fs/xfs/xfs_fsops.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_btree.h"
#include "xfs_error.h"
#include "xfs_alloc.h"
#include "xfs_ialloc.h"
#include "xfs_fsops.h"
#include "xfs_itable.h"
#include "xfs_trans_space.h"
#include "xfs_rtalloc.h"
#include "xfs_filestream.h"
#include "xfs_trace.h"

/*
 * File system operations
 */

int
xfs_fs_geometry(
	xfs_mount_t		*mp,
	xfs_fsop_geom_t		*geo,
	int			new_version)
{

	memset(geo, 0, sizeof(*geo));

	geo->blocksize = mp->m_sb.sb_blocksize;
	geo->rtextsize = mp->m_sb.sb_rextsize;
	geo->agblocks = mp->m_sb.sb_agblocks;
	geo->agcount = mp->m_sb.sb_agcount;
	geo->logblocks = mp->m_sb.sb_logblocks;
	geo->sectsize = mp->m_sb.sb_sectsize;
	geo->inodesize = mp->m_sb.sb_inodesize;
	geo->imaxpct = mp->m_sb.sb_imax_pct;
	geo->datablocks = mp->m_sb.sb_dblocks;
	geo->rtblocks = mp->m_sb.sb_rblocks;
	geo->rtextents = mp->m_sb.sb_rextents;
	geo->logstart = mp->m_sb.sb_logstart;
	ASSERT(sizeof(geo->uuid)==sizeof(mp->m_sb.sb_uuid));
	memcpy(geo->uuid, &mp->m_sb.sb_uuid, sizeof(mp->m_sb.sb_uuid));
	if (new_version >= 2) {
		geo->sunit = mp->m_sb.sb_unit;
		geo->swidth = mp->m_sb.sb_width;
	}
	if (new_version >= 3) {
		geo->version = XFS_FSOP_GEOM_VERSION;
		geo->flags =
			(xfs_sb_version_hasattr(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_ATTR : 0) |
			(xfs_sb_version_hasnlink(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_NLINK : 0) |
			(xfs_sb_version_hasquota(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_QUOTA : 0) |
			(xfs_sb_version_hasalign(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_IALIGN : 0) |
			(xfs_sb_version_hasdalign(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_DALIGN : 0) |
			(xfs_sb_version_hasshared(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_SHARED : 0) |
			(xfs_sb_version_hasextflgbit(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_EXTFLG : 0) |
			(xfs_sb_version_hasdirv2(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_DIRV2 : 0) |
			(xfs_sb_version_hassector(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_SECTOR : 0) |
			(xfs_sb_version_hasasciici(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_DIRV2CI : 0) |
			(xfs_sb_version_haslazysbcount(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_LAZYSB : 0) |
			(xfs_sb_version_hasattr2(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_ATTR2 : 0) |
			(xfs_sb_version_hasprojid32bit(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_PROJID32 : 0);
		geo->logsectsize = xfs_sb_version_hassector(&mp->m_sb) ?
				mp->m_sb.sb_logsectsize : BBSIZE;
		geo->rtsectsize = mp->m_sb.sb_blocksize;
		geo->dirblocksize = mp->m_dirblksize;
	}
	if (new_version >= 4) {
		geo->flags |=
			(xfs_sb_version_haslogv2(&mp->m_sb) ?
				XFS_FSOP_GEOM_FLAGS_LOGV2 : 0);
		geo->logsunit = mp->m_sb.sb_logsunit;
	}
	return 0;
}

static struct xfs_buf *
xfs_growfs_get_hdr_buf(
	struct xfs_mount	*mp,
	xfs_daddr_t		blkno,
	size_t			numblks,
	int			flags,
	const struct xfs_buf_ops *ops)
{
	struct xfs_buf		*bp;

	bp = xfs_buf_get_uncached(mp->m_ddev_targp, numblks, flags);
	if (!bp)
		return NULL;

