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linux/fs/xfs/libxfs/xfs_defer.c
Darrick J. Wong d5c88131db xfs: allow queued AG intents to drain before scrubbing 
When a writer thread executes a chain of log intent items, the AG header
buffer locks will cycle during a transaction roll to get from one intent
item to the next in a chain.  Although scrub takes all AG header buffer
locks, this isn't sufficient to guard against scrub checking an AG while
that writer thread is in the middle of finishing a chain because there's
no higher level locking primitive guarding allocation groups.

When there's a collision, cross-referencing between data structures
(e.g. rmapbt and refcountbt) yields false corruption events; if repair
is running, this results in incorrect repairs, which is catastrophic.

Fix this by adding to the perag structure the count of active intents
and make scrub wait until it has both AG header buffer locks and the
intent counter reaches zero.

One quirk of the drain code is that deferred bmap updates also bump and
drop the intent counter.  A fundamental decision made during the design
phase of the reverse mapping feature is that updates to the rmapbt
records are always made by the same code that updates the primary
metadata.  In other words, callers of bmapi functions expect that the
bmapi functions will queue deferred rmap updates.

Some parts of the reflink code queue deferred refcount (CUI) and bmap
(BUI) updates in the same head transaction, but the deferred work
manager completely finishes the CUI before the BUI work is started.  As
a result, the CUI drops the intent count long before the deferred rmap
(RUI) update even has a chance to bump the intent count.  The only way
to keep the intent count elevated between the CUI and RUI is for the BUI
to bump the counter until the RUI has been created.

A second quirk of the intent drain code is that deferred work items must
increment the intent counter as soon as the work item is added to the
transaction.  When a BUI completes and queues an RUI, the RUI must
increment the counter before the BUI decrements it.  The only way to
accomplish this is to require that the counter be bumped as soon as the
deferred work item is created in memory.

In the next patches we'll improve on this facility, but this patch
provides the basic functionality.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
2023-04-11 18:59:58 -07:00

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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_log.h"
#include "xfs_rmap.h"
#include "xfs_refcount.h"
#include "xfs_bmap.h"
#include "xfs_alloc.h"
#include "xfs_buf.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_attr.h"
static struct kmem_cache *xfs_defer_pending_cache;
/*
* Deferred Operations in XFS
*
* Due to the way locking rules work in XFS, certain transactions (block
* mapping and unmapping, typically) have permanent reservations so that
* we can roll the transaction to adhere to AG locking order rules and
* to unlock buffers between metadata updates. Prior to rmap/reflink,
* the mapping code had a mechanism to perform these deferrals for
* extents that were going to be freed; this code makes that facility
* more generic.
*
* When adding the reverse mapping and reflink features, it became
* necessary to perform complex remapping multi-transactions to comply
* with AG locking order rules, and to be able to spread a single
* refcount update operation (an operation on an n-block extent can
* update as many as n records!) among multiple transactions. XFS can
* roll a transaction to facilitate this, but using this facility
* requires us to log "intent" items in case log recovery needs to
* redo the operation, and to log "done" items to indicate that redo
* is not necessary.
*
* Deferred work is tracked in xfs_defer_pending items. Each pending
* item tracks one type of deferred work. Incoming work items (which
* have not yet had an intent logged) are attached to a pending item
* on the dop_intake list, where they wait for the caller to finish
* the deferred operations.
*
* Finishing a set of deferred operations is an involved process. To
* start, we define "rolling a deferred-op transaction" as follows:
*
* > For each xfs_defer_pending item on the dop_intake list,
* - Sort the work items in AG order. XFS locking
* order rules require us to lock buffers in AG order.
* - Create a log intent item for that type.
* - Attach it to the pending item.
* - Move the pending item from the dop_intake list to the
* dop_pending list.
* > Roll the transaction.
*
* NOTE: To avoid exceeding the transaction reservation, we limit the
* number of items that we attach to a given xfs_defer_pending.
*
* The actual finishing process looks like this:
*
* > For each xfs_defer_pending in the dop_pending list,
* - Roll the deferred-op transaction as above.
* - Create a log done item for that type, and attach it to the
* log intent item.
