Commit 84d69619 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: preallocate blocks for worst-case btree expansion 



To gracefully handle the situation where a CoW operation turns a
single refcount extent into a lot of tiny ones and then run out of
space when a tree split has to happen, use the per-AG reserved block
pool to pre-allocate all the space we'll ever need for a maximal
btree.  For a 4K block size, this only costs an overhead of 0.3% of
available disk space.

When reflink is enabled, we have an unfortunate problem with rmap --
since we can share a block billions of times, this means that the
reverse mapping btree can expand basically infinitely.  When an AG is
so full that there are no free blocks with which to expand the rmapbt,
the filesystem will shut down hard.

This is rather annoying to the user, so use the AG reservation code to
reserve a "reasonable" amount of space for rmap.  We'll prevent
reflinks and CoW operations if we think we're getting close to
exhausting an AG's free space rather than shutting down, but this
permanent reservation should be enough for "most" users.  Hopefully.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
[hch@lst.de: ensure that we invalidate the freed btree buffer]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent f7ca3522

fs/xfs/libxfs/xfs_ag_resv.c

+11 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include "xfs_trans_space.h"

#include "xfs_rmap_btree.h"

#include "xfs_btree.h"

#include "xfs_refcount_btree.h"



/*

 * Per-AG Block Reservations
@@ -228,6 +229,11 @@ xfs_ag_resv_init( 
	if (pag->pag_meta_resv.ar_asked == 0) {

		ask = used = 0;



		error = xfs_refcountbt_calc_reserves(pag->pag_mount,

				pag->pag_agno, &ask, &used);

		if (error)

			goto out;



		error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,

				ask, used);

		if (error)
@@ -238,6 +244,11 @@ xfs_ag_resv_init( 
	if (pag->pag_agfl_resv.ar_asked == 0) {

		ask = used = 0;



		error = xfs_rmapbt_calc_reserves(pag->pag_mount, pag->pag_agno,

				&ask, &used);

		if (error)

			goto out;



		error = __xfs_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);

		if (error)

			goto out;

fs/xfs/libxfs/xfs_refcount_btree.c

+65 −3
Original line number Diff line number Diff line
@@ -79,6 +79,8 @@ xfs_refcountbt_alloc_block( 
	struct xfs_alloc_arg	args;		/* block allocation args */

	int			error;		/* error return value */



	XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);



	memset(&args, 0, sizeof(args));

	args.tp = cur->bc_tp;

	args.mp = cur->bc_mp;
@@ -88,6 +90,7 @@ xfs_refcountbt_alloc_block( 
	args.firstblock = args.fsbno;

	xfs_rmap_ag_owner(&args.oinfo, XFS_RMAP_OWN_REFC);

	args.minlen = args.maxlen = args.prod = 1;

	args.resv = XFS_AG_RESV_METADATA;



	error = xfs_alloc_vextent(&args);

	if (error)
@@ -125,16 +128,19 @@ xfs_refcountbt_free_block( 
	struct xfs_agf		*agf = XFS_BUF_TO_AGF(agbp);

	xfs_fsblock_t		fsbno = XFS_DADDR_TO_FSB(mp, XFS_BUF_ADDR(bp));

	struct xfs_owner_info	oinfo;

	int			error;



	trace_xfs_refcountbt_free_block(cur->bc_mp, cur->bc_private.a.agno,

			XFS_FSB_TO_AGBNO(cur->bc_mp, fsbno), 1);

	xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_REFC);

	be32_add_cpu(&agf->agf_refcount_blocks, -1);

	xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_REFCOUNT_BLOCKS);

	xfs_bmap_add_free(mp, cur->bc_private.a.dfops, fsbno, 1,

			&oinfo);

	error = xfs_free_extent(cur->bc_tp, fsbno, 1, &oinfo,

			XFS_AG_RESV_METADATA);

	if (error)

		return error;



	return 0;

	return error;

}



STATIC int
@@ -387,3 +393,59 @@ xfs_refcountbt_compute_maxlevels( 
	mp->m_refc_maxlevels = xfs_btree_compute_maxlevels(mp,

			mp->m_refc_mnr, mp->m_sb.sb_agblocks);

}



/* Calculate the refcount btree size for some records. */

xfs_extlen_t

xfs_refcountbt_calc_size(

	struct xfs_mount	*mp,

	unsigned long long	len)

{

	return xfs_btree_calc_size(mp, mp->m_refc_mnr, len);

}



/*

 * Calculate the maximum refcount btree size.

 */

xfs_extlen_t

xfs_refcountbt_max_size(

	struct xfs_mount	*mp)

{

	/* Bail out if we're uninitialized, which can happen in mkfs. */

	if (mp->m_refc_mxr[0] == 0)

		return 0;



	return xfs_refcountbt_calc_size(mp, mp->m_sb.sb_agblocks);

}



/*

 * Figure out how many blocks to reserve and how many are used by this btree.

