Btrfs: fix race in sync and freeze again
I screwed this up, there is a race between checking if there is a running
transaction and actually starting a transaction in sync where we could race
with a freezer and get ourselves into trouble. To fix this we need to make
a new join type to only do the try lock on the freeze stuff. If it fails
we'll return EPERM and just return from sync. This fixes a hang Liu Bo
reported when running xfstest 68 in a loop. Thanks,
Reported-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 867e8e7..903ab2d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -854,16 +854,13 @@
btrfs_wait_ordered_extents(root, 0, 0);
- spin_lock(&fs_info->trans_lock);
- if (!fs_info->running_transaction) {
- spin_unlock(&fs_info->trans_lock);
- return 0;
- }
- spin_unlock(&fs_info->trans_lock);
-
- trans = btrfs_join_transaction(root);
- if (IS_ERR(trans))
+ trans = btrfs_join_transaction_freeze(root);
+ if (IS_ERR(trans)) {
+ /* Frozen, don't bother */
+ if (PTR_ERR(trans) == -EPERM)
+ return 0;
return PTR_ERR(trans);
+ }
return btrfs_commit_transaction(trans, root);
}
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c01dec7..e4bfac8 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -272,6 +272,7 @@
TRANS_JOIN,
TRANS_USERSPACE,
TRANS_JOIN_NOLOCK,
+ TRANS_JOIN_FREEZE,
};
static int may_wait_transaction(struct btrfs_root *root, int type)
@@ -341,7 +342,11 @@
if (!h)
return ERR_PTR(-ENOMEM);
- sb_start_intwrite(root->fs_info->sb);
+ if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
+ if (type == TRANS_JOIN_FREEZE)
+ return ERR_PTR(-EPERM);
+ sb_start_intwrite(root->fs_info->sb);
+ }
if (may_wait_transaction(root, type))
wait_current_trans(root);
@@ -424,6 +429,11 @@
return start_transaction(root, 0, TRANS_USERSPACE, 0);
}
+struct btrfs_trans_handle *btrfs_join_transaction_freeze(struct btrfs_root *root)
+{
+ return start_transaction(root, 0, TRANS_JOIN_FREEZE, 0);
+}
+
/* wait for a transaction commit to be fully complete */
static noinline void wait_for_commit(struct btrfs_root *root,
struct btrfs_transaction *commit)
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index b6463e1..fbf8313 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -102,6 +102,7 @@
struct btrfs_root *root, int num_items);
struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root);
+struct btrfs_trans_handle *btrfs_join_transaction_freeze(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root);
int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid);
int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,