// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * Copyright (c) 2012 Red Hat, Inc.
 * All Rights Reserved.
 */
#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_defer.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_trans.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_iomap.h"
#include "xfs_reflink.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)
{
        if (XFS_IS_REALTIME_INODE(ip))
                return XFS_FSB_TO_BB(ip->i_mount, fsb);
        return 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;
        struct xfs_buftarg      *target = xfs_inode_buftarg(ip);
        xfs_daddr_t             sector = xfs_fsb_to_db(ip, start_fsb);
        sector_t                block = XFS_BB_TO_FSBT(mp, sector);

        return blkdev_issue_zeroout(target->bt_bdev,
                block << (mp->m_super->s_blocksize_bits - 9),
                count_fsb << (mp->m_super->s_blocksize_bits - 9),
                GFP_NOFS, 0);
}

#ifdef CONFIG_XFS_RT
int
xfs_bmap_rtalloc(
        struct xfs_bmalloca     *ap)    /* bmap alloc argument struct */
{
        int             error;          /* error return value */
        xfs_mount_t     *mp;            /* mount point structure */
        xfs_extlen_t    prod = 0;       /* product factor for allocators */
        xfs_extlen_t    mod = 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.
         */
        div_u64_rem(ap->offset, align, &mod);
        if (mod || 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 modifications to both the RT bitmap and summary inodes
         */
        xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL|XFS_ILOCK_RTBITMAP);
        xfs_trans_ijoin(ap->tp, mp->m_rbmip, XFS_ILOCK_EXCL);
        xfs_ilock(mp->m_rsumip, XFS_ILOCK_EXCL|XFS_ILOCK_RTSUM);
        xfs_trans_ijoin(ap->tp, mp->m_rsumip, 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 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.
         */
        do_div(ap->blkno, mp->m_sb.sb_rextsize);
        rtb = ap->blkno;
        ap->length = ralen;
        error = xfs_rtallocate_extent(ap->tp, ap->blkno, 1, ap->length,
                                &ralen, ap->wasdel, prod, &rtb);
        if (error)
                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);
        } else {
                ap->length = 0;
        }
        return 0;
}
#endif /* CONFIG_XFS_RT */

/*
 * Extent tree block counting routines.
 */

/*
 * Count leaf blocks given a range of extent records.  Delayed allocation
 * extents are not counted towards the totals.
 */
xfs_extnum_t
xfs_bmap_count_leaves(
        struct xfs_ifork        *ifp,
        xfs_filblks_t           *count)
{
        struct xfs_iext_cursor  icur;
        struct xfs_bmbt_irec    got;
        xfs_extnum_t            numrecs = 0;

        for_each_xfs_iext(ifp, &icur, &got) {
                if (!isnullstartblock(got.br_startblock)) {
                        *count += got.br_blockcount;
                        numrecs++;
                }
        }

        return numrecs;
}

/*
 * Count fsblocks of the given fork.  Delayed allocation extents are
 * not counted towards the totals.
 */
int
xfs_bmap_count_blocks(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_extnum_t            *nextents,
        xfs_filblks_t           *count)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        struct xfs_btree_cur    *cur;
        xfs_extlen_t            btblocks = 0;
        int                     error;

        *nextents = 0;
        *count = 0;

        if (!ifp)
                return 0;

        switch (ifp->if_format) {
        case XFS_DINODE_FMT_BTREE:
                if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                        error = xfs_iread_extents(tp, ip, whichfork);
                        if (error)
                                return error;
                }

                cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
                error = xfs_btree_count_blocks(cur, &btblocks);
                xfs_btree_del_cursor(cur, error);
                if (error)
                        return error;

                /*
                 * xfs_btree_count_blocks includes the root block contained in
                 * the inode fork in @btblocks, so subtract one because we're
                 * only interested in allocated disk blocks.
                 */
                *count += btblocks - 1;

