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md/raid5: Ensure batch_last is released before sleeping for quiesce 

A race condition exists where if raid5_quiesce() is called in the
middle of a request that has set batch_last, it will deadlock.

batch_last will hold a reference to a stripe when raid5_quiesce() is
called. This will cause the next raid5_get_active_stripe() call to
sleep waiting for the quiesce to finish, but the raid5_quiesce() thread
will wait for active_stripes to go to zero which will never happen
because request thread is waiting for the quiesce to stop.

Fix this by creating a special __raid5_get_active_stripe() function
which takes the request context and clears the last_batch before
sleeping.

While we're at it, change the arguments of raid5_get_active_stripe()
to bools.

Fixes: 3312e6c887 ("md/raid5: Keep a reference to last stripe_head for batch")
Reported-by: David Sloan <David.Sloan@eideticom.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Logan Gunthorpe 2022-07-27 15:06:00 -06:00 committed by Jens Axboe
parent df6b0e205d
commit 20313b1b8c
2 changed files with 29 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/md/raid5.c
View File

@ -800,9 +800,9 @@ static bool is_inactive_blocked(struct r5conf *conf, int hash)
return active < (conf->max_nr_stripes * 3 / 4);
}
struct stripe_head *
raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
int previous, int noblock, int noquiesce)
static struct stripe_head *__raid5_get_active_stripe(struct r5conf *conf,
struct stripe_request_ctx *ctx, sector_t sector,
bool previous, bool noblock, bool noquiesce)
{
struct stripe_head *sh;
int hash = stripe_hash_locks_hash(conf, sector);
@ -812,9 +812,22 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
spin_lock_irq(conf->hash_locks + hash);
retry:
wait_event_lock_irq(conf->wait_for_quiescent,
conf->quiesce == 0 || noquiesce,
*(conf->hash_locks + hash));
if (!noquiesce && conf->quiesce) {
/*
* Must release the reference to batch_last before waiting,
* on quiesce, otherwise the batch_last will hold a reference
* to a stripe and raid5_quiesce() will deadlock waiting for
* active_stripes to go to zero.
*/
if (ctx && ctx->batch_last) {
raid5_release_stripe(ctx->batch_last);
ctx->batch_last = NULL;
}
wait_event_lock_irq(conf->wait_for_quiescent, !conf->quiesce,
*(conf->hash_locks + hash));
}
sh = find_get_stripe(conf, sector, conf->generation - previous, hash);
if (sh)
goto out;
@ -850,6 +863,13 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
return sh;
}
struct stripe_head *raid5_get_active_stripe(struct r5conf *conf,
sector_t sector, bool previous, bool noblock, bool noquiesce)
{
return __raid5_get_active_stripe(conf, NULL, sector, previous, noblock,
noquiesce);
}
static bool is_full_stripe_write(struct stripe_head *sh)
{
BUG_ON(sh->overwrite_disks > (sh->disks - sh->raid_conf->max_degraded));
@ -5992,8 +6012,8 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
pr_debug("raid456: %s, sector %llu logical %llu\n", __func__,
new_sector, logical_sector);
sh = raid5_get_active_stripe(conf, new_sector, previous,
(bi->bi_opf & REQ_RAHEAD), 0);
sh = __raid5_get_active_stripe(conf, ctx, new_sector, previous,
(bi->bi_opf & REQ_RAHEAD), 0);
if (unlikely(!sh)) {
/* cannot get stripe, just give-up */
bi->bi_status = BLK_STS_IOERR;

2
drivers/md/raid5.h
View File

@ -812,7 +812,7 @@ extern sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
struct stripe_head *sh);
extern struct stripe_head *
raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
int previous, int noblock, int noquiesce);
bool previous, bool noblock, bool noquiesce);
extern int raid5_calc_degraded(struct r5conf *conf);
extern int r5c_journal_mode_set(struct mddev *mddev, int journal_mode);
#endif