* - For each work item attached to the log intent item,
* * Perform the described action.
* * Attach the work item to the log done item.
* * If the result of doing the work was -EAGAIN, ->finish work
* wants a new transaction. See the "Requesting a Fresh
* Transaction while Finishing Deferred Work" section below for
* details.
*
* The key here is that we must log an intent item for all pending
* work items every time we roll the transaction, and that we must log
* a done item as soon as the work is completed. With this mechanism
* we can perform complex remapping operations, chaining intent items
* as needed.
*
* Requesting a Fresh Transaction while Finishing Deferred Work
*
* If ->finish_item decides that it needs a fresh transaction to
* finish the work, it must ask its caller (xfs_defer_finish) for a
* continuation. The most likely cause of this circumstance are the
* refcount adjust functions deciding that they've logged enough items
* to be at risk of exceeding the transaction reservation.
*
* To get a fresh transaction, we want to log the existing log done
* item to prevent the log intent item from replaying, immediately log
* a new log intent item with the unfinished work items, roll the
* transaction, and re-call ->finish_item wherever it left off. The
* log done item and the new log intent item must be in the same
* transaction or atomicity cannot be guaranteed; defer_finish ensures
* that this happens.
*
* This requires some coordination between ->finish_item and
* defer_finish. Upon deciding to request a new transaction,
* ->finish_item should update the current work item to reflect the
* unfinished work. Next, it should reset the log done item's list
* count to the number of items finished, and return -EAGAIN.
* defer_finish sees the -EAGAIN, logs the new log intent item
* with the remaining work items, and leaves the xfs_defer_pending
* item at the head of the dop_work queue. Then it rolls the
* transaction and picks up processing where it left off. It is
* required that ->finish_item must be careful to leave enough
* transaction reservation to fit the new log intent item.
*
* This is an example of remapping the extent (E, E+B) into file X at
* offset A and dealing with the extent (C, C+B) already being mapped
* there:
* +-------------------------------------------------+
* | Unmap file X startblock C offset A length B | t0
* | Intent to reduce refcount for extent (C, B) |
* | Intent to remove rmap (X, C, A, B) |
* | Intent to free extent (D, 1) (bmbt block) |
* | Intent to map (X, A, B) at startblock E |
* +-------------------------------------------------+
* | Map file X startblock E offset A length B | t1
* | Done mapping (X, E, A, B) |
* | Intent to increase refcount for extent (E, B) |
* | Intent to add rmap (X, E, A, B) |
* +-------------------------------------------------+
* | Reduce refcount for extent (C, B) | t2
* | Done reducing refcount for extent (C, 9) |
* | Intent to reduce refcount for extent (C+9, B-9) |
* | (ran out of space after 9 refcount updates) |
* +-------------------------------------------------+
* | Reduce refcount for extent (C+9, B+9) | t3
* | Done reducing refcount for extent (C+9, B-9) |
* | Increase refcount for extent (E, B) |
* | Done increasing refcount for extent (E, B) |
* | Intent to free extent (C, B) |
* | Intent to free extent (F, 1) (refcountbt block) |
* | Intent to remove rmap (F, 1, REFC) |
* +-------------------------------------------------+
* | Remove rmap (X, C, A, B) | t4
* | Done removing rmap (X, C, A, B) |
* | Add rmap (X, E, A, B) |
* | Done adding rmap (X, E, A, B) |
* | Remove rmap (F, 1, REFC) |
* | Done removing rmap (F, 1, REFC) |
* +-------------------------------------------------+
* | Free extent (C, B) | t5
* | Done freeing extent (C, B) |
* | Free extent (D, 1) |
* | Done freeing extent (D, 1) |
* | Free extent (F, 1) |
* | Done freeing extent (F, 1) |
* +-------------------------------------------------+
*
* If we should crash before t2 commits, log recovery replays
* the following intent items:
*
* - Intent to reduce refcount for extent (C, B)
* - Intent to remove rmap (X, C, A, B)
* - Intent to free extent (D, 1) (bmbt block)
* - Intent to increase refcount for extent (E, B)
* - Intent to add rmap (X, E, A, B)
*
* In the process of recovering, it should also generate and take care
* of these intent items:
*
* - Intent to free extent (C, B)
* - Intent to free extent (F, 1) (refcountbt block)
* - Intent to remove rmap (F, 1, REFC)
*
* Note that the continuation requested between t2 and t3 is likely to
* reoccur.
