Before the patch, btrfs_freeze() does not start a transaction if there
is pending changes but no transaction is running.
This will lead to deadlock if the fs is frozen but there are pending
changes, since sync_fs will start a transaction with s_umount mutex,
blocked by frozen fs. And later unfreeze will wait sync_fs to release
the s_umount mutex.
This patch will ensure the frozen fs from having pending changes, except
some one use sysfs interfaces to create pending changes again.
Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
fs/btrfs/super.c | 52 +++++++++++++++++++++++++---------------------------
1 file changed, 25 insertions(+), 27 deletions(-)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 60f7cbe..5229786 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -975,32 +975,22 @@ fail_close:
return err;
}
-int btrfs_sync_fs(struct super_block *sb, int wait)
+static int commit_current_or_new_trans(struct btrfs_fs_info *fs_info,
+ int freezing)
{
struct btrfs_trans_handle *trans;
- struct btrfs_fs_info *fs_info = btrfs_sb(sb);
struct btrfs_root *root = fs_info->tree_root;
- trace_btrfs_sync_fs(wait);
-
- if (!wait) {
- filemap_flush(fs_info->btree_inode->i_mapping);
- return 0;
- }
-
- btrfs_wait_ordered_roots(fs_info, -1);
-
trans = btrfs_attach_transaction_barrier(root);
if (IS_ERR(trans)) {
- /* no transaction, don't bother */
if (PTR_ERR(trans) == -ENOENT) {
- /*
- * Exit unless we have some pending changes
- * that need to go through commit
- */
+ /* No pending changes, don't bother*/
if (fs_info->pending_changes == 0)
return 0;
- trans = btrfs_start_transaction(root, 0);
+ if (freezing)
+ trans = btrfs_start_transaction_freeze(root, 0);
+ else
+ trans = btrfs_start_transaction(root, 0);
} else {
return PTR_ERR(trans);
}
@@ -1008,6 +998,22 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
return btrfs_commit_transaction(trans, root);
}
+int btrfs_sync_fs(struct super_block *sb, int wait)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+
+ trace_btrfs_sync_fs(wait);
+
+ if (!wait) {
+ filemap_flush(fs_info->btree_inode->i_mapping);
+ return 0;
+ }
+
+ btrfs_wait_ordered_roots(fs_info, -1);
+
+ return commit_current_or_new_trans(fs_info, 0);
+}
+
static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
{
struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
@@ -1935,17 +1941,9 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
static int btrfs_freeze(struct super_block *sb)
{
- struct btrfs_trans_handle *trans;
- struct btrfs_root *root = btrfs_sb(sb)->tree_root;
+ struct btrfs_fs_info *fs_info = btrfs_sb(sb);
- trans = btrfs_attach_transaction_barrier(root);
- if (IS_ERR(trans)) {
- /* no transaction, don't bother */
- if (PTR_ERR(trans) == -ENOENT)
- return 0;
- return PTR_ERR(trans);
- }
- return btrfs_commit_transaction(trans, root);
+ return commit_current_or_new_trans(fs_info, 1);
}
static int btrfs_unfreeze(struct super_block *sb)
--
2.2.2
--
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