On Mon, 2016-05-16 at 17:22 +0200, Jan Kara wrote:

On Thu 12-05-16 12:45:22, Ross Zwisler wrote:

quoted

On Wed, May 11, 2016 at 11:58:49AM +0200, Jan Kara wrote:

quoted

Currently ext2 zeroes any data blocks allocated for DAX inode
however it
still returns them as BH_New. Thus DAX code zeroes them again in
dax_insert_mapping() which can possibly overwrite the data that
has been
already stored to those blocks by a racing dax_io(). Avoid
marking
pre-zeroed buffers as new.

Reviewed-by: Ross Zwisler <redacted>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext2/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 6bd58e6ff038..1f07b758b968 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c

@@ -745,11 +745,11 @@ static int ext2_get_blocks(struct inode

*inode,
 			mutex_unlock(&ei->truncate_mutex);
 			goto cleanup;
 		}
-	}
+	} else
+		set_buffer_new(bh_result);
 
 	ext2_splice_branch(inode, iblock, partial,
indirect_blks, count);
 	mutex_unlock(&ei->truncate_mutex);
-	set_buffer_new(bh_result);
 got_it:
 	map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-
1].key));
 	if (count > blocks_to_boundary)
-- 
2.6.6

Interestingly this change is causing a bunch of xfstests
regressions for me
with ext2 + DAX.  All of these tests pass without this one change.

Good catch. Attached patch fixes this issue for me. Preferably it
should be
merged before the above ext2 change.

								Honza

Hey Jan,

In my patch 3 of the error handling series, I have:

-               err = dax_clear_sectors(inode->i_sb->s_bdev,
-                               le32_to_cpu(chain[depth-1].key) <<
-                               (inode->i_blkbits - 9),
-                               1 << inode->i_blkbits);
+               err = sb_issue_zeroout(inode->i_sb,
+                               le32_to_cpu(chain[depth-1].key), 1, GFP_NOFS);

Does this mean I have to change to send the sb_issue_zeroout for
'count' blocks.. i.e.

-               err = dax_clear_sectors(inode->i_sb->s_bdev,
-                               le32_to_cpu(chain[depth-1].key) <<
-                               (inode->i_blkbits - 9),
-                               1 << inode->i_blkbits);
+               err = sb_issue_zeroout(inode->i_sb,
+                               le32_to_cpu(chain[depth-1].key), count, GFP_NOFS);

If so, I'll update my series tomorrow to include in both of these changes.

Thanks,
	-Vishal