Commit b7a7a834 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: make reflinks respect O_SYNC O_DSYNC and S_SYNC flags 

If we reflink to or from a file opened with O_SYNC/O_DSYNC or to/from a
file that has the S_SYNC attribute set, we totally ignore that and do not
durably persist the reflink changes. Since a reflink can change the data
readable from a file (and mtime/ctime, or a file size), it makes sense to
durably persist (fsync) the source and destination files/ranges.

This was previously discussed at:

https://lore.kernel.org/linux-btrfs/20200903035225.GJ6090@magnolia/



The recently introduced test case generic/628, from fstests, exercises
these scenarios and currently fails without this change.

So make sure we fsync the source and destination files/ranges when either
of them was opened with O_SYNC/O_DSYNC or has the S_SYNC attribute set,
just like XFS already does.

Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent bb05b298

fs/btrfs/reflink.c

+25 −0
Original line number Diff line number Diff line
@@ -834,6 +834,16 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in, 
					    len, remap_flags);

}



static bool file_sync_write(const struct file *file)

{

	if (file->f_flags & (__O_SYNC | O_DSYNC))

		return true;

	if (IS_SYNC(file_inode(file)))

		return true;



	return false;

}



loff_t btrfs_remap_file_range(struct file *src_file, loff_t off,

		struct file *dst_file, loff_t destoff, loff_t len,

		unsigned int remap_flags)
@@ -871,5 +881,20 @@ loff_t btrfs_remap_file_range(struct file *src_file, loff_t off, 
		unlock_two_nondirectories(src_inode, dst_inode);

	}



	/*

	 * If either the source or the destination file was opened with O_SYNC,

	 * O_DSYNC or has the S_SYNC attribute, fsync both the destination and

	 * source files/ranges, so that after a successful return (0) followed

	 * by a power failure results in the reflinked data to be readable from

	 * both files/ranges.

	 */

	if (ret == 0 && len > 0 &&

	    (file_sync_write(src_file) || file_sync_write(dst_file))) {

		ret = btrfs_sync_file(src_file, off, off + len - 1, 0);

		if (ret == 0)

			ret = btrfs_sync_file(dst_file, destoff,

					      destoff + len - 1, 0);

	}



	return ret < 0 ? ret : len;

}