Commit 6fa164b8 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: don't allow reflink when the AG is low on space 



If the AG free space is down to the reserves, refuse to reflink our
way out of space.  Hopefully userspace will make a real copy and/or go
elsewhere.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 84d69619

fs/xfs/xfs_reflink.c

+35 −0
Original line number Diff line number Diff line
@@ -54,6 +54,8 @@ 
#include "xfs_reflink.h"

#include "xfs_iomap.h"

#include "xfs_rmap_btree.h"

#include "xfs_sb.h"

#include "xfs_ag_resv.h"



/*

 * Copy on Write of Shared Blocks
@@ -977,6 +979,31 @@ xfs_reflink_update_dest( 
	return error;

}



/*

 * Do we have enough reserve in this AG to handle a reflink?  The refcount

 * btree already reserved all the space it needs, but the rmap btree can grow

 * infinitely, so we won't allow more reflinks when the AG is down to the

 * btree reserves.

 */

static int

xfs_reflink_ag_has_free_space(

	struct xfs_mount	*mp,

	xfs_agnumber_t		agno)

{

	struct xfs_perag	*pag;

	int			error = 0;



	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))

		return 0;



	pag = xfs_perag_get(mp, agno);

	if (xfs_ag_resv_critical(pag, XFS_AG_RESV_AGFL) ||

	    xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))

		error = -ENOSPC;

	xfs_perag_put(pag);

	return error;

}



/*

 * Unmap a range of blocks from a file, then map other blocks into the hole.

 * The range to unmap is (destoff : destoff + srcioff + irec->br_blockcount).
@@ -1009,6 +1036,14 @@ xfs_reflink_remap_extent( 
			irec->br_startblock != DELAYSTARTBLOCK &&

			!ISUNWRITTEN(irec));



	/* No reflinking if we're low on space */

	if (real_extent) {

		error = xfs_reflink_ag_has_free_space(mp,

				XFS_FSB_TO_AGNO(mp, irec->br_startblock));

		if (error)

			goto out;

	}



	/* Start a rolling transaction to switch the mappings */

	resblks = XFS_EXTENTADD_SPACE_RES(ip->i_mount, XFS_DATA_FORK);

	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);