of: MSI: Simplify irqdomain lookup

[linux/fpc-iii.git] / fs / xfs / xfs_bmap_util.c

/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * Copyright (c) 2012 Red Hat, 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_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_trans.h"
#include "xfs_extfree_item.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_quota.h"
#include "xfs_trans_space.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_log.h"

/* Kernel only BMAP related definitions and functions */

/*
 * Convert the given file system block to a disk block.  We have to treat it
 * differently based on whether the file is a real time file or not, because the
 * bmap code does.
 */
xfs_daddr_t
xfs_fsb_to_db(struct xfs_inode *ip, xfs_fsblock_t fsb)
{
        return (XFS_IS_REALTIME_INODE(ip) ? \
                 (xfs_daddr_t)XFS_FSB_TO_BB((ip)->i_mount, (fsb)) : \
                 XFS_FSB_TO_DADDR((ip)->i_mount, (fsb)));
}

/*
 * Routine to zero an extent on disk allocated to the specific inode.
 *
 * The VFS functions take a linearised filesystem block offset, so we have to
 * convert the sparse xfs fsb to the right format first.
 * VFS types are real funky, too.
 */
int
xfs_zero_extent(
        struct xfs_inode *ip,
        xfs_fsblock_t   start_fsb,
        xfs_off_t       count_fsb)
{
        struct xfs_mount *mp = ip->i_mount;
        xfs_daddr_t     sector = xfs_fsb_to_db(ip, start_fsb);
        sector_t        block = XFS_BB_TO_FSBT(mp, sector);
        ssize_t         size = XFS_FSB_TO_B(mp, count_fsb);

        if (IS_DAX(VFS_I(ip)))
                return dax_clear_blocks(VFS_I(ip), block, size);

        /*
         * let the block layer decide on the fastest method of
         * implementing the zeroing.
         */
        return sb_issue_zeroout(mp->m_super, block, count_fsb, GFP_NOFS);

}

/*
 * Routine to be called at transaction's end by xfs_bmapi, xfs_bunmapi
 * caller.  Frees all the extents that need freeing, which must be done
 * last due to locking considerations.  We never free any extents in
 * the first transaction.
 *
 * Return 1 if the given transaction was committed and a new one
 * started, and 0 otherwise in the committed parameter.
 */
int                                             /* error */
xfs_bmap_finish(
        struct xfs_trans                **tp,   /* transaction pointer addr */
        struct xfs_bmap_free            *flist, /* i/o: list extents to free */
        int                             *committed)/* xact committed or not */
{
        struct xfs_efd_log_item         *efd;   /* extent free data */
        struct xfs_efi_log_item         *efi;   /* extent free intention */
        int                             error;  /* error return value */
        struct xfs_bmap_free_item       *free;  /* free extent item */
        struct xfs_bmap_free_item       *next;  /* next item on free list */

        ASSERT((*tp)->t_flags & XFS_TRANS_PERM_LOG_RES);
        if (flist->xbf_count == 0) {
                *committed = 0;
                return 0;
        }
        efi = xfs_trans_get_efi(*tp, flist->xbf_count);
        for (free = flist->xbf_first; free; free = free->xbfi_next)
                xfs_trans_log_efi_extent(*tp, efi, free->xbfi_startblock,
                        free->xbfi_blockcount);

        error = __xfs_trans_roll(tp, NULL, committed);
        if (error) {
                /*
                 * If the transaction was committed, drop the EFD reference
                 * since we're bailing out of here. The other reference is
                 * dropped when the EFI hits the AIL.
                 *
                 * If the transaction was not committed, the EFI is freed by the
                 * EFI item unlock handler on abort. Also, we have a new
                 * transaction so we should return committed=1 even though we're
                 * returning an error.
                 */
                if (*committed) {
                        xfs_efi_release(efi);
                        xfs_force_shutdown((*tp)->t_mountp,
                                (error == -EFSCORRUPTED) ?
                                        SHUTDOWN_CORRUPT_INCORE :
                                        SHUTDOWN_META_IO_ERROR);
                } else {
                        *committed = 1;
                }

                return error;
        }

        /*
         * Get an EFD and free each extent in the list, logging to the EFD in
         * the process. The remaining bmap free list is cleaned up by the caller
         * on error.
         */
        efd = xfs_trans_get_efd(*tp, efi, flist->xbf_count);
        for (free = flist->xbf_first; free != NULL; free = next) {
                next = free->xbfi_next;

                error = xfs_trans_free_extent(*tp, efd, free->xbfi_startblock,
                                              free->xbfi_blockcount);
                if (error)
                        return error;

                xfs_bmap_del_free(flist, NULL, free);
        }

        return 0;
}

int
xfs_bmap_rtalloc(
        struct xfs_bmalloca     *ap)    /* bmap alloc argument struct */
{
        xfs_alloctype_t atype = 0;      /* type for allocation routines */
        int             error;          /* error return value */
        xfs_mount_t     *mp;            /* mount point structure */
        xfs_extlen_t    prod = 0;       /* product factor for allocators */
        xfs_extlen_t    ralen = 0;      /* realtime allocation length */
        xfs_extlen_t    align;          /* minimum allocation alignment */
        xfs_rtblock_t   rtb;

        mp = ap->ip->i_mount;
        align = xfs_get_extsz_hint(ap->ip);
        prod = align / mp->m_sb.sb_rextsize;
        error = xfs_bmap_extsize_align(mp, &ap->got, &ap->prev,
                                        align, 1, ap->eof, 0,
                                        ap->conv, &ap->offset, &ap->length);
        if (error)
                return error;
        ASSERT(ap->length);
        ASSERT(ap->length % mp->m_sb.sb_rextsize == 0);

        /*
         * If the offset & length are not perfectly aligned
         * then kill prod, it will just get us in trouble.
         */
        if (do_mod(ap->offset, align) || ap->length % align)
                prod = 1;
        /*
         * Set ralen to be the actual requested length in rtextents.
         */
        ralen = ap->length / mp->m_sb.sb_rextsize;
        /*
         * If the old value was close enough to MAXEXTLEN that
         * we rounded up to it, cut it back so it's valid again.
         * Note that if it's a really large request (bigger than
         * MAXEXTLEN), we don't hear about that number, and can't
         * adjust the starting point to match it.
         */
        if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
                ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;

        /*
         * Lock out other modifications to the RT bitmap inode.
         */
        xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(ap->tp, mp->m_rbmip, XFS_ILOCK_EXCL);

        /*
         * If it's an allocation to an empty file at offset 0,
         * pick an extent that will space things out in the rt area.
         */
        if (ap->eof && ap->offset == 0) {
                xfs_rtblock_t uninitialized_var(rtx); /* realtime extent no */

                error = xfs_rtpick_extent(mp, ap->tp, ralen, &rtx);
                if (error)
                        return error;
                ap->blkno = rtx * mp->m_sb.sb_rextsize;
        } else {
                ap->blkno = 0;
        }

        xfs_bmap_adjacent(ap);

        /*
         * Realtime allocation, done through xfs_rtallocate_extent.
         */
        atype = ap->blkno == 0 ?  XFS_ALLOCTYPE_ANY_AG : XFS_ALLOCTYPE_NEAR_BNO;
        do_div(ap->blkno, mp->m_sb.sb_rextsize);
        rtb = ap->blkno;
        ap->length = ralen;
        if ((error = xfs_rtallocate_extent(ap->tp, ap->blkno, 1, ap->length,
                                &ralen, atype, ap->wasdel, prod, &rtb)))
                return error;
        if (rtb == NULLFSBLOCK && prod > 1 &&
            (error = xfs_rtallocate_extent(ap->tp, ap->blkno, 1,
                                           ap->length, &ralen, atype,
                                           ap->wasdel, 1, &rtb)))
                return error;
        ap->blkno = rtb;
        if (ap->blkno != NULLFSBLOCK) {
                ap->blkno *= mp->m_sb.sb_rextsize;
                ralen *= mp->m_sb.sb_rextsize;
                ap->length = ralen;
                ap->ip->i_d.di_nblocks += ralen;
                xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
                if (ap->wasdel)
                        ap->ip->i_delayed_blks -= ralen;
                /*
                 * Adjust the disk quota also. This was reserved
                 * earlier.
                 */
                xfs_trans_mod_dquot_byino(ap->tp, ap->ip,
                        ap->wasdel ? XFS_TRANS_DQ_DELRTBCOUNT :
                                        XFS_TRANS_DQ_RTBCOUNT, (long) ralen);

