[PATCH 2/3] vfs: Add a super block operation to check for writeback errors

[Vivek Goyal <vgoyal@redhat.com>]

Right now we check for errors on super block in syncfs().

ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);

overlayfs does not update sb->s_wb_err and it is tracked on upper filesystem.
So provide a superblock operation to check errors so that filesystem
can provide override generic method and provide its own method to
check for writeback errors.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/sync.c          | 5 ++++-
 include/linux/fs.h | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/sync.c b/fs/sync.c
index b5fb83a734cd..57e43a16dfca 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -176,7 +176,10 @@ SYSCALL_DEFINE1(syncfs, int, fd)
 	ret = sync_filesystem(sb);
 	up_read(&sb->s_umount);
 
-	ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
+	if (sb->s_op->errseq_check_advance)
+		ret2 = sb->s_op->errseq_check_advance(sb, f.file);
+	else
+		ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
 
 	fdput(f);
 	return ret ? ret : ret2;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8667d0cdc71e..4297b6127adf 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1965,6 +1965,7 @@ struct super_operations {
 				  struct shrink_control *);
 	long (*free_cached_objects)(struct super_block *,
 				    struct shrink_control *);
+	int (*errseq_check_advance)(struct super_block *, struct file *);
 };
 
 /*
-- 
2.25.4