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raid5-ppl: Partial Parity Log write logging implementation

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Implement the calculation of partial parity for a stripe and PPL write
logging functionality. The description of PPL is added to the
documentation. More details can be found in the comments in raid5-ppl.c.

Attach a page for holding the partial parity data to stripe_head.
Allocate it only if mddev has the MD_HAS_PPL flag set.

Partial parity is the xor of not modified data chunks of a stripe and is
calculated as follows:

- reconstruct-write case:
  xor data from all not updated disks in a stripe

- read-modify-write case:
  xor old data and parity from all updated disks in a stripe

Implement it using the async_tx API and integrate into raid_run_ops().
It must be called when we still have access to old data, so do it when
STRIPE_OP_BIODRAIN is set, but before ops_run_prexor5(). The result is
stored into sh->ppl_page.

Partial parity is not meaningful for full stripe write and is not stored
in the log or used for recovery, so don't attempt to calculate it when
stripe has STRIPE_FULL_WRITE.

Put the PPL metadata structures to md_p.h because userspace tools
(mdadm) will also need to read/write PPL.

Warn about using PPL with enabled disk volatile write-back cache for
now. It can be removed once disk cache flushing before writing PPL is
implemented.

Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
Artur Paszkiewicz 2017-03-09 09:59:59 +01:00 committed by Shaohua Li
parent ff875738ed
commit 3418d036c8
7 changed files with 869 additions and 5 deletions
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44
Documentation/md/raid5-ppl.txt Normal file
View File

@ -0,0 +1,44 @@
Partial Parity Log
Partial Parity Log (PPL) is a feature available for RAID5 arrays. The issue
addressed by PPL is that after a dirty shutdown, parity of a particular stripe
may become inconsistent with data on other member disks. If the array is also
in degraded state, there is no way to recalculate parity, because one of the
disks is missing. This can lead to silent data corruption when rebuilding the
array or using it is as degraded - data calculated from parity for array blocks
that have not been touched by a write request during the unclean shutdown can
be incorrect. Such condition is known as the RAID5 Write Hole. Because of
this, md by default does not allow starting a dirty degraded array.
Partial parity for a write operation is the XOR of stripe data chunks not
modified by this write. It is just enough data needed for recovering from the
write hole. XORing partial parity with the modified chunks produces parity for
the stripe, consistent with its state before the write operation, regardless of
which chunk writes have completed. If one of the not modified data disks of
this stripe is missing, this updated parity can be used to recover its
contents. PPL recovery is also performed when starting an array after an
unclean shutdown and all disks are available, eliminating the need to resync
the array. Because of this, using write-intent bitmap and PPL together is not
supported.
When handling a write request PPL writes partial parity before new data and
parity are dispatched to disks. PPL is a distributed log - it is stored on
array member drives in the metadata area, on the parity drive of a particular
stripe. It does not require a dedicated journaling drive. Write performance is
reduced by up to 30%-40% but it scales with the number of drives in the array
and the journaling drive does not become a bottleneck or a single point of
failure.
Unlike raid5-cache, the other solution in md for closing the write hole, PPL is
not a true journal. It does not protect from losing in-flight data, only from
silent data corruption. If a dirty disk of a stripe is lost, no PPL recovery is
performed for this stripe (parity is not updated). So it is possible to have
arbitrary data in the written part of a stripe if that disk is lost. In such
case the behavior is the same as in plain raid5.
PPL is available for md version-1 metadata and external (specifically IMSM)
metadata arrays. It can be enabled using mdadm option --consistency-policy=ppl.
Currently, volatile write-back cache should be disabled on all member drives
when using PPL. Otherwise it cannot guarantee consistency in case of power
failure.

2
drivers/md/Makefile
View File

@ -18,7 +18,7 @@ dm-cache-cleaner-y += dm-cache-policy-cleaner.o
dm-era-y += dm-era-target.o
dm-verity-y += dm-verity-target.o
md-mod-y += md.o bitmap.o
raid456-y += raid5.o raid5-cache.o
raid456-y += raid5.o raid5-cache.o raid5-ppl.o
# Note: link order is important. All raid personalities
# and must come before md.o, as they each initialise