                /* Zero the extent if we were asked to do so */
                if (ap->userdata & XFS_ALLOC_USERDATA_ZERO) {
                        error = xfs_zero_extent(ap->ip, ap->blkno, ap->length);
                        if (error)
                                return error;
                }
        } else {
                ap->length = 0;
        }
        return 0;
}

/*
 * Check if the endoff is outside the last extent. If so the caller will grow
 * the allocation to a stripe unit boundary.  All offsets are considered outside
 * the end of file for an empty fork, so 1 is returned in *eof in that case.
 */
int
xfs_bmap_eof(
        struct xfs_inode        *ip,
        xfs_fileoff_t           endoff,
        int                     whichfork,
        int                     *eof)
{
        struct xfs_bmbt_irec    rec;
        int                     error;

        error = xfs_bmap_last_extent(NULL, ip, whichfork, &rec, eof);
        if (error || *eof)
                return error;

        *eof = endoff >= rec.br_startoff + rec.br_blockcount;
        return 0;
}

/*
 * Extent tree block counting routines.
 */

/*
 * Count leaf blocks given a range of extent records.
 */
STATIC void
xfs_bmap_count_leaves(
        xfs_ifork_t             *ifp,
        xfs_extnum_t            idx,
        int                     numrecs,
        int                     *count)
{
        int             b;

        for (b = 0; b < numrecs; b++) {
                xfs_bmbt_rec_host_t *frp = xfs_iext_get_ext(ifp, idx + b);
                *count += xfs_bmbt_get_blockcount(frp);
        }
}

/*
 * Count leaf blocks given a range of extent records originally
 * in btree format.
 */
STATIC void
xfs_bmap_disk_count_leaves(
        struct xfs_mount        *mp,
        struct xfs_btree_block  *block,
        int                     numrecs,
        int                     *count)
{
        int             b;
        xfs_bmbt_rec_t  *frp;

        for (b = 1; b <= numrecs; b++) {
                frp = XFS_BMBT_REC_ADDR(mp, block, b);
                *count += xfs_bmbt_disk_get_blockcount(frp);
        }
}

/*
 * Recursively walks each level of a btree
 * to count total fsblocks in use.
 */
STATIC int                                     /* error */
xfs_bmap_count_tree(
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_ifork_t     *ifp,           /* inode fork pointer */
        xfs_fsblock_t   blockno,        /* file system block number */
        int             levelin,        /* level in btree */
        int             *count)         /* Count of blocks */
{
        int                     error;
        xfs_buf_t               *bp, *nbp;
        int                     level = levelin;
        __be64                  *pp;
        xfs_fsblock_t           bno = blockno;
        xfs_fsblock_t           nextbno;
        struct xfs_btree_block  *block, *nextblock;
        int                     numrecs;

        error = xfs_btree_read_bufl(mp, tp, bno, 0, &bp, XFS_BMAP_BTREE_REF,
                                                &xfs_bmbt_buf_ops);
        if (error)
                return error;
        *count += 1;
        block = XFS_BUF_TO_BLOCK(bp);

        if (--level) {
                /* Not at node above leaves, count this level of nodes */
                nextbno = be64_to_cpu(block->bb_u.l.bb_rightsib);
                while (nextbno != NULLFSBLOCK) {
                        error = xfs_btree_read_bufl(mp, tp, nextbno, 0, &nbp,
                                                XFS_BMAP_BTREE_REF,
                                                &xfs_bmbt_buf_ops);
                        if (error)
                                return error;
                        *count += 1;
                        nextblock = XFS_BUF_TO_BLOCK(nbp);
                        nextbno = be64_to_cpu(nextblock->bb_u.l.bb_rightsib);
                        xfs_trans_brelse(tp, nbp);
                }

                /* Dive to the next level */
                pp = XFS_BMBT_PTR_ADDR(mp, block, 1, mp->m_bmap_dmxr[1]);
                bno = be64_to_cpu(*pp);
                if (unlikely((error =
                     xfs_bmap_count_tree(mp, tp, ifp, bno, level, count)) < 0)) {
                        xfs_trans_brelse(tp, bp);
                        XFS_ERROR_REPORT("xfs_bmap_count_tree(1)",
                                         XFS_ERRLEVEL_LOW, mp);
                        return -EFSCORRUPTED;
                }
                xfs_trans_brelse(tp, bp);
        } else {
                /* count all level 1 nodes and their leaves */
                for (;;) {
                        nextbno = be64_to_cpu(block->bb_u.l.bb_rightsib);
                        numrecs = be16_to_cpu(block->bb_numrecs);
                        xfs_bmap_disk_count_leaves(mp, block, numrecs, count);
                        xfs_trans_brelse(tp, bp);
                        if (nextbno == NULLFSBLOCK)
                                break;
                        bno = nextbno;
                        error = xfs_btree_read_bufl(mp, tp, bno, 0, &bp,
                                                XFS_BMAP_BTREE_REF,
                                                &xfs_bmbt_buf_ops);
                        if (error)
                                return error;
                        *count += 1;
                        block = XFS_BUF_TO_BLOCK(bp);
                }
        }
        return 0;
}

/*
 * Count fsblocks of the given fork.
 */
int                                             /* error */
xfs_bmap_count_blocks(
        xfs_trans_t             *tp,            /* transaction pointer */
        xfs_inode_t             *ip,            /* incore inode */
        int                     whichfork,      /* data or attr fork */
        int                     *count)         /* out: count of blocks */
{
        struct xfs_btree_block  *block; /* current btree block */
        xfs_fsblock_t           bno;    /* block # of "block" */
        xfs_ifork_t             *ifp;   /* fork structure */
        int                     level;  /* btree level, for checking */
        xfs_mount_t             *mp;    /* file system mount structure */
        __be64                  *pp;    /* pointer to block address */

        bno = NULLFSBLOCK;
        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        if ( XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS ) {
                xfs_bmap_count_leaves(ifp, 0,
                        ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t),
                        count);
                return 0;
        }

        /*
         * Root level must use BMAP_BROOT_PTR_ADDR macro to get ptr out.
         */
        block = ifp->if_broot;
        level = be16_to_cpu(block->bb_level);
        ASSERT(level > 0);
        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, block, 1, ifp->if_broot_bytes);
        bno = be64_to_cpu(*pp);
        ASSERT(bno != NULLFSBLOCK);
        ASSERT(XFS_FSB_TO_AGNO(mp, bno) < mp->m_sb.sb_agcount);
        ASSERT(XFS_FSB_TO_AGBNO(mp, bno) < mp->m_sb.sb_agblocks);

        if (unlikely(xfs_bmap_count_tree(mp, tp, ifp, bno, level, count) < 0)) {
                XFS_ERROR_REPORT("xfs_bmap_count_blocks(2)", XFS_ERRLEVEL_LOW,
                                 mp);
                return -EFSCORRUPTED;
        }

        return 0;
}

/*
 * returns 1 for success, 0 if we failed to map the extent.
 */
STATIC int
xfs_getbmapx_fix_eof_hole(
        xfs_inode_t             *ip,            /* xfs incore inode pointer */
        struct getbmapx         *out,           /* output structure */
        int                     prealloced,     /* this is a file with
                                                 * preallocated data space */
        __int64_t               end,            /* last block requested */
        xfs_fsblock_t           startblock)
{
        __int64_t               fixlen;
        xfs_mount_t             *mp;            /* file system mount point */
        xfs_ifork_t             *ifp;           /* inode fork pointer */
        xfs_extnum_t            lastx;          /* last extent pointer */
        xfs_fileoff_t           fileblock;