*/
static const struct xfs_defer_op_type *defer_op_types[] = {
[XFS_DEFER_OPS_TYPE_BMAP] = &xfs_bmap_update_defer_type,
[XFS_DEFER_OPS_TYPE_REFCOUNT] = &xfs_refcount_update_defer_type,
[XFS_DEFER_OPS_TYPE_RMAP] = &xfs_rmap_update_defer_type,
[XFS_DEFER_OPS_TYPE_FREE] = &xfs_extent_free_defer_type,
[XFS_DEFER_OPS_TYPE_AGFL_FREE] = &xfs_agfl_free_defer_type,
[XFS_DEFER_OPS_TYPE_ATTR] = &xfs_attr_defer_type,
};
/*
* Ensure there's a log intent item associated with this deferred work item if
* the operation must be restarted on crash. Returns 1 if there's a log item;
* 0 if there isn't; or a negative errno.
*/
static int
xfs_defer_create_intent(
struct xfs_trans *tp,
struct xfs_defer_pending *dfp,
bool sort)
{
const struct xfs_defer_op_type *ops = defer_op_types[dfp->dfp_type];
struct xfs_log_item *lip;
if (dfp->dfp_intent)
return 1;
lip = ops->create_intent(tp, &dfp->dfp_work, dfp->dfp_count, sort);
if (!lip)
return 0;
if (IS_ERR(lip))
return PTR_ERR(lip);
dfp->dfp_intent = lip;
return 1;
}
/*
* For each pending item in the intake list, log its intent item and the
* associated extents, then add the entire intake list to the end of
* the pending list.
*
* Returns 1 if at least one log item was associated with the deferred work;
* 0 if there are no log items; or a negative errno.
*/
static int
xfs_defer_create_intents(
struct xfs_trans *tp)
{
struct xfs_defer_pending *dfp;
int ret = 0;
list_for_each_entry(dfp, &tp->t_dfops, dfp_list) {
int ret2;
trace_xfs_defer_create_intent(tp->t_mountp, dfp);
ret2 = xfs_defer_create_intent(tp, dfp, true);
if (ret2 < 0)
return ret2;
ret |= ret2;
}
return ret;
}
/* Abort all the intents that were committed. */
STATIC void
xfs_defer_trans_abort(
struct xfs_trans *tp,
struct list_head *dop_pending)
{
struct xfs_defer_pending *dfp;
const struct xfs_defer_op_type *ops;
trace_xfs_defer_trans_abort(tp, _RET_IP_);
/* Abort intent items that don't have a done item. */
list_for_each_entry(dfp, dop_pending, dfp_list) {
ops = defer_op_types[dfp->dfp_type];
trace_xfs_defer_pending_abort(tp->t_mountp, dfp);
if (dfp->dfp_intent && !dfp->dfp_done) {
ops->abort_intent(dfp->dfp_intent);
dfp->dfp_intent = NULL;
}
}
}
/*
* Capture resources that the caller said not to release ("held") when the
* transaction commits. Caller is responsible for zero-initializing @dres.
