request(BlockDriverState *bs)
{
BdrvTrackedRequest *req;
Coroutine *self = qemu_coroutine_self();
IO_CODE();
QLIST_FOREACH(req, &bs->tracked_requests, list) {
if (req->co == self) {
return req;
}
}
return NULL;
}
/**
* Round a region to subcluster (if supported) or cluster boundaries
*/
void coroutine_fn GRAPH_RDLOCK
bdrv_round_to_subclusters(BlockDriverState *bs, int64_t offset, int64_t bytes,
int64_t *align_offset, int64_t *align_bytes)
{
BlockDriverInfo bdi;
IO_CODE();
if (bdrv_co_get_info(bs, &bdi) < 0 || bdi.subcluster_size == 0) {
*align_offset = offset;
*align_bytes = bytes;
} else {
int64_t c = bdi.subcluster_size;
*align_offset = QEMU_ALIGN_DOWN(offset, c);
*align_bytes = QEMU_ALIGN_UP(offset - *align_offset + bytes, c);
}
}
static int coroutine_fn GRAPH_RDLOCK bdrv_get_cluster_size(BlockDriverState *bs)
{
BlockDriverInfo bdi;
int ret;
ret = bdrv_co_get_info(bs, &bdi);
if (ret < 0 || bdi.cluster_size == 0) {
return bs->bl.request_alignment;
} else {
return bdi.cluster_size;
}
}
void bdrv_inc_in_flight(BlockDriverState *bs)
{
IO_CODE();
qatomic_inc(&bs->in_flight);
}
void bdrv_wakeup(BlockDriverState *bs)
{
IO_CODE();
aio_wait_kick();
}
void bdrv_dec_in_flight(BlockDriverState *bs)
{
IO_CODE();
qatomic_dec(&bs->in_flight);
bdrv_wakeup(bs);
}
static void coroutine_fn
bdrv_wait_serialising_requests(BdrvTrackedRequest *self)
{
BlockDriverState *bs = self->bs;
if (!qatomic_read(&bs->serialising_in_flight)) {
return;
}
qemu_mutex_lock(&bs->reqs_lock);
bdrv_wait_serialising_requests_locked(self);
qemu_mutex_unlock(&bs->reqs_lock);
}
void coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
uint64_t align)
{
IO_CODE();
qemu_mutex_lock(&req->bs->reqs_lock);
tracked_request_set_serialising(req, align);
bdrv_wait_serialising_requests_locked(req);
qemu_mutex_unlock(&req->bs->reqs_lock);
}
int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset,
Error **errp)
{
/*
* Check generic offset/bytes correctness
*/
if (offset < 0) {
error_setg(errp, "offset is negative: %" PRIi64, offset);
return -EIO;
}
if (bytes < 0) {
error_setg(errp, "bytes is negative: %" PRIi64, bytes);
return -EIO;
}
if (bytes > BDRV_MAX_LENGTH) {
error_setg(errp, "bytes(%" PRIi64 ") exceeds maximum(%" PRIi64 ")",
bytes, BDRV_MAX_LENGTH);
return -EIO;
}
if (offset > BDRV_MAX_LENGTH) {
error_setg(errp, "offset(%" PRIi64 ") exceeds maximum(%" PRIi64 ")",
offset, BDRV_MAX_LENGTH);
return -EIO;
}
if (offset > BDRV_MAX_LENGTH - bytes) {
error_setg(errp, "sum of offset(%" PRIi64 ") and bytes(%" PRIi64 ") "
"exceeds maximum(%" PRIi64 ")", offset, bytes,
BDRV_MAX_LENGTH);
return -EIO;
}
if (!qiov) {
return 0;
}
/*
* Check qiov and qiov_offset
*/
if (qiov_offset > qiov->size) {
error_setg(errp, "qiov_offset(%zu) overflow io vector size(%zu)",
qiov_offset, qiov->size);
return -EIO;
}
if (bytes > qiov->size - qiov_offset) {
error_setg(errp, "bytes(%" PRIi64 ") + qiov_offset(%zu) overflow io "
"vector size(%zu)", bytes, qiov_offset, qiov->size);
return -EIO;
}
return 0;
}
int bdrv_check_request(int64_t offset, int64_t bytes, Error **errp)
{
return bdrv_check_qiov_request(offset, bytes, NULL, 0, errp);
}
static int bdrv_check_request32(int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset)
{
int ret = bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, NULL);
if (ret < 0) {
return ret;
}
if (bytes > BDRV_REQUEST_MAX_BYTES) {
return -EIO;
}
return 0;
}
/*
* Completely zero out a block device with the help of bdrv_pwrite_zeroes.
* The operation is sped up by checking the block status and only writing
* zeroes to the device if they currently do not return zeroes. Optional
* flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
* BDRV_REQ_FUA).
*
* Returns < 0 on error, 0 on success. For error codes see bdrv_pwrite().
*/
int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
{
int ret;
int64_t target_size, bytes, offset = 0;
BlockDriverState *bs = child->bs;
IO_CODE();
target_size = bdrv_getlength(bs);
if (target_size < 0) {
return target_size;
}
for (;;) {
bytes = MIN(target_size - offset, BDRV_REQUEST_MAX_BYTES);
if (bytes <= 0) {
return 0;
}
ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL);
if (ret < 0) {
return ret;
}
if (ret & BDRV_BLOCK_ZERO) {
offset += bytes;
continue;
}
ret = bdrv_pwrite_zeroes(child, offset, bytes, flags);
if (ret < 0) {
return ret;
}
offset += bytes;
}
}
/*
* Writes to the file and ensures that no writes are reordered across this
* request (acts as a barrier)
*
* Returns 0 on success, -errno in error cases.
*/
int coroutine_fn bdrv_co_pwrite_sync(BdrvChild *child, int64_t offset,
int64_t bytes, const void *buf,
BdrvRequestFlags flags)
{
int ret;
IO_CODE();
assert_bdrv_graph_readable();
ret = bdrv_co_pwrite(child, offset, bytes, buf, flags);
if (ret < 0) {
return ret;
}
ret = bdrv_co_flush(child->bs);
if (ret < 0) {
return ret;
}
return 0;
}
typedef struct CoroutineIOCompletion {
Coroutine *coroutine;
int ret;
} CoroutineIOCompletion;
static void bdrv_co_io_em_complete(void *opaque, int ret)
{
CoroutineIOCompletion *co = opaque;
co->ret = ret;
aio_co_wake(co->coroutine);
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_driver_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset, int flags)
{
BlockDriver *drv = bs->drv;
int64_t sector_num;
unsigned int nb_sectors;
QEMUIOVector local_qiov;
int ret;
assert_bdrv_graph_readable();
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
assert(!(flags & ~bs->supported_read_flags));
if (!drv) {
return -ENOMEDIUM;
}
if (drv->bdrv_co_preadv_part) {
return drv->bdrv_co_preadv_part(bs, offset, bytes, qiov, qiov_offset,
flags);
}
if (qiov_offset > 0 || bytes != qiov->size) {
qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
qiov = &local_qiov;
}
if (drv->bdrv_co_preadv) {
ret = drv->bdrv_co_preadv(bs, offset, bytes, qiov, flags);
goto out;
}
if (drv->bdrv_aio_preadv) {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = drv->bdrv_aio_preadv(bs, offset, bytes, qiov, flags,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
goto out;
} else {
qemu_coroutine_yield();
ret = co.ret;
goto out;
}
}
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
assert(bytes <= BDRV_REQUEST_MAX_BYTES);
assert(drv->bdrv_co_readv);
ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
out:
if (qiov == &local_qiov) {
qemu_iovec_destroy(&local_qiov);
}
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_driver_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset,
BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
bool emulate_fua = false;
int64_t sector_num;
unsigned int nb_sectors;
QEMUIOVector local_qiov;
int ret;
assert_bdrv_graph_readable();
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
if (!drv) {
return -ENOMEDIUM;
}
if ((flags & BDRV_REQ_FUA) &&
(~bs->supported_write_flags & BDRV_REQ_FUA)) {
flags &= ~BDRV_REQ_FUA;
emulate_fua = true;
}
flags &= bs->supported_write_flags;
if (drv->bdrv_co_pwritev_part) {
ret = drv->bdrv_co_pwritev_part(bs, offset, bytes, qiov, qiov_offset,
flags);
goto emulate_flags;
}
if (qiov_offset > 0 || bytes != qiov->size) {
qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
qiov = &local_qiov;
}
if (drv->bdrv_co_pwritev) {
ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov, flags);
goto emulate_flags;
}
if (drv->bdrv_aio_pwritev) {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = drv->bdrv_aio_pwritev(bs, offset, bytes, qiov, flags,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
goto emulate_flags;
}
sector_num = offset >> BDRV_SECTOR_BITS;
nb_sectors = bytes >> BDRV_SECTOR_BITS;
assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
assert(bytes <= BDRV_REQUEST_MAX_BYTES);
assert(drv->bdrv_co_writev);
ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov, flags);
emulate_flags:
if (ret == 0 && emulate_fua) {
ret = bdrv_co_flush(bs);
}
if (qiov == &local_qiov) {
qemu_iovec_destroy(&local_qiov);
}
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_driver_pwritev_compressed(BlockDriverState *bs, int64_t offset,
int64_t bytes, QEMUIOVector *qiov,
size_t qiov_offset)
{
BlockDriver *drv = bs->drv;
QEMUIOVector local_qiov;
int ret;
assert_bdrv_graph_readable();
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
if (!drv) {
return -ENOMEDIUM;
}
if (!block_driver_can_compress(drv)) {
return -ENOTSUP;
}
if (drv->bdrv_co_pwritev_compressed_part) {
return drv->bdrv_co_pwritev_compressed_part(bs, offset, bytes,
qiov, qiov_offset);
}
if (qiov_offset == 0) {
return drv->bdrv_co_pwritev_compressed(bs, offset, bytes, qiov);
}
qemu_iovec_init_slice(&local_qiov, qiov, qiov_offset, bytes);
ret = drv->bdrv_co_pwritev_compressed(bs, offset, bytes, &local_qiov);
qemu_iovec_destroy(&local_qiov);
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_co_do_copy_on_readv(BdrvChild *child, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset, int flags)
{
BlockDriverState *bs = child->bs;
/* Perform I/O through a temporary buffer so that users who scribble over
* their read buffer while the operation is in progress do not end up
* modifying the image file. This is critical for zero-copy guest I/O
* where anything might happen inside guest memory.
