The patch titled
Subject: ext4: online defrag not supported with DAX
has been added to the -mm tree. Its filename is
ext4-online-defrag-not-supported-with-dax.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ext4-online-defrag-not-supported-with-dax.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ext4-online-defrag-not-supported-with-dax.patch
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------------------------------------------------------
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Subject: 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 <ross.zwisler@xxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ext4/ioctl.c | 5 +++++
1 file changed, 5 insertions(+)
diff -puN fs/ext4/ioctl.c~ext4-online-defrag-not-supported-with-dax fs/ext4/ioctl.c
--- a/fs/ext4/ioctl.c~ext4-online-defrag-not-supported-with-dax
+++ a/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);
_
Patches currently in -mm which might be from ross.zwisler@xxxxxxxxxxxxxxx are
ext2-ext4-only-set-s_dax-for-regular-inodes.patch
ext4-online-defrag-not-supported-with-dax.patch
dax-give-dax-clearing-code-correct-bdev.patch
dax-move-writeback-calls-into-the-filesystems.patch
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