Messages in this thread Patch in this message | | | From | Ross Zwisler <> | Subject | [PATCH v4 3/5] ext4: Online defrag not supported with DAX | Date | Mon, 22 Feb 2016 11:59:20 -0700 |
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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 <ross.zwisler@linux.intel.com> Reviewed-by: Jan Kara <jack@suse.cz> --- fs/ext4/ioctl.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index a99b010..eae5917 100644 --- 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); -- 2.5.0
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