	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
	bp->b_bn = blkno;
	bp->b_maps[0].bm_bn = blkno;
	bp->b_ops = ops;

	return bp;
}

static int
xfs_growfs_data_private(
	xfs_mount_t		*mp,		/* mount point for filesystem */
	xfs_growfs_data_t	*in)		/* growfs data input struct */
{
	xfs_agf_t		*agf;
	struct xfs_agfl		*agfl;
	xfs_agi_t		*agi;
	xfs_agnumber_t		agno;
	xfs_extlen_t		agsize;
	xfs_extlen_t		tmpsize;
	xfs_alloc_rec_t		*arec;
	xfs_buf_t		*bp;
	int			bucket;
	int			dpct;
	int			error;
	xfs_agnumber_t		nagcount;
	xfs_agnumber_t		nagimax = 0;
	xfs_rfsblock_t		nb, nb_mod;
	xfs_rfsblock_t		new;
	xfs_rfsblock_t		nfree;
	xfs_agnumber_t		oagcount;
	int			pct;
	xfs_trans_t		*tp;

	nb = in->newblocks;
	pct = in->imaxpct;
	if (nb < mp->m_sb.sb_dblocks || pct < 0 || pct > 100)
		return XFS_ERROR(EINVAL);
	if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
		return error;
	dpct = pct - mp->m_sb.sb_imax_pct;
	bp = xfs_buf_read_uncached(mp->m_ddev_targp,
				XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
				XFS_FSS_TO_BB(mp, 1), 0, NULL);
	if (!bp)
		return EIO;
	if (bp->b_error) {
		int	error = bp->b_error;
		xfs_buf_relse(bp);
		return error;
	}
	xfs_buf_relse(bp);

	new = nb;	/* use new as a temporary here */
	nb_mod = do_div(new, mp->m_sb.sb_agblocks);
	nagcount = new + (nb_mod != 0);
	if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) {
		nagcount--;
		nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks;
		if (nb < mp->m_sb.sb_dblocks)
			return XFS_ERROR(EINVAL);
	}
	new = nb - mp->m_sb.sb_dblocks;
	oagcount = mp->m_sb.sb_agcount;

	/* allocate the new per-ag structures */
	if (nagcount > oagcount) {
		error = xfs_initialize_perag(mp, nagcount, &nagimax);
		if (error)
			return error;
	}

	tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFS);
	tp->t_flags |= XFS_TRANS_RESERVE;
	if ((error = xfs_trans_reserve(tp, XFS_GROWFS_SPACE_RES(mp),
			XFS_GROWDATA_LOG_RES(mp), 0, 0, 0))) {
		xfs_trans_cancel(tp, 0);
		return error;
	}

	/*
	 * Write new AG headers to disk. Non-transactional, but written
	 * synchronously so they are completed prior to the growfs transaction
	 * being logged.
	 */
	nfree = 0;
	for (agno = nagcount - 1; agno >= oagcount; agno--, new -= agsize) {
		/*
		 * AG freespace header block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
				XFS_FSS_TO_BB(mp, 1), 0,
				&xfs_agf_buf_ops);
		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		agf = XFS_BUF_TO_AGF(bp);
		agf->agf_magicnum = cpu_to_be32(XFS_AGF_MAGIC);
		agf->agf_versionnum = cpu_to_be32(XFS_AGF_VERSION);
		agf->agf_seqno = cpu_to_be32(agno);
		if (agno == nagcount - 1)
			agsize =
				nb -
				(agno * (xfs_rfsblock_t)mp->m_sb.sb_agblocks);
		else
			agsize = mp->m_sb.sb_agblocks;
		agf->agf_length = cpu_to_be32(agsize);
		agf->agf_roots[XFS_BTNUM_BNOi] = cpu_to_be32(XFS_BNO_BLOCK(mp));
		agf->agf_roots[XFS_BTNUM_CNTi] = cpu_to_be32(XFS_CNT_BLOCK(mp));
		agf->agf_levels[XFS_BTNUM_BNOi] = cpu_to_be32(1);
		agf->agf_levels[XFS_BTNUM_CNTi] = cpu_to_be32(1);
		agf->agf_flfirst = 0;
		agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
		agf->agf_flcount = 0;
		tmpsize = agsize - XFS_PREALLOC_BLOCKS(mp);
		agf->agf_freeblks = cpu_to_be32(tmpsize);
		agf->agf_longest = cpu_to_be32(tmpsize);
		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;

		/*
		 * AG freelist header block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AG_DADDR(mp, agno, XFS_AGFL_DADDR(mp)),
				XFS_FSS_TO_BB(mp, 1), 0,
				&xfs_agfl_buf_ops);
		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		agfl = XFS_BUF_TO_AGFL(bp);
		for (bucket = 0; bucket < XFS_AGFL_SIZE(mp); bucket++)
			agfl->agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);

		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;