        if (startblock == HOLESTARTBLOCK) {
                mp = ip->i_mount;
                out->bmv_block = -1;
                fixlen = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, XFS_ISIZE(ip)));
                fixlen -= out->bmv_offset;
                if (prealloced && out->bmv_offset + out->bmv_length == end) {
                        /* Came to hole at EOF. Trim it. */
                        if (fixlen <= 0)
                                return 0;
                        out->bmv_length = fixlen;
                }
        } else {
                if (startblock == DELAYSTARTBLOCK)
                        out->bmv_block = -2;
                else
                        out->bmv_block = xfs_fsb_to_db(ip, startblock);
                fileblock = XFS_BB_TO_FSB(ip->i_mount, out->bmv_offset);
                ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
                if (xfs_iext_bno_to_ext(ifp, fileblock, &lastx) &&
                   (lastx == (ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t))-1))
                        out->bmv_oflags |= BMV_OF_LAST;
        }

        return 1;
}

/*
 * Get inode's extents as described in bmv, and format for output.
 * Calls formatter to fill the user's buffer until all extents
 * are mapped, until the passed-in bmv->bmv_count slots have
 * been filled, or until the formatter short-circuits the loop,
 * if it is tracking filled-in extents on its own.
 */
int                                             /* error code */
xfs_getbmap(
        xfs_inode_t             *ip,
        struct getbmapx         *bmv,           /* user bmap structure */
        xfs_bmap_format_t       formatter,      /* format to user */
        void                    *arg)           /* formatter arg */
{
        __int64_t               bmvend;         /* last block requested */
        int                     error = 0;      /* return value */
        __int64_t               fixlen;         /* length for -1 case */
        int                     i;              /* extent number */
        int                     lock;           /* lock state */
        xfs_bmbt_irec_t         *map;           /* buffer for user's data */
        xfs_mount_t             *mp;            /* file system mount point */
        int                     nex;            /* # of user extents can do */
        int                     nexleft;        /* # of user extents left */
        int                     subnex;         /* # of bmapi's can do */
        int                     nmap;           /* number of map entries */
        struct getbmapx         *out;           /* output structure */
        int                     whichfork;      /* data or attr fork */
        int                     prealloced;     /* this is a file with
                                                 * preallocated data space */
        int                     iflags;         /* interface flags */
        int                     bmapi_flags;    /* flags for xfs_bmapi */
        int                     cur_ext = 0;

        mp = ip->i_mount;
        iflags = bmv->bmv_iflags;
        whichfork = iflags & BMV_IF_ATTRFORK ? XFS_ATTR_FORK : XFS_DATA_FORK;

        if (whichfork == XFS_ATTR_FORK) {
                if (XFS_IFORK_Q(ip)) {
                        if (ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS &&
                            ip->i_d.di_aformat != XFS_DINODE_FMT_BTREE &&
                            ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL)
                                return -EINVAL;
                } else if (unlikely(
                           ip->i_d.di_aformat != 0 &&
                           ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS)) {
                        XFS_ERROR_REPORT("xfs_getbmap", XFS_ERRLEVEL_LOW,
                                         ip->i_mount);
                        return -EFSCORRUPTED;
                }

                prealloced = 0;
                fixlen = 1LL << 32;
        } else {
                if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
                    ip->i_d.di_format != XFS_DINODE_FMT_BTREE &&
                    ip->i_d.di_format != XFS_DINODE_FMT_LOCAL)
                        return -EINVAL;

                if (xfs_get_extsz_hint(ip) ||
                    ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC|XFS_DIFLAG_APPEND)){
                        prealloced = 1;
                        fixlen = mp->m_super->s_maxbytes;
                } else {
                        prealloced = 0;
                        fixlen = XFS_ISIZE(ip);
                }
        }

        if (bmv->bmv_length == -1) {
                fixlen = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, fixlen));
                bmv->bmv_length =
                        max_t(__int64_t, fixlen - bmv->bmv_offset, 0);
        } else if (bmv->bmv_length == 0) {
                bmv->bmv_entries = 0;
                return 0;
        } else if (bmv->bmv_length < 0) {
                return -EINVAL;
        }

        nex = bmv->bmv_count - 1;
        if (nex <= 0)
                return -EINVAL;
        bmvend = bmv->bmv_offset + bmv->bmv_length;


        if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx))
                return -ENOMEM;
        out = kmem_zalloc_large(bmv->bmv_count * sizeof(struct getbmapx), 0);
        if (!out)
                return -ENOMEM;

        xfs_ilock(ip, XFS_IOLOCK_SHARED);
        if (whichfork == XFS_DATA_FORK) {
                if (!(iflags & BMV_IF_DELALLOC) &&
                    (ip->i_delayed_blks || XFS_ISIZE(ip) > ip->i_d.di_size)) {
                        error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
                        if (error)
                                goto out_unlock_iolock;

                        /*
                         * Even after flushing the inode, there can still be
                         * delalloc blocks on the inode beyond EOF due to
                         * speculative preallocation.  These are not removed
                         * until the release function is called or the inode
                         * is inactivated.  Hence we cannot assert here that
                         * ip->i_delayed_blks == 0.
                         */
                }

                lock = xfs_ilock_data_map_shared(ip);
        } else {
                lock = xfs_ilock_attr_map_shared(ip);
        }

        /*
         * Don't let nex be bigger than the number of extents
         * we can have assuming alternating holes and real extents.
         */
        if (nex > XFS_IFORK_NEXTENTS(ip, whichfork) * 2 + 1)
                nex = XFS_IFORK_NEXTENTS(ip, whichfork) * 2 + 1;

        bmapi_flags = xfs_bmapi_aflag(whichfork);
        if (!(iflags & BMV_IF_PREALLOC))
                bmapi_flags |= XFS_BMAPI_IGSTATE;

        /*
         * Allocate enough space to handle "subnex" maps at a time.
         */
        error = -ENOMEM;
        subnex = 16;
        map = kmem_alloc(subnex * sizeof(*map), KM_MAYFAIL | KM_NOFS);
        if (!map)
                goto out_unlock_ilock;

        bmv->bmv_entries = 0;

        if (XFS_IFORK_NEXTENTS(ip, whichfork) == 0 &&
            (whichfork == XFS_ATTR_FORK || !(iflags & BMV_IF_DELALLOC))) {
                error = 0;
                goto out_free_map;
        }

        nexleft = nex;

        do {
                nmap = (nexleft > subnex) ? subnex : nexleft;
                error = xfs_bmapi_read(ip, XFS_BB_TO_FSBT(mp, bmv->bmv_offset),
                                       XFS_BB_TO_FSB(mp, bmv->bmv_length),
                                       map, &nmap, bmapi_flags);
                if (error)
                        goto out_free_map;
                ASSERT(nmap <= subnex);

                for (i = 0; i < nmap && nexleft && bmv->bmv_length; i++) {
                        out[cur_ext].bmv_oflags = 0;
                        if (map[i].br_state == XFS_EXT_UNWRITTEN)
                                out[cur_ext].bmv_oflags |= BMV_OF_PREALLOC;
                        else if (map[i].br_startblock == DELAYSTARTBLOCK)
                                out[cur_ext].bmv_oflags |= BMV_OF_DELALLOC;
                        out[cur_ext].bmv_offset =
                                XFS_FSB_TO_BB(mp, map[i].br_startoff);
                        out[cur_ext].bmv_length =
                                XFS_FSB_TO_BB(mp, map[i].br_blockcount);
                        out[cur_ext].bmv_unused1 = 0;
                        out[cur_ext].bmv_unused2 = 0;

                        /*
                         * delayed allocation extents that start beyond EOF can
                         * occur due to speculative EOF allocation when the
                         * delalloc extent is larger than the largest freespace
                         * extent at conversion time. These extents cannot be
                         * converted by data writeback, so can exist here even
                         * if we are not supposed to be finding delalloc
                         * extents.
                         */
                        if (map[i].br_startblock == DELAYSTARTBLOCK &&
                            map[i].br_startoff <= XFS_B_TO_FSB(mp, XFS_ISIZE(ip)))
                                ASSERT((iflags & BMV_IF_DELALLOC) != 0);