*/
static int
xfs_defer_save_resources(
struct xfs_defer_resources *dres,
struct xfs_trans *tp)
{
struct xfs_buf_log_item *bli;
struct xfs_inode_log_item *ili;
struct xfs_log_item *lip;
BUILD_BUG_ON(NBBY * sizeof(dres->dr_ordered) < XFS_DEFER_OPS_NR_BUFS);
list_for_each_entry(lip, &tp->t_items, li_trans) {
switch (lip->li_type) {
case XFS_LI_BUF:
bli = container_of(lip, struct xfs_buf_log_item,
bli_item);
if (bli->bli_flags & XFS_BLI_HOLD) {
if (dres->dr_bufs >= XFS_DEFER_OPS_NR_BUFS) {
ASSERT(0);
return -EFSCORRUPTED;
}
if (bli->bli_flags & XFS_BLI_ORDERED)
dres->dr_ordered |=
(1U << dres->dr_bufs);
else
xfs_trans_dirty_buf(tp, bli->bli_buf);
dres->dr_bp[dres->dr_bufs++] = bli->bli_buf;
}
break;
case XFS_LI_INODE:
ili = container_of(lip, struct xfs_inode_log_item,
ili_item);
if (ili->ili_lock_flags == 0) {
if (dres->dr_inos >= XFS_DEFER_OPS_NR_INODES) {
ASSERT(0);
return -EFSCORRUPTED;
}
xfs_trans_log_inode(tp, ili->ili_inode,
XFS_ILOG_CORE);
dres->dr_ip[dres->dr_inos++] = ili->ili_inode;
}
break;
default:
break;
}
}
return 0;
}
/* Attach the held resources to the transaction. */
static void
xfs_defer_restore_resources(
struct xfs_trans *tp,
struct xfs_defer_resources *dres)
{
unsigned short i;
/* Rejoin the joined inodes. */
for (i = 0; i < dres->dr_inos; i++)
xfs_trans_ijoin(tp, dres->dr_ip[i], 0);
/* Rejoin the buffers and dirty them so the log moves forward. */
for (i = 0; i < dres->dr_bufs; i++) {
xfs_trans_bjoin(tp, dres->dr_bp[i]);
if (dres->dr_ordered & (1U << i))
xfs_trans_ordered_buf(tp, dres->dr_bp[i]);
xfs_trans_bhold(tp, dres->dr_bp[i]);
}
}
/* Roll a transaction so we can do some deferred op processing. */
STATIC int
xfs_defer_trans_roll(
struct xfs_trans **tpp)
{
struct xfs_defer_resources dres = { };
int error;
error = xfs_defer_save_resources(&dres, *tpp);
if (error)
return error;
trace_xfs_defer_trans_roll(*tpp, _RET_IP_);
/*
* Roll the transaction. Rolling always given a new transaction (even
* if committing the old one fails!) to hand back to the caller, so we
* join the held resources to the new transaction so that we always
* return with the held resources joined to @tpp, no matter what
* happened.
*/
error = xfs_trans_roll(tpp);
xfs_defer_restore_resources(*tpp, &dres);
if (error)
trace_xfs_defer_trans_roll_error(*tpp, error);
return error;
}
/*
* Free up any items left in the list.
*/
static void
xfs_defer_cancel_list(
struct xfs_mount *mp,
struct list_head *dop_list)
{
struct xfs_defer_pending *dfp;
struct xfs_defer_pending *pli;
struct list_head *pwi;
struct list_head *n;
const struct xfs_defer_op_type *ops;
/*
* Free the pending items. Caller should already have arranged
* for the intent items to be released.
*/
list_for_each_entry_safe(dfp, pli, dop_list, dfp_list) {
ops = defer_op_types[dfp->dfp_type];
trace_xfs_defer_cancel_list(mp, dfp);
list_del(&dfp->dfp_list);
list_for_each_safe(pwi, n, &dfp->dfp_work) {
list_del(pwi);
dfp->dfp_count--;
trace_xfs_defer_cancel_item(mp, dfp, pwi);
ops->cancel_item(pwi);
}
ASSERT(dfp->dfp_count == 0);
kmem_cache_free(xfs_defer_pending_cache, dfp);
}
}
/*
* Prevent a log intent item from pinning the tail of the log by logging a
* done item to release the intent item; and then log a new intent item.
* The caller should provide a fresh transaction and roll it after we're done.
*/
static int
xfs_defer_relog(
struct xfs_trans **tpp,
struct list_head *dfops)
{
struct xlog *log = (*tpp)->t_mountp->m_log;
struct xfs_defer_pending *dfp;
xfs_lsn_t threshold_lsn = NULLCOMMITLSN;
ASSERT((*tpp)->t_flags & XFS_TRANS_PERM_LOG_RES);
list_for_each_entry(dfp, dfops, dfp_list) {
/*
* If the log intent item for this deferred op is not a part of
* the current log checkpoint, relog the intent item to keep
* the log tail moving forward. We're ok with this being racy
* because an incorrect decision means we'll be a little slower
* at pushing the tail.
