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md: avoid races when stopping resync. 

There has been a race in raid10 and raid1 for a long time
which has only recently started showing up due to a scheduler changed.

When a sync_read request finishes, as soon as reschedule_retry
is called, another thread can mark the resync request as having
completed, so md_do_sync can finish, ->stop can be called, and
->conf can be freed.  So using conf after reschedule_retry is not
safe.

Similarly, when finishing a sync_write, calling md_done_sync must be
the last thing we do, as it allows a chain of events which will free
conf and other data structures.

The first of these requires action in raid10.c
The second requires action in raid1.c and raid10.c

Cc: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2009-02-25 13:18:47 +11:00
parent 78200d45cd
commit 73d5c38a95
2 changed files with 6 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/md/raid1.c
View File

@ -1237,8 +1237,9 @@ static void end_sync_write(struct bio *bio, int error)
update_head_pos(mirror, r1_bio);
if (atomic_dec_and_test(&r1_bio->remaining)) {
md_done_sync(mddev, r1_bio->sectors, uptodate);
sector_t s = r1_bio->sectors;
put_buf(r1_bio);
md_done_sync(mddev, s, uptodate);
}
}

7
drivers/md/raid10.c
View File

@ -1236,6 +1236,7 @@ static void end_sync_read(struct bio *bio, int error)
/* for reconstruct, we always reschedule after a read.
* for resync, only after all reads
*/
rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||
atomic_dec_and_test(&r10_bio->remaining)) {
/* we have read all the blocks,
@ -1243,7 +1244,6 @@ static void end_sync_read(struct bio *bio, int error)
*/
reschedule_retry(r10_bio);
}
rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
}
static void end_sync_write(struct bio *bio, int error)
@ -1264,11 +1264,13 @@ static void end_sync_write(struct bio *bio, int error)
update_head_pos(i, r10_bio);
rdev_dec_pending(conf->mirrors[d].rdev, mddev);
while (atomic_dec_and_test(&r10_bio->remaining)) {
if (r10_bio->master_bio == NULL) {
/* the primary of several recovery bios */
md_done_sync(mddev, r10_bio->sectors, 1);
sector_t s = r10_bio->sectors;
put_buf(r10_bio);
md_done_sync(mddev, s, 1);
break;
} else {
r10bio_t *r10_bio2 = (r10bio_t *)r10_bio->master_bio;
@ -1276,7 +1278,6 @@ static void end_sync_write(struct bio *bio, int error)
r10_bio = r10_bio2;
}
}
rdev_dec_pending(conf->mirrors[d].rdev, mddev);
}
/*