Btrfs: fix skipped error handle when log sync failed

It is possible that many tasks sync the log tree at the same time, but
only one task can do the sync work, the others will wait for it. But those
wait tasks didn't get the result of the log sync, and returned 0 when they
ended the wait. It caused those tasks skipped the error handle, and the
serious problem was they told the users the file sync succeeded but in
fact they failed.

This patch fixes this problem by introducing a log context structure,
we insert it into the a global list. When the sync fails, we will set
the error number of every log context in the list, then the waiting tasks
get the error number of the log context and handle the error if need.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.h b/fs/btrfs/tree-log.h
index 1d4ae0d15a70..59c1edb31d19 100644
--- a/fs/btrfs/tree-log.h
+++ b/fs/btrfs/tree-log.h
@@ -22,14 +22,26 @@
 /* return value for btrfs_log_dentry_safe that means we don't need to log it at all */
 #define BTRFS_NO_LOG_SYNC 256
 
+struct btrfs_log_ctx {
+        int log_ret;
+        struct list_head list;
+};
+
+static inline void btrfs_init_log_ctx(struct btrfs_log_ctx *ctx)
+{
+        ctx->log_ret = 0;
+        INIT_LIST_HEAD(&ctx->list);
+}
+
 int btrfs_sync_log(struct btrfs_trans_handle *trans,
-                   struct btrfs_root *root);
+                   struct btrfs_root *root, struct btrfs_log_ctx *ctx);
 int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root);
 int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,
                              struct btrfs_fs_info *fs_info);
 int btrfs_recover_log_trees(struct btrfs_root *tree_root);
 int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
-                          struct btrfs_root *root, struct dentry *dentry);
+                          struct btrfs_root *root, struct dentry *dentry,
+                          struct btrfs_log_ctx *ctx);
 int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root,
                                  const char *name, int name_len,