linux-ext4 - [PATCH] mm: have filemap_check_and_advance_wb_err clear AS_EIO/AS

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Date:   Fri, 22 Sep 2017 09:33:31 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     Eryu Guan <eguan@...hat.com>, Jan Kara <jack@...e.cz>,
        linux-ext4@...r.kernel.org
Subject: [PATCH] mm: have filemap_check_and_advance_wb_err clear AS_EIO/AS_ENOSPC

From: Jeff Layton <jlayton@...hat.com>

Eryu noticed that he could sometimes get a leftover error reported when
it shouldn't be on fsync with ext2 and non-journalled ext4. The problem
is that writeback_single_inode still uses filemap_fdatawait. That picks
up a previously set AS_EIO flag, which would ordinarily have been
cleared before.

Since we're mostly using this function as a replacement for
filemap_check_errors, have filemap_check_and_advance_wb_err clear AS_EIO
and AS_ENOSPC when reporting an error. That should allow the new
function to better emulate the behavior of the old with respect to these
flags.

Reported-by: Eryu Guan <eguan@...hat.com>
Signed-off-by: Jeff Layton <jlayton@...hat.com>
---
 mm/filemap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 870971e20967..404722ea0fdd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -620,6 +620,14 @@ int file_check_and_advance_wb_err(struct file *file)
 		trace_file_check_and_advance_wb_err(file, old);
 		spin_unlock(&file->f_lock);
 	}
+
+	/*
+	 * We're mostly using this function as a drop in replacement for
+	 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
+	 * that the legacy code would have had on these flags.
+	 */
+	clear_bit(AS_EIO, &mapping->flags);
+	clear_bit(AS_ENOSPC, &mapping->flags);
 	return err;
 }
 EXPORT_SYMBOL(file_check_and_advance_wb_err);
-- 
2.13.5