                /* fall through */
        case XFS_DINODE_FMT_EXTENTS:
                *nextents = xfs_bmap_count_leaves(ifp, count);
                break;
        }

        return 0;
}

static int
xfs_getbmap_report_one(
        struct xfs_inode        *ip,
        struct getbmapx         *bmv,
        struct kgetbmap         *out,
        int64_t                 bmv_end,
        struct xfs_bmbt_irec    *got)
{
        struct kgetbmap         *p = out + bmv->bmv_entries;
        bool                    shared = false;
        int                     error;

        error = xfs_reflink_trim_around_shared(ip, got, &shared);
        if (error)
                return error;

        if (isnullstartblock(got->br_startblock) ||
            got->br_startblock == DELAYSTARTBLOCK) {
                /*
                 * Delalloc 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 (got->br_startoff < XFS_B_TO_FSB(ip->i_mount, XFS_ISIZE(ip)))
                        ASSERT((bmv->bmv_iflags & BMV_IF_DELALLOC) != 0);

                p->bmv_oflags |= BMV_OF_DELALLOC;
                p->bmv_block = -2;
        } else {
                p->bmv_block = xfs_fsb_to_db(ip, got->br_startblock);
        }

        if (got->br_state == XFS_EXT_UNWRITTEN &&
            (bmv->bmv_iflags & BMV_IF_PREALLOC))
                p->bmv_oflags |= BMV_OF_PREALLOC;

        if (shared)
                p->bmv_oflags |= BMV_OF_SHARED;

        p->bmv_offset = XFS_FSB_TO_BB(ip->i_mount, got->br_startoff);
        p->bmv_length = XFS_FSB_TO_BB(ip->i_mount, got->br_blockcount);

        bmv->bmv_offset = p->bmv_offset + p->bmv_length;
        bmv->bmv_length = max(0LL, bmv_end - bmv->bmv_offset);
        bmv->bmv_entries++;
        return 0;
}

static void
xfs_getbmap_report_hole(
        struct xfs_inode        *ip,
        struct getbmapx         *bmv,
        struct kgetbmap         *out,
        int64_t                 bmv_end,
        xfs_fileoff_t           bno,
        xfs_fileoff_t           end)
{
        struct kgetbmap         *p = out + bmv->bmv_entries;

        if (bmv->bmv_iflags & BMV_IF_NO_HOLES)
                return;

        p->bmv_block = -1;
        p->bmv_offset = XFS_FSB_TO_BB(ip->i_mount, bno);
        p->bmv_length = XFS_FSB_TO_BB(ip->i_mount, end - bno);

        bmv->bmv_offset = p->bmv_offset + p->bmv_length;
        bmv->bmv_length = max(0LL, bmv_end - bmv->bmv_offset);
        bmv->bmv_entries++;
}

static inline bool
xfs_getbmap_full(
        struct getbmapx         *bmv)
{
        return bmv->bmv_length == 0 || bmv->bmv_entries >= bmv->bmv_count - 1;
}

static bool
xfs_getbmap_next_rec(
        struct xfs_bmbt_irec    *rec,
        xfs_fileoff_t           total_end)
{
        xfs_fileoff_t           end = rec->br_startoff + rec->br_blockcount;

        if (end == total_end)
                return false;

        rec->br_startoff += rec->br_blockcount;
        if (!isnullstartblock(rec->br_startblock) &&
            rec->br_startblock != DELAYSTARTBLOCK)
                rec->br_startblock += rec->br_blockcount;
        rec->br_blockcount = total_end - end;
        return true;
}

/*
 * 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(
        struct xfs_inode        *ip,
        struct getbmapx         *bmv,           /* user bmap structure */
        struct kgetbmap         *out)
{
        struct xfs_mount        *mp = ip->i_mount;
        int                     iflags = bmv->bmv_iflags;
        int                     whichfork, lock, error = 0;
        int64_t                 bmv_end, max_len;
        xfs_fileoff_t           bno, first_bno;
        struct xfs_ifork        *ifp;
        struct xfs_bmbt_irec    got, rec;
        xfs_filblks_t           len;
        struct xfs_iext_cursor  icur;

        if (bmv->bmv_iflags & ~BMV_IF_VALID)
                return -EINVAL;
#ifndef DEBUG
        /* Only allow CoW fork queries if we're debugging. */
        if (iflags & BMV_IF_COWFORK)
                return -EINVAL;
#endif
        if ((iflags & BMV_IF_ATTRFORK) && (iflags & BMV_IF_COWFORK))
                return -EINVAL;

        if (bmv->bmv_length < -1)
                return -EINVAL;
        bmv->bmv_entries = 0;
        if (bmv->bmv_length == 0)
                return 0;