*/
void *bounce_buffer = NULL;
BlockDriver *drv = bs->drv;
int64_t align_offset;
int64_t align_bytes;
int64_t skip_bytes;
int ret;
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
BDRV_REQUEST_MAX_BYTES);
int64_t progress = 0;
bool skip_write;
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
if (!drv) {
return -ENOMEDIUM;
}
/*
* Do not write anything when the BDS is inactive. That is not
* allowed, and it would not help.
*/
skip_write = (bs->open_flags & BDRV_O_INACTIVE);
/* FIXME We cannot require callers to have write permissions when all they
* are doing is a read request. If we did things right, write permissions
* would be obtained anyway, but internally by the copy-on-read code. As
* long as it is implemented here rather than in a separate filter driver,
* the copy-on-read code doesn't have its own BdrvChild, however, for which
* it could request permissions. Therefore we have to bypass the permission
* system for the moment. */
// assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
/* Cover entire cluster so no additional backing file I/O is required when
* allocating cluster in the image file. Note that this value may exceed
* BDRV_REQUEST_MAX_BYTES (even when the original read did not), which
* is one reason we loop rather than doing it all at once.
*/
bdrv_round_to_subclusters(bs, offset, bytes, &align_offset, &align_bytes);
skip_bytes = offset - align_offset;
trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
align_offset, align_bytes);
while (align_bytes) {
int64_t pnum;
if (skip_write) {
ret = 1; /* "already allocated", so nothing will be copied */
pnum = MIN(align_bytes, max_transfer);
} else {
ret = bdrv_co_is_allocated(bs, align_offset,
MIN(align_bytes, max_transfer), &pnum);
if (ret < 0) {
/*
* Safe to treat errors in querying allocation as if
* unallocated; we'll probably fail again soon on the
* read, but at least that will set a decent errno.
*/
pnum = MIN(align_bytes, max_transfer);
}
/* Stop at EOF if the image ends in the middle of the cluster */
if (ret == 0 && pnum == 0) {
assert(progress >= bytes);
break;
}
assert(skip_bytes < pnum);
}
if (ret <= 0) {
QEMUIOVector local_qiov;
/* Must copy-on-read; use the bounce buffer */
pnum = MIN(pnum, MAX_BOUNCE_BUFFER);
if (!bounce_buffer) {
int64_t max_we_need = MAX(pnum, align_bytes - pnum);
int64_t max_allowed = MIN(max_transfer, MAX_BOUNCE_BUFFER);
int64_t bounce_buffer_len = MIN(max_we_need, max_allowed);
bounce_buffer = qemu_try_blockalign(bs, bounce_buffer_len);
if (!bounce_buffer) {
ret = -ENOMEM;
goto err;
}
}
qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum);
ret = bdrv_driver_preadv(bs, align_offset, pnum,
&local_qiov, 0, 0);
if (ret < 0) {
goto err;
}
bdrv_co_debug_event(bs, BLKDBG_COR_WRITE);
if (drv->bdrv_co_pwrite_zeroes &&
buffer_is_zero(bounce_buffer, pnum)) {
/* FIXME: Should we (perhaps conditionally) be setting
* BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy
* that still correctly reads as zero? */
ret = bdrv_co_do_pwrite_zeroes(bs, align_offset, pnum,
BDRV_REQ_WRITE_UNCHANGED);
} else {
/* This does not change the data on the disk, it is not
* necessary to flush even in cache=writethrough mode.
*/
ret = bdrv_driver_pwritev(bs, align_offset, pnum,
&local_qiov, 0,
BDRV_REQ_WRITE_UNCHANGED);
}
if (ret < 0) {
/* It might be okay to ignore write errors for guest
* requests. If this is a deliberate copy-on-read
* then we don't want to ignore the error. Simply
* report it in all cases.
*/
goto err;
}
if (!(flags & BDRV_REQ_PREFETCH)) {
qemu_iovec_from_buf(qiov, qiov_offset + progress,
bounce_buffer + skip_bytes,
MIN(pnum - skip_bytes, bytes - progress));
}
} else if (!(flags & BDRV_REQ_PREFETCH)) {
/* Read directly into the destination */
ret = bdrv_driver_preadv(bs, offset + progress,
MIN(pnum - skip_bytes, bytes - progress),
qiov, qiov_offset + progress, 0);
if (ret < 0) {
goto err;
}
}
align_offset += pnum;
align_bytes -= pnum;
progress += pnum - skip_bytes;
skip_bytes = 0;
}
ret = 0;
err:
qemu_vfree(bounce_buffer);
return ret;
}
/*
* Forwards an already correctly aligned request to the BlockDriver. This
* handles copy on read, zeroing after EOF, and fragmentation of large
* reads; any other features must be implemented by the caller.
*/
static int coroutine_fn GRAPH_RDLOCK
bdrv_aligned_preadv(BdrvChild *child, BdrvTrackedRequest *req,
int64_t offset, int64_t bytes, int64_t align,
QEMUIOVector *qiov, size_t qiov_offset, int flags)
{
BlockDriverState *bs = child->bs;
int64_t total_bytes, max_bytes;
int ret = 0;
int64_t bytes_remaining = bytes;
int max_transfer;
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
assert(is_power_of_2(align));
assert((offset & (align - 1)) == 0);
assert((bytes & (align - 1)) == 0);
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
/*
* TODO: We would need a per-BDS .supported_read_flags and
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
* passthrough flags except the BDRV_REQ_REGISTERED_BUF optimization hint.
*/
assert(!(flags & ~(BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH |
BDRV_REQ_REGISTERED_BUF)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
/* If we touch the same cluster it counts as an overlap. This
* guarantees that allocating writes will be serialized and not race
* with each other for the same cluster. For example, in copy-on-read
* it ensures that the CoR read and write operations are atomic and
* guest writes cannot interleave between them. */
bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
} else {
bdrv_wait_serialising_requests(req);
}
if (flags & BDRV_REQ_COPY_ON_READ) {
int64_t pnum;
/* The flag BDRV_REQ_COPY_ON_READ has reached its addressee */
flags &= ~BDRV_REQ_COPY_ON_READ;
ret = bdrv_co_is_allocated(bs, offset, bytes, &pnum);
if (ret < 0) {
goto out;
}
if (!ret || pnum != bytes) {
ret = bdrv_co_do_copy_on_readv(child, offset, bytes,
qiov, qiov_offset, flags);
goto out;
} else if (flags & BDRV_REQ_PREFETCH) {
goto out;
}
}
/* Forward the request to the BlockDriver, possibly fragmenting it */
total_bytes = bdrv_co_getlength(bs);
if (total_bytes < 0) {
ret = total_bytes;
goto out;
}
assert(!(flags & ~(bs->supported_read_flags | BDRV_REQ_REGISTERED_BUF)));
max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
if (bytes <= max_bytes && bytes <= max_transfer) {
ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, flags);
goto out;
}
while (bytes_remaining) {
int64_t num;
if (max_bytes) {
num = MIN(bytes_remaining, MIN(max_bytes, max_transfer));
assert(num);
ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
num, qiov,
qiov_offset + bytes - bytes_remaining,
flags);
max_bytes -= num;
} else {
num = bytes_remaining;
ret = qemu_iovec_memset(qiov, qiov_offset + bytes - bytes_remaining,
0, bytes_remaining);
}
if (ret < 0) {
goto out;
}
bytes_remaining -= num;
}
out:
return ret < 0 ? ret : 0;
}
/*
* Request padding
*
* |<---- align ----->| |<----- align ---->|
* |<- head ->|<------------- bytes ------------->|<-- tail -->|
* | | | | | |
* -*----------$-------*-------- ... --------*-----$------------*---
* | | | | | |
* | offset | | end |
* ALIGN_DOWN(offset) ALIGN_UP(offset) ALIGN_DOWN(end) ALIGN_UP(end)
* [buf ... ) [tail_buf )
*
* @buf is an aligned allocation needed to store @head and @tail paddings. @head
* is placed at the beginning of @buf and @tail at the @end.
*
* @tail_buf is a pointer to sub-buffer, corresponding to align-sized chunk
* around tail, if tail exists.
*
* @merge_reads is true for small requests,
* if @buf_len == @head + bytes + @tail. In this case it is possible that both
* head and tail exist but @buf_len == align and @tail_buf == @buf.
*
* @write is true for write requests, false for read requests.
*
* If padding makes the vector too long (exceeding IOV_MAX), then we need to
* merge existing vector elements into a single one. @collapse_bounce_buf acts
* as the bounce buffer in such cases. @pre_collapse_qiov has the pre-collapse
* I/O vector elements so for read requests, the data can be copied back after
* the read is done.
*/
typedef struct BdrvRequestPadding {
uint8_t *buf;
size_t buf_len;
uint8_t *tail_buf;
size_t head;
size_t tail;
bool merge_reads;
bool write;
QEMUIOVector local_qiov;
uint8_t *collapse_bounce_buf;
size_t collapse_len;
QEMUIOVector pre_collapse_qiov;
} BdrvRequestPadding;
static bool bdrv_init_padding(BlockDriverState *bs,
int64_t offset, int64_t bytes,
bool write,
BdrvRequestPadding *pad)
{
int64_t align = bs->bl.request_alignment;
int64_t sum;
bdrv_check_request(offset, bytes, &error_abort);
assert(align <= INT_MAX); /* documented in block/block_int.h */
assert(align <= SIZE_MAX / 2); /* so we can allocate the buffer */
memset(pad, 0, sizeof(*pad));
pad->head = offset & (align - 1);
pad->tail = ((offset + bytes) & (align - 1));
if (pad->tail) {
pad->tail = align - pad->tail;
}
if (!pad->head && !pad->tail) {
return false;
}
assert(bytes); /* Nothing good in aligning zero-length requests */
sum = pad->head + bytes + pad->tail;
pad->buf_len = (sum > align && pad->head && pad->tail) ? 2 * align : align;
pad->buf = qemu_blockalign(bs, pad->buf_len);
pad->merge_reads = sum == pad->buf_len;
if (pad->tail) {
pad->tail_buf = pad->buf + pad->buf_len - align;
}
pad->write = write;
return true;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_padding_rmw_read(BdrvChild *child, BdrvTrackedRequest *req,
BdrvRequestPadding *pad, bool zero_middle)
{
QEMUIOVector local_qiov;
BlockDriverState *bs = child->bs;
uint64_t align = bs->bl.request_alignment;
int ret;
assert(req->serialising && pad->buf);
if (pad->head || pad->merge_reads) {
int64_t bytes = pad->merge_reads ? pad->buf_len : align;
qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
if (pad->head) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
}
if (pad->merge_reads && pad->tail) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
}
ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
align, &local_qiov, 0, 0);
if (ret < 0) {
return ret;
}
if (pad->head) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
}
if (pad->merge_reads && pad->tail) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
}
if (pad->merge_reads) {
goto zero_mem;
}
}
if (pad->tail) {
qemu_iovec_init_buf(&local_qiov, pad->tail_buf, align);
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
ret = bdrv_aligned_preadv(
child, req,
req->overlap_offset + req->overlap_bytes - align,
align, align, &local_qiov, 0, 0);
if (ret < 0) {
return ret;
}
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
}
zero_mem:
if (zero_middle) {
memset(pad->buf + pad->head, 0, pad->buf_len - pad->head - pad->tail);
}
return 0;
}
/**
* Free *pad's associated buffers, and perform any necessary finalization steps.