                        if (map[i].br_startblock == HOLESTARTBLOCK &&
                            whichfork == XFS_ATTR_FORK) {
                                /* came to the end of attribute fork */
                                out[cur_ext].bmv_oflags |= BMV_OF_LAST;
                                goto out_free_map;
                        }

                        if (!xfs_getbmapx_fix_eof_hole(ip, &out[cur_ext],
                                        prealloced, bmvend,
                                        map[i].br_startblock))
                                goto out_free_map;

                        bmv->bmv_offset =
                                out[cur_ext].bmv_offset +
                                out[cur_ext].bmv_length;
                        bmv->bmv_length =
                                max_t(__int64_t, 0, bmvend - bmv->bmv_offset);

                        /*
                         * In case we don't want to return the hole,
                         * don't increase cur_ext so that we can reuse
                         * it in the next loop.
                         */
                        if ((iflags & BMV_IF_NO_HOLES) &&
                            map[i].br_startblock == HOLESTARTBLOCK) {
                                memset(&out[cur_ext], 0, sizeof(out[cur_ext]));
                                continue;
                        }

                        nexleft--;
                        bmv->bmv_entries++;
                        cur_ext++;
                }
        } while (nmap && nexleft && bmv->bmv_length);

 out_free_map:
        kmem_free(map);
 out_unlock_ilock:
        xfs_iunlock(ip, lock);
 out_unlock_iolock:
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);

        for (i = 0; i < cur_ext; i++) {
                int full = 0;   /* user array is full */

                /* format results & advance arg */
                error = formatter(&arg, &out[i], &full);
                if (error || full)
                        break;
        }

        kmem_free(out);
        return error;
}

/*
 * dead simple method of punching delalyed allocation blocks from a range in
 * the inode. Walks a block at a time so will be slow, but is only executed in
 * rare error cases so the overhead is not critical. This will always punch out
 * both the start and end blocks, even if the ranges only partially overlap
 * them, so it is up to the caller to ensure that partial blocks are not
 * passed in.
 */
int
xfs_bmap_punch_delalloc_range(
        struct xfs_inode        *ip,
        xfs_fileoff_t           start_fsb,
        xfs_fileoff_t           length)
{
        xfs_fileoff_t           remaining = length;
        int                     error = 0;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        do {
                int             done;
                xfs_bmbt_irec_t imap;
                int             nimaps = 1;
                xfs_fsblock_t   firstblock;
                xfs_bmap_free_t flist;

                /*
                 * Map the range first and check that it is a delalloc extent
                 * before trying to unmap the range. Otherwise we will be
                 * trying to remove a real extent (which requires a
                 * transaction) or a hole, which is probably a bad idea...
                 */
                error = xfs_bmapi_read(ip, start_fsb, 1, &imap, &nimaps,
                                       XFS_BMAPI_ENTIRE);

                if (error) {
                        /* something screwed, just bail */
                        if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
                                xfs_alert(ip->i_mount,
                        "Failed delalloc mapping lookup ino %lld fsb %lld.",
                                                ip->i_ino, start_fsb);
                        }
                        break;
                }
                if (!nimaps) {
                        /* nothing there */
                        goto next_block;
                }
                if (imap.br_startblock != DELAYSTARTBLOCK) {
                        /* been converted, ignore */
                        goto next_block;
                }
                WARN_ON(imap.br_blockcount == 0);

                /*
                 * Note: while we initialise the firstblock/flist pair, they
                 * should never be used because blocks should never be
                 * allocated or freed for a delalloc extent and hence we need
                 * don't cancel or finish them after the xfs_bunmapi() call.
                 */
                xfs_bmap_init(&flist, &firstblock);
                error = xfs_bunmapi(NULL, ip, start_fsb, 1, 0, 1, &firstblock,
                                        &flist, &done);
                if (error)
                        break;

                ASSERT(!flist.xbf_count && !flist.xbf_first);
next_block:
                start_fsb++;
                remaining--;
        } while(remaining > 0);

        return error;
}

/*
 * Test whether it is appropriate to check an inode for and free post EOF
 * blocks. The 'force' parameter determines whether we should also consider
 * regular files that are marked preallocated or append-only.
 */
bool
xfs_can_free_eofblocks(struct xfs_inode *ip, bool force)
{
        /* prealloc/delalloc exists only on regular files */
        if (!S_ISREG(ip->i_d.di_mode))
                return false;

        /*
         * Zero sized files with no cached pages and delalloc blocks will not
         * have speculative prealloc/delalloc blocks to remove.
         */
        if (VFS_I(ip)->i_size == 0 &&
            VFS_I(ip)->i_mapping->nrpages == 0 &&
            ip->i_delayed_blks == 0)
                return false;

        /* If we haven't read in the extent list, then don't do it now. */
        if (!(ip->i_df.if_flags & XFS_IFEXTENTS))
                return false;

        /*
         * Do not free real preallocated or append-only files unless the file
         * has delalloc blocks and we are forced to remove them.
         */
        if (ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND))
                if (!force || ip->i_delayed_blks == 0)
                        return false;

        return true;
}

/*
 * This is called by xfs_inactive to free any blocks beyond eof
 * when the link count isn't zero and by xfs_dm_punch_hole() when
 * punching a hole to EOF.
 */
int
xfs_free_eofblocks(
        xfs_mount_t     *mp,
        xfs_inode_t     *ip,
        bool            need_iolock)
{
        xfs_trans_t     *tp;
        int             error;
        xfs_fileoff_t   end_fsb;
        xfs_fileoff_t   last_fsb;
        xfs_filblks_t   map_len;
        int             nimaps;
        xfs_bmbt_irec_t imap;

        /*
         * Figure out if there are any blocks beyond the end
         * of the file.  If not, then there is nothing to do.
         */
        end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
        last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
        if (last_fsb <= end_fsb)
                return 0;
        map_len = last_fsb - end_fsb;

        nimaps = 1;
        xfs_ilock(ip, XFS_ILOCK_SHARED);
        error = xfs_bmapi_read(ip, end_fsb, map_len, &imap, &nimaps, 0);
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        if (!error && (nimaps != 0) &&
            (imap.br_startblock != HOLESTARTBLOCK ||
             ip->i_delayed_blks)) {
                /*
                 * Attach the dquots to the inode up front.
                 */
                error = xfs_qm_dqattach(ip, 0);
                if (error)
                        return error;

                /*
                 * There are blocks after the end of file.
                 * Free them up now by truncating the file to
                 * its current size.
                 */
                tp = xfs_trans_alloc(mp, XFS_TRANS_INACTIVE);

                if (need_iolock) {
                        if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
                                xfs_trans_cancel(tp);
                                return -EAGAIN;
                        }
                }

                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_itruncate, 0, 0);
                if (error) {
                        ASSERT(XFS_FORCED_SHUTDOWN(mp));
                        xfs_trans_cancel(tp);
                        if (need_iolock)
                                xfs_iunlock(ip, XFS_IOLOCK_EXCL);
                        return error;
                }

                xfs_ilock(ip, XFS_ILOCK_EXCL);
                xfs_trans_ijoin(tp, ip, 0);

                /*
                 * Do not update the on-disk file size.  If we update the
                 * on-disk file size and then the system crashes before the
                 * contents of the file are flushed to disk then the files
                 * may be full of holes (ie NULL files bug).
                 */
                error = xfs_itruncate_extents(&tp, ip, XFS_DATA_FORK,
                                              XFS_ISIZE(ip));
                if (error) {
                        /*
                         * If we get an error at this point we simply don't
                         * bother truncating the file.
                         */
                        xfs_trans_cancel(tp);
                } else {
                        error = xfs_trans_commit(tp);
                        if (!error)
                                xfs_inode_clear_eofblocks_tag(ip);
                }