*/
if (dfp->dfp_intent == NULL ||
xfs_log_item_in_current_chkpt(dfp->dfp_intent))
continue;
/*
* Figure out where we need the tail to be in order to maintain
* the minimum required free space in the log. Only sample
* the log threshold once per call.
*/
if (threshold_lsn == NULLCOMMITLSN) {
threshold_lsn = xlog_grant_push_threshold(log, 0);
if (threshold_lsn == NULLCOMMITLSN)
break;
}
if (XFS_LSN_CMP(dfp->dfp_intent->li_lsn, threshold_lsn) >= 0)
continue;
trace_xfs_defer_relog_intent((*tpp)->t_mountp, dfp);
XFS_STATS_INC((*tpp)->t_mountp, defer_relog);
dfp->dfp_intent = xfs_trans_item_relog(dfp->dfp_intent, *tpp);
}
if ((*tpp)->t_flags & XFS_TRANS_DIRTY)
return xfs_defer_trans_roll(tpp);
return 0;
}
/*
* Log an intent-done item for the first pending intent, and finish the work
* items.
*/
static int
xfs_defer_finish_one(
struct xfs_trans *tp,
struct xfs_defer_pending *dfp)
{
const struct xfs_defer_op_type *ops = defer_op_types[dfp->dfp_type];
struct xfs_btree_cur *state = NULL;
struct list_head *li, *n;
int error;
trace_xfs_defer_pending_finish(tp->t_mountp, dfp);
dfp->dfp_done = ops->create_done(tp, dfp->dfp_intent, dfp->dfp_count);
list_for_each_safe(li, n, &dfp->dfp_work) {
list_del(li);
dfp->dfp_count--;
trace_xfs_defer_finish_item(tp->t_mountp, dfp, li);
error = ops->finish_item(tp, dfp->dfp_done, li, &state);
if (error == -EAGAIN) {
int ret;
/*
* Caller wants a fresh transaction; put the work item
* back on the list and log a new log intent item to
* replace the old one. See "Requesting a Fresh
* Transaction while Finishing Deferred Work" above.
*/
list_add(li, &dfp->dfp_work);
dfp->dfp_count++;
dfp->dfp_done = NULL;
dfp->dfp_intent = NULL;
ret = xfs_defer_create_intent(tp, dfp, false);
if (ret < 0)
error = ret;
}
if (error)
goto out;
}
/* Done with the dfp, free it. */
list_del(&dfp->dfp_list);
kmem_cache_free(xfs_defer_pending_cache, dfp);
out:
if (ops->finish_cleanup)
ops->finish_cleanup(tp, state, error);
return error;
}
/*
* Finish all the pending work. This involves logging intent items for
* any work items that wandered in since the last transaction roll (if
* one has even happened), rolling the transaction, and finishing the
* work items in the first item on the logged-and-pending list.
*
* If an inode is provided, relog it to the new transaction.
*/
int
xfs_defer_finish_noroll(
struct xfs_trans **tp)
{
struct xfs_defer_pending *dfp = NULL;
int error = 0;
LIST_HEAD(dop_pending);
ASSERT((*tp)->t_flags & XFS_TRANS_PERM_LOG_RES);
trace_xfs_defer_finish(*tp, _RET_IP_);
/* Until we run out of pending work to finish... */
while (!list_empty(&dop_pending) || !list_empty(&(*tp)->t_dfops)) {
/*
* Deferred items that are created in the process of finishing
* other deferred work items should be queued at the head of
* the pending list, which puts them ahead of the deferred work
* that was created by the caller. This keeps the number of
* pending work items to a minimum, which decreases the amount
* of time that any one intent item can stick around in memory,
* pinning the log tail.