*/
static void bdrv_padding_finalize(BdrvRequestPadding *pad)
{
if (pad->collapse_bounce_buf) {
if (!pad->write) {
/*
* If padding required elements in the vector to be collapsed into a
* bounce buffer, copy the bounce buffer content back
*/
qemu_iovec_from_buf(&pad->pre_collapse_qiov, 0,
pad->collapse_bounce_buf, pad->collapse_len);
}
qemu_vfree(pad->collapse_bounce_buf);
qemu_iovec_destroy(&pad->pre_collapse_qiov);
}
if (pad->buf) {
qemu_vfree(pad->buf);
qemu_iovec_destroy(&pad->local_qiov);
}
memset(pad, 0, sizeof(*pad));
}
/*
* Create pad->local_qiov by wrapping @iov in the padding head and tail, while
* ensuring that the resulting vector will not exceed IOV_MAX elements.
*
* To ensure this, when necessary, the first two or three elements of @iov are
* merged into pad->collapse_bounce_buf and replaced by a reference to that
* bounce buffer in pad->local_qiov.
*
* After performing a read request, the data from the bounce buffer must be
* copied back into pad->pre_collapse_qiov (e.g. by bdrv_padding_finalize()).
*/
static int bdrv_create_padded_qiov(BlockDriverState *bs,
BdrvRequestPadding *pad,
struct iovec *iov, int niov,
size_t iov_offset, size_t bytes)
{
int padded_niov, surplus_count, collapse_count;
/* Assert this invariant */
assert(niov <= IOV_MAX);
/*
* Cannot pad if resulting length would exceed SIZE_MAX. Returning an error
* to the guest is not ideal, but there is little else we can do. At least
* this will practically never happen on 64-bit systems.
*/
if (SIZE_MAX - pad->head < bytes ||
SIZE_MAX - pad->head - bytes < pad->tail)
{
return -EINVAL;
}
/* Length of the resulting IOV if we just concatenated everything */
padded_niov = !!pad->head + niov + !!pad->tail;
qemu_iovec_init(&pad->local_qiov, MIN(padded_niov, IOV_MAX));
if (pad->head) {
qemu_iovec_add(&pad->local_qiov, pad->buf, pad->head);
}
/*
* If padded_niov > IOV_MAX, we cannot just concatenate everything.
* Instead, merge the first two or three elements of @iov to reduce the
* number of vector elements as necessary.
*/
if (padded_niov > IOV_MAX) {
/*
* Only head and tail can have lead to the number of entries exceeding
* IOV_MAX, so we can exceed it by the head and tail at most. We need
* to reduce the number of elements by `surplus_count`, so we merge that
* many elements plus one into one element.
*/
surplus_count = padded_niov - IOV_MAX;
assert(surplus_count <= !!pad->head + !!pad->tail);
collapse_count = surplus_count + 1;
/*
* Move the elements to collapse into `pad->pre_collapse_qiov`, then
* advance `iov` (and associated variables) by those elements.
*/
qemu_iovec_init(&pad->pre_collapse_qiov, collapse_count);
qemu_iovec_concat_iov(&pad->pre_collapse_qiov, iov,
collapse_count, iov_offset, SIZE_MAX);
iov += collapse_count;
iov_offset = 0;
niov -= collapse_count;
bytes -= pad->pre_collapse_qiov.size;
/*
* Construct the bounce buffer to match the length of the to-collapse
* vector elements, and for write requests, initialize it with the data
* from those elements. Then add it to `pad->local_qiov`.
*/
pad->collapse_len = pad->pre_collapse_qiov.size;
pad->collapse_bounce_buf = qemu_blockalign(bs, pad->collapse_len);
if (pad->write) {
qemu_iovec_to_buf(&pad->pre_collapse_qiov, 0,
pad->collapse_bounce_buf, pad->collapse_len);
}
qemu_iovec_add(&pad->local_qiov,
pad->collapse_bounce_buf, pad->collapse_len);
}
qemu_iovec_concat_iov(&pad->local_qiov, iov, niov, iov_offset, bytes);
if (pad->tail) {
qemu_iovec_add(&pad->local_qiov,
pad->buf + pad->buf_len - pad->tail, pad->tail);
}
assert(pad->local_qiov.niov == MIN(padded_niov, IOV_MAX));
return 0;
}
/*
* bdrv_pad_request
*
* Exchange request parameters with padded request if needed. Don't include RMW
* read of padding, bdrv_padding_rmw_read() should be called separately if
* needed.
*
* @write is true for write requests, false for read requests.
*
* Request parameters (@qiov, &qiov_offset, &offset, &bytes) are in-out:
* - on function start they represent original request
* - on failure or when padding is not needed they are unchanged
* - on success when padding is needed they represent padded request
*/
static int bdrv_pad_request(BlockDriverState *bs,
QEMUIOVector **qiov, size_t *qiov_offset,
int64_t *offset, int64_t *bytes,
bool write,
BdrvRequestPadding *pad, bool *padded,
BdrvRequestFlags *flags)
{
int ret;
struct iovec *sliced_iov;
int sliced_niov;
size_t sliced_head, sliced_tail;
/* Should have been checked by the caller already */
ret = bdrv_check_request32(*offset, *bytes, *qiov, *qiov_offset);
if (ret < 0) {
return ret;
}
if (!bdrv_init_padding(bs, *offset, *bytes, write, pad)) {
if (padded) {
*padded = false;
}
return 0;
}
/*
* For prefetching in stream_populate(), no qiov is passed along, because
* only copy-on-read matters.
*/
if (*qiov) {
sliced_iov = qemu_iovec_slice(*qiov, *qiov_offset, *bytes,
&sliced_head, &sliced_tail,
&sliced_niov);
/* Guaranteed by bdrv_check_request32() */
assert(*bytes <= SIZE_MAX);
ret = bdrv_create_padded_qiov(bs, pad, sliced_iov, sliced_niov,
sliced_head, *bytes);
if (ret < 0) {
bdrv_padding_finalize(pad);
return ret;
}
*qiov = &pad->local_qiov;
*qiov_offset = 0;
}
*bytes += pad->head + pad->tail;
*offset -= pad->head;
if (padded) {
*padded = true;
}
if (flags) {
/* Can't use optimization hint with bounce buffer */
*flags &= ~BDRV_REQ_REGISTERED_BUF;
}
return 0;
}
int coroutine_fn bdrv_co_preadv(BdrvChild *child,
int64_t offset, int64_t bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
IO_CODE();
return bdrv_co_preadv_part(child, offset, bytes, qiov, 0, flags);
}
int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset,
BdrvRequestFlags flags)
{
BlockDriverState *bs = child->bs;
BdrvTrackedRequest req;
BdrvRequestPadding pad;
int ret;
IO_CODE();
trace_bdrv_co_preadv_part(bs, offset, bytes, flags);
if (!bdrv_co_is_inserted(bs)) {
return -ENOMEDIUM;
}
ret = bdrv_check_request32(offset, bytes, qiov, qiov_offset);
if (ret < 0) {
return ret;
}
if (bytes == 0 && !QEMU_IS_ALIGNED(offset, bs->bl.request_alignment)) {
/*
* Aligning zero request is nonsense. Even if driver has special meaning
* of zero-length (like qcow2_co_pwritev_compressed_part), we can't pass
* it to driver due to request_alignment.
*
* Still, no reason to return an error if someone do unaligned
* zero-length read occasionally.
*/
return 0;
}
bdrv_inc_in_flight(bs);
/* Don't do copy-on-read if we read data before write operation */
if (qatomic_read(&bs->copy_on_read)) {
flags |= BDRV_REQ_COPY_ON_READ;
}
ret = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, false,
&pad, NULL, &flags);
if (ret < 0) {
goto fail;
}
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
ret = bdrv_aligned_preadv(child, &req, offset, bytes,
bs->bl.request_alignment,
qiov, qiov_offset, flags);
tracked_request_end(&req);
bdrv_padding_finalize(&pad);
fail:
bdrv_dec_in_flight(bs);
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int64_t bytes,
BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
QEMUIOVector qiov;
void *buf = NULL;
int ret = 0;
bool need_flush = false;
int head = 0;
int tail = 0;
int64_t max_write_zeroes = MIN_NON_ZERO(bs->bl.max_pwrite_zeroes,
INT64_MAX);
int alignment = MAX(bs->bl.pwrite_zeroes_alignment,
bs->bl.request_alignment);
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer, MAX_BOUNCE_BUFFER);
assert_bdrv_graph_readable();
bdrv_check_request(offset, bytes, &error_abort);
if (!drv) {
return -ENOMEDIUM;
}
if ((flags & ~bs->supported_zero_flags) & BDRV_REQ_NO_FALLBACK) {
return -ENOTSUP;
}
/* By definition there is no user buffer so this flag doesn't make sense */
if (flags & BDRV_REQ_REGISTERED_BUF) {
return -EINVAL;
}
/* If opened with discard=off we should never unmap. */
if (!(bs->open_flags & BDRV_O_UNMAP)) {
flags &= ~BDRV_REQ_MAY_UNMAP;
}
/* Invalidate the cached block-status data range if this write overlaps */
bdrv_bsc_invalidate_range(bs, offset, bytes);
assert(alignment % bs->bl.request_alignment == 0);
head = offset % alignment;
tail = (offset + bytes) % alignment;
max_write_zeroes = QEMU_ALIGN_DOWN(max_write_zeroes, alignment);
assert(max_write_zeroes >= bs->bl.request_alignment);
while (bytes > 0 && !ret) {
int64_t num = bytes;
/* Align request. Block drivers can expect the "bulk" of the request
* to be aligned, and that unaligned requests do not cross cluster
* boundaries.