		/*
		 * AG inode header block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
				XFS_FSS_TO_BB(mp, 1), 0,
				&xfs_agi_buf_ops);
		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		agi = XFS_BUF_TO_AGI(bp);
		agi->agi_magicnum = cpu_to_be32(XFS_AGI_MAGIC);
		agi->agi_versionnum = cpu_to_be32(XFS_AGI_VERSION);
		agi->agi_seqno = cpu_to_be32(agno);
		agi->agi_length = cpu_to_be32(agsize);
		agi->agi_count = 0;
		agi->agi_root = cpu_to_be32(XFS_IBT_BLOCK(mp));
		agi->agi_level = cpu_to_be32(1);
		agi->agi_freecount = 0;
		agi->agi_newino = cpu_to_be32(NULLAGINO);
		agi->agi_dirino = cpu_to_be32(NULLAGINO);
		for (bucket = 0; bucket < XFS_AGI_UNLINKED_BUCKETS; bucket++)
			agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;

		/*
		 * BNO btree root block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AGB_TO_DADDR(mp, agno, XFS_BNO_BLOCK(mp)),
				BTOBB(mp->m_sb.sb_blocksize), 0,
				&xfs_allocbt_buf_ops);

		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		if (xfs_sb_version_hascrc(&mp->m_sb))
			xfs_btree_init_block(mp, bp, XFS_ABTB_CRC_MAGIC, 0, 1,
						agno, XFS_BTREE_CRC_BLOCKS);
		else
			xfs_btree_init_block(mp, bp, XFS_ABTB_MAGIC, 0, 1,
						agno, 0);

		arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
		arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
		arec->ar_blockcount = cpu_to_be32(
			agsize - be32_to_cpu(arec->ar_startblock));

		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;

		/*
		 * CNT btree root block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AGB_TO_DADDR(mp, agno, XFS_CNT_BLOCK(mp)),
				BTOBB(mp->m_sb.sb_blocksize), 0,
				&xfs_allocbt_buf_ops);
		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		if (xfs_sb_version_hascrc(&mp->m_sb))
			xfs_btree_init_block(mp, bp, XFS_ABTC_CRC_MAGIC, 0, 1,
						agno, XFS_BTREE_CRC_BLOCKS);
		else
			xfs_btree_init_block(mp, bp, XFS_ABTC_MAGIC, 0, 1,
						agno, 0);

		arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
		arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
		arec->ar_blockcount = cpu_to_be32(
			agsize - be32_to_cpu(arec->ar_startblock));
		nfree += be32_to_cpu(arec->ar_blockcount);

		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;

		/*
		 * INO btree root block
		 */
		bp = xfs_growfs_get_hdr_buf(mp,
				XFS_AGB_TO_DADDR(mp, agno, XFS_IBT_BLOCK(mp)),
				BTOBB(mp->m_sb.sb_blocksize), 0,
				&xfs_inobt_buf_ops);
		if (!bp) {
			error = ENOMEM;
			goto error0;
		}

		if (xfs_sb_version_hascrc(&mp->m_sb))
			xfs_btree_init_block(mp, bp, XFS_IBT_CRC_MAGIC, 0, 0,
						agno, XFS_BTREE_CRC_BLOCKS);
		else
			xfs_btree_init_block(mp, bp, XFS_IBT_MAGIC, 0, 0,
						agno, 0);

		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error)
			goto error0;
	}
	xfs_trans_agblocks_delta(tp, nfree);
	/*
	 * There are new blocks in the old last a.g.
	 */
	if (new) {
		/*
		 * Change the agi length.
		 */
		error = xfs_ialloc_read_agi(mp, tp, agno, &bp);
		if (error) {
			goto error0;
		}
		ASSERT(bp);
		agi = XFS_BUF_TO_AGI(bp);
		be32_add_cpu(&agi->agi_length, new);
		ASSERT(nagcount == oagcount ||
		       be32_to_cpu(agi->agi_length) == mp->m_sb.sb_agblocks);
		xfs_ialloc_log_agi(tp, bp, XFS_AGI_LENGTH);
		/*
		 * Change agf length.
		 */
		error = xfs_alloc_read_agf(mp, tp, agno, 0, &bp);
		if (error) {
			goto error0;
		}
		ASSERT(bp);
		agf = XFS_BUF_TO_AGF(bp);
		be32_add_cpu(&agf->agf_length, new);
		ASSERT(be32_to_cpu(agf->agf_length) ==
		       be32_to_cpu(agi->agi_length));

		xfs_alloc_log_agf(tp, bp, XFS_AGF_LENGTH);
		/*
		 * Free the new space.
		 */
		error = xfs_free_extent(tp, XFS_AGB_TO_FSB(mp, agno,
			be32_to_cpu(agf->agf_length) - new), new);
		if (error) {
			goto error0;
		}
	}

