diff options
| author | NeilBrown <neilb@suse.de> | 2007-01-26 00:57:11 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-01-26 13:51:00 -0800 |
| commit | 2a2275d630b982e5f90206f9bc497f6695a3ec5d (patch) | |
| tree | 88cddee709b2107b74e5424810d4ffb6e3772382 /drivers/md/md.c | |
| parent | a0ad13ef643a5829d63c456ab6143bbda60b44a9 (diff) | |
[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>
Diffstat (limited to 'drivers/md/md.c')
| -rw-r--r-- | drivers/md/md.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c index ec3d8e8a0bd..e8807ea5377 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -3564,6 +3564,8 @@ static int get_bitmap_file(mddev_t * mddev, void __user * arg) char *ptr, *buf = NULL; int err = -ENOMEM; + md_allow_write(mddev); + file = kmalloc(sizeof(*file), GFP_KERNEL); if (!file) goto out; @@ -5032,6 +5034,33 @@ void md_write_end(mddev_t *mddev) } } +/* md_allow_write(mddev) + * Calling this ensures that the array is marked 'active' so that writes + * may proceed without blocking. It is important to call this before + * attempting a GFP_KERNEL allocation while holding the mddev lock. + * Must be called with mddev_lock held. + */ +void md_allow_write(mddev_t *mddev) +{ + if (!mddev->pers) + return; + if (mddev->ro) + return; + + spin_lock_irq(&mddev->write_lock); + if (mddev->in_sync) { + mddev->in_sync = 0; + set_bit(MD_CHANGE_CLEAN, &mddev->flags); + if (mddev->safemode_delay && + mddev->safemode == 0) + mddev->safemode = 1; + spin_unlock_irq(&mddev->write_lock); + md_update_sb(mddev, 0); + } else + spin_unlock_irq(&mddev->write_lock); +} +EXPORT_SYMBOL_GPL(md_allow_write); + static DECLARE_WAIT_QUEUE_HEAD(resync_wait); #define SYNC_MARKS 10 |