*/
if (head) {
/* Make a small request up to the first aligned sector. For
* convenience, limit this request to max_transfer even if
* we don't need to fall back to writes. */
num = MIN(MIN(bytes, max_transfer), alignment - head);
head = (head + num) % alignment;
assert(num < max_write_zeroes);
} else if (tail && num > alignment) {
/* Shorten the request to the last aligned sector. */
num -= tail;
}
/* limit request size */
if (num > max_write_zeroes) {
num = max_write_zeroes;
}
ret = -ENOTSUP;
/* First try the efficient write zeroes operation */
if (drv->bdrv_co_pwrite_zeroes) {
ret = drv->bdrv_co_pwrite_zeroes(bs, offset, num,
flags & bs->supported_zero_flags);
if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) &&
!(bs->supported_zero_flags & BDRV_REQ_FUA)) {
need_flush = true;
}
} else {
assert(!bs->supported_zero_flags);
}
if (ret == -ENOTSUP && !(flags & BDRV_REQ_NO_FALLBACK)) {
/* Fall back to bounce buffer if write zeroes is unsupported */
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
if ((flags & BDRV_REQ_FUA) &&
!(bs->supported_write_flags & BDRV_REQ_FUA)) {
/* No need for bdrv_driver_pwrite() to do a fallback
* flush on each chunk; use just one at the end */
write_flags &= ~BDRV_REQ_FUA;
need_flush = true;
}
num = MIN(num, max_transfer);
if (buf == NULL) {
buf = qemu_try_blockalign0(bs, num);
if (buf == NULL) {
ret = -ENOMEM;
goto fail;
}
}
qemu_iovec_init_buf(&qiov, buf, num);
ret = bdrv_driver_pwritev(bs, offset, num, &qiov, 0, write_flags);
/* Keep bounce buffer around if it is big enough for all
* all future requests.
*/
if (num < max_transfer) {
qemu_vfree(buf);
buf = NULL;
}
}
offset += num;
bytes -= num;
}
fail:
if (ret == 0 && need_flush) {
ret = bdrv_co_flush(bs);
}
qemu_vfree(buf);
return ret;
}
static inline int coroutine_fn GRAPH_RDLOCK
bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, int64_t bytes,
BdrvTrackedRequest *req, int flags)
{
BlockDriverState *bs = child->bs;
bdrv_check_request(offset, bytes, &error_abort);
if (bdrv_is_read_only(bs)) {
return -EPERM;
}
assert(!(bs->open_flags & BDRV_O_INACTIVE));
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
assert(!(flags & ~BDRV_REQ_MASK));
assert(!((flags & BDRV_REQ_NO_WAIT) && !(flags & BDRV_REQ_SERIALISING)));
if (flags & BDRV_REQ_SERIALISING) {
QEMU_LOCK_GUARD(&bs->reqs_lock);
tracked_request_set_serialising(req, bdrv_get_cluster_size(bs));
if ((flags & BDRV_REQ_NO_WAIT) && bdrv_find_conflicting_request(req)) {
return -EBUSY;
}
bdrv_wait_serialising_requests_locked(req);
} else {
bdrv_wait_serialising_requests(req);
}
assert(req->overlap_offset <= offset);
assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
assert(offset + bytes <= bs->total_sectors * BDRV_SECTOR_SIZE ||
child->perm & BLK_PERM_RESIZE);
switch (req->type) {
case BDRV_TRACKED_WRITE:
case BDRV_TRACKED_DISCARD:
if (flags & BDRV_REQ_WRITE_UNCHANGED) {
assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
} else {
assert(child->perm & BLK_PERM_WRITE);
}
bdrv_write_threshold_check_write(bs, offset, bytes);
return 0;
case BDRV_TRACKED_TRUNCATE:
assert(child->perm & BLK_PERM_RESIZE);
return 0;
default:
abort();
}
}
static inline void coroutine_fn GRAPH_RDLOCK
bdrv_co_write_req_finish(BdrvChild *child, int64_t offset, int64_t bytes,
BdrvTrackedRequest *req, int ret)
{
int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
BlockDriverState *bs = child->bs;
bdrv_check_request(offset, bytes, &error_abort);
qatomic_inc(&bs->write_gen);
/*
* Discard cannot extend the image, but in error handling cases, such as
* when reverting a qcow2 cluster allocation, the discarded range can pass
* the end of image file, so we cannot assert about BDRV_TRACKED_DISCARD
* here. Instead, just skip it, since semantically a discard request
* beyond EOF cannot expand the image anyway.
*/
if (ret == 0 &&
(req->type == BDRV_TRACKED_TRUNCATE ||
end_sector > bs->total_sectors) &&
req->type != BDRV_TRACKED_DISCARD) {
bs->total_sectors = end_sector;
bdrv_parent_cb_resize(bs);
bdrv_dirty_bitmap_truncate(bs, end_sector << BDRV_SECTOR_BITS);
}
if (req->bytes) {
switch (req->type) {
case BDRV_TRACKED_WRITE:
stat64_max(&bs->wr_highest_offset, offset + bytes);
/* fall through, to set dirty bits */
case BDRV_TRACKED_DISCARD:
bdrv_set_dirty(bs, offset, bytes);
break;
default:
break;
}
}
}
/*
* Forwards an already correctly aligned write request to the BlockDriver,
* after possibly fragmenting it.
*/
static int coroutine_fn GRAPH_RDLOCK
bdrv_aligned_pwritev(BdrvChild *child, BdrvTrackedRequest *req,
int64_t offset, int64_t bytes, int64_t align,
QEMUIOVector *qiov, size_t qiov_offset,
BdrvRequestFlags flags)
{
BlockDriverState *bs = child->bs;
BlockDriver *drv = bs->drv;
int ret;
int64_t bytes_remaining = bytes;
int max_transfer;
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
if (!drv) {
return -ENOMEDIUM;
}
if (bdrv_has_readonly_bitmaps(bs)) {
return -EPERM;
}
assert(is_power_of_2(align));
assert((offset & (align - 1)) == 0);
assert((bytes & (align - 1)) == 0);
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
ret = bdrv_co_write_req_prepare(child, offset, bytes, req, flags);
if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
!(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes &&
qemu_iovec_is_zero(qiov, qiov_offset, bytes)) {
flags |= BDRV_REQ_ZERO_WRITE;
if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
flags |= BDRV_REQ_MAY_UNMAP;
}
/* Can't use optimization hint with bufferless zero write */
flags &= ~BDRV_REQ_REGISTERED_BUF;
}
if (ret < 0) {
/* Do nothing, write notifier decided to fail this request */
} else if (flags & BDRV_REQ_ZERO_WRITE) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_ZERO);
ret = bdrv_co_do_pwrite_zeroes(bs, offset, bytes, flags);
} else if (flags & BDRV_REQ_WRITE_COMPRESSED) {
ret = bdrv_driver_pwritev_compressed(bs, offset, bytes,
qiov, qiov_offset);
} else if (bytes <= max_transfer) {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV);
ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, qiov_offset, flags);
} else {
bdrv_co_debug_event(bs, BLKDBG_PWRITEV);
while (bytes_remaining) {
int num = MIN(bytes_remaining, max_transfer);
int local_flags = flags;
assert(num);
if (num < bytes_remaining && (flags & BDRV_REQ_FUA) &&
!(bs->supported_write_flags & BDRV_REQ_FUA)) {
/* If FUA is going to be emulated by flush, we only
* need to flush on the last iteration */
local_flags &= ~BDRV_REQ_FUA;
}
ret = bdrv_driver_pwritev(bs, offset + bytes - bytes_remaining,
num, qiov,
qiov_offset + bytes - bytes_remaining,
local_flags);
if (ret < 0) {
break;
}
bytes_remaining -= num;
}
}
bdrv_co_debug_event(bs, BLKDBG_PWRITEV_DONE);
if (ret >= 0) {
ret = 0;
}
bdrv_co_write_req_finish(child, offset, bytes, req, ret);
return ret;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_co_do_zero_pwritev(BdrvChild *child, int64_t offset, int64_t bytes,
BdrvRequestFlags flags, BdrvTrackedRequest *req)
{
BlockDriverState *bs = child->bs;
QEMUIOVector local_qiov;
uint64_t align = bs->bl.request_alignment;
int ret = 0;
bool padding;
BdrvRequestPadding pad;
/* This flag doesn't make sense for padding or zero writes */
flags &= ~BDRV_REQ_REGISTERED_BUF;
padding = bdrv_init_padding(bs, offset, bytes, true, &pad);
if (padding) {
assert(!(flags & BDRV_REQ_NO_WAIT));
bdrv_make_request_serialising(req, align);
bdrv_padding_rmw_read(child, req, &pad, true);
if (pad.head || pad.merge_reads) {
int64_t aligned_offset = offset & ~(align - 1);
int64_t write_bytes = pad.merge_reads ? pad.buf_len : align;
qemu_iovec_init_buf(&local_qiov, pad.buf, write_bytes);
ret = bdrv_aligned_pwritev(child, req, aligned_offset, write_bytes,
align, &local_qiov, 0,
flags & ~BDRV_REQ_ZERO_WRITE);
if (ret < 0 || pad.merge_reads) {
/* Error or all work is done */
goto out;
}
offset += write_bytes - pad.head;
bytes -= write_bytes - pad.head;
}
}
assert(!bytes || (offset & (align - 1)) == 0);
if (bytes >= align) {
/* Write the aligned part in the middle. */
int64_t aligned_bytes = bytes & ~(align - 1);
ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
NULL, 0, flags);
if (ret < 0) {
goto out;
}
bytes -= aligned_bytes;
offset += aligned_bytes;
}
assert(!bytes || (offset & (align - 1)) == 0);
if (bytes) {
assert(align == pad.tail + bytes);
qemu_iovec_init_buf(&local_qiov, pad.tail_buf, align);
ret = bdrv_aligned_pwritev(child, req, offset, align, align,
&local_qiov, 0,
flags & ~BDRV_REQ_ZERO_WRITE);
}
out:
bdrv_padding_finalize(&pad);
return ret;
}
/*
* Handle a write request in coroutine context
*/
int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
int64_t offset, int64_t bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
IO_CODE();
return bdrv_co_pwritev_part(child, offset, bytes, qiov, 0, flags);
}
int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset,
BdrvRequestFlags flags)
{
BlockDriverState *bs = child->bs;
BdrvTrackedRequest req;
uint64_t align = bs->bl.request_alignment;
BdrvRequestPadding pad;
int ret;
bool padded = false;
IO_CODE();
trace_bdrv_co_pwritev_part(child->bs, offset, bytes, flags);
if (!bdrv_co_is_inserted(bs)) {
return -ENOMEDIUM;
}
if (flags & BDRV_REQ_ZERO_WRITE) {
ret = bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, NULL);
} else {
ret = bdrv_check_request32(offset, bytes, qiov, qiov_offset);
}
if (ret < 0) {
return ret;
}
/* If the request is misaligned then we can't make it efficient */
if ((flags & BDRV_REQ_NO_FALLBACK) &&
!QEMU_IS_ALIGNED(offset | bytes, align))
{
return -ENOTSUP;
}
if (bytes == 0 && !QEMU_IS_ALIGNED(offset, bs->bl.request_alignment)) {
/*
* Aligning zero request is nonsense. Even if driver has special meaning
* of zero-length (like qcow2_co_pwritev_compressed_part), we can't pass
* it to driver due to request_alignment.
