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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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2
include/linux/raid/md.h
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@ -94,7 +94,7 @@ extern int sync_page_io(struct block_device *bdev, sector_t sector, int size,
struct page *page, int rw);
extern void md_do_sync(mddev_t *mddev);
extern void md_new_event(mddev_t *mddev);
extern void md_allow_write(mddev_t *mddev);
#endif /* CONFIG_MD */
#endif