24
drivers/md/raid5-log.h
View File

@ -31,6 +31,20 @@ extern struct md_sysfs_entry r5c_journal_mode;
extern void r5c_update_on_rdev_error(struct mddev *mddev);
extern bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect);
extern struct dma_async_tx_descriptor *
ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu,
struct dma_async_tx_descriptor *tx);
extern int ppl_init_log(struct r5conf *conf);
extern void ppl_exit_log(struct r5conf *conf);
extern int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh);
extern void ppl_write_stripe_run(struct r5conf *conf);
extern void ppl_stripe_write_finished(struct stripe_head *sh);
static inline bool raid5_has_ppl(struct r5conf *conf)
{
return test_bit(MD_HAS_PPL, &conf->mddev->flags);
}
static inline int log_stripe(struct stripe_head *sh, struct stripe_head_state *s)
{
struct r5conf *conf = sh->raid_conf;
@ -45,6 +59,8 @@ static inline int log_stripe(struct stripe_head *sh, struct stripe_head_state *s
/* caching phase */
return r5c_cache_data(conf->log, sh);
}
} else if (raid5_has_ppl(conf)) {
return ppl_write_stripe(conf, sh);
}
return -EAGAIN;
@ -56,24 +72,32 @@ static inline void log_stripe_write_finished(struct stripe_head *sh)
if (conf->log)
r5l_stripe_write_finished(sh);
else if (raid5_has_ppl(conf))
ppl_stripe_write_finished(sh);
}
static inline void log_write_stripe_run(struct r5conf *conf)
{
if (conf->log)
r5l_write_stripe_run(conf->log);
else if (raid5_has_ppl(conf))
ppl_write_stripe_run(conf);
}
static inline void log_exit(struct r5conf *conf)
{
if (conf->log)
r5l_exit_log(conf);
else if (raid5_has_ppl(conf))
ppl_exit_log(conf);
}
static inline int log_init(struct r5conf *conf, struct md_rdev *journal_dev)
{
if (journal_dev)
return r5l_init_log(conf, journal_dev);
else if (raid5_has_ppl(conf))
return ppl_init_log(conf);
return 0;
}