	/*
	 * Update changed superblock fields transactionally. These are not
	 * seen by the rest of the world until the transaction commit applies
	 * them atomically to the superblock.
	 */
	if (nagcount > oagcount)
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount);
	if (nb > mp->m_sb.sb_dblocks)
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS,
				 nb - mp->m_sb.sb_dblocks);
	if (nfree)
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, nfree);
	if (dpct)
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_IMAXPCT, dpct);
	error = xfs_trans_commit(tp, 0);
	if (error)
		return error;

	/* New allocation groups fully initialized, so update mount struct */
	if (nagimax)
		mp->m_maxagi = nagimax;
	if (mp->m_sb.sb_imax_pct) {
		__uint64_t icount = mp->m_sb.sb_dblocks * mp->m_sb.sb_imax_pct;
		do_div(icount, 100);
		mp->m_maxicount = icount << mp->m_sb.sb_inopblog;
	} else
		mp->m_maxicount = 0;
	xfs_set_low_space_thresholds(mp);

	/* update secondary superblocks. */
	for (agno = 1; agno < nagcount; agno++) {
		error = 0;
		/*
		 * new secondary superblocks need to be zeroed, not read from
		 * disk as the contents of the new area we are growing into is
		 * completely unknown.
		 */
		if (agno < oagcount) {
			error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
				  XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
				  XFS_FSS_TO_BB(mp, 1), 0, &bp,
				  &xfs_sb_buf_ops);
		} else {
			bp = xfs_trans_get_buf(NULL, mp->m_ddev_targp,
				  XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
				  XFS_FSS_TO_BB(mp, 1), 0);
			if (bp) {
				bp->b_ops = &xfs_sb_buf_ops;
				xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
			} else
				error = ENOMEM;
		}

		if (error) {
			xfs_warn(mp,
		"error %d reading secondary superblock for ag %d",
				error, agno);
			break;
		}
		xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, XFS_SB_ALL_BITS);

		/*
		 * If we get an error writing out the alternate superblocks,
		 * just issue a warning and continue.  The real work is
		 * already done and committed.
		 */
		error = xfs_bwrite(bp);
		xfs_buf_relse(bp);
		if (error) {
			xfs_warn(mp,
		"write error %d updating secondary superblock for ag %d",
				error, agno);
			break; /* no point in continuing */
		}
	}
	return error;

 error0:
	xfs_trans_cancel(tp, XFS_TRANS_ABORT);
	return error;
}

static int
xfs_growfs_log_private(
	xfs_mount_t		*mp,	/* mount point for filesystem */
	xfs_growfs_log_t	*in)	/* growfs log input struct */
{
	xfs_extlen_t		nb;

	nb = in->newblocks;
	if (nb < XFS_MIN_LOG_BLOCKS || nb < XFS_B_TO_FSB(mp, XFS_MIN_LOG_BYTES))
		return XFS_ERROR(EINVAL);
	if (nb == mp->m_sb.sb_logblocks &&
	    in->isint == (mp->m_sb.sb_logstart != 0))
		return XFS_ERROR(EINVAL);
	/*
	 * Moving the log is hard, need new interfaces to sync
	 * the log first, hold off all activity while moving it.
	 * Can have shorter or longer log in the same space,
	 * or transform internal to external log or vice versa.
	 */
	return XFS_ERROR(ENOSYS);
}

/*
 * protected versions of growfs function acquire and release locks on the mount
 * point - exported through ioctls: XFS_IOC_FSGROWFSDATA, XFS_IOC_FSGROWFSLOG,
 * XFS_IOC_FSGROWFSRT
 */


int
xfs_growfs_data(
	xfs_mount_t		*mp,
	xfs_growfs_data_t	*in)
{
	int error;

	if (!capable(CAP_SYS_ADMIN))
		return XFS_ERROR(EPERM);
	if (!mutex_trylock(&mp->m_growlock))
		return XFS_ERROR(EWOULDBLOCK);
	error = xfs_growfs_data_private(mp, in);
	mutex_unlock(&mp->m_growlock);
	return error;
}

int
xfs_growfs_log(
	xfs_mount_t		*mp,
	xfs_growfs_log_t	*in)
{
	int error;

	if (!capable(CAP_SYS_ADMIN))
		return XFS_ERROR(EPERM);
	if (!mutex_trylock(&mp->m_growlock))
		return XFS_ERROR(EWOULDBLOCK);
	error = xfs_growfs_log_private(mp, in);
	mutex_unlock(&mp->m_growlock);
	return error;
}