                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                if (need_iolock)
                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        }
        return error;
}

int
xfs_alloc_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len,
        int                     alloc_type)
{
        xfs_mount_t             *mp = ip->i_mount;
        xfs_off_t               count;
        xfs_filblks_t           allocated_fsb;
        xfs_filblks_t           allocatesize_fsb;
        xfs_extlen_t            extsz, temp;
        xfs_fileoff_t           startoffset_fsb;
        xfs_fsblock_t           firstfsb;
        int                     nimaps;
        int                     quota_flag;
        int                     rt;
        xfs_trans_t             *tp;
        xfs_bmbt_irec_t         imaps[1], *imapp;
        xfs_bmap_free_t         free_list;
        uint                    qblocks, resblks, resrtextents;
        int                     committed;
        int                     error;

        trace_xfs_alloc_file_space(ip);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        error = xfs_qm_dqattach(ip, 0);
        if (error)
                return error;

        if (len <= 0)
                return -EINVAL;

        rt = XFS_IS_REALTIME_INODE(ip);
        extsz = xfs_get_extsz_hint(ip);

        count = len;
        imapp = &imaps[0];
        nimaps = 1;
        startoffset_fsb = XFS_B_TO_FSBT(mp, offset);
        allocatesize_fsb = XFS_B_TO_FSB(mp, count);

        /*
         * Allocate file space until done or until there is an error
         */
        while (allocatesize_fsb && !error) {
                xfs_fileoff_t   s, e;

                /*
                 * Determine space reservations for data/realtime.
                 */
                if (unlikely(extsz)) {
                        s = startoffset_fsb;
                        do_div(s, extsz);
                        s *= extsz;
                        e = startoffset_fsb + allocatesize_fsb;
                        if ((temp = do_mod(startoffset_fsb, extsz)))
                                e += temp;
                        if ((temp = do_mod(e, extsz)))
                                e += extsz - temp;
                } else {
                        s = 0;
                        e = allocatesize_fsb;
                }

                /*
                 * The transaction reservation is limited to a 32-bit block
                 * count, hence we need to limit the number of blocks we are
                 * trying to reserve to avoid an overflow. We can't allocate
                 * more than @nimaps extents, and an extent is limited on disk
                 * to MAXEXTLEN (21 bits), so use that to enforce the limit.
                 */
                resblks = min_t(xfs_fileoff_t, (e - s), (MAXEXTLEN * nimaps));
                if (unlikely(rt)) {
                        resrtextents = qblocks = resblks;
                        resrtextents /= mp->m_sb.sb_rextsize;
                        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
                        quota_flag = XFS_QMOPT_RES_RTBLKS;
                } else {
                        resrtextents = 0;
                        resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resblks);
                        quota_flag = XFS_QMOPT_RES_REGBLKS;
                }

                /*
                 * Allocate and setup the transaction.
                 */
                tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
                                          resblks, resrtextents);
                /*
                 * Check for running out of space
                 */
                if (error) {
                        /*
                         * Free the transaction structure.
                         */
                        ASSERT(error == -ENOSPC || XFS_FORCED_SHUTDOWN(mp));
                        xfs_trans_cancel(tp);
                        break;
                }
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks,
                                                      0, quota_flag);
                if (error)
                        goto error1;

                xfs_trans_ijoin(tp, ip, 0);

                xfs_bmap_init(&free_list, &firstfsb);
                error = xfs_bmapi_write(tp, ip, startoffset_fsb,
                                        allocatesize_fsb, alloc_type, &firstfsb,
                                        resblks, imapp, &nimaps, &free_list);
                if (error) {
                        goto error0;
                }

                /*
                 * Complete the transaction
                 */
                error = xfs_bmap_finish(&tp, &free_list, &committed);
                if (error) {
                        goto error0;
                }

                error = xfs_trans_commit(tp);
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                if (error) {
                        break;
                }

                allocated_fsb = imapp->br_blockcount;

                if (nimaps == 0) {
                        error = -ENOSPC;
                        break;
                }

                startoffset_fsb += allocated_fsb;
                allocatesize_fsb -= allocated_fsb;
        }

        return error;

error0: /* Cancel bmap, unlock inode, unreserve quota blocks, cancel trans */
        xfs_bmap_cancel(&free_list);
        xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);

error1: /* Just cancel transaction */
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * Zero file bytes between startoff and endoff inclusive.
 * The iolock is held exclusive and no blocks are buffered.
 *
 * This function is used by xfs_free_file_space() to zero
 * partial blocks when the range to free is not block aligned.
 * When unreserving space with boundaries that are not block
 * aligned we round up the start and round down the end
 * boundaries and then use this function to zero the parts of
 * the blocks that got dropped during the rounding.
 */
STATIC int
xfs_zero_remaining_bytes(
        xfs_inode_t             *ip,
        xfs_off_t               startoff,
        xfs_off_t               endoff)
{
        xfs_bmbt_irec_t         imap;
        xfs_fileoff_t           offset_fsb;
        xfs_off_t               lastoffset;
        xfs_off_t               offset;
        xfs_buf_t               *bp;
        xfs_mount_t             *mp = ip->i_mount;
        int                     nimap;
        int                     error = 0;

        /*
         * Avoid doing I/O beyond eof - it's not necessary
         * since nothing can read beyond eof.  The space will
         * be zeroed when the file is extended anyway.
         */
        if (startoff >= XFS_ISIZE(ip))
                return 0;

        if (endoff > XFS_ISIZE(ip))
                endoff = XFS_ISIZE(ip);

        for (offset = startoff; offset <= endoff; offset = lastoffset + 1) {
                uint lock_mode;

                offset_fsb = XFS_B_TO_FSBT(mp, offset);
                nimap = 1;

                lock_mode = xfs_ilock_data_map_shared(ip);
                error = xfs_bmapi_read(ip, offset_fsb, 1, &imap, &nimap, 0);
                xfs_iunlock(ip, lock_mode);

                if (error || nimap < 1)
                        break;
                ASSERT(imap.br_blockcount >= 1);
                ASSERT(imap.br_startoff == offset_fsb);
                ASSERT(imap.br_startblock != DELAYSTARTBLOCK);

                if (imap.br_startblock == HOLESTARTBLOCK ||
                    imap.br_state == XFS_EXT_UNWRITTEN) {
                        /* skip the entire extent */
                        lastoffset = XFS_FSB_TO_B(mp, imap.br_startoff +
                                                      imap.br_blockcount) - 1;
                        continue;
                }

                lastoffset = XFS_FSB_TO_B(mp, imap.br_startoff + 1) - 1;
                if (lastoffset > endoff)
                        lastoffset = endoff;

                /* DAX can just zero the backing device directly */
                if (IS_DAX(VFS_I(ip))) {
                        error = dax_zero_page_range(VFS_I(ip), offset,
                                                    lastoffset - offset + 1,
                                                    xfs_get_blocks_direct);
                        if (error)
                                return error;
                        continue;
                }

                error = xfs_buf_read_uncached(XFS_IS_REALTIME_INODE(ip) ?
                                mp->m_rtdev_targp : mp->m_ddev_targp,
                                xfs_fsb_to_db(ip, imap.br_startblock),
                                BTOBB(mp->m_sb.sb_blocksize),
                                0, &bp, NULL);
                if (error)
                        return error;

                memset(bp->b_addr +
                                (offset - XFS_FSB_TO_B(mp, imap.br_startoff)),
                       0, lastoffset - offset + 1);

                error = xfs_bwrite(bp);
                xfs_buf_relse(bp);
                if (error)
                        return error;
        }
        return error;
}

int
xfs_free_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len)
{
        int                     committed;
        int                     done;
        xfs_fileoff_t           endoffset_fsb;
        int                     error;
        xfs_fsblock_t           firstfsb;
        xfs_bmap_free_t         free_list;
        xfs_bmbt_irec_t         imap;
        xfs_off_t               ioffset;
        xfs_off_t               iendoffset;
        xfs_extlen_t            mod=0;
        xfs_mount_t             *mp;
        int                     nimap;
        uint                    resblks;
        xfs_off_t               rounding;
        int                     rt;
        xfs_fileoff_t           startoffset_fsb;
        xfs_trans_t             *tp;

        mp = ip->i_mount;

        trace_xfs_free_file_space(ip);

        error = xfs_qm_dqattach(ip, 0);
        if (error)
                return error;

        error = 0;
        if (len <= 0)   /* if nothing being freed */
                return error;
        rt = XFS_IS_REALTIME_INODE(ip);
        startoffset_fsb = XFS_B_TO_FSB(mp, offset);
        endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len);