        if (iflags & BMV_IF_ATTRFORK)
                whichfork = XFS_ATTR_FORK;
        else if (iflags & BMV_IF_COWFORK)
                whichfork = XFS_COW_FORK;
        else
                whichfork = XFS_DATA_FORK;
        ifp = XFS_IFORK_PTR(ip, whichfork);

        xfs_ilock(ip, XFS_IOLOCK_SHARED);
        switch (whichfork) {
        case XFS_ATTR_FORK:
                if (!XFS_IFORK_Q(ip))
                        goto out_unlock_iolock;

                max_len = 1LL << 32;
                lock = xfs_ilock_attr_map_shared(ip);
                break;
        case XFS_COW_FORK:
                /* No CoW fork? Just return */
                if (!ifp)
                        goto out_unlock_iolock;

                if (xfs_get_cowextsz_hint(ip))
                        max_len = mp->m_super->s_maxbytes;
                else
                        max_len = XFS_ISIZE(ip);

                lock = XFS_ILOCK_SHARED;
                xfs_ilock(ip, lock);
                break;
        case 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.
                         */
                }

                if (xfs_get_extsz_hint(ip) ||
                    (ip->i_d.di_flags &
                     (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)))
                        max_len = mp->m_super->s_maxbytes;
                else
                        max_len = XFS_ISIZE(ip);

                lock = xfs_ilock_data_map_shared(ip);
                break;
        }

        switch (ifp->if_format) {
        case XFS_DINODE_FMT_EXTENTS:
        case XFS_DINODE_FMT_BTREE:
                break;
        case XFS_DINODE_FMT_LOCAL:
                /* Local format inode forks report no extents. */
                goto out_unlock_ilock;
        default:
                error = -EINVAL;
                goto out_unlock_ilock;
        }

        if (bmv->bmv_length == -1) {
                max_len = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, max_len));
                bmv->bmv_length = max(0LL, max_len - bmv->bmv_offset);
        }

        bmv_end = bmv->bmv_offset + bmv->bmv_length;

        first_bno = bno = XFS_BB_TO_FSBT(mp, bmv->bmv_offset);
        len = XFS_BB_TO_FSB(mp, bmv->bmv_length);

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(NULL, ip, whichfork);
                if (error)
                        goto out_unlock_ilock;
        }

        if (!xfs_iext_lookup_extent(ip, ifp, bno, &icur, &got)) {
                /*
                 * Report a whole-file hole if the delalloc flag is set to
                 * stay compatible with the old implementation.
                 */
                if (iflags & BMV_IF_DELALLOC)
                        xfs_getbmap_report_hole(ip, bmv, out, bmv_end, bno,
                                        XFS_B_TO_FSB(mp, XFS_ISIZE(ip)));
                goto out_unlock_ilock;
        }

        while (!xfs_getbmap_full(bmv)) {
                xfs_trim_extent(&got, first_bno, len);

                /*
                 * Report an entry for a hole if this extent doesn't directly
                 * follow the previous one.
                 */
                if (got.br_startoff > bno) {
                        xfs_getbmap_report_hole(ip, bmv, out, bmv_end, bno,
                                        got.br_startoff);
                        if (xfs_getbmap_full(bmv))
                                break;
                }

                /*
                 * In order to report shared extents accurately, we report each
                 * distinct shared / unshared part of a single bmbt record with
                 * an individual getbmapx record.
                 */
                bno = got.br_startoff + got.br_blockcount;
                rec = got;
                do {
                        error = xfs_getbmap_report_one(ip, bmv, out, bmv_end,
                                        &rec);
                        if (error || xfs_getbmap_full(bmv))
                                goto out_unlock_ilock;
                } while (xfs_getbmap_next_rec(&rec, bno));

                if (!xfs_iext_next_extent(ifp, &icur, &got)) {
                        xfs_fileoff_t   end = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));

                        out[bmv->bmv_entries - 1].bmv_oflags |= BMV_OF_LAST;

                        if (whichfork != XFS_ATTR_FORK && bno < end &&
                            !xfs_getbmap_full(bmv)) {
                                xfs_getbmap_report_hole(ip, bmv, out, bmv_end,
                                                bno, end);
                        }
                        break;
                }

                if (bno >= first_bno + len)
                        break;
        }

out_unlock_ilock:
        xfs_iunlock(ip, lock);
out_unlock_iolock:
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
        return error;
}

