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[PATCH] md: Improve comments about locking situation in raid5 make_request

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Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown 2006-03-27 01:18:15 -08:00 committed by Linus Torvalds
parent e464eafdb4
commit df8e7f7639
1 changed files with 14 additions and 1 deletions
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15
drivers/md/raid5.c
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@ -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);