ext4: online defrag not supported with DAX

Online defrag operations for ext4 are hard coded to use the page cache.
See ext4_ioctl() -> ext4_move_extents() -> move_extent_per_page()

When combined with DAX I/O, which circumvents the page cache, this can
result in data corruption.  This was observed with xfstests ext4/307 and
ext4/308.

Fix this by only allowing online defrag for non-DAX files.

Signed-off-by: Ross Zwisler <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a99b010e2194e32adafcef2f8b721d208f64d0c6..eae5917c534e51b2fddf7bcebfa1293ed76a2841 100644 (file)
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -583,6 +583,11 @@ group_extend_out:
                                 "Online defrag not supported with bigalloc");
                        err = -EOPNOTSUPP;
                        goto mext_out;
+               } else if (IS_DAX(inode)) {
+                       ext4_msg(sb, KERN_ERR,
+                                "Online defrag not supported with DAX");
+                       err = -EOPNOTSUPP;
+                       goto mext_out;
                }
 
                err = mnt_want_write_file(filp);