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Commit 73f34a5e authored by Ross Zwisler's avatar Ross Zwisler Committed by Linus Torvalds
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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: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0a6cf913

fs/ext4/ioctl.c

+5 −0
Original line number Diff line number Diff line
@@ -583,6 +583,11 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 
				 "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);