[PATCH] md: fix potential memalloc deadlock in md

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h
index 866a1e2b0ce..fbaeda79b2e 100644
--- a/include/linux/raid/md.h
+++ b/include/linux/raid/md.h
@@ -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