 */

int

xfs_refcountbt_calc_reserves(

	struct xfs_mount	*mp,

	xfs_agnumber_t		agno,

	xfs_extlen_t		*ask,

	xfs_extlen_t		*used)

{

	struct xfs_buf		*agbp;

	struct xfs_agf		*agf;

	xfs_extlen_t		tree_len;

	int			error;



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

		return 0;



	*ask += xfs_refcountbt_max_size(mp);



	error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);

	if (error)

		return error;



	agf = XFS_BUF_TO_AGF(agbp);

	tree_len = be32_to_cpu(agf->agf_refcount_blocks);

	xfs_buf_relse(agbp);



	*used += tree_len;



	return error;

}

fs/xfs/libxfs/xfs_refcount_btree.h

+7 −0
Original line number Diff line number Diff line
@@ -64,4 +64,11 @@ extern int xfs_refcountbt_maxrecs(struct xfs_mount *mp, int blocklen, 
		bool leaf);

extern void xfs_refcountbt_compute_maxlevels(struct xfs_mount *mp);



extern xfs_extlen_t xfs_refcountbt_calc_size(struct xfs_mount *mp,

		unsigned long long len);

extern xfs_extlen_t xfs_refcountbt_max_size(struct xfs_mount *mp);



extern int xfs_refcountbt_calc_reserves(struct xfs_mount *mp,

		xfs_agnumber_t agno, xfs_extlen_t *ask, xfs_extlen_t *used);



#endif	/* __XFS_REFCOUNT_BTREE_H__ */

fs/xfs/libxfs/xfs_rmap_btree.c

+60 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ 
#include "xfs_cksum.h"

#include "xfs_error.h"

#include "xfs_extent_busy.h"

#include "xfs_ag_resv.h"



/*

 * Reverse map btree.
@@ -533,3 +534,62 @@ xfs_rmapbt_compute_maxlevels( 
		mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels(mp,

				mp->m_rmap_mnr, mp->m_sb.sb_agblocks);

}



/* Calculate the refcount btree size for some records. */

xfs_extlen_t

xfs_rmapbt_calc_size(

	struct xfs_mount	*mp,

	unsigned long long	len)

{

	return xfs_btree_calc_size(mp, mp->m_rmap_mnr, len);

}



/*

 * Calculate the maximum refcount btree size.

 */

xfs_extlen_t

xfs_rmapbt_max_size(

	struct xfs_mount	*mp)

{

	/* Bail out if we're uninitialized, which can happen in mkfs. */

	if (mp->m_rmap_mxr[0] == 0)

		return 0;



	return xfs_rmapbt_calc_size(mp, mp->m_sb.sb_agblocks);

}



/*

 * Figure out how many blocks to reserve and how many are used by this btree.

 */

int

xfs_rmapbt_calc_reserves(

	struct xfs_mount	*mp,

	xfs_agnumber_t		agno,

	xfs_extlen_t		*ask,

	xfs_extlen_t		*used)

{

	struct xfs_buf		*agbp;

	struct xfs_agf		*agf;

	xfs_extlen_t		pool_len;

	xfs_extlen_t		tree_len;

	int			error;



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

		return 0;



	/* Reserve 1% of the AG or enough for 1 block per record. */

	pool_len = max(mp->m_sb.sb_agblocks / 100, xfs_rmapbt_max_size(mp));

	*ask += pool_len;



	error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);

	if (error)

		return error;



	agf = XFS_BUF_TO_AGF(agbp);

	tree_len = be32_to_cpu(agf->agf_rmap_blocks);

	xfs_buf_relse(agbp);



	*used += tree_len;



	return error;

}

fs/xfs/libxfs/xfs_rmap_btree.h

+7 −0
Original line number Diff line number Diff line
@@ -58,4 +58,11 @@ struct xfs_btree_cur *xfs_rmapbt_init_cursor(struct xfs_mount *mp, 
int xfs_rmapbt_maxrecs(struct xfs_mount *mp, int blocklen, int leaf);

extern void xfs_rmapbt_compute_maxlevels(struct xfs_mount *mp);



extern xfs_extlen_t xfs_rmapbt_calc_size(struct xfs_mount *mp,

		unsigned long long len);

extern xfs_extlen_t xfs_rmapbt_max_size(struct xfs_mount *mp);



extern int xfs_rmapbt_calc_reserves(struct xfs_mount *mp,

		xfs_agnumber_t agno, xfs_extlen_t *ask, xfs_extlen_t *used);



#endif	/* __XFS_RMAP_BTREE_H__ */

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