703
drivers/md/raid5-ppl.c Normal file
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@ -0,0 +1,703 @@
/*
* Partial Parity Log for closing the RAID5 write hole
* Copyright (c) 2017, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/crc32c.h>
#include <linux/flex_array.h>
#include <linux/async_tx.h>
#include <linux/raid/md_p.h>
#include "md.h"
#include "raid5.h"
/*
* PPL consists of a 4KB header (struct ppl_header) and at least 128KB for
* partial parity data. The header contains an array of entries
* (struct ppl_header_entry) which describe the logged write requests.
* Partial parity for the entries comes after the header, written in the same
* sequence as the entries:
*
* Header
* entry0
* ...
* entryN
* PP data
* PP for entry0
* ...
* PP for entryN
*
* An entry describes one or more consecutive stripe_heads, up to a full
* stripe. The modifed raid data chunks form an m-by-n matrix, where m is the
* number of stripe_heads in the entry and n is the number of modified data
* disks. Every stripe_head in the entry must write to the same data disks.
* An example of a valid case described by a single entry (writes to the first
* stripe of a 4 disk array, 16k chunk size):
*
* sh->sector dd0 dd1 dd2 ppl
* +-----+-----+-----+
* 0 | --- | --- | --- | +----+
* 8 | -W- | -W- | --- | | pp | data_sector = 8
* 16 | -W- | -W- | --- | | pp | data_size = 3 * 2 * 4k
* 24 | -W- | -W- | --- | | pp | pp_size = 3 * 4k
* +-----+-----+-----+ +----+
*
* data_sector is the first raid sector of the modified data, data_size is the
* total size of modified data and pp_size is the size of partial parity for
* this entry. Entries for full stripe writes contain no partial parity
* (pp_size = 0), they only mark the stripes for which parity should be
* recalculated after an unclean shutdown. Every entry holds a checksum of its
* partial parity, the header also has a checksum of the header itself.
*
* A write request is always logged to the PPL instance stored on the parity
* disk of the corresponding stripe. For each member disk there is one ppl_log
* used to handle logging for this disk, independently from others. They are
* grouped in child_logs array in struct ppl_conf, which is assigned to
* r5conf->log_private.
*
* ppl_io_unit represents a full PPL write, header_page contains the ppl_header.
* PPL entries for logged stripes are added in ppl_log_stripe(). A stripe_head
* can be appended to the last entry if it meets the conditions for a valid
* entry described above, otherwise a new entry is added. Checksums of entries
* are calculated incrementally as stripes containing partial parity are being
* added. ppl_submit_iounit() calculates the checksum of the header and submits
* a bio containing the header page and partial parity pages (sh->ppl_page) for
* all stripes of the io_unit. When the PPL write completes, the stripes
* associated with the io_unit are released and raid5d starts writing their data
* and parity. When all stripes are written, the io_unit is freed and the next
* can be submitted.
*
* An io_unit is used to gather stripes until it is submitted or becomes full
* (if the maximum number of entries or size of PPL is reached). Another io_unit
* can't be submitted until the previous has completed (PPL and stripe
* data+parity is written). The log->io_list tracks all io_units of a log
* (for a single member disk). New io_units are added to the end of the list
* and the first io_unit is submitted, if it is not submitted already.
* The current io_unit accepting new stripes is always at the end of the list.
*/
struct ppl_conf {
struct mddev *mddev;
/* array of child logs, one for each raid disk */
struct ppl_log *child_logs;
int count;
int block_size; /* the logical block size used for data_sector
* in ppl_header_entry */
u32 signature; /* raid array identifier */
atomic64_t seq; /* current log write sequence number */
struct kmem_cache *io_kc;
mempool_t *io_pool;
struct bio_set *bs;
mempool_t *meta_pool;
};
struct ppl_log {
struct ppl_conf *ppl_conf; /* shared between all log instances */
struct md_rdev *rdev; /* array member disk associated with
* this log instance */
struct mutex io_mutex;
struct ppl_io_unit *current_io; /* current io_unit accepting new data
* always at the end of io_list */
spinlock_t io_list_lock;
struct list_head io_list; /* all io_units of this log */
struct list_head no_mem_stripes;/* stripes to retry if failed to
* allocate io_unit */
};
#define PPL_IO_INLINE_BVECS 32
struct ppl_io_unit {
struct ppl_log *log;
struct page *header_page; /* for ppl_header */
unsigned int entries_count; /* number of entries in ppl_header */
unsigned int pp_size; /* total size current of partial parity */
u64 seq; /* sequence number of this log write */