*
* Still, no reason to return an error if someone do unaligned
* zero-length write occasionally.
*/
return 0;
}
if (!(flags & BDRV_REQ_ZERO_WRITE)) {
/*
* Pad request for following read-modify-write cycle.
* bdrv_co_do_zero_pwritev() does aligning by itself, so, we do
* alignment only if there is no ZERO flag.
*/
ret = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, true,
&pad, &padded, &flags);
if (ret < 0) {
return ret;
}
}
bdrv_inc_in_flight(bs);
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
if (flags & BDRV_REQ_ZERO_WRITE) {
assert(!padded);
ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
goto out;
}
if (padded) {
/*
* Request was unaligned to request_alignment and therefore
* padded. We are going to do read-modify-write, and must
* serialize the request to prevent interactions of the
* widened region with other transactions.
*/
assert(!(flags & BDRV_REQ_NO_WAIT));
bdrv_make_request_serialising(&req, align);
bdrv_padding_rmw_read(child, &req, &pad, false);
}
ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
qiov, qiov_offset, flags);
bdrv_padding_finalize(&pad);
out:
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
int64_t bytes, BdrvRequestFlags flags)
{
IO_CODE();
trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags);
assert_bdrv_graph_readable();
return bdrv_co_pwritev(child, offset, bytes, NULL,
BDRV_REQ_ZERO_WRITE | flags);
}
/*
* Flush ALL BDSes regardless of if they are reachable via a BlkBackend or not.
*/
int bdrv_flush_all(void)
{
BdrvNextIterator it;
BlockDriverState *bs = NULL;
int result = 0;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
/*
* bdrv queue is managed by record/replay,
* creating new flush request for stopping
* the VM may break the determinism
*/
if (replay_events_enabled()) {
return result;
}
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
int ret = bdrv_flush(bs);
if (ret < 0 && !result) {
result = ret;
}
}
return result;
}
/*
* Returns the allocation status of the specified sectors.
* Drivers not implementing the functionality are assumed to not support
* backing files, hence all their sectors are reported as allocated.
*
* If 'want_zero' is true, the caller is querying for mapping
* purposes, with a focus on valid BDRV_BLOCK_OFFSET_VALID, _DATA, and
* _ZERO where possible; otherwise, the result favors larger 'pnum',
* with a focus on accurate BDRV_BLOCK_ALLOCATED.
*
* If 'offset' is beyond the end of the disk image the return value is
* BDRV_BLOCK_EOF and 'pnum' is set to 0.
*
* 'bytes' is the max value 'pnum' should be set to. If bytes goes
* beyond the end of the disk image it will be clamped; if 'pnum' is set to
* the end of the image, then the returned value will include BDRV_BLOCK_EOF.
*
* 'pnum' is set to the number of bytes (including and immediately
* following the specified offset) that are easily known to be in the
* same allocated/unallocated state. Note that a second call starting
* at the original offset plus returned pnum may have the same status.
* The returned value is non-zero on success except at end-of-file.
*
* Returns negative errno on failure. Otherwise, if the
* BDRV_BLOCK_OFFSET_VALID bit is set, 'map' and 'file' (if non-NULL) are
* set to the host mapping and BDS corresponding to the guest offset.
*/
static int coroutine_fn GRAPH_RDLOCK
bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
int64_t offset, int64_t bytes,
int64_t *pnum, int64_t *map, BlockDriverState **file)
{
int64_t total_size;
int64_t n; /* bytes */
int ret;
int64_t local_map = 0;
BlockDriverState *local_file = NULL;
int64_t aligned_offset, aligned_bytes;
uint32_t align;
bool has_filtered_child;
assert(pnum);
assert_bdrv_graph_readable();
*pnum = 0;
total_size = bdrv_co_getlength(bs);
if (total_size < 0) {
ret = total_size;
goto early_out;
}
if (offset >= total_size) {
ret = BDRV_BLOCK_EOF;
goto early_out;
}
if (!bytes) {
ret = 0;
goto early_out;
}
n = total_size - offset;
if (n < bytes) {
bytes = n;
}
/* Must be non-NULL or bdrv_co_getlength() would have failed */
assert(bs->drv);
has_filtered_child = bdrv_filter_child(bs);
if (!bs->drv->bdrv_co_block_status && !has_filtered_child) {
*pnum = bytes;
ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
if (offset + bytes == total_size) {
ret |= BDRV_BLOCK_EOF;
}
if (bs->drv->protocol_name) {
ret |= BDRV_BLOCK_OFFSET_VALID;
local_map = offset;
local_file = bs;
}
goto early_out;
}
bdrv_inc_in_flight(bs);
/* Round out to request_alignment boundaries */
align = bs->bl.request_alignment;
aligned_offset = QEMU_ALIGN_DOWN(offset, align);
aligned_bytes = ROUND_UP(offset + bytes, align) - aligned_offset;
if (bs->drv->bdrv_co_block_status) {
/*
* Use the block-status cache only for protocol nodes: Format
* drivers are generally quick to inquire the status, but protocol
* drivers often need to get information from outside of qemu, so
* we do not have control over the actual implementation. There
* have been cases where inquiring the status took an unreasonably
* long time, and we can do nothing in qemu to fix it.
* This is especially problematic for images with large data areas,
* because finding the few holes in them and giving them special
* treatment does not gain much performance. Therefore, we try to
* cache the last-identified data region.
*
* Second, limiting ourselves to protocol nodes allows us to assume
* the block status for data regions to be DATA | OFFSET_VALID, and
* that the host offset is the same as the guest offset.
*
* Note that it is possible that external writers zero parts of
* the cached regions without the cache being invalidated, and so
* we may report zeroes as data. This is not catastrophic,
* however, because reporting zeroes as data is fine.
*/
if (QLIST_EMPTY(&bs->children) &&
bdrv_bsc_is_data(bs, aligned_offset, pnum))
{
ret = BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
local_file = bs;
local_map = aligned_offset;
} else {
ret = bs->drv->bdrv_co_block_status(bs, want_zero, aligned_offset,
aligned_bytes, pnum, &local_map,
&local_file);
/*
* Note that checking QLIST_EMPTY(&bs->children) is also done when
* the cache is queried above. Technically, we do not need to check
* it here; the worst that can happen is that we fill the cache for
* non-protocol nodes, and then it is never used. However, filling
* the cache requires an RCU update, so double check here to avoid
* such an update if possible.
*
* Check want_zero, because we only want to update the cache when we
* have accurate information about what is zero and what is data.
*/
if (want_zero &&
ret == (BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID) &&
QLIST_EMPTY(&bs->children))
{
/*
* When a protocol driver reports BLOCK_OFFSET_VALID, the
* returned local_map value must be the same as the offset we
* have passed (aligned_offset), and local_bs must be the node
* itself.
* Assert this, because we follow this rule when reading from
* the cache (see the `local_file = bs` and
* `local_map = aligned_offset` assignments above), and the
* result the cache delivers must be the same as the driver
* would deliver.
*/
assert(local_file == bs);
assert(local_map == aligned_offset);
bdrv_bsc_fill(bs, aligned_offset, *pnum);
}
}
} else {
/* Default code for filters */
local_file = bdrv_filter_bs(bs);
assert(local_file);
*pnum = aligned_bytes;
local_map = aligned_offset;
ret = BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID;
}
if (ret < 0) {
*pnum = 0;
goto out;
}
/*
* The driver's result must be a non-zero multiple of request_alignment.
* Clamp pnum and adjust map to original request.
*/
assert(*pnum && QEMU_IS_ALIGNED(*pnum, align) &&
align > offset - aligned_offset);
if (ret & BDRV_BLOCK_RECURSE) {
assert(ret & BDRV_BLOCK_DATA);
assert(ret & BDRV_BLOCK_OFFSET_VALID);
assert(!(ret & BDRV_BLOCK_ZERO));
}
*pnum -= offset - aligned_offset;
if (*pnum > bytes) {
*pnum = bytes;
}
if (ret & BDRV_BLOCK_OFFSET_VALID) {
local_map += offset - aligned_offset;
}
if (ret & BDRV_BLOCK_RAW) {
assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
ret = bdrv_co_do_block_status(local_file, want_zero, local_map,
*pnum, pnum, &local_map, &local_file);
goto out;
}
if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
ret |= BDRV_BLOCK_ALLOCATED;
} else if (bs->drv->supports_backing) {
BlockDriverState *cow_bs = bdrv_cow_bs(bs);
if (!cow_bs) {
ret |= BDRV_BLOCK_ZERO;
} else if (want_zero) {
int64_t size2 = bdrv_co_getlength(cow_bs);
if (size2 >= 0 && offset >= size2) {
ret |= BDRV_BLOCK_ZERO;
}
}
}
if (want_zero && ret & BDRV_BLOCK_RECURSE &&
local_file && local_file != bs &&
(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
(ret & BDRV_BLOCK_OFFSET_VALID)) {
int64_t file_pnum;
int ret2;
ret2 = bdrv_co_do_block_status(local_file, want_zero, local_map,
*pnum, &file_pnum, NULL, NULL);
if (ret2 >= 0) {
/* Ignore errors. This is just providing extra information, it
* is useful but not necessary.
*/
if (ret2 & BDRV_BLOCK_EOF &&
(!file_pnum || ret2 & BDRV_BLOCK_ZERO)) {
/*
* It is valid for the format block driver to read
* beyond the end of the underlying file's current
* size; such areas read as zero.