/*
 * exported through ioctl XFS_IOC_FSCOUNTS
 */

int
xfs_fs_counts(
	xfs_mount_t		*mp,
	xfs_fsop_counts_t	*cnt)
{
	xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
	spin_lock(&mp->m_sb_lock);
	cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
	cnt->freertx = mp->m_sb.sb_frextents;
	cnt->freeino = mp->m_sb.sb_ifree;
	cnt->allocino = mp->m_sb.sb_icount;
	spin_unlock(&mp->m_sb_lock);
	return 0;
}

/*
 * exported through ioctl XFS_IOC_SET_RESBLKS & XFS_IOC_GET_RESBLKS
 *
 * xfs_reserve_blocks is called to set m_resblks
 * in the in-core mount table. The number of unused reserved blocks
 * is kept in m_resblks_avail.
 *
 * Reserve the requested number of blocks if available. Otherwise return
 * as many as possible to satisfy the request. The actual number
 * reserved are returned in outval
 *
 * A null inval pointer indicates that only the current reserved blocks
 * available  should  be returned no settings are changed.
 */

int
xfs_reserve_blocks(
	xfs_mount_t             *mp,
	__uint64_t              *inval,
	xfs_fsop_resblks_t      *outval)
{
	__int64_t		lcounter, delta, fdblks_delta;
	__uint64_t		request;

	/* If inval is null, report current values and return */
	if (inval == (__uint64_t *)NULL) {
		if (!outval)
			return EINVAL;
		outval->resblks = mp->m_resblks;
		outval->resblks_avail = mp->m_resblks_avail;
		return 0;
	}

	request = *inval;

	/*
	 * With per-cpu counters, this becomes an interesting
	 * problem. we needto work out if we are freeing or allocation
	 * blocks first, then we can do the modification as necessary.
	 *
	 * We do this under the m_sb_lock so that if we are near
	 * ENOSPC, we will hold out any changes while we work out
	 * what to do. This means that the amount of free space can
	 * change while we do this, so we need to retry if we end up
	 * trying to reserve more space than is available.
	 *
	 * We also use the xfs_mod_incore_sb() interface so that we
	 * don't have to care about whether per cpu counter are
	 * enabled, disabled or even compiled in....
	 */
retry:
	spin_lock(&mp->m_sb_lock);
	xfs_icsb_sync_counters_locked(mp, 0);

	/*
	 * If our previous reservation was larger than the current value,
	 * then move any unused blocks back to the free pool.
	 */
	fdblks_delta = 0;
	if (mp->m_resblks > request) {
		lcounter = mp->m_resblks_avail - request;
		if (lcounter  > 0) {		/* release unused blocks */
			fdblks_delta = lcounter;
			mp->m_resblks_avail -= lcounter;
		}
		mp->m_resblks = request;
	} else {
		__int64_t	free;

		free =  mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
		if (!free)
			goto out; /* ENOSPC and fdblks_delta = 0 */

		delta = request - mp->m_resblks;
		lcounter = free - delta;
		if (lcounter < 0) {
			/* We can't satisfy the request, just get what we can */
			mp->m_resblks += free;
			mp->m_resblks_avail += free;
			fdblks_delta = -free;
		} else {
			fdblks_delta = -delta;
			mp->m_resblks = request;
			mp->m_resblks_avail += delta;
		}
	}
out:
	if (outval) {
		outval->resblks = mp->m_resblks;
		outval->resblks_avail = mp->m_resblks_avail;
	}
	spin_unlock(&mp->m_sb_lock);

	if (fdblks_delta) {
		/*
		 * If we are putting blocks back here, m_resblks_avail is
		 * already at its max so this will put it in the free pool.
		 *
		 * If we need space, we'll either succeed in getting it
		 * from the free block count or we'll get an enospc. If
		 * we get a ENOSPC, it means things changed while we were
		 * calculating fdblks_delta and so we should try again to
		 * see if there is anything left to reserve.
		 *
		 * Don't set the reserved flag here - we don't want to reserve
		 * the extra reserve blocks from the reserve.....
		 */
		int error;
		error = xfs_icsb_modify_counters(mp, XFS_SBS_FDBLOCKS,
						 fdblks_delta, 0);
		if (error == ENOSPC)
			goto retry;
	}
	return 0;
}

