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[PATCH] md: fix potential memalloc deadlock in md

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If a GFP_KERNEL allocation is attempted in md while the mddev_lock is held,
it is possible for a deadlock to eventuate.

This happens if the array was marked 'clean', and the memalloc triggers a
write-out to the md device.

For the writeout to succeed, the array must be marked 'dirty', and that
requires getting the mddev_lock.

So, before attempting a GFP_KERNEL allocation while holding the lock, make
sure the array is marked 'dirty' (unless it is currently read-only).

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
NeilBrown
2007-01-26 00:57:11 -08:00
committed by Linus Torvalds
parent a0ad13ef64
commit 2a2275d630
4 changed files with 35 additions and 1 deletions
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3
drivers/md/raid5.c
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@@ -405,6 +405,8 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
if (newsize <= conf->pool_size)
return 0; /* never bother to shrink */
md_allow_write(conf->mddev);
/* Step 1 */
sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
@@ -3250,6 +3252,7 @@ raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
else
break;
}
md_allow_write(mddev);
while (new > conf->max_nr_stripes) {
if (grow_one_stripe(conf))
conf->max_nr_stripes++;