        /* wait for the completion of any pending DIOs */
        inode_dio_wait(VFS_I(ip));

        rounding = max_t(xfs_off_t, 1 << mp->m_sb.sb_blocklog, PAGE_CACHE_SIZE);
        ioffset = round_down(offset, rounding);
        iendoffset = round_up(offset + len, rounding) - 1;
        error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping, ioffset,
                                             iendoffset);
        if (error)
                goto out;
        truncate_pagecache_range(VFS_I(ip), ioffset, iendoffset);

        /*
         * Need to zero the stuff we're not freeing, on disk.
         * If it's a realtime file & can't use unwritten extents then we
         * actually need to zero the extent edges.  Otherwise xfs_bunmapi
         * will take care of it for us.
         */
        if (rt && !xfs_sb_version_hasextflgbit(&mp->m_sb)) {
                nimap = 1;
                error = xfs_bmapi_read(ip, startoffset_fsb, 1,
                                        &imap, &nimap, 0);
                if (error)
                        goto out;
                ASSERT(nimap == 0 || nimap == 1);
                if (nimap && imap.br_startblock != HOLESTARTBLOCK) {
                        xfs_daddr_t     block;

                        ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
                        block = imap.br_startblock;
                        mod = do_div(block, mp->m_sb.sb_rextsize);
                        if (mod)
                                startoffset_fsb += mp->m_sb.sb_rextsize - mod;
                }
                nimap = 1;
                error = xfs_bmapi_read(ip, endoffset_fsb - 1, 1,
                                        &imap, &nimap, 0);
                if (error)
                        goto out;
                ASSERT(nimap == 0 || nimap == 1);
                if (nimap && imap.br_startblock != HOLESTARTBLOCK) {
                        ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
                        mod++;
                        if (mod && (mod != mp->m_sb.sb_rextsize))
                                endoffset_fsb -= mod;
                }
        }
        if ((done = (endoffset_fsb <= startoffset_fsb)))
                /*
                 * One contiguous piece to clear
                 */
                error = xfs_zero_remaining_bytes(ip, offset, offset + len - 1);
        else {
                /*
                 * Some full blocks, possibly two pieces to clear
                 */
                if (offset < XFS_FSB_TO_B(mp, startoffset_fsb))
                        error = xfs_zero_remaining_bytes(ip, offset,
                                XFS_FSB_TO_B(mp, startoffset_fsb) - 1);
                if (!error &&
                    XFS_FSB_TO_B(mp, endoffset_fsb) < offset + len)
                        error = xfs_zero_remaining_bytes(ip,
                                XFS_FSB_TO_B(mp, endoffset_fsb),
                                offset + len - 1);
        }

        /*
         * free file space until done or until there is an error
         */
        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
        while (!error && !done) {

                /*
                 * allocate and setup the transaction. Allow this
                 * transaction to dip into the reserve blocks to ensure
                 * the freeing of the space succeeds at ENOSPC.
                 */
                tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write, resblks, 0);

                /*
                 * check for running out of space
                 */
                if (error) {
                        /*
                         * Free the transaction structure.
                         */
                        ASSERT(error == -ENOSPC || XFS_FORCED_SHUTDOWN(mp));
                        xfs_trans_cancel(tp);
                        break;
                }
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                error = xfs_trans_reserve_quota(tp, mp,
                                ip->i_udquot, ip->i_gdquot, ip->i_pdquot,
                                resblks, 0, XFS_QMOPT_RES_REGBLKS);
                if (error)
                        goto error1;

                xfs_trans_ijoin(tp, ip, 0);

                /*
                 * issue the bunmapi() call to free the blocks
                 */
                xfs_bmap_init(&free_list, &firstfsb);
                error = xfs_bunmapi(tp, ip, startoffset_fsb,
                                  endoffset_fsb - startoffset_fsb,
                                  0, 2, &firstfsb, &free_list, &done);
                if (error) {
                        goto error0;
                }

                /*
                 * complete the transaction
                 */
                error = xfs_bmap_finish(&tp, &free_list, &committed);
                if (error) {
                        goto error0;
                }

                error = xfs_trans_commit(tp);
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        }

 out:
        return error;

 error0:
        xfs_bmap_cancel(&free_list);
 error1:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        goto out;
}

/*
 * Preallocate and zero a range of a file. This mechanism has the allocation
 * semantics of fallocate and in addition converts data in the range to zeroes.
 */
int
xfs_zero_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len)
{
        struct xfs_mount        *mp = ip->i_mount;
        uint                    blksize;
        int                     error;

        trace_xfs_zero_file_space(ip);

        blksize = 1 << mp->m_sb.sb_blocklog;

        /*
         * Punch a hole and prealloc the range. We use hole punch rather than
         * unwritten extent conversion for two reasons:
         *
         * 1.) Hole punch handles partial block zeroing for us.
         *
         * 2.) If prealloc returns ENOSPC, the file range is still zero-valued
         * by virtue of the hole punch.
         */
        error = xfs_free_file_space(ip, offset, len);
        if (error)
                goto out;

        error = xfs_alloc_file_space(ip, round_down(offset, blksize),
                                     round_up(offset + len, blksize) -
                                     round_down(offset, blksize),
                                     XFS_BMAPI_PREALLOC);
out:
        return error;

}

/*
 * @next_fsb will keep track of the extent currently undergoing shift.
 * @stop_fsb will keep track of the extent at which we have to stop.
 * If we are shifting left, we will start with block (offset + len) and
 * shift each extent till last extent.
 * If we are shifting right, we will start with last extent inside file space
 * and continue until we reach the block corresponding to offset.
 */
static int
xfs_shift_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len,
        enum shift_direction    direction)
{
        int                     done = 0;
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;
        struct xfs_bmap_free    free_list;
        xfs_fsblock_t           first_block;
        int                     committed;
        xfs_fileoff_t           stop_fsb;
        xfs_fileoff_t           next_fsb;
        xfs_fileoff_t           shift_fsb;

        ASSERT(direction == SHIFT_LEFT || direction == SHIFT_RIGHT);

        if (direction == SHIFT_LEFT) {
                next_fsb = XFS_B_TO_FSB(mp, offset + len);
                stop_fsb = XFS_B_TO_FSB(mp, VFS_I(ip)->i_size);
        } else {
                /*
                 * If right shift, delegate the work of initialization of
                 * next_fsb to xfs_bmap_shift_extent as it has ilock held.
                 */
                next_fsb = NULLFSBLOCK;
                stop_fsb = XFS_B_TO_FSB(mp, offset);
        }

        shift_fsb = XFS_B_TO_FSB(mp, len);

        /*
         * Trim eofblocks to avoid shifting uninitialized post-eof preallocation
         * into the accessible region of the file.
         */
        if (xfs_can_free_eofblocks(ip, true)) {
                error = xfs_free_eofblocks(mp, ip, false);
                if (error)
                        return error;
        }

        /*
         * Writeback and invalidate cache for the remainder of the file as we're
         * about to shift down every extent from offset to EOF.
         */
        error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
                                             offset, -1);
        if (error)
                return error;
        error = invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
                                        offset >> PAGE_CACHE_SHIFT, -1);
        if (error)
                return error;