*/
int has_intents = xfs_defer_create_intents(*tp);
list_splice_init(&(*tp)->t_dfops, &dop_pending);
if (has_intents < 0) {
error = has_intents;
goto out_shutdown;
}
if (has_intents || dfp) {
error = xfs_defer_trans_roll(tp);
if (error)
goto out_shutdown;
/* Relog intent items to keep the log moving. */
error = xfs_defer_relog(tp, &dop_pending);
if (error)
goto out_shutdown;
}
dfp = list_first_entry(&dop_pending, struct xfs_defer_pending,
dfp_list);
error = xfs_defer_finish_one(*tp, dfp);
if (error && error != -EAGAIN)
goto out_shutdown;
}
trace_xfs_defer_finish_done(*tp, _RET_IP_);
return 0;
out_shutdown:
xfs_defer_trans_abort(*tp, &dop_pending);
xfs_force_shutdown((*tp)->t_mountp, SHUTDOWN_CORRUPT_INCORE);
trace_xfs_defer_finish_error(*tp, error);
xfs_defer_cancel_list((*tp)->t_mountp, &dop_pending);
xfs_defer_cancel(*tp);
return error;
}
int
xfs_defer_finish(
struct xfs_trans **tp)
{
int error;
/*
* Finish and roll the transaction once more to avoid returning to the
* caller with a dirty transaction.
*/
error = xfs_defer_finish_noroll(tp);
if (error)
return error;
if ((*tp)->t_flags & XFS_TRANS_DIRTY) {
error = xfs_defer_trans_roll(tp);
if (error) {
xfs_force_shutdown((*tp)->t_mountp,
SHUTDOWN_CORRUPT_INCORE);
return error;
}
}
/* Reset LOWMODE now that we've finished all the dfops. */
ASSERT(list_empty(&(*tp)->t_dfops));
(*tp)->t_flags &= ~XFS_TRANS_LOWMODE;
return 0;
}
void
xfs_defer_cancel(
struct xfs_trans *tp)
{
struct xfs_mount *mp = tp->t_mountp;
trace_xfs_defer_cancel(tp, _RET_IP_);
xfs_defer_cancel_list(mp, &tp->t_dfops);
}
/* Add an item for later deferred processing. */
void
xfs_defer_add(
struct xfs_trans *tp,
enum xfs_defer_ops_type type,
struct list_head *li)
{
struct xfs_defer_pending *dfp = NULL;
const struct xfs_defer_op_type *ops = defer_op_types[type];
ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
BUILD_BUG_ON(ARRAY_SIZE(defer_op_types) != XFS_DEFER_OPS_TYPE_MAX);
/*
* Add the item to a pending item at the end of the intake list.
* If the last pending item has the same type, reuse it. Else,
* create a new pending item at the end of the intake list.
*/
if (!list_empty(&tp->t_dfops)) {
dfp = list_last_entry(&tp->t_dfops,
struct xfs_defer_pending, dfp_list);
if (dfp->dfp_type != type ||
(ops->max_items && dfp->dfp_count >= ops->max_items))
dfp = NULL;
}
if (!dfp) {
dfp = kmem_cache_zalloc(xfs_defer_pending_cache,
GFP_NOFS | __GFP_NOFAIL);
dfp->dfp_type = type;
dfp->dfp_intent = NULL;
dfp->dfp_done = NULL;
dfp->dfp_count = 0;
INIT_LIST_HEAD(&dfp->dfp_work);
list_add_tail(&dfp->dfp_list, &tp->t_dfops);
}
list_add_tail(li, &dfp->dfp_work);
trace_xfs_defer_add_item(tp->t_mountp, dfp, li);
dfp->dfp_count++;
}
/*
* Move deferred ops from one transaction to another and reset the source to
* initial state. This is primarily used to carry state forward across
* transaction rolls with pending dfops.
*/
void
xfs_defer_move(
struct xfs_trans *dtp,
struct xfs_trans *stp)
{
list_splice_init(&stp->t_dfops, &dtp->t_dfops);
/*
* Low free space mode was historically controlled by a dfops field.
* This meant that low mode state potentially carried across multiple
* transaction rolls. Transfer low mode on a dfops move to preserve
* that behavior.