struct list_head log_sibling; /* log->io_list */
struct list_head stripe_list; /* stripes added to the io_unit */
atomic_t pending_stripes; /* how many stripes not written to raid */
bool submitted; /* true if write to log started */
/* inline bio and its biovec for submitting the iounit */
struct bio bio;
struct bio_vec biovec[PPL_IO_INLINE_BVECS];
};
struct dma_async_tx_descriptor *
ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu,
struct dma_async_tx_descriptor *tx)
{
int disks = sh->disks;
struct page **xor_srcs = flex_array_get(percpu->scribble, 0);
int count = 0, pd_idx = sh->pd_idx, i;
struct async_submit_ctl submit;
pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
/*
* Partial parity is the XOR of stripe data chunks that are not changed
* during the write request. Depending on available data
* (read-modify-write vs. reconstruct-write case) we calculate it
* differently.
*/
if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
/* rmw: xor old data and parity from updated disks */
for (i = disks; i--;) {
struct r5dev *dev = &sh->dev[i];
if (test_bit(R5_Wantdrain, &dev->flags) || i == pd_idx)
xor_srcs[count++] = dev->page;
}
} else if (sh->reconstruct_state == reconstruct_state_drain_run) {
/* rcw: xor data from all not updated disks */
for (i = disks; i--;) {
struct r5dev *dev = &sh->dev[i];
if (test_bit(R5_UPTODATE, &dev->flags))
xor_srcs[count++] = dev->page;
}
} else {
return tx;
}
init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST, tx,
NULL, sh, flex_array_get(percpu->scribble, 0)
+ sizeof(struct page *) * (sh->disks + 2));
if (count == 1)
tx = async_memcpy(sh->ppl_page, xor_srcs[0], 0, 0, PAGE_SIZE,
&submit);
else
tx = async_xor(sh->ppl_page, xor_srcs, 0, count, PAGE_SIZE,
&submit);
return tx;
}
static struct ppl_io_unit *ppl_new_iounit(struct ppl_log *log,
struct stripe_head *sh)
{
struct ppl_conf *ppl_conf = log->ppl_conf;
struct ppl_io_unit *io;
struct ppl_header *pplhdr;
io = mempool_alloc(ppl_conf->io_pool, GFP_ATOMIC);
if (!io)
return NULL;
memset(io, 0, sizeof(*io));
io->log = log;
INIT_LIST_HEAD(&io->log_sibling);
INIT_LIST_HEAD(&io->stripe_list);
atomic_set(&io->pending_stripes, 0);
bio_init(&io->bio, io->biovec, PPL_IO_INLINE_BVECS);
io->header_page = mempool_alloc(ppl_conf->meta_pool, GFP_NOIO);
pplhdr = page_address(io->header_page);
clear_page(pplhdr);
memset(pplhdr->reserved, 0xff, PPL_HDR_RESERVED);
pplhdr->signature = cpu_to_le32(ppl_conf->signature);
io->seq = atomic64_add_return(1, &ppl_conf->seq);
pplhdr->generation = cpu_to_le64(io->seq);
return io;
}
static int ppl_log_stripe(struct ppl_log *log, struct stripe_head *sh)
{
struct ppl_io_unit *io = log->current_io;
struct ppl_header_entry *e = NULL;
struct ppl_header *pplhdr;
int i;
sector_t data_sector = 0;
int data_disks = 0;
unsigned int entry_space = (log->rdev->ppl.size << 9) - PPL_HEADER_SIZE;
struct r5conf *conf = sh->raid_conf;
pr_debug("%s: stripe: %llu\n", __func__, (unsigned long long)sh->sector);
/* check if current io_unit is full */
if (io && (io->pp_size == entry_space ||
io->entries_count == PPL_HDR_MAX_ENTRIES)) {
pr_debug("%s: add io_unit blocked by seq: %llu\n",
__func__, io->seq);
io = NULL;
}
/* add a new unit if there is none or the current is full */
if (!io) {
io = ppl_new_iounit(log, sh);
if (!io)
return -ENOMEM;
spin_lock_irq(&log->io_list_lock);
list_add_tail(&io->log_sibling, &log->io_list);
spin_unlock_irq(&log->io_list_lock);
log->current_io = io;
}
for (i = 0; i < sh->disks; i++) {
struct r5dev *dev = &sh->dev[i];
if (i != sh->pd_idx && test_bit(R5_Wantwrite, &dev->flags)) {
if (!data_disks || dev->sector < data_sector)
data_sector = dev->sector;
data_disks++;
}
}
BUG_ON(!data_disks);
pr_debug("%s: seq: %llu data_sector: %llu data_disks: %d\n", __func__,
io->seq, (unsigned long long)data_sector, data_disks);
pplhdr = page_address(io->header_page);
if (io->entries_count > 0) {
struct ppl_header_entry *last =
&pplhdr->entries[io->entries_count - 1];
struct stripe_head *sh_last = list_last_entry(
&io->stripe_list, struct stripe_head, log_list);
u64 data_sector_last = le64_to_cpu(last->data_sector);
u32 data_size_last = le32_to_cpu(last->data_size);
/*
* Check if we can append the stripe to the last entry. It must
* be just after the last logged stripe and write to the same
* disks. Use bit shift and logarithm to avoid 64-bit division.
*/
if ((sh->sector == sh_last->sector + STRIPE_SECTORS) &&
(data_sector >> ilog2(conf->chunk_sectors) ==
data_sector_last >> ilog2(conf->chunk_sectors)) &&
((data_sector - data_sector_last) * data_disks ==
data_size_last >> 9))
e = last;
}
if (!e) {
e = &pplhdr->entries[io->entries_count++];
e->data_sector = cpu_to_le64(data_sector);