        /*
         * The extent shiting code works on extent granularity. So, if
         * stop_fsb is not the starting block of extent, we need to split
         * the extent at stop_fsb.
         */
        if (direction == SHIFT_RIGHT) {
                error = xfs_bmap_split_extent(ip, stop_fsb);
                if (error)
                        return error;
        }

        while (!error && !done) {
                tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
                /*
                 * We would need to reserve permanent block for transaction.
                 * This will come into picture when after shifting extent into
                 * hole we found that adjacent extents can be merged which
                 * may lead to freeing of a block during record update.
                 */
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
                                XFS_DIOSTRAT_SPACE_RES(mp, 0), 0);
                if (error) {
                        xfs_trans_cancel(tp);
                        break;
                }

                xfs_ilock(ip, XFS_ILOCK_EXCL);
                error = xfs_trans_reserve_quota(tp, mp, ip->i_udquot,
                                ip->i_gdquot, ip->i_pdquot,
                                XFS_DIOSTRAT_SPACE_RES(mp, 0), 0,
                                XFS_QMOPT_RES_REGBLKS);
                if (error)
                        goto out_trans_cancel;

                xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

                xfs_bmap_init(&free_list, &first_block);

                /*
                 * We are using the write transaction in which max 2 bmbt
                 * updates are allowed
                 */
                error = xfs_bmap_shift_extents(tp, ip, &next_fsb, shift_fsb,
                                &done, stop_fsb, &first_block, &free_list,
                                direction, XFS_BMAP_MAX_SHIFT_EXTENTS);
                if (error)
                        goto out_bmap_cancel;

                error = xfs_bmap_finish(&tp, &free_list, &committed);
                if (error)
                        goto out_bmap_cancel;

                error = xfs_trans_commit(tp);
        }

        return error;

out_bmap_cancel:
        xfs_bmap_cancel(&free_list);
out_trans_cancel:
        xfs_trans_cancel(tp);
        return error;
}

/*
 * xfs_collapse_file_space()
 *      This routine frees disk space and shift extent for the given file.
 *      The first thing we do is to free data blocks in the specified range
 *      by calling xfs_free_file_space(). It would also sync dirty data
 *      and invalidate page cache over the region on which collapse range
 *      is working. And Shift extent records to the left to cover a hole.
 * RETURNS:
 *      0 on success
 *      errno on error
 *
 */
int
xfs_collapse_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len)
{
        int error;

        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        trace_xfs_collapse_file_space(ip);

        error = xfs_free_file_space(ip, offset, len);
        if (error)
                return error;

        return xfs_shift_file_space(ip, offset, len, SHIFT_LEFT);
}

/*
 * xfs_insert_file_space()
 *      This routine create hole space by shifting extents for the given file.
 *      The first thing we do is to sync dirty data and invalidate page cache
 *      over the region on which insert range is working. And split an extent
 *      to two extents at given offset by calling xfs_bmap_split_extent.
 *      And shift all extent records which are laying between [offset,
 *      last allocated extent] to the right to reserve hole range.
 * RETURNS:
 *      0 on success
 *      errno on error
 */
int
xfs_insert_file_space(
        struct xfs_inode        *ip,
        loff_t                  offset,
        loff_t                  len)
{
        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        trace_xfs_insert_file_space(ip);

        return xfs_shift_file_space(ip, offset, len, SHIFT_RIGHT);
}

/*
 * We need to check that the format of the data fork in the temporary inode is
 * valid for the target inode before doing the swap. This is not a problem with
 * attr1 because of the fixed fork offset, but attr2 has a dynamically sized
 * data fork depending on the space the attribute fork is taking so we can get
 * invalid formats on the target inode.
 *
 * E.g. target has space for 7 extents in extent format, temp inode only has
 * space for 6.  If we defragment down to 7 extents, then the tmp format is a
 * btree, but when swapped it needs to be in extent format. Hence we can't just
 * blindly swap data forks on attr2 filesystems.
 *
 * Note that we check the swap in both directions so that we don't end up with
 * a corrupt temporary inode, either.
 *
 * Note that fixing the way xfs_fsr sets up the attribute fork in the source
 * inode will prevent this situation from occurring, so all we do here is
 * reject and log the attempt. basically we are putting the responsibility on
 * userspace to get this right.
 */
static int
xfs_swap_extents_check_format(
        xfs_inode_t     *ip,    /* target inode */
        xfs_inode_t     *tip)   /* tmp inode */
{

        /* Should never get a local format */
        if (ip->i_d.di_format == XFS_DINODE_FMT_LOCAL ||
            tip->i_d.di_format == XFS_DINODE_FMT_LOCAL)
                return -EINVAL;

        /*
         * if the target inode has less extents that then temporary inode then
         * why did userspace call us?
         */
        if (ip->i_d.di_nextents < tip->i_d.di_nextents)
                return -EINVAL;

        /*
         * if the target inode is in extent form and the temp inode is in btree
         * form then we will end up with the target inode in the wrong format
         * as we already know there are less extents in the temp inode.
         */
        if (ip->i_d.di_format == XFS_DINODE_FMT_EXTENTS &&
            tip->i_d.di_format == XFS_DINODE_FMT_BTREE)
                return -EINVAL;

        /* Check temp in extent form to max in target */
        if (tip->i_d.di_format == XFS_DINODE_FMT_EXTENTS &&
            XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) >
                        XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK))
                return -EINVAL;

        /* Check target in extent form to max in temp */
        if (ip->i_d.di_format == XFS_DINODE_FMT_EXTENTS &&
            XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) >
                        XFS_IFORK_MAXEXT(tip, XFS_DATA_FORK))
                return -EINVAL;

        /*
         * If we are in a btree format, check that the temp root block will fit
         * in the target and that it has enough extents to be in btree format
         * in the target.
         *
         * Note that we have to be careful to allow btree->extent conversions
         * (a common defrag case) which will occur when the temp inode is in
         * extent format...
         */
        if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
                if (XFS_IFORK_BOFF(ip) &&
                    XFS_BMAP_BMDR_SPACE(tip->i_df.if_broot) > XFS_IFORK_BOFF(ip))
                        return -EINVAL;
                if (XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) <=
                    XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK))
                        return -EINVAL;
        }

        /* Reciprocal target->temp btree format checks */
        if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
                if (XFS_IFORK_BOFF(tip) &&
                    XFS_BMAP_BMDR_SPACE(ip->i_df.if_broot) > XFS_IFORK_BOFF(tip))
                        return -EINVAL;
                if (XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) <=
                    XFS_IFORK_MAXEXT(tip, XFS_DATA_FORK))
                        return -EINVAL;
        }

        return 0;
}

static int
xfs_swap_extent_flush(
        struct xfs_inode        *ip)
{
        int     error;

        error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
        if (error)
                return error;
        truncate_pagecache_range(VFS_I(ip), 0, -1);

        /* Verify O_DIRECT for ftmp */
        if (VFS_I(ip)->i_mapping->nrpages)
                return -EINVAL;
        return 0;
}

int
xfs_swap_extents(
        xfs_inode_t     *ip,    /* target inode */
        xfs_inode_t     *tip,   /* tmp inode */
        xfs_swapext_t   *sxp)
{
        xfs_mount_t     *mp = ip->i_mount;
        xfs_trans_t     *tp;
        xfs_bstat_t     *sbp = &sxp->sx_stat;
        xfs_ifork_t     *tempifp, *ifp, *tifp;
        int             src_log_flags, target_log_flags;
        int             error = 0;
        int             aforkblks = 0;
        int             taforkblks = 0;
        __uint64_t      tmp;
        int             lock_flags;

        tempifp = kmem_alloc(sizeof(xfs_ifork_t), KM_MAYFAIL);
        if (!tempifp) {
                error = -ENOMEM;
                goto out;
        }

        /*
         * Lock the inodes against other IO, page faults and truncate to
         * begin with.  Then we can ensure the inodes are flushed and have no
         * page cache safely. Once we have done this we can take the ilocks and
         * do the rest of the checks.
         */
        lock_flags = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
        xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL);
        xfs_lock_two_inodes(ip, tip, XFS_MMAPLOCK_EXCL);

