A side effect of adding support for multi-device filesystem to the bdev level
API is that we can have nested calls to thaw_super() from the bdev layer (for
example, the user may try to dm-snapshot all the devices of a btrfs filesystem
at the same time), which means that the lock for the sb-level freeze counter
needs to become a counter.
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Josef Bacik <jbacik@xxxxxxxxxxxx>
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---
diff -urNp linux-3.8-rc1-orig/fs/super.c linux-3.8-rc1/fs/super.c
--- linux-3.8-rc1-orig/fs/super.c 2012-12-25 16:37:51.172018000 +0900
+++ linux-3.8-rc1/fs/super.c 2012-12-25 16:55:22.240018000 +0900
@@ -1346,24 +1346,19 @@ static void sb_wait_write(struct super_b
* freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
* mostly auxiliary for filesystems to verify they do not modify frozen fs.
*
- * sb->s_writers.frozen, sb->s_freeze_count and sb->s_freeze_locked are
+ * sb->s_writers.frozen, sb->s_freeze_count and sb->s_freeze_lock_count are
* protected by sb->s_umount.
*/
int __freeze_super(struct super_block *sb, bool lock)
{
int ret = 0;
- bool locked_old = sb->s_freeze_locked;
+ int lock_count_old = sb->s_freeze_lock_count;
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
- /* The freeze counter lock does not nest. */
- if (sb->s_freeze_locked && lock) {
- ret = -EBUSY;
- goto out_deactivate;
- }
-
- sb->s_freeze_locked = lock ? true : sb->s_freeze_locked;
+ if (lock)
+ sb->s_freeze_lock_count++;
if (++sb->s_freeze_count > 1)
goto out_deactivate;
@@ -1411,7 +1406,7 @@ int __freeze_super(struct super_block *s
if (ret) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
- sb->s_freeze_locked = locked_old;
+ sb->s_freeze_lock_count = lock_count_old;
sb->s_freeze_count--;
sb->s_writers.frozen = SB_UNFROZEN;
smp_wmb();
@@ -1507,7 +1502,7 @@ int __thaw_super(struct super_block *sb,
* An unfrozen filesystem cannot be thawed. Similarly, an unlocked
* freeze counter cannot be unlocked.
*/
- if (!sb->s_freeze_count || (!sb->s_freeze_locked && unlock)) {
+ if (!sb->s_freeze_count || (!sb->s_freeze_lock_count && unlock)) {
error = -EINVAL;
goto out_unlock;
}
@@ -1517,12 +1512,13 @@ int __thaw_super(struct super_block *sb,
* trigger the actual filesystem thaw.
*/
if (sb->s_freeze_count > 1) {
+ if (unlock)
+ sb->s_freeze_lock_count--;
sb->s_freeze_count--;
- sb->s_freeze_locked = unlock ? false: sb->s_freeze_locked;
goto out_unlock;
}
/* A locked filesystem cannot be thawed unless unlock was requested. */
- else if (sb->s_freeze_locked && !unlock) {
+ else if (sb->s_freeze_lock_count && !unlock) {
error = -EINVAL;
goto out_unlock;
}
@@ -1531,7 +1527,7 @@ int __thaw_super(struct super_block *sb,
if (!error) {
sb->s_freeze_count = 0;
- sb->s_freeze_locked = false;
+ sb->s_freeze_lock_count = 0;
}
else
goto out_unlock;
@@ -1577,9 +1573,9 @@ int thaw_super_force(struct super_block
return -EINVAL;
}
- if (sb->s_freeze_locked) {
+ if (sb->s_freeze_lock_count) {
/* Ensure superblock gets thawed at unlock time */
- sb->s_freeze_count = 1;
+ sb->s_freeze_count = sb->s_freeze_lock_count;
up_write(&sb->s_umount);
return -EINVAL;
}
diff -urNp linux-3.8-rc1-orig/include/linux/fs.h linux-3.8-rc1/include/linux/fs.h
--- linux-3.8-rc1-orig/include/linux/fs.h 2012-12-25 16:35:43.104018000 +0900
+++ linux-3.8-rc1/include/linux/fs.h 2012-12-25 16:55:22.244018000 +0900
@@ -1325,7 +1325,7 @@ struct super_block {
int s_freeze_count;
/* Is freeze state locked? */
- bool s_freeze_locked;
+ int s_freeze_lock_count;
};
/* superblock cache pruning functions */
--
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