path: root/drivers/md/bitmap.c
diff options
authorNeilBrown <neilb@suse.de>2008-07-21 17:05:25 +1000
committerNeilBrown <neilb@suse.de>2008-07-21 17:05:25 +1000
commit4b80991c6cb9efa607bc4fd6f3ecdf5511c31bb0 (patch)
tree5e2ba7d509af245c29bdf04b00960cc367972c44 /drivers/md/bitmap.c
parentf2ea68cf42aafdd93393b6b8b20fc3c2b5f4390c (diff)
md: Protect access to mddev->disks list using RCU
All modifications and most access to the mddev->disks list are made under the reconfig_mutex lock. However there are three places where the list is walked without any locking. If a reconfig happens at this time, havoc (and oops) can ensue. So use RCU to protect these accesses: - wrap them in rcu_read_{,un}lock() - use list_for_each_entry_rcu - add to the list with list_add_rcu - delete from the list with list_del_rcu - delay the 'free' with call_rcu rather than schedule_work Note that export_rdev did a list_del_init on this list. In almost all cases the entry was not in the list anymore so it was a no-op and so safe. It is no longer safe as after list_del_rcu we may not touch the list_head. An audit shows that export_rdev is called: - after unbind_rdev_from_array, in which case the delete has already been done, - after bind_rdev_to_array fails, in which case the delete isn't needed. - before the device has been put on a list at all (e.g. in add_new_disk where reading the superblock fails). - and in autorun devices after a failure when the device is on a different list. So remove the list_del_init call from export_rdev, and add it back immediately before the called to export_rdev for that last case. Note also that ->same_set is sometimes used for lists other than mddev->list (e.g. candidates). In these cases rcu is not needed. Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/bitmap.c')
1 files changed, 10 insertions, 5 deletions
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index eba83e25b678..621a272a2c74 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -241,10 +241,10 @@ static struct page *read_sb_page(mddev_t *mddev, long offset, unsigned long inde
static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
mdk_rdev_t *rdev;
- struct list_head *tmp;
mddev_t *mddev = bitmap->mddev;
- rdev_for_each(rdev, tmp, mddev)
+ rcu_read_lock();
+ rdev_for_each_rcu(rdev, mddev)
if (test_bit(In_sync, &rdev->flags)
&& !test_bit(Faulty, &rdev->flags)) {
int size = PAGE_SIZE;
@@ -260,11 +260,11 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
+ (long)(page->index * (PAGE_SIZE/512))
+ size/512 > 0)
/* bitmap runs in to metadata */
- return -EINVAL;
+ goto bad_alignment;
if (rdev->data_offset + mddev->size*2
> rdev->sb_start + bitmap->offset)
/* data runs in to bitmap */
- return -EINVAL;
+ goto bad_alignment;
} else if (rdev->sb_start < rdev->data_offset) {
if (rdev->sb_start
@@ -272,7 +272,7 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
+ page->index*(PAGE_SIZE/512) + size/512
> rdev->data_offset)
/* bitmap runs in to data */
- return -EINVAL;
+ goto bad_alignment;
} else {
/* DATA METADATA BITMAP - no problems */
@@ -282,10 +282,15 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
+ rcu_read_unlock();
if (wait)
return 0;
+ bad_alignment:
+ rcu_read_unlock();
+ return -EINVAL;
static void bitmap_file_kick(struct bitmap *bitmap);