*/
dtp->t_flags |= (stp->t_flags & XFS_TRANS_LOWMODE);
stp->t_flags &= ~XFS_TRANS_LOWMODE;
}
/*
* Prepare a chain of fresh deferred ops work items to be completed later. Log
* recovery requires the ability to put off until later the actual finishing
* work so that it can process unfinished items recovered from the log in
* correct order.
*
* Create and log intent items for all the work that we're capturing so that we
* can be assured that the items will get replayed if the system goes down
* before log recovery gets a chance to finish the work it put off. The entire
* deferred ops state is transferred to the capture structure and the
* transaction is then ready for the caller to commit it. If there are no
* intent items to capture, this function returns NULL.
*
* If capture_ip is not NULL, the capture structure will obtain an extra
* reference to the inode.
*/
static struct xfs_defer_capture *
xfs_defer_ops_capture(
struct xfs_trans *tp)
{
struct xfs_defer_capture *dfc;
unsigned short i;
int error;
if (list_empty(&tp->t_dfops))
return NULL;
error = xfs_defer_create_intents(tp);
if (error < 0)
return ERR_PTR(error);
/* Create an object to capture the defer ops. */
dfc = kmem_zalloc(sizeof(*dfc), KM_NOFS);
INIT_LIST_HEAD(&dfc->dfc_list);
INIT_LIST_HEAD(&dfc->dfc_dfops);
/* Move the dfops chain and transaction state to the capture struct. */
list_splice_init(&tp->t_dfops, &dfc->dfc_dfops);
dfc->dfc_tpflags = tp->t_flags & XFS_TRANS_LOWMODE;
tp->t_flags &= ~XFS_TRANS_LOWMODE;
/* Capture the remaining block reservations along with the dfops. */
dfc->dfc_blkres = tp->t_blk_res - tp->t_blk_res_used;
dfc->dfc_rtxres = tp->t_rtx_res - tp->t_rtx_res_used;
/* Preserve the log reservation size. */
dfc->dfc_logres = tp->t_log_res;
error = xfs_defer_save_resources(&dfc->dfc_held, tp);
if (error) {
/*
* Resource capture should never fail, but if it does, we
* still have to shut down the log and release things
* properly.
*/
xfs_force_shutdown(tp->t_mountp, SHUTDOWN_CORRUPT_INCORE);
}
/*
* Grab extra references to the inodes and buffers because callers are
* expected to release their held references after we commit the
* transaction.
*/
for (i = 0; i < dfc->dfc_held.dr_inos; i++) {
ASSERT(xfs_isilocked(dfc->dfc_held.dr_ip[i], XFS_ILOCK_EXCL));
ihold(VFS_I(dfc->dfc_held.dr_ip[i]));
}
for (i = 0; i < dfc->dfc_held.dr_bufs; i++)
xfs_buf_hold(dfc->dfc_held.dr_bp[i]);
return dfc;
}
/* Release all resources that we used to capture deferred ops. */
void
xfs_defer_ops_capture_free(
struct xfs_mount *mp,
struct xfs_defer_capture *dfc)
{
unsigned short i;
xfs_defer_cancel_list(mp, &dfc->dfc_dfops);
for (i = 0; i < dfc->dfc_held.dr_bufs; i++)
xfs_buf_relse(dfc->dfc_held.dr_bp[i]);
for (i = 0; i < dfc->dfc_held.dr_inos; i++)
xfs_irele(dfc->dfc_held.dr_ip[i]);
kmem_free(dfc);
}
/*
* Capture any deferred ops and commit the transaction. This is the last step
* needed to finish a log intent item that we recovered from the log. If any
* of the deferred ops operate on an inode, the caller must pass in that inode
* so that the reference can be transferred to the capture structure. The
* caller must hold ILOCK_EXCL on the inode, and must unlock it before calling
* xfs_defer_ops_continue.
