[patch 029/114] md: avoid races when stopping resync.

Greg KH
2009-03-14T01:31:20Z

[-- Attachment #1: md-avoid-races-when-stopping-resync.patch --]
[-- Type: text/plain, Size: 2711 bytes --]

2.6.28-stable review patch. If anyone has any objections, please let us know.

------------------

From: NeilBrown <neilb@suse.de>

commit 73d5c38a9536142e062c35997b044e89166e063b upstream.

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

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/md/raid1.c | 3 ++-
drivers/md/raid10.c | 7 ++++---
2 files changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1236,6 +1236,7 @@ static void end_sync_read(struct bio *bi
/* 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 *bi
*/
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 *b

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 *b
r10_bio = r10_bio2;
}
}
- rdev_dec_pending(conf->mirrors[d].rdev, mddev);
}

/*
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1233,8 +1233,9 @@ static void end_sync_write(struct bio *b
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);
}
}