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Commit db1327b1 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: report shared extent mappings to userspace correctly 



Report shared extents through the iomap interface so that FIEMAP flags
shared blocks accurately.  Have xfs_vm_bmap return zero for reflinked
files because the bmap-based swap code requires static block mappings,
which is incompatible with copy on write.

NOTE: Existing userspace bmap users such as lilo will have the same
problem with reflink files.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 43caeb18

fs/xfs/xfs_aops.c

+11 −0
Original line number Diff line number Diff line
@@ -1508,6 +1508,17 @@ xfs_vm_bmap( 


	trace_xfs_vm_bmap(XFS_I(inode));

	xfs_ilock(ip, XFS_IOLOCK_SHARED);



	/*

	 * The swap code (ab-)uses ->bmap to get a block mapping and then

	 * bypasseѕ the file system for actual I/O.  We really can't allow

	 * that on reflinks inodes, so we have to skip out here.  And yes,

	 * 0 is the magic code for a bmap error..

	 */

	if (xfs_is_reflink_inode(ip)) {

		xfs_iunlock(ip, XFS_IOLOCK_SHARED);

		return 0;

	}

	filemap_write_and_wait(mapping);

	xfs_iunlock(ip, XFS_IOLOCK_SHARED);

	return generic_block_bmap(mapping, block, xfs_get_blocks);

fs/xfs/xfs_iomap.c

+11 −1
Original line number Diff line number Diff line
@@ -961,6 +961,7 @@ xfs_file_iomap_begin( 
	struct xfs_mount	*mp = ip->i_mount;

	struct xfs_bmbt_irec	imap;

	xfs_fileoff_t		offset_fsb, end_fsb;

	bool			shared, trimmed;

	int			nimaps = 1, error = 0;

	unsigned		lockmode;
@@ -989,7 +990,14 @@ xfs_file_iomap_begin( 
	end_fsb = XFS_B_TO_FSB(mp, offset + length);



	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,

			       &nimaps, XFS_BMAPI_ENTIRE);

			       &nimaps, 0);

	if (error) {

		xfs_iunlock(ip, lockmode);

		return error;

	}



	/* Trim the mapping to the nearest shared extent boundary. */

	error = xfs_reflink_trim_around_shared(ip, &imap, &shared, &trimmed);

	if (error) {

		xfs_iunlock(ip, lockmode);

		return error;
@@ -1028,6 +1036,8 @@ xfs_file_iomap_begin( 
	}



	xfs_bmbt_to_iomap(ip, iomap, &imap);

	if (shared)

		iomap->flags |= IOMAP_F_SHARED;

	return 0;

}