/*
 * Dump a transaction into the log that contains no real change. This is needed
 * to be able to make the log dirty or stamp the current tail LSN into the log
 * during the covering operation.
 *
 * We cannot use an inode here for this - that will push dirty state back up
 * into the VFS and then periodic inode flushing will prevent log covering from
 * making progress. Hence we log a field in the superblock instead and use a
 * synchronous transaction to ensure the superblock is immediately unpinned
 * and can be written back.
 */
int
xfs_fs_log_dummy(
	xfs_mount_t	*mp)
{
	xfs_trans_t	*tp;
	int		error;

	tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP);
	error = xfs_trans_reserve(tp, 0, XFS_SB_LOG_RES(mp), 0, 0,
				  XFS_DEFAULT_LOG_COUNT);
	if (error) {
		xfs_trans_cancel(tp, 0);
		return error;
	}

	/* log the UUID because it is an unchanging field */
	xfs_mod_sb(tp, XFS_SB_UUID);
	xfs_trans_set_sync(tp);
	return xfs_trans_commit(tp, 0);
}

int
xfs_fs_goingdown(
	xfs_mount_t	*mp,
	__uint32_t	inflags)
{
	switch (inflags) {
	case XFS_FSOP_GOING_FLAGS_DEFAULT: {
		struct super_block *sb = freeze_bdev(mp->m_super->s_bdev);

		if (sb && !IS_ERR(sb)) {
			xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
			thaw_bdev(sb->s_bdev, sb);
		}

		break;
	}
	case XFS_FSOP_GOING_FLAGS_LOGFLUSH:
		xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
		break;
	case XFS_FSOP_GOING_FLAGS_NOLOGFLUSH:
		xfs_force_shutdown(mp,
				SHUTDOWN_FORCE_UMOUNT | SHUTDOWN_LOG_IO_ERROR);
		break;
	default:
		return XFS_ERROR(EINVAL);
	}

	return 0;
}

/*
 * Force a shutdown of the filesystem instantly while keeping the filesystem
 * consistent. We don't do an unmount here; just shutdown the shop, make sure
 * that absolutely nothing persistent happens to this filesystem after this
 * point.
 */
void
xfs_do_force_shutdown(
	xfs_mount_t	*mp,
	int		flags,
	char		*fname,
	int		lnnum)
{
	int		logerror;

	logerror = flags & SHUTDOWN_LOG_IO_ERROR;

	if (!(flags & SHUTDOWN_FORCE_UMOUNT)) {
		xfs_notice(mp,
	"%s(0x%x) called from line %d of file %s.  Return address = 0x%p",
			__func__, flags, lnnum, fname, __return_address);
	}
	/*
	 * No need to duplicate efforts.
	 */
	if (XFS_FORCED_SHUTDOWN(mp) && !logerror)
		return;

	/*
	 * This flags XFS_MOUNT_FS_SHUTDOWN, makes sure that we don't
	 * queue up anybody new on the log reservations, and wakes up
	 * everybody who's sleeping on log reservations to tell them
	 * the bad news.
	 */
	if (xfs_log_force_umount(mp, logerror))
		return;

	if (flags & SHUTDOWN_CORRUPT_INCORE) {
		xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_CORRUPT,
    "Corruption of in-memory data detected.  Shutting down filesystem");
		if (XFS_ERRLEVEL_HIGH <= xfs_error_level)
			xfs_stack_trace();
	} else if (!(flags & SHUTDOWN_FORCE_UMOUNT)) {
		if (logerror) {
			xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_LOGERROR,
		"Log I/O Error Detected.  Shutting down filesystem");
		} else if (flags & SHUTDOWN_DEVICE_REQ) {
			xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_IOERROR,
		"All device paths lost.  Shutting down filesystem");
		} else if (!(flags & SHUTDOWN_REMOTE_REQ)) {
			xfs_alert_tag(mp, XFS_PTAG_SHUTDOWN_IOERROR,
		"I/O Error Detected. Shutting down filesystem");
		}
	}
	if (!(flags & SHUTDOWN_FORCE_UMOUNT)) {
		xfs_alert(mp,
	"Please umount the filesystem and rectify the problem(s)");
	}
}