This reverts commit a6f69dc8018d ("btrfs: move commit out of sysfs when
changing label").
Unlike most btrfs file operations, sysfs don't go through the normal
open/read/write routine which will initiate a sb_start_*write/read.
This is very dangerous on frozen btrfs, if using the pending changes
method, sysfs change can make fs_info->pending_changes to 1, and later
sync_fs() call will cause deadlock.
So revert the patch to deal the deadlock caused by the following
workload:
freeze() -> change lable -> sync() -> unfreeze()
Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
fs/btrfs/sysfs.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 92db3f6..226f726 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -369,6 +369,9 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
const char *buf, size_t len)
{
struct btrfs_fs_info *fs_info = to_fs_info(kobj);
+ struct btrfs_trans_handle *trans;
+ struct btrfs_root *root = fs_info->fs_root;
+ int ret;
size_t p_len;
if (fs_info->sb->s_flags & MS_RDONLY)
@@ -383,18 +386,20 @@ static ssize_t btrfs_label_store(struct kobject *kobj,
if (p_len >= BTRFS_LABEL_SIZE)
return -EINVAL;
- spin_lock(&fs_info->super_lock);
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans))
+ return PTR_ERR(trans);
+
+ spin_lock(&root->fs_info->super_lock);
memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
memcpy(fs_info->super_copy->label, buf, p_len);
- spin_unlock(&fs_info->super_lock);
+ spin_unlock(&root->fs_info->super_lock);
+ ret = btrfs_commit_transaction(trans, root);
- /*
- * We don't want to do full transaction commit from inside sysfs
- */
- btrfs_set_pending(fs_info, COMMIT);
- wake_up_process(fs_info->transaction_kthread);
+ if (!ret)
+ return len;
- return len;
+ return ret;
}
BTRFS_ATTR_RW(label, btrfs_label_show, btrfs_label_store);
--
2.2.2
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