fs: check for writeback errors after syncing out buffers in generic_file_fsync

ext2 currently does a test+clear of the AS_EIO flag, which is
is problematic for some coming changes.

What we really need to do instead is call filemap_check_errors
in __generic_file_fsync after syncing out the buffers. That
will be sufficient for this case, and help other callers detect
these errors properly as well.

With that, we don't need to twiddle it in ext2.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>

fs/ext2/file.c

@@ -174,15 +174,12 @@ int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	int ret;
 	struct super_block *sb = file->f_mapping->host->i_sb;
-	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 
 	ret = generic_file_fsync(file, start, end, datasync);
-	if (ret == -EIO || test_and_clear_bit(AS_EIO, &mapping->flags)) {
+	if (ret == -EIO)
 		/* We don't really know where the IO error happened... */
 		ext2_error(sb, __func__,
 			   "detected IO error when writing metadata buffers");
-		ret = -EIO;
-	}
 	return ret;
 }
 

fs/libfs.c

@@ -991,7 +991,9 @@ int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
 
 out:
 	inode_unlock(inode);
-	return ret;
+	/* must call this unconditionally as it clears AS_* error flags */
+	err = filemap_check_errors(inode->i_mapping);
+	return ret ? ret : err;
 }
 EXPORT_SYMBOL(__generic_file_fsync);