e->parity_disk = cpu_to_le32(sh->pd_idx);
e->checksum = cpu_to_le32(~0);
}
le32_add_cpu(&e->data_size, data_disks << PAGE_SHIFT);
/* don't write any PP if full stripe write */
if (!test_bit(STRIPE_FULL_WRITE, &sh->state)) {
le32_add_cpu(&e->pp_size, PAGE_SIZE);
io->pp_size += PAGE_SIZE;
e->checksum = cpu_to_le32(crc32c_le(le32_to_cpu(e->checksum),
page_address(sh->ppl_page),
PAGE_SIZE));
}
list_add_tail(&sh->log_list, &io->stripe_list);
atomic_inc(&io->pending_stripes);
sh->ppl_io = io;
return 0;
}
int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh)
{
struct ppl_conf *ppl_conf = conf->log_private;
struct ppl_io_unit *io = sh->ppl_io;
struct ppl_log *log;
if (io || test_bit(STRIPE_SYNCING, &sh->state) ||
!test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags) ||
!test_bit(R5_Insync, &sh->dev[sh->pd_idx].flags)) {
clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
return -EAGAIN;
}
log = &ppl_conf->child_logs[sh->pd_idx];
mutex_lock(&log->io_mutex);
if (!log->rdev || test_bit(Faulty, &log->rdev->flags)) {
mutex_unlock(&log->io_mutex);
return -EAGAIN;
}
set_bit(STRIPE_LOG_TRAPPED, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);
atomic_inc(&sh->count);
if (ppl_log_stripe(log, sh)) {
spin_lock_irq(&log->io_list_lock);
list_add_tail(&sh->log_list, &log->no_mem_stripes);
spin_unlock_irq(&log->io_list_lock);
}
mutex_unlock(&log->io_mutex);
return 0;
}
static void ppl_log_endio(struct bio *bio)
{
struct ppl_io_unit *io = bio->bi_private;
struct ppl_log *log = io->log;
struct ppl_conf *ppl_conf = log->ppl_conf;
struct stripe_head *sh, *next;
pr_debug("%s: seq: %llu\n", __func__, io->seq);
if (bio->bi_error)
md_error(ppl_conf->mddev, log->rdev);
mempool_free(io->header_page, ppl_conf->meta_pool);
list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) {
list_del_init(&sh->log_list);
set_bit(STRIPE_HANDLE, &sh->state);
raid5_release_stripe(sh);
}
}
static void ppl_submit_iounit_bio(struct ppl_io_unit *io, struct bio *bio)
{
char b[BDEVNAME_SIZE];
pr_debug("%s: seq: %llu size: %u sector: %llu dev: %s\n",
__func__, io->seq, bio->bi_iter.bi_size,
(unsigned long long)bio->bi_iter.bi_sector,
bdevname(bio->bi_bdev, b));
submit_bio(bio);
}
static void ppl_submit_iounit(struct ppl_io_unit *io)
{
struct ppl_log *log = io->log;
struct ppl_conf *ppl_conf = log->ppl_conf;
struct ppl_header *pplhdr = page_address(io->header_page);
struct bio *bio = &io->bio;
struct stripe_head *sh;
int i;
for (i = 0; i < io->entries_count; i++) {
struct ppl_header_entry *e = &pplhdr->entries[i];
pr_debug("%s: seq: %llu entry: %d data_sector: %llu pp_size: %u data_size: %u\n",
__func__, io->seq, i, le64_to_cpu(e->data_sector),
le32_to_cpu(e->pp_size), le32_to_cpu(e->data_size));
e->data_sector = cpu_to_le64(le64_to_cpu(e->data_sector) >>
ilog2(ppl_conf->block_size >> 9));
e->checksum = cpu_to_le32(~le32_to_cpu(e->checksum));
}
pplhdr->entries_count = cpu_to_le32(io->entries_count);
pplhdr->checksum = cpu_to_le32(~crc32c_le(~0, pplhdr, PPL_HEADER_SIZE));
bio->bi_private = io;
bio->bi_end_io = ppl_log_endio;
bio->bi_opf = REQ_OP_WRITE | REQ_FUA;
bio->bi_bdev = log->rdev->bdev;
bio->bi_iter.bi_sector = log->rdev->ppl.sector;
bio_add_page(bio, io->header_page, PAGE_SIZE, 0);
list_for_each_entry(sh, &io->stripe_list, log_list) {
/* entries for full stripe writes have no partial parity */
if (test_bit(STRIPE_FULL_WRITE, &sh->state))
continue;
if (!bio_add_page(bio, sh->ppl_page, PAGE_SIZE, 0)) {
struct bio *prev = bio;
bio = bio_alloc_bioset(GFP_NOIO, BIO_MAX_PAGES,
ppl_conf->bs);
bio->bi_opf = prev->bi_opf;
bio->bi_bdev = prev->bi_bdev;
bio->bi_iter.bi_sector = bio_end_sector(prev);
bio_add_page(bio, sh->ppl_page, PAGE_SIZE, 0);
bio_chain(bio, prev);
ppl_submit_iounit_bio(io, prev);
}
}
ppl_submit_iounit_bio(io, bio);
}
static void ppl_submit_current_io(struct ppl_log *log)
{
struct ppl_io_unit *io;
spin_lock_irq(&log->io_list_lock);
io = list_first_entry_or_null(&log->io_list, struct ppl_io_unit,
log_sibling);
if (io && io->submitted)
io = NULL;
spin_unlock_irq(&log->io_list_lock);
if (io) {
io->submitted = true;
if (io == log->current_io)
log->current_io = NULL;
ppl_submit_iounit(io);
}
}
void ppl_write_stripe_run(struct r5conf *conf)
{
struct ppl_conf *ppl_conf = conf->log_private;
struct ppl_log *log;
int i;
for (i = 0; i < ppl_conf->count; i++) {
log = &ppl_conf->child_logs[i];
mutex_lock(&log->io_mutex);
ppl_submit_current_io(log);
mutex_unlock(&log->io_mutex);
}
}
static void ppl_io_unit_finished(struct ppl_io_unit *io)
{
struct ppl_log *log = io->log;
unsigned long flags;
pr_debug("%s: seq: %llu\n", __func__, io->seq);
spin_lock_irqsave(&log->io_list_lock, flags);
list_del(&io->log_sibling);
mempool_free(io, log->ppl_conf->io_pool);
