Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2a2275d630b982e5f90206f9bc497f6695a3ec5d
Commit: 2a2275d630b982e5f90206f9bc497f6695a3ec5d
Parent: a0ad13ef643a5829d63c456ab6143bbda60b44a9
Author: NeilBrown <[EMAIL PROTECTED]>
AuthorDate: Fri Jan 26 00:57:11 2007 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri Jan 26 13:51:00 2007 -0800
[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 <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
drivers/md/md.c | 29 +++++++++++++++++++++++++++++
drivers/md/raid1.c | 2 ++
drivers/md/raid5.c | 3 +++
include/linux/raid/md.h | 2 +-
4 files changed, 35 insertions(+), 1 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index ec3d8e8..e8807ea 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
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index ab74d40..97ee870 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2104,6 +2104,8 @@ static int raid1_reshape(mddev_t *mddev)
return -EINVAL;
}
+ md_allow_write(mddev);
+
raid_disks = mddev->raid_disks + mddev->delta_disks;
if (raid_disks < conf->raid_disks) {
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index be008f0..8a30b29 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -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++;
diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h
index 866a1e2..fbaeda7 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
-
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