On Thu, 2017-06-29 at 07:17 -0700, Christoph Hellwig wrote:

On Thu, Jun 29, 2017 at 09:19:54AM -0400, jlayton@kernel.org wrote:

quoted

From: Jeff Layton <redacted>

Just check and advance the errseq_t in the file before returning.
Internal callers of filemap_* functions are left as-is.

Signed-off-by: Jeff Layton <redacted>
---
 fs/btrfs/file.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index da1096eb1a40..1f57e1a523d9 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c

@@ -2011,7 +2011,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
 	struct btrfs_log_ctx ctx;
-	int ret = 0;
+	int ret = 0, err;
 	bool full_sync = 0;
 	u64 len;
 

@@ -2030,7 +2030,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	 */
 	ret = start_ordered_ops(inode, start, end);
 	if (ret)
-		return ret;
+		goto out;
 
 	inode_lock(inode);
 	atomic_inc(&root->log_batch);

@@ -2227,6 +2227,9 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 		ret = btrfs_end_transaction(trans);
 	}
 out:
+	err = file_check_and_advance_wb_err(file);
+	if (!ret)
+		ret = err;
 	return ret > 0 ? -EIO : ret;

This means that we'll lose the exact error returned from
start_ordered_ops.  Beyond that I can't really provide good feedback
as the btrfs fsync code looks so much different from all the other
fs fsync code..

Well, no...we'll keep the error from start_ordered_ops if there was one.
 We just advance the cursor past any stored error in that case without
returning it.

I have another fix for this patch too: there's a call to
filemap_check_errors in this function that I think should probably use
filemap_check_wb_err instead. Fixed in my tree.

I do agree though that while this works in my testing I'd like the btrfs
guys to ACK this as I don't fully grok the btrfs fsync code at all.
-- 
Jeff Layton [off-list ref]