if (!list_empty(&log->no_mem_stripes)) {
struct stripe_head *sh = list_first_entry(&log->no_mem_stripes,
struct stripe_head,
log_list);
list_del_init(&sh->log_list);
set_bit(STRIPE_HANDLE, &sh->state);
raid5_release_stripe(sh);
}
spin_unlock_irqrestore(&log->io_list_lock, flags);
}
void ppl_stripe_write_finished(struct stripe_head *sh)
{
struct ppl_io_unit *io;
io = sh->ppl_io;
sh->ppl_io = NULL;
if (io && atomic_dec_and_test(&io->pending_stripes))
ppl_io_unit_finished(io);
}
static void __ppl_exit_log(struct ppl_conf *ppl_conf)
{
clear_bit(MD_HAS_PPL, &ppl_conf->mddev->flags);
kfree(ppl_conf->child_logs);
mempool_destroy(ppl_conf->meta_pool);
if (ppl_conf->bs)
bioset_free(ppl_conf->bs);
mempool_destroy(ppl_conf->io_pool);
kmem_cache_destroy(ppl_conf->io_kc);
kfree(ppl_conf);
}
void ppl_exit_log(struct r5conf *conf)
{
struct ppl_conf *ppl_conf = conf->log_private;
if (ppl_conf) {
__ppl_exit_log(ppl_conf);
conf->log_private = NULL;
}
}
static int ppl_validate_rdev(struct md_rdev *rdev)
{
char b[BDEVNAME_SIZE];
int ppl_data_sectors;
int ppl_size_new;
/*
* The configured PPL size must be enough to store
* the header and (at the very least) partial parity
* for one stripe. Round it down to ensure the data
* space is cleanly divisible by stripe size.
*/
ppl_data_sectors = rdev->ppl.size - (PPL_HEADER_SIZE >> 9);
if (ppl_data_sectors > 0)
ppl_data_sectors = rounddown(ppl_data_sectors, STRIPE_SECTORS);
if (ppl_data_sectors <= 0) {
pr_warn("md/raid:%s: PPL space too small on %s\n",
mdname(rdev->mddev), bdevname(rdev->bdev, b));
return -ENOSPC;
}
ppl_size_new = ppl_data_sectors + (PPL_HEADER_SIZE >> 9);
if ((rdev->ppl.sector < rdev->data_offset &&
rdev->ppl.sector + ppl_size_new > rdev->data_offset) ||
(rdev->ppl.sector >= rdev->data_offset &&
rdev->data_offset + rdev->sectors > rdev->ppl.sector)) {
pr_warn("md/raid:%s: PPL space overlaps with data on %s\n",
mdname(rdev->mddev), bdevname(rdev->bdev, b));
return -EINVAL;
}
if (!rdev->mddev->external &&
((rdev->ppl.offset > 0 && rdev->ppl.offset < (rdev->sb_size >> 9)) ||
(rdev->ppl.offset <= 0 && rdev->ppl.offset + ppl_size_new > 0))) {
pr_warn("md/raid:%s: PPL space overlaps with superblock on %s\n",
mdname(rdev->mddev), bdevname(rdev->bdev, b));
return -EINVAL;
}
rdev->ppl.size = ppl_size_new;
return 0;
}
int ppl_init_log(struct r5conf *conf)
{
struct ppl_conf *ppl_conf;
struct mddev *mddev = conf->mddev;
int ret = 0;
int i;
bool need_cache_flush;
pr_debug("md/raid:%s: enabling distributed Partial Parity Log\n",
mdname(conf->mddev));
if (PAGE_SIZE != 4096)
return -EINVAL;
if (mddev->level != 5) {
pr_warn("md/raid:%s PPL is not compatible with raid level %d\n",
mdname(mddev), mddev->level);
return -EINVAL;
}
if (mddev->bitmap_info.file || mddev->bitmap_info.offset) {
pr_warn("md/raid:%s PPL is not compatible with bitmap\n",
mdname(mddev));
return -EINVAL;
}
if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
pr_warn("md/raid:%s PPL is not compatible with journal\n",
mdname(mddev));
return -EINVAL;
}
ppl_conf = kzalloc(sizeof(struct ppl_conf), GFP_KERNEL);
if (!ppl_conf)
return -ENOMEM;
ppl_conf->mddev = mddev;
ppl_conf->io_kc = KMEM_CACHE(ppl_io_unit, 0);
if (!ppl_conf->io_kc) {
ret = -EINVAL;
goto err;
}
ppl_conf->io_pool = mempool_create_slab_pool(conf->raid_disks, ppl_conf->io_kc);
if (!ppl_conf->io_pool) {
ret = -EINVAL;
goto err;
}
ppl_conf->bs = bioset_create(conf->raid_disks, 0);
if (!ppl_conf->bs) {
ret = -EINVAL;
goto err;
}
ppl_conf->meta_pool = mempool_create_page_pool(conf->raid_disks, 0);
if (!ppl_conf->meta_pool) {
ret = -EINVAL;
goto err;
}
ppl_conf->count = conf->raid_disks;
ppl_conf->child_logs = kcalloc(ppl_conf->count, sizeof(struct ppl_log),
GFP_KERNEL);
if (!ppl_conf->child_logs) {
ret = -ENOMEM;
goto err;
}
atomic64_set(&ppl_conf->seq, 0);
if (!mddev->external) {
ppl_conf->signature = ~crc32c_le(~0, mddev->uuid, sizeof(mddev->uuid));
ppl_conf->block_size = 512;
} else {
ppl_conf->block_size = queue_logical_block_size(mddev->queue);
}
for (i = 0; i < ppl_conf->count; i++) {
struct ppl_log *log = &ppl_conf->child_logs[i];
struct md_rdev *rdev = conf->disks[i].rdev;
mutex_init(&log->io_mutex);
spin_lock_init(&log->io_list_lock);
INIT_LIST_HEAD(&log->io_list);
INIT_LIST_HEAD(&log->no_mem_stripes);
log->ppl_conf = ppl_conf;
log->rdev = rdev;
if (rdev) {
struct request_queue *q;
ret = ppl_validate_rdev(rdev);
if (ret)
goto err;
q = bdev_get_queue(rdev->bdev);
if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
need_cache_flush = true;
}
}
if (need_cache_flush)
pr_warn("md/raid:%s: Volatile write-back cache should be disabled on all member drives when using PPL!\n",
mdname(mddev));
conf->log_private = ppl_conf;
return 0;
err:
__ppl_exit_log(ppl_conf);
return ret;
}

