diff options
| author | NeilBrown <neilb@suse.de> | 2006-03-27 01:18:15 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-27 08:45:02 -0800 |
| commit | df8e7f7639bab3b2cc536a1d30d5593d65251778 (patch) | |
| tree | 93eb1e93e5f6e0f27f85b8b5d925c2dad2929c2e | |
| parent | e464eafdb4400c6d6576ba3840d8bd40340f8a96 (diff) | |
[PATCH] md: Improve comments about locking situation in raid5 make_request
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | drivers/md/raid5.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index bb16ac231a4..8eded08411f 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -1768,6 +1768,14 @@ static int make_request(request_queue_t *q, struct bio * bi) if (likely(conf->expand_progress == MaxSector)) disks = conf->raid_disks; else { + /* spinlock is needed as expand_progress may be + * 64bit on a 32bit platform, and so it might be + * possible to see a half-updated value + * Ofcourse expand_progress could change after + * the lock is dropped, so once we get a reference + * to the stripe that we think it is, we will have + * to check again. + */ spin_lock_irq(&conf->device_lock); disks = conf->raid_disks; if (logical_sector >= conf->expand_progress) @@ -1791,7 +1799,12 @@ static int make_request(request_queue_t *q, struct bio * bi) if (sh) { if (unlikely(conf->expand_progress != MaxSector)) { /* expansion might have moved on while waiting for a - * stripe, so we much do the range check again. + * stripe, so we must do the range check again. + * Expansion could still move past after this + * test, but as we are holding a reference to + * 'sh', we know that if that happens, + * STRIPE_EXPANDING will get set and the expansion + * won't proceed until we finish with the stripe. */ int must_retry = 0; spin_lock_irq(&conf->device_lock); |