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md/raid5: use mempool to allocate stripe_request_ctx

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On the one hand, stripe_request_ctx is 72 bytes, and it's a bit huge for
a stack variable.

On the other hand, the bitmap sectors_to_do is a fixed size, result in
max_hw_sector_kb of raid5 array is at most 256 * 4k = 1Mb, and this will
make full stripe IO impossible for the array that chunk_size * data_disks
is bigger. Allocate ctx during runtime will make it possible to get rid
of this limit.

Link: https://lore.kernel.org/linux-raid/20260114171241.3043364-6-yukuai@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Li Nan <linan122@huawei.com>
This commit is contained in:
Yu Kuai 2026-01-15 01:12:33 +08:00
parent 10787568cc
commit 9340a95d48
4 changed files with 45 additions and 27 deletions
Download patch file Download diff file Expand all files Collapse all files

4
drivers/md/md.h
View file

@ -22,6 +22,10 @@
#include <trace/events/block.h>
#define MaxSector (~(sector_t)0)
/*
* Number of guaranteed raid bios in case of extreme VM load:
*/
#define NR_RAID_BIOS 256
enum md_submodule_type {
MD_PERSONALITY = 0,

5
drivers/md/raid1-10.c
View file

@ -3,11 +3,6 @@
#define RESYNC_BLOCK_SIZE (64*1024)
#define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
/*
* Number of guaranteed raid bios in case of extreme VM load:
*/
#define NR_RAID_BIOS 256
/* when we get a read error on a read-only array, we redirect to another
* device without failing the first device, or trying to over-write to
* correct the read error. To keep track of bad blocks on a per-bio

61
drivers/md/raid5.c
View file

@ -6084,13 +6084,13 @@ static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
bool on_wq;
struct r5conf *conf = mddev->private;
sector_t logical_sector;
struct stripe_request_ctx ctx = {};
const int rw = bio_data_dir(bi);
struct stripe_request_ctx *ctx;
sector_t logical_sector;
enum stripe_result res;
int s, stripe_cnt;
bool on_wq;
if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
int ret = log_handle_flush_request(conf, bi);
@ -6102,11 +6102,6 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
return true;
}
/* ret == -EAGAIN, fallback */
/*
* if r5l_handle_flush_request() didn't clear REQ_PREFLUSH,
* we need to flush journal device
*/
ctx.do_flush = bi->bi_opf & REQ_PREFLUSH;
}
md_write_start(mddev, bi);
@ -6129,16 +6124,25 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
}
logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
ctx.first_sector = logical_sector;
ctx.last_sector = bio_end_sector(bi);
bi->bi_next = NULL;
stripe_cnt = DIV_ROUND_UP_SECTOR_T(ctx.last_sector - logical_sector,
ctx = mempool_alloc(conf->ctx_pool, GFP_NOIO);
memset(ctx, 0, sizeof(*ctx));
ctx->first_sector = logical_sector;
ctx->last_sector = bio_end_sector(bi);
/*
* if r5l_handle_flush_request() didn't clear REQ_PREFLUSH,
* we need to flush journal device
*/
if (unlikely(bi->bi_opf & REQ_PREFLUSH))
ctx->do_flush = true;
stripe_cnt = DIV_ROUND_UP_SECTOR_T(ctx->last_sector - logical_sector,
RAID5_STRIPE_SECTORS(conf));
bitmap_set(ctx.sectors_to_do, 0, stripe_cnt);
bitmap_set(ctx->sectors_to_do, 0, stripe_cnt);
pr_debug("raid456: %s, logical %llu to %llu\n", __func__,
bi->bi_iter.bi_sector, ctx.last_sector);
bi->bi_iter.bi_sector, ctx->last_sector);
/* Bail out if conflicts with reshape and REQ_NOWAIT is set */
if ((bi->bi_opf & REQ_NOWAIT) &&
@ -6146,6 +6150,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
bio_wouldblock_error(bi);
if (rw == WRITE)
md_write_end(mddev);
mempool_free(ctx, conf->ctx_pool);
return true;
}
md_account_bio(mddev, &bi);
@ -6164,10 +6169,10 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
add_wait_queue(&conf->wait_for_reshape, &wait);
on_wq = true;
}
s = (logical_sector - ctx.first_sector) >> RAID5_STRIPE_SHIFT(conf);
s = (logical_sector - ctx->first_sector) >> RAID5_STRIPE_SHIFT(conf);
while (1) {
res = make_stripe_request(mddev, conf, &ctx, logical_sector,
res = make_stripe_request(mddev, conf, ctx, logical_sector,
bi);
if (res == STRIPE_FAIL || res == STRIPE_WAIT_RESHAPE)
break;
@ -6184,9 +6189,9 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
* raid5_activate_delayed() from making progress
* and thus deadlocking.
*/
if (ctx.batch_last) {
raid5_release_stripe(ctx.batch_last);
ctx.batch_last = NULL;
if (ctx->batch_last) {
raid5_release_stripe(ctx->batch_last);
ctx->batch_last = NULL;
}
wait_woken(&wait, TASK_UNINTERRUPTIBLE,
@ -6194,21 +6199,23 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
continue;
}
s = find_next_bit_wrap(ctx.sectors_to_do, stripe_cnt, s);
s = find_next_bit_wrap(ctx->sectors_to_do, stripe_cnt, s);
if (s == stripe_cnt)
break;
logical_sector = ctx.first_sector +
logical_sector = ctx->first_sector +
(s << RAID5_STRIPE_SHIFT(conf));
}
if (unlikely(on_wq))
remove_wait_queue(&conf->wait_for_reshape, &wait);
if (ctx.batch_last)
raid5_release_stripe(ctx.batch_last);
if (ctx->batch_last)
raid5_release_stripe(ctx->batch_last);
if (rw == WRITE)
md_write_end(mddev);
mempool_free(ctx, conf->ctx_pool);
if (res == STRIPE_WAIT_RESHAPE) {
md_free_cloned_bio(bi);
return false;
@ -7378,6 +7385,9 @@ static void free_conf(struct r5conf *conf)
bioset_exit(&conf->bio_split);
kfree(conf->stripe_hashtbl);
kfree(conf->pending_data);
mempool_destroy(conf->ctx_pool);
kfree(conf);
}
@ -8061,6 +8071,13 @@ static int raid5_run(struct mddev *mddev)
goto abort;
}
conf->ctx_pool = mempool_create_kmalloc_pool(NR_RAID_BIOS,
sizeof(struct stripe_request_ctx));
if (!conf->ctx_pool) {
ret = -ENOMEM;
goto abort;
}
ret = log_init(conf, journal_dev, raid5_has_ppl(conf));
if (ret)
goto abort;

2
drivers/md/raid5.h
View file

@ -690,6 +690,8 @@ struct r5conf {
struct list_head pending_list;
int pending_data_cnt;
struct r5pending_data *next_pending_data;
mempool_t *ctx_pool;
};
#if PAGE_SIZE == DEFAULT_STRIPE_SIZE