        /* Verify that both files have the same format */
        if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) {
                error = -EINVAL;
                goto out_unlock;
        }

        /* Verify both files are either real-time or non-realtime */
        if (XFS_IS_REALTIME_INODE(ip) != XFS_IS_REALTIME_INODE(tip)) {
                error = -EINVAL;
                goto out_unlock;
        }

        error = xfs_swap_extent_flush(ip);
        if (error)
                goto out_unlock;
        error = xfs_swap_extent_flush(tip);
        if (error)
                goto out_unlock;

        tp = xfs_trans_alloc(mp, XFS_TRANS_SWAPEXT);
        error = xfs_trans_reserve(tp, &M_RES(mp)->tr_ichange, 0, 0);
        if (error) {
                xfs_trans_cancel(tp);
                goto out_unlock;
        }

        /*
         * Lock and join the inodes to the tansaction so that transaction commit
         * or cancel will unlock the inodes from this point onwards.
         */
        xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
        lock_flags |= XFS_ILOCK_EXCL;
        xfs_trans_ijoin(tp, ip, lock_flags);
        xfs_trans_ijoin(tp, tip, lock_flags);


        /* Verify all data are being swapped */
        if (sxp->sx_offset != 0 ||
            sxp->sx_length != ip->i_d.di_size ||
            sxp->sx_length != tip->i_d.di_size) {
                error = -EFAULT;
                goto out_trans_cancel;
        }

        trace_xfs_swap_extent_before(ip, 0);
        trace_xfs_swap_extent_before(tip, 1);

        /* check inode formats now that data is flushed */
        error = xfs_swap_extents_check_format(ip, tip);
        if (error) {
                xfs_notice(mp,
                    "%s: inode 0x%llx format is incompatible for exchanging.",
                                __func__, ip->i_ino);
                goto out_trans_cancel;
        }

        /*
         * Compare the current change & modify times with that
         * passed in.  If they differ, we abort this swap.
         * This is the mechanism used to ensure the calling
         * process that the file was not changed out from
         * under it.
         */
        if ((sbp->bs_ctime.tv_sec != VFS_I(ip)->i_ctime.tv_sec) ||
            (sbp->bs_ctime.tv_nsec != VFS_I(ip)->i_ctime.tv_nsec) ||
            (sbp->bs_mtime.tv_sec != VFS_I(ip)->i_mtime.tv_sec) ||
            (sbp->bs_mtime.tv_nsec != VFS_I(ip)->i_mtime.tv_nsec)) {
                error = -EBUSY;
                goto out_trans_cancel;
        }
        /*
         * Count the number of extended attribute blocks
         */
        if ( ((XFS_IFORK_Q(ip) != 0) && (ip->i_d.di_anextents > 0)) &&
             (ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL)) {
                error = xfs_bmap_count_blocks(tp, ip, XFS_ATTR_FORK, &aforkblks);
                if (error)
                        goto out_trans_cancel;
        }
        if ( ((XFS_IFORK_Q(tip) != 0) && (tip->i_d.di_anextents > 0)) &&
             (tip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL)) {
                error = xfs_bmap_count_blocks(tp, tip, XFS_ATTR_FORK,
                        &taforkblks);
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * Before we've swapped the forks, lets set the owners of the forks
         * appropriately. We have to do this as we are demand paging the btree
         * buffers, and so the validation done on read will expect the owner
         * field to be correctly set. Once we change the owners, we can swap the
         * inode forks.
         *
         * Note the trickiness in setting the log flags - we set the owner log
         * flag on the opposite inode (i.e. the inode we are setting the new
         * owner to be) because once we swap the forks and log that, log
         * recovery is going to see the fork as owned by the swapped inode,
         * not the pre-swapped inodes.
         */
        src_log_flags = XFS_ILOG_CORE;
        target_log_flags = XFS_ILOG_CORE;
        if (ip->i_d.di_version == 3 &&
            ip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
                target_log_flags |= XFS_ILOG_DOWNER;
                error = xfs_bmbt_change_owner(tp, ip, XFS_DATA_FORK,
                                              tip->i_ino, NULL);
                if (error)
                        goto out_trans_cancel;
        }

        if (tip->i_d.di_version == 3 &&
            tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
                src_log_flags |= XFS_ILOG_DOWNER;
                error = xfs_bmbt_change_owner(tp, tip, XFS_DATA_FORK,
                                              ip->i_ino, NULL);
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * Swap the data forks of the inodes
         */
        ifp = &ip->i_df;
        tifp = &tip->i_df;
        *tempifp = *ifp;        /* struct copy */
        *ifp = *tifp;           /* struct copy */
        *tifp = *tempifp;       /* struct copy */

        /*
         * Fix the on-disk inode values
         */
        tmp = (__uint64_t)ip->i_d.di_nblocks;
        ip->i_d.di_nblocks = tip->i_d.di_nblocks - taforkblks + aforkblks;
        tip->i_d.di_nblocks = tmp + taforkblks - aforkblks;

        tmp = (__uint64_t) ip->i_d.di_nextents;
        ip->i_d.di_nextents = tip->i_d.di_nextents;
        tip->i_d.di_nextents = tmp;

        tmp = (__uint64_t) ip->i_d.di_format;
        ip->i_d.di_format = tip->i_d.di_format;
        tip->i_d.di_format = tmp;

        /*
         * The extents in the source inode could still contain speculative
         * preallocation beyond EOF (e.g. the file is open but not modified
         * while defrag is in progress). In that case, we need to copy over the
         * number of delalloc blocks the data fork in the source inode is
         * tracking beyond EOF so that when the fork is truncated away when the
         * temporary inode is unlinked we don't underrun the i_delayed_blks
         * counter on that inode.
         */
        ASSERT(tip->i_delayed_blks == 0);
        tip->i_delayed_blks = ip->i_delayed_blks;
        ip->i_delayed_blks = 0;

        switch (ip->i_d.di_format) {
        case XFS_DINODE_FMT_EXTENTS:
                /* If the extents fit in the inode, fix the
                 * pointer.  Otherwise it's already NULL or
                 * pointing to the extent.
                 */
                if (ip->i_d.di_nextents <= XFS_INLINE_EXTS) {
                        ifp->if_u1.if_extents =
                                ifp->if_u2.if_inline_ext;
                }
                src_log_flags |= XFS_ILOG_DEXT;
                break;
        case XFS_DINODE_FMT_BTREE:
                ASSERT(ip->i_d.di_version < 3 ||
                       (src_log_flags & XFS_ILOG_DOWNER));
                src_log_flags |= XFS_ILOG_DBROOT;
                break;
        }

        switch (tip->i_d.di_format) {
        case XFS_DINODE_FMT_EXTENTS:
                /* If the extents fit in the inode, fix the
                 * pointer.  Otherwise it's already NULL or
                 * pointing to the extent.
                 */
                if (tip->i_d.di_nextents <= XFS_INLINE_EXTS) {
                        tifp->if_u1.if_extents =
                                tifp->if_u2.if_inline_ext;
                }
                target_log_flags |= XFS_ILOG_DEXT;
                break;
        case XFS_DINODE_FMT_BTREE:
                target_log_flags |= XFS_ILOG_DBROOT;
                ASSERT(tip->i_d.di_version < 3 ||
                       (target_log_flags & XFS_ILOG_DOWNER));
                break;
        }

        xfs_trans_log_inode(tp, ip,  src_log_flags);
        xfs_trans_log_inode(tp, tip, target_log_flags);

        /*
         * If this is a synchronous mount, make sure that the
         * transaction goes to disk before returning to the user.
         */
        if (mp->m_flags & XFS_MOUNT_WSYNC)
                xfs_trans_set_sync(tp);

        error = xfs_trans_commit(tp);

        trace_xfs_swap_extent_after(ip, 0);
        trace_xfs_swap_extent_after(tip, 1);
out:
        kmem_free(tempifp);
        return error;

out_unlock:
        xfs_iunlock(ip, lock_flags);
        xfs_iunlock(tip, lock_flags);
        goto out;

out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out;
}