*/
int
xfs_defer_ops_capture_and_commit(
struct xfs_trans *tp,
struct list_head *capture_list)
{
struct xfs_mount *mp = tp->t_mountp;
struct xfs_defer_capture *dfc;
int error;
/* If we don't capture anything, commit transaction and exit. */
dfc = xfs_defer_ops_capture(tp);
if (IS_ERR(dfc)) {
xfs_trans_cancel(tp);
return PTR_ERR(dfc);
}
if (!dfc)
return xfs_trans_commit(tp);
/* Commit the transaction and add the capture structure to the list. */
error = xfs_trans_commit(tp);
if (error) {
xfs_defer_ops_capture_free(mp, dfc);
return error;
}
list_add_tail(&dfc->dfc_list, capture_list);
return 0;
}
/*
* Attach a chain of captured deferred ops to a new transaction and free the
* capture structure. If an inode was captured, it will be passed back to the
* caller with ILOCK_EXCL held and joined to the transaction with lockflags==0.
* The caller now owns the inode reference.
*/
void
xfs_defer_ops_continue(
struct xfs_defer_capture *dfc,
struct xfs_trans *tp,
struct xfs_defer_resources *dres)
{
unsigned int i;
ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
ASSERT(!(tp->t_flags & XFS_TRANS_DIRTY));
/* Lock the captured resources to the new transaction. */
if (dfc->dfc_held.dr_inos == 2)
xfs_lock_two_inodes(dfc->dfc_held.dr_ip[0], XFS_ILOCK_EXCL,
dfc->dfc_held.dr_ip[1], XFS_ILOCK_EXCL);
else if (dfc->dfc_held.dr_inos == 1)
xfs_ilock(dfc->dfc_held.dr_ip[0], XFS_ILOCK_EXCL);
for (i = 0; i < dfc->dfc_held.dr_bufs; i++)
xfs_buf_lock(dfc->dfc_held.dr_bp[i]);
/* Join the captured resources to the new transaction. */
xfs_defer_restore_resources(tp, &dfc->dfc_held);
memcpy(dres, &dfc->dfc_held, sizeof(struct xfs_defer_resources));
dres->dr_bufs = 0;
/* Move captured dfops chain and state to the transaction. */
list_splice_init(&dfc->dfc_dfops, &tp->t_dfops);
tp->t_flags |= dfc->dfc_tpflags;
kmem_free(dfc);
}
/* Release the resources captured and continued during recovery. */
void
xfs_defer_resources_rele(
struct xfs_defer_resources *dres)
{
unsigned short i;
for (i = 0; i < dres->dr_inos; i++) {
xfs_iunlock(dres->dr_ip[i], XFS_ILOCK_EXCL);
xfs_irele(dres->dr_ip[i]);
dres->dr_ip[i] = NULL;
}
for (i = 0; i < dres->dr_bufs; i++) {
xfs_buf_relse(dres->dr_bp[i]);
dres->dr_bp[i] = NULL;
}
dres->dr_inos = 0;
dres->dr_bufs = 0;
dres->dr_ordered = 0;
}
static inline int __init
xfs_defer_init_cache(void)
{
xfs_defer_pending_cache = kmem_cache_create("xfs_defer_pending",
sizeof(struct xfs_defer_pending),
0, 0, NULL);
return xfs_defer_pending_cache != NULL ? 0 : -ENOMEM;
}
static inline void
xfs_defer_destroy_cache(void)
{
kmem_cache_destroy(xfs_defer_pending_cache);
xfs_defer_pending_cache = NULL;
}
/* Set up caches for deferred work items. */
int __init
xfs_defer_init_item_caches(void)
{
int error;
error = xfs_defer_init_cache();
if (error)
return error;
error = xfs_rmap_intent_init_cache();
if (error)
goto err;
error = xfs_refcount_intent_init_cache();
if (error)
goto err;
error = xfs_bmap_intent_init_cache();
if (error)
goto err;
error = xfs_extfree_intent_init_cache();
if (error)
goto err;
error = xfs_attr_intent_init_cache();
if (error)
goto err;
return 0;
err:
xfs_defer_destroy_item_caches();
return error;
}
/* Destroy all the deferred work item caches, if they've been allocated. */
void
xfs_defer_destroy_item_caches(void)
{
xfs_attr_intent_destroy_cache();
xfs_extfree_intent_destroy_cache();
xfs_bmap_intent_destroy_cache();
xfs_refcount_intent_destroy_cache();
xfs_rmap_intent_destroy_cache();
xfs_defer_destroy_cache();
}
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