64
drivers/md/raid5.c
View File

@ -482,6 +482,11 @@ static void shrink_buffers(struct stripe_head *sh)
sh->dev[i].page = NULL;
put_page(p);
}
if (sh->ppl_page) {
put_page(sh->ppl_page);
sh->ppl_page = NULL;
}
}
static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
@ -498,6 +503,13 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
sh->dev[i].page = page;
sh->dev[i].orig_page = page;
}
if (raid5_has_ppl(sh->raid_conf)) {
sh->ppl_page = alloc_page(gfp);
if (!sh->ppl_page)
return 1;
}
return 0;
}
@ -746,7 +758,7 @@ static bool stripe_can_batch(struct stripe_head *sh)
{
struct r5conf *conf = sh->raid_conf;
if (conf->log)
if (conf->log || raid5_has_ppl(conf))
return false;
return test_bit(STRIPE_BATCH_READY, &sh->state) &&
!test_bit(STRIPE_BITMAP_PENDING, &sh->state) &&
@ -2093,6 +2105,9 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
async_tx_ack(tx);
}
if (test_bit(STRIPE_OP_PARTIAL_PARITY, &ops_request))
tx = ops_run_partial_parity(sh, percpu, tx);
if (test_bit(STRIPE_OP_PREXOR, &ops_request)) {
if (level < 6)
tx = ops_run_prexor5(sh, percpu, tx);
@ -3168,6 +3183,12 @@ schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
s->locked++;
}
if (raid5_has_ppl(sh->raid_conf) &&
test_bit(STRIPE_OP_BIODRAIN, &s->ops_request) &&
!test_bit(STRIPE_FULL_WRITE, &sh->state) &&
test_bit(R5_Insync, &sh->dev[pd_idx].flags))
set_bit(STRIPE_OP_PARTIAL_PARITY, &s->ops_request);
pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
__func__, (unsigned long long)sh->sector,
s->locked, s->ops_request);
@ -3215,6 +3236,36 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
goto overlap;
if (forwrite && raid5_has_ppl(conf)) {
/*
* With PPL only writes to consecutive data chunks within a
* stripe are allowed because for a single stripe_head we can
* only have one PPL entry at a time, which describes one data
* range. Not really an overlap, but wait_for_overlap can be
* used to handle this.
*/
sector_t sector;
sector_t first = 0;
sector_t last = 0;
int count = 0;
int i;
for (i = 0; i < sh->disks; i++) {
if (i != sh->pd_idx &&
(i == dd_idx || sh->dev[i].towrite)) {
sector = sh->dev[i].sector;
if (count == 0 || sector < first)
first = sector;
if (sector > last)
last = sector;
count++;
}
}
if (first + conf->chunk_sectors * (count - 1) != last)
goto overlap;
}
if (!forwrite || previous)
clear_bit(STRIPE_BATCH_READY, &sh->state);
@ -7208,6 +7259,13 @@ static int raid5_run(struct mddev *mddev)
BUG_ON(mddev->delta_disks != 0);
}
if (test_bit(MD_HAS_JOURNAL, &mddev->flags) &&
test_bit(MD_HAS_PPL, &mddev->flags)) {
pr_warn("md/raid:%s: using journal device and PPL not allowed - disabling PPL\n",
mdname(mddev));
clear_bit(MD_HAS_PPL, &mddev->flags);
}
if (mddev->private == NULL)
conf = setup_conf(mddev);
else
@ -7689,7 +7747,7 @@ static int raid5_resize(struct mddev *mddev, sector_t sectors)
sector_t newsize;
struct r5conf *conf = mddev->private;
if (conf->log)
if (conf->log || raid5_has_ppl(conf))
return -EINVAL;
sectors &= ~((sector_t)conf->chunk_sectors - 1);
newsize = raid5_size(mddev, sectors, mddev->raid_disks);
@ -7740,7 +7798,7 @@ static int check_reshape(struct mddev *mddev)
{
struct r5conf *conf = mddev->private;
if (conf->log)
if (conf->log || raid5_has_ppl(conf))
return -EINVAL;
if (mddev->delta_disks == 0 &&
mddev->new_layout == mddev->layout &&