*/
ret |= BDRV_BLOCK_ZERO;
} else {
/* Limit request to the range reported by the protocol driver */
*pnum = file_pnum;
ret |= (ret2 & BDRV_BLOCK_ZERO);
}
}
/*
* Now that the recursive search was done, clear the flag. Otherwise,
* with more complicated block graphs like snapshot-access ->
* copy-before-write -> qcow2, where the return value will be propagated
* further up to a parent bdrv_co_do_block_status() call, both the
* BDRV_BLOCK_RECURSE and BDRV_BLOCK_ZERO flags would be set, which is
* not allowed.
*/
ret &= ~BDRV_BLOCK_RECURSE;
}
out:
bdrv_dec_in_flight(bs);
if (ret >= 0 && offset + *pnum == total_size) {
ret |= BDRV_BLOCK_EOF;
}
early_out:
if (file) {
*file = local_file;
}
if (map) {
*map = local_map;
}
return ret;
}
int coroutine_fn
bdrv_co_common_block_status_above(BlockDriverState *bs,
BlockDriverState *base,
bool include_base,
bool want_zero,
int64_t offset,
int64_t bytes,
int64_t *pnum,
int64_t *map,
BlockDriverState **file,
int *depth)
{
int ret;
BlockDriverState *p;
int64_t eof = 0;
int dummy;
IO_CODE();
assert(!include_base || base); /* Can't include NULL base */
assert_bdrv_graph_readable();
if (!depth) {
depth = &dummy;
}
*depth = 0;
if (!include_base && bs == base) {
*pnum = bytes;
return 0;
}
ret = bdrv_co_do_block_status(bs, want_zero, offset, bytes, pnum,
map, file);
++*depth;
if (ret < 0 || *pnum == 0 || ret & BDRV_BLOCK_ALLOCATED || bs == base) {
return ret;
}
if (ret & BDRV_BLOCK_EOF) {
eof = offset + *pnum;
}
assert(*pnum <= bytes);
bytes = *pnum;
for (p = bdrv_filter_or_cow_bs(bs); include_base || p != base;
p = bdrv_filter_or_cow_bs(p))
{
ret = bdrv_co_do_block_status(p, want_zero, offset, bytes, pnum,
map, file);
++*depth;
if (ret < 0) {
return ret;
}
if (*pnum == 0) {
/*
* The top layer deferred to this layer, and because this layer is
* short, any zeroes that we synthesize beyond EOF behave as if they
* were allocated at this layer.
*
* We don't include BDRV_BLOCK_EOF into ret, as upper layer may be
* larger. We'll add BDRV_BLOCK_EOF if needed at function end, see
* below.
*/
assert(ret & BDRV_BLOCK_EOF);
*pnum = bytes;
if (file) {
*file = p;
}
ret = BDRV_BLOCK_ZERO | BDRV_BLOCK_ALLOCATED;
break;
}
if (ret & BDRV_BLOCK_ALLOCATED) {
/*
* We've found the node and the status, we must break.
*
* Drop BDRV_BLOCK_EOF, as it's not for upper layer, which may be
* larger. We'll add BDRV_BLOCK_EOF if needed at function end, see
* below.
*/
ret &= ~BDRV_BLOCK_EOF;
break;
}
if (p == base) {
assert(include_base);
break;
}
/*
* OK, [offset, offset + *pnum) region is unallocated on this layer,
* let's continue the diving.
*/
assert(*pnum <= bytes);
bytes = *pnum;
}
if (offset + *pnum == eof) {
ret |= BDRV_BLOCK_EOF;
}
return ret;
}
int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
BlockDriverState *base,
int64_t offset, int64_t bytes,
int64_t *pnum, int64_t *map,
BlockDriverState **file)
{
IO_CODE();
return bdrv_co_common_block_status_above(bs, base, false, true, offset,
bytes, pnum, map, file, NULL);
}
int coroutine_fn bdrv_co_block_status(BlockDriverState *bs, int64_t offset,
int64_t bytes, int64_t *pnum,
int64_t *map, BlockDriverState **file)
{
IO_CODE();
return bdrv_co_block_status_above(bs, bdrv_filter_or_cow_bs(bs),
offset, bytes, pnum, map, file);
}
/*
* Check @bs (and its backing chain) to see if the range defined
* by @offset and @bytes is known to read as zeroes.
* Return 1 if that is the case, 0 otherwise and -errno on error.
* This test is meant to be fast rather than accurate so returning 0
* does not guarantee non-zero data.
*/
int coroutine_fn bdrv_co_is_zero_fast(BlockDriverState *bs, int64_t offset,
int64_t bytes)
{
int ret;
int64_t pnum = bytes;
IO_CODE();
if (!bytes) {
return 1;
}
ret = bdrv_co_common_block_status_above(bs, NULL, false, false, offset,
bytes, &pnum, NULL, NULL, NULL);
if (ret < 0) {
return ret;
}
return (pnum == bytes) && (ret & BDRV_BLOCK_ZERO);
}
int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t offset,
int64_t bytes, int64_t *pnum)
{
int ret;
int64_t dummy;
IO_CODE();
ret = bdrv_co_common_block_status_above(bs, bs, true, false, offset,
bytes, pnum ? pnum : &dummy, NULL,
NULL, NULL);
if (ret < 0) {
return ret;
}
return !!(ret & BDRV_BLOCK_ALLOCATED);
}
/*
* Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
*
* Return a positive depth if (a prefix of) the given range is allocated
* in any image between BASE and TOP (BASE is only included if include_base
* is set). Depth 1 is TOP, 2 is the first backing layer, and so forth.
* BASE can be NULL to check if the given offset is allocated in any
* image of the chain. Return 0 otherwise, or negative errno on
* failure.
*
* 'pnum' is set to the number of bytes (including and immediately
* following the specified offset) that are known to be in the same
* allocated/unallocated state. Note that a subsequent call starting
* at 'offset + *pnum' may return the same allocation status (in other
* words, the result is not necessarily the maximum possible range);
* but 'pnum' will only be 0 when end of file is reached.
*/
int coroutine_fn bdrv_co_is_allocated_above(BlockDriverState *bs,
BlockDriverState *base,
bool include_base, int64_t offset,
int64_t bytes, int64_t *pnum)
{
int depth;
int ret;
IO_CODE();
ret = bdrv_co_common_block_status_above(bs, base, include_base, false,
offset, bytes, pnum, NULL, NULL,
&depth);
if (ret < 0) {
return ret;
}
if (ret & BDRV_BLOCK_ALLOCATED) {
return depth;
}
return 0;
}
int coroutine_fn
bdrv_co_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
{
BlockDriver *drv = bs->drv;
BlockDriverState *child_bs = bdrv_primary_bs(bs);
int ret;
IO_CODE();
assert_bdrv_graph_readable();
ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
if (ret < 0) {
return ret;
}
if (!drv) {
return -ENOMEDIUM;
}
bdrv_inc_in_flight(bs);
if (drv->bdrv_co_load_vmstate) {
ret = drv->bdrv_co_load_vmstate(bs, qiov, pos);
} else if (child_bs) {
ret = bdrv_co_readv_vmstate(child_bs, qiov, pos);
} else {
ret = -ENOTSUP;
}
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn
bdrv_co_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
{
BlockDriver *drv = bs->drv;
BlockDriverState *child_bs = bdrv_primary_bs(bs);
int ret;
IO_CODE();
assert_bdrv_graph_readable();
ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
if (ret < 0) {
return ret;
}
if (!drv) {
return -ENOMEDIUM;
}
bdrv_inc_in_flight(bs);
if (drv->bdrv_co_save_vmstate) {
ret = drv->bdrv_co_save_vmstate(bs, qiov, pos);
} else if (child_bs) {
ret = bdrv_co_writev_vmstate(child_bs, qiov, pos);
} else {
ret = -ENOTSUP;
}
bdrv_dec_in_flight(bs);
return ret;
}
int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
int64_t pos, int size)
{
QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, size);
int ret = bdrv_writev_vmstate(bs, &qiov, pos);
IO_CODE();
return ret < 0 ? ret : size;
}
int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
int64_t pos, int size)
{
QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, size);
int ret = bdrv_readv_vmstate(bs, &qiov, pos);
IO_CODE();
return ret < 0 ? ret : size;
}
/**************************************************************/
/* async I/Os */
/**
* Synchronously cancels an acb. Must be called with the BQL held and the acb
* must be processed with the BQL held too (IOThreads are not allowed).
*
* Use bdrv_aio_cancel_async() instead when possible.
*/
void bdrv_aio_cancel(BlockAIOCB *acb)
{
GLOBAL_STATE_CODE();
qemu_aio_ref(acb);
bdrv_aio_cancel_async(acb);
AIO_WAIT_WHILE_UNLOCKED(NULL, acb->refcnt > 1);
qemu_aio_unref(acb);
}
/* Async version of aio cancel. The caller is not blocked if the acb implements
* cancel_async, otherwise we do nothing and let the request normally complete.
* In either case the completion callback must be called. */
void bdrv_aio_cancel_async(BlockAIOCB *acb)
{
IO_CODE();
if (acb->aiocb_info->cancel_async) {
acb->aiocb_info->cancel_async(acb);
}
}
/**************************************************************/
/* Coroutine block device emulation */
int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
{
BdrvChild *primary_child = bdrv_primary_child(bs);
BdrvChild *child;
int current_gen;
int ret = 0;
IO_CODE();
assert_bdrv_graph_readable();
bdrv_inc_in_flight(bs);
if (!bdrv_co_is_inserted(bs) || bdrv_is_read_only(bs) ||
bdrv_is_sg(bs)) {
goto early_exit;
}
qemu_mutex_lock(&bs->reqs_lock);
current_gen = qatomic_read(&bs->write_gen);
/* Wait until any previous flushes are completed */
while (bs->active_flush_req) {
qemu_co_queue_wait(&bs->flush_queue, &bs->reqs_lock);
}
/* Flushes reach this point in nondecreasing current_gen order. */
bs->active_flush_req = true;
qemu_mutex_unlock(&bs->reqs_lock);
/* Write back all layers by calling one driver function */
if (bs->drv->bdrv_co_flush) {
ret = bs->drv->bdrv_co_flush(bs);
goto out;
}
/* Write back cached data to the OS even with cache=unsafe */
BLKDBG_CO_EVENT(primary_child, BLKDBG_FLUSH_TO_OS);
if (bs->drv->bdrv_co_flush_to_os) {
ret = bs->drv->bdrv_co_flush_to_os(bs);
if (ret < 0) {
goto out;
}
}
/* But don't actually force it to the disk with cache=unsafe */
if (bs->open_flags & BDRV_O_NO_FLUSH) {
goto flush_children;
}
/* Check if we really need to flush anything */
if (bs->flushed_gen == current_gen) {
goto flush_children;
}
BLKDBG_CO_EVENT(primary_child, BLKDBG_FLUSH_TO_DISK);
if (!bs->drv) {
/* bs->drv->bdrv_co_flush() might have ejected the BDS
* (even in case of apparent success) */
ret = -ENOMEDIUM;
goto out;
}
if (bs->drv->bdrv_co_flush_to_disk) {
ret = bs->drv->bdrv_co_flush_to_disk(bs);
} else if (bs->drv->bdrv_aio_flush) {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_flush(bs, bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
} else {
/*
* Some block drivers always operate in either writethrough or unsafe
* mode and don't support bdrv_flush therefore. Usually qemu doesn't
* know how the server works (because the behaviour is hardcoded or
* depends on server-side configuration), so we can't ensure that
* everything is safe on disk. Returning an error doesn't work because
* that would break guests even if the server operates in writethrough
* mode.