10
drivers/md/raid5.h
View File

@ -224,10 +224,16 @@ struct stripe_head {
spinlock_t batch_lock; /* only header's lock is useful */
struct list_head batch_list; /* protected by head's batch lock*/
struct r5l_io_unit *log_io;
union {
struct r5l_io_unit *log_io;
struct ppl_io_unit *ppl_io;
};
struct list_head log_list;
sector_t log_start; /* first meta block on the journal */
struct list_head r5c; /* for r5c_cache->stripe_in_journal */
struct page *ppl_page; /* partial parity of this stripe */
/**
* struct stripe_operations
* @target - STRIPE_OP_COMPUTE_BLK target
@ -400,6 +406,7 @@ enum {
STRIPE_OP_BIODRAIN,
STRIPE_OP_RECONSTRUCT,
STRIPE_OP_CHECK,
STRIPE_OP_PARTIAL_PARITY,
};
/*
@ -696,6 +703,7 @@ struct r5conf {
int group_cnt;
int worker_cnt_per_group;
struct r5l_log *log;
void *log_private;
spinlock_t pending_bios_lock;
bool batch_bio_dispatch;

27
include/uapi/linux/raid/md_p.h
View File

@ -398,4 +398,31 @@ struct r5l_meta_block {
#define R5LOG_VERSION 0x1
#define R5LOG_MAGIC 0x6433c509
struct ppl_header_entry {
__le64 data_sector; /* raid sector of the new data */
__le32 pp_size; /* length of partial parity */
__le32 data_size; /* length of data */
__le32 parity_disk; /* member disk containing parity */
__le32 checksum; /* checksum of partial parity data for this
* entry (~crc32c) */
} __attribute__ ((__packed__));
#define PPL_HEADER_SIZE 4096
#define PPL_HDR_RESERVED 512
#define PPL_HDR_ENTRY_SPACE \
(PPL_HEADER_SIZE - PPL_HDR_RESERVED - 4 * sizeof(u32) - sizeof(u64))
#define PPL_HDR_MAX_ENTRIES \
(PPL_HDR_ENTRY_SPACE / sizeof(struct ppl_header_entry))
struct ppl_header {
__u8 reserved[PPL_HDR_RESERVED];/* reserved space, fill with 0xff */
__le32 signature; /* signature (family number of volume) */
__le32 padding; /* zero pad */
__le64 generation; /* generation number of the header */
__le32 entries_count; /* number of entries in entry array */
__le32 checksum; /* checksum of the header (~crc32c) */
struct ppl_header_entry entries[PPL_HDR_MAX_ENTRIES];
} __attribute__ ((__packed__));
#endif