*
* Let's hope the user knows what he's doing.
*/
ret = 0;
}
if (ret < 0) {
goto out;
}
/* Now flush the underlying protocol. It will also have BDRV_O_NO_FLUSH
* in the case of cache=unsafe, so there are no useless flushes.
*/
flush_children:
ret = 0;
QLIST_FOREACH(child, &bs->children, next) {
if (child->perm & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) {
int this_child_ret = bdrv_co_flush(child->bs);
if (!ret) {
ret = this_child_ret;
}
}
}
out:
/* Notify any pending flushes that we have completed */
if (ret == 0) {
bs->flushed_gen = current_gen;
}
qemu_mutex_lock(&bs->reqs_lock);
bs->active_flush_req = false;
/* Return value is ignored - it's ok if wait queue is empty */
qemu_co_queue_next(&bs->flush_queue);
qemu_mutex_unlock(&bs->reqs_lock);
early_exit:
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn bdrv_co_pdiscard(BdrvChild *child, int64_t offset,
int64_t bytes)
{
BdrvTrackedRequest req;
int ret;
int64_t max_pdiscard;
int head, tail, align;
BlockDriverState *bs = child->bs;
IO_CODE();
assert_bdrv_graph_readable();
if (!bs || !bs->drv || !bdrv_co_is_inserted(bs)) {
return -ENOMEDIUM;
}
if (bdrv_has_readonly_bitmaps(bs)) {
return -EPERM;
}
ret = bdrv_check_request(offset, bytes, NULL);
if (ret < 0) {
return ret;
}
/* Do nothing if disabled. */
if (!(bs->open_flags & BDRV_O_UNMAP)) {
return 0;
}
if (!bs->drv->bdrv_co_pdiscard && !bs->drv->bdrv_aio_pdiscard) {
return 0;
}
/* Invalidate the cached block-status data range if this discard overlaps */
bdrv_bsc_invalidate_range(bs, offset, bytes);
/* Discard is advisory, but some devices track and coalesce
* unaligned requests, so we must pass everything down rather than
* round here. Still, most devices will just silently ignore
* unaligned requests (by returning -ENOTSUP), so we must fragment
* the request accordingly. */
align = MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment);
assert(align % bs->bl.request_alignment == 0);
head = offset % align;
tail = (offset + bytes) % align;
bdrv_inc_in_flight(bs);
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_DISCARD);
ret = bdrv_co_write_req_prepare(child, offset, bytes, &req, 0);
if (ret < 0) {
goto out;
}
max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT64_MAX),
align);
assert(max_pdiscard >= bs->bl.request_alignment);
while (bytes > 0) {
int64_t num = bytes;
if (head) {
/* Make small requests to get to alignment boundaries. */
num = MIN(bytes, align - head);
if (!QEMU_IS_ALIGNED(num, bs->bl.request_alignment)) {
num %= bs->bl.request_alignment;
}
head = (head + num) % align;
assert(num < max_pdiscard);
} else if (tail) {
if (num > align) {
/* Shorten the request to the last aligned cluster. */
num -= tail;
} else if (!QEMU_IS_ALIGNED(tail, bs->bl.request_alignment) &&
tail > bs->bl.request_alignment) {
tail %= bs->bl.request_alignment;
num -= tail;
}
}
/* limit request size */
if (num > max_pdiscard) {
num = max_pdiscard;
}
if (!bs->drv) {
ret = -ENOMEDIUM;
goto out;
}
if (bs->drv->bdrv_co_pdiscard) {
ret = bs->drv->bdrv_co_pdiscard(bs, offset, num);
} else {
BlockAIOCB *acb;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
acb = bs->drv->bdrv_aio_pdiscard(bs, offset, num,
bdrv_co_io_em_complete, &co);
if (acb == NULL) {
ret = -EIO;
goto out;
} else {
qemu_coroutine_yield();
ret = co.ret;
}
}
if (ret && ret != -ENOTSUP) {
goto out;
}
offset += num;
bytes -= num;
}
ret = 0;
out:
bdrv_co_write_req_finish(child, req.offset, req.bytes, &req, ret);
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
{
BlockDriver *drv = bs->drv;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
BlockAIOCB *acb;
IO_CODE();
assert_bdrv_graph_readable();
bdrv_inc_in_flight(bs);
if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
co.ret = -ENOTSUP;
goto out;
}
if (drv->bdrv_co_ioctl) {
co.ret = drv->bdrv_co_ioctl(bs, req, buf);
} else {
acb = drv->bdrv_aio_ioctl(bs, req, buf, bdrv_co_io_em_complete, &co);
if (!acb) {
co.ret = -ENOTSUP;
goto out;
}
qemu_coroutine_yield();
}
out:
bdrv_dec_in_flight(bs);
return co.ret;
}
int coroutine_fn bdrv_co_zone_report(BlockDriverState *bs, int64_t offset,
unsigned int *nr_zones,
BlockZoneDescriptor *zones)
{
BlockDriver *drv = bs->drv;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
IO_CODE();
bdrv_inc_in_flight(bs);
if (!drv || !drv->bdrv_co_zone_report || bs->bl.zoned == BLK_Z_NONE) {
co.ret = -ENOTSUP;
goto out;
}
co.ret = drv->bdrv_co_zone_report(bs, offset, nr_zones, zones);
out:
bdrv_dec_in_flight(bs);
return co.ret;
}
int coroutine_fn bdrv_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
int64_t offset, int64_t len)
{
BlockDriver *drv = bs->drv;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
IO_CODE();
bdrv_inc_in_flight(bs);
if (!drv || !drv->bdrv_co_zone_mgmt || bs->bl.zoned == BLK_Z_NONE) {
co.ret = -ENOTSUP;
goto out;
}
co.ret = drv->bdrv_co_zone_mgmt(bs, op, offset, len);
out:
bdrv_dec_in_flight(bs);
return co.ret;
}
int coroutine_fn bdrv_co_zone_append(BlockDriverState *bs, int64_t *offset,
QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
int ret;
BlockDriver *drv = bs->drv;
CoroutineIOCompletion co = {
.coroutine = qemu_coroutine_self(),
};
IO_CODE();
ret = bdrv_check_qiov_request(*offset, qiov->size, qiov, 0, NULL);
if (ret < 0) {
return ret;
}
bdrv_inc_in_flight(bs);
if (!drv || !drv->bdrv_co_zone_append || bs->bl.zoned == BLK_Z_NONE) {
co.ret = -ENOTSUP;
goto out;
}
co.ret = drv->bdrv_co_zone_append(bs, offset, qiov, flags);
out:
bdrv_dec_in_flight(bs);
return co.ret;
}
void *qemu_blockalign(BlockDriverState *bs, size_t size)
{
IO_CODE();
return qemu_memalign(bdrv_opt_mem_align(bs), size);
}
void *qemu_blockalign0(BlockDriverState *bs, size_t size)
{
IO_CODE();
return memset(qemu_blockalign(bs, size), 0, size);
}
void *qemu_try_blockalign(BlockDriverState *bs, size_t size)
{
size_t align = bdrv_opt_mem_align(bs);
IO_CODE();
/* Ensure that NULL is never returned on success */
assert(align > 0);
if (size == 0) {
size = align;
}
return qemu_try_memalign(align, size);
}
void *qemu_try_blockalign0(BlockDriverState *bs, size_t size)
{
void *mem = qemu_try_blockalign(bs, size);
IO_CODE();
if (mem) {
memset(mem, 0, size);
}
return mem;
}
/* Helper that undoes bdrv_register_buf() when it fails partway through */
static void GRAPH_RDLOCK
bdrv_register_buf_rollback(BlockDriverState *bs, void *host, size_t size,
BdrvChild *final_child)
{
BdrvChild *child;
GLOBAL_STATE_CODE();
assert_bdrv_graph_readable();
QLIST_FOREACH(child, &bs->children, next) {
if (child == final_child) {
break;
}
bdrv_unregister_buf(child->bs, host, size);
}
if (bs->drv && bs->drv->bdrv_unregister_buf) {
bs->drv->bdrv_unregister_buf(bs, host, size);
}
}
bool bdrv_register_buf(BlockDriverState *bs, void *host, size_t size,
Error **errp)
{
BdrvChild *child;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
if (bs->drv && bs->drv->bdrv_register_buf) {
if (!bs->drv->bdrv_register_buf(bs, host, size, errp)) {
return false;
}
}
QLIST_FOREACH(child, &bs->children, next) {
if (!bdrv_register_buf(child->bs, host, size, errp)) {
bdrv_register_buf_rollback(bs, host, size, child);
return false;
}
}
return true;
}
void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size)
{
BdrvChild *child;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
if (bs->drv && bs->drv->bdrv_unregister_buf) {
bs->drv->bdrv_unregister_buf(bs, host, size);
}
QLIST_FOREACH(child, &bs->children, next) {
bdrv_unregister_buf(child->bs, host, size);
}
}
static int coroutine_fn GRAPH_RDLOCK bdrv_co_copy_range_internal(
BdrvChild *src, int64_t src_offset, BdrvChild *dst,
int64_t dst_offset, int64_t bytes,
BdrvRequestFlags read_flags, BdrvRequestFlags write_flags,
bool recurse_src)
{
BdrvTrackedRequest req;
int ret;
assert_bdrv_graph_readable();
/* TODO We can support BDRV_REQ_NO_FALLBACK here */
assert(!(read_flags & BDRV_REQ_NO_FALLBACK));
assert(!(write_flags & BDRV_REQ_NO_FALLBACK));
assert(!(read_flags & BDRV_REQ_NO_WAIT));
assert(!(write_flags & BDRV_REQ_NO_WAIT));
if (!dst || !dst->bs || !bdrv_co_is_inserted(dst->bs)) {
return -ENOMEDIUM;
}
ret = bdrv_check_request32(dst_offset, bytes, NULL, 0);
if (ret) {
return ret;
}
if (write_flags & BDRV_REQ_ZERO_WRITE) {
return bdrv_co_pwrite_zeroes(dst, dst_offset, bytes, write_flags);
}
if (!src || !src->bs || !bdrv_co_is_inserted(src->bs)) {
return -ENOMEDIUM;
}
ret = bdrv_check_request32(src_offset, bytes, NULL, 0);
if (ret) {
return ret;
}
if (!src->bs->drv->bdrv_co_copy_range_from
|| !dst->bs->drv->bdrv_co_copy_range_to
|| src->bs->encrypted || dst->bs->encrypted) {
return -ENOTSUP;
}
if (recurse_src) {
bdrv_inc_in_flight(src->bs);
tracked_request_begin(&req, src->bs, src_offset, bytes,
BDRV_TRACKED_READ);
/* BDRV_REQ_SERIALISING is only for write operation */
assert(!(read_flags & BDRV_REQ_SERIALISING));
bdrv_wait_serialising_requests(&req);
ret = src->bs->drv->bdrv_co_copy_range_from(src->bs,
src, src_offset,
dst, dst_offset,
bytes,
read_flags, write_flags);
tracked_request_end(&req);
bdrv_dec_in_flight(src->bs);
} else {
bdrv_inc_in_flight(dst->bs);
tracked_request_begin(&req, dst->bs, dst_offset, bytes,
BDRV_TRACKED_WRITE);
ret = bdrv_co_write_req_prepare(dst, dst_offset, bytes, &req,
write_flags);
if (!ret) {
ret = dst->bs->drv->bdrv_co_copy_range_to(dst->bs,
src, src_offset,
dst, dst_offset,
bytes,
read_flags, write_flags);
}
bdrv_co_write_req_finish(dst, dst_offset, bytes, &req, ret);
tracked_request_end(&req);
bdrv_dec_in_flight(dst->bs);
}
return ret;
}
/* Copy range from @src to @dst.
*
* See the comment of bdrv_co_copy_range for the parameter and return value
* semantics. */
int coroutine_fn bdrv_co_copy_range_from(BdrvChild *src, int64_t src_offset,
BdrvChild *dst, int64_t dst_offset,
int64_t bytes,
BdrvRequestFlags read_flags,
BdrvRequestFlags write_flags)
{
IO_CODE();
assert_bdrv_graph_readable();
trace_bdrv_co_copy_range_from(src, src_offset, dst, dst_offset, bytes,
read_flags, write_flags);
return bdrv_co_copy_range_internal(src, src_offset, dst, dst_offset,
bytes, read_flags, write_flags, true);
}
/* Copy range from @src to @dst.
*
* See the comment of bdrv_co_copy_range for the parameter and return value
* semantics. */
int coroutine_fn bdrv_co_copy_range_to(BdrvChild *src, int64_t src_offset,
BdrvChild *dst, int64_t dst_offset,
int64_t bytes,
BdrvRequestFlags read_flags,
BdrvRequestFlags write_flags)
{
IO_CODE();
assert_bdrv_graph_readable();
trace_bdrv_co_copy_range_to(src, src_offset, dst, dst_offset, bytes,
read_flags, write_flags);
return bdrv_co_copy_range_internal(src, src_offset, dst, dst_offset,
bytes, read_flags, write_flags, false);
}
int coroutine_fn bdrv_co_copy_range(BdrvChild *src, int64_t src_offset,
BdrvChild *dst, int64_t dst_offset,
int64_t bytes, BdrvRequestFlags read_flags,
BdrvRequestFlags write_flags)
{
IO_CODE();
assert_bdrv_graph_readable();
return bdrv_co_copy_range_from(src, src_offset,
dst, dst_offset,
bytes, read_flags, write_flags);
}
static void coroutine_fn GRAPH_RDLOCK
bdrv_parent_cb_resize(BlockDriverState *bs)
{
BdrvChild *c;
assert_bdrv_graph_readable();
QLIST_FOREACH(c, &bs->parents, next_parent) {
if (c->klass->resize) {
c->klass->resize(c);
}
}
}
/**
* Truncate file to 'offset' bytes (needed only for file protocols)
*
* If 'exact' is true, the file must be resized to exactly the given
* 'offset'. Otherwise, it is sufficient for the node to be at least
* 'offset' bytes in length.
*/
int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
PreallocMode prealloc, BdrvRequestFlags flags,
Error **errp)
{
BlockDriverState *bs = child->bs;
BdrvChild *filtered, *backing;
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
int64_t old_size, new_bytes;
int ret;
IO_CODE();
assert_bdrv_graph_readable();
/* if bs->drv == NULL, bs is closed, so there's nothing to do here */
if (!drv) {
error_setg(errp, "No medium inserted");
return -ENOMEDIUM;
}
if (offset < 0) {
error_setg(errp, "Image size cannot be negative");
return -EINVAL;
}
ret = bdrv_check_request(offset, 0, errp);
if (ret < 0) {
return ret;
}
old_size = bdrv_co_getlength(bs);
if (old_size < 0) {
error_setg_errno(errp, -old_size, "Failed to get old image size");
return old_size;
}
if (bdrv_is_read_only(bs)) {
error_setg(errp, "Image is read-only");
return -EACCES;
}
if (offset > old_size) {
new_bytes = offset - old_size;
} else {
new_bytes = 0;
}
bdrv_inc_in_flight(bs);
tracked_request_begin(&req, bs, offset - new_bytes, new_bytes,
BDRV_TRACKED_TRUNCATE);
/* If we are growing the image and potentially using preallocation for the
* new area, we need to make sure that no write requests are made to it
* concurrently or they might be overwritten by preallocation. */
if (new_bytes) {
bdrv_make_request_serialising(&req, 1);
}
ret = bdrv_co_write_req_prepare(child, offset - new_bytes, new_bytes, &req,
0);
if (ret < 0) {
error_setg_errno(errp, -ret,
"Failed to prepare request for truncation");
goto out;
}
filtered = bdrv_filter_child(bs);
backing = bdrv_cow_child(bs);
/*
* If the image has a backing file that is large enough that it would
* provide data for the new area, we cannot leave it unallocated because
* then the backing file content would become visible. Instead, zero-fill
* the new area.
*
* Note that if the image has a backing file, but was opened without the
* backing file, taking care of keeping things consistent with that backing
* file is the user's responsibility.
*/
if (new_bytes && backing) {
int64_t backing_len;
backing_len = bdrv_co_getlength(backing->bs);
if (backing_len < 0) {
ret = backing_len;
error_setg_errno(errp, -ret, "Could not get backing file size");
goto out;
}
if (backing_len > old_size) {
flags |= BDRV_REQ_ZERO_WRITE;
}
}
if (drv->bdrv_co_truncate) {
if (flags & ~bs->supported_truncate_flags) {
error_setg(errp, "Block driver does not support requested flags");
ret = -ENOTSUP;
goto out;
}
ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, flags, errp);
} else if (filtered) {
ret = bdrv_co_truncate(filtered, offset, exact, prealloc, flags, errp);
} else {
error_setg(errp, "Image format driver does not support resize");
ret = -ENOTSUP;
goto out;
}
if (ret < 0) {
goto out;
}
ret = bdrv_co_refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not refresh total sector count");
} else {
offset = bs->total_sectors * BDRV_SECTOR_SIZE;
}
/*
* It's possible that truncation succeeded but bdrv_refresh_total_sectors
* failed, but the latter doesn't affect how we should finish the request.
* Pass 0 as the last parameter so that dirty bitmaps etc. are handled.
*/
bdrv_co_write_req_finish(child, offset - new_bytes, new_bytes, &req, 0);
out:
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
return ret;
}
void bdrv_cancel_in_flight(BlockDriverState *bs)
{
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
if (!bs || !bs->drv) {
return;
}
if (bs->drv->bdrv_cancel_in_flight) {
bs->drv->bdrv_cancel_in_flight(bs);
}
}
int coroutine_fn
bdrv_co_preadv_snapshot(BdrvChild *child, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, size_t qiov_offset)
{
BlockDriverState *bs = child->bs;
BlockDriver *drv = bs->drv;
int ret;
IO_CODE();
assert_bdrv_graph_readable();
if (!drv) {
return -ENOMEDIUM;
}
if (!drv->bdrv_co_preadv_snapshot) {
return -ENOTSUP;
}
bdrv_inc_in_flight(bs);
ret = drv->bdrv_co_preadv_snapshot(bs, offset, bytes, qiov, qiov_offset);
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn
bdrv_co_snapshot_block_status(BlockDriverState *bs,
bool want_zero, int64_t offset, int64_t bytes,
int64_t *pnum, int64_t *map,
BlockDriverState **file)
{
BlockDriver *drv = bs->drv;
int ret;
IO_CODE();
assert_bdrv_graph_readable();
if (!drv) {
return -ENOMEDIUM;
}
if (!drv->bdrv_co_snapshot_block_status) {
return -ENOTSUP;
}
bdrv_inc_in_flight(bs);
ret = drv->bdrv_co_snapshot_block_status(bs, want_zero, offset, bytes,
pnum, map, file);
bdrv_dec_in_flight(bs);
return ret;
}
int coroutine_fn
bdrv_co_pdiscard_snapshot(BlockDriverState *bs, int64_t offset, int64_t bytes)
{
BlockDriver *drv = bs->drv;
int ret;
IO_CODE();
assert_bdrv_graph_readable();
if (!drv) {
return -ENOMEDIUM;
}
if (!drv->bdrv_co_pdiscard_snapshot) {
return -ENOTSUP;
}
bdrv_inc_in_flight(bs);
ret = drv->bdrv_co_pdiscard_snapshot(bs, offset, bytes);
bdrv_dec_in_flight(bs);
return ret;
}
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