/*
 * Dead simple method of punching delalyed allocation blocks from a range in
 * the inode.  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)
{
        struct xfs_ifork        *ifp = &ip->i_df;
        xfs_fileoff_t           end_fsb = start_fsb + length;
        struct xfs_bmbt_irec    got, del;
        struct xfs_iext_cursor  icur;
        int                     error = 0;

        ASSERT(ifp->if_flags & XFS_IFEXTENTS);

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
                goto out_unlock;

        while (got.br_startoff + got.br_blockcount > start_fsb) {
                del = got;
                xfs_trim_extent(&del, start_fsb, length);

                /*
                 * A delete can push the cursor forward. Step back to the
                 * previous extent on non-delalloc or extents outside the
                 * target range.
                 */
                if (!del.br_blockcount ||
                    !isnullstartblock(del.br_startblock)) {
                        if (!xfs_iext_prev_extent(ifp, &icur, &got))
                                break;
                        continue;
                }

                error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, &icur,
                                                  &got, &del);
                if (error || !xfs_iext_get_extent(ifp, &icur, &got))
                        break;
        }

out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        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(VFS_I(ip)->i_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 to free any blocks beyond eof. The caller must hold
 * IOLOCK_EXCL unless we are in the inode reclaim path and have the only
 * reference to the inode.
 */
int
xfs_free_eofblocks(
        struct xfs_inode        *ip)
{
        struct xfs_trans        *tp;
        int                     error;
        xfs_fileoff_t           end_fsb;
        xfs_fileoff_t           last_fsb;
        xfs_filblks_t           map_len;
        int                     nimaps;
        struct xfs_bmbt_irec    imap;
        struct xfs_mount        *mp = ip->i_mount;

        /*
         * 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 there are blocks after the end of file, truncate the file to its
         * current size to free them up.
         */
        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);
                if (error)
                        return error;

                /* wait on dio to ensure i_size has settled */
                inode_dio_wait(VFS_I(ip));

                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0,
                                &tp);
                if (error) {
                        ASSERT(XFS_FORCED_SHUTDOWN(mp));
                        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_flags(&tp, ip, XFS_DATA_FORK,
                                        XFS_ISIZE(ip), XFS_BMAPI_NODISCARD);
                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);
        }
        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_fileoff_t           endoffset_fsb;
        int                     nimaps;
        int                     quota_flag;
        int                     rt;
        xfs_trans_t             *tp;
        xfs_bmbt_irec_t         imaps[1], *imapp;
        uint                    qblocks, resblks, resrtextents;
        int                     error;

        trace_xfs_alloc_file_space(ip);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        error = xfs_qm_dqattach(ip);
        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);
        endoffset_fsb = XFS_B_TO_FSB(mp, offset + count);
        allocatesize_fsb = endoffset_fsb - startoffset_fsb;

        /*
         * 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;
                        div_u64_rem(startoffset_fsb, extsz, &temp);
                        if (temp)
                                e += temp;
                        div_u64_rem(e, extsz, &temp);
                        if (temp)
                                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.
                 */
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks,
                                resrtextents, 0, &tp);

                /*
                 * Check for running out of space
                 */
                if (error) {
                        /*
                         * Free the transaction structure.
                         */
                        ASSERT(error == -ENOSPC || XFS_FORCED_SHUTDOWN(mp));
                        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);

                error = xfs_bmapi_write(tp, ip, startoffset_fsb,
                                        allocatesize_fsb, alloc_type, 0, imapp,
                                        &nimaps);
                if (error)
                        goto error0;

                /*
                 * Complete the transaction
                 */
                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: /* unlock inode, unreserve quota blocks, cancel trans */
        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;
}

static int
xfs_unmap_extent(
        struct xfs_inode        *ip,
        xfs_fileoff_t           startoffset_fsb,
        xfs_filblks_t           len_fsb,
        int                     *done)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        uint                    resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
        int                     error;

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
        if (error) {
                ASSERT(error == -ENOSPC || XFS_FORCED_SHUTDOWN(mp));
                return error;
        }

        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 out_trans_cancel;

        xfs_trans_ijoin(tp, ip, 0);

        error = xfs_bunmapi(tp, ip, startoffset_fsb, len_fsb, 0, 2, done);
        if (error)
                goto out_trans_cancel;

        error = xfs_trans_commit(tp);
out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;

out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out_unlock;
}

/* Caller must first wait for the completion of any pending DIOs if required. */
int
xfs_flush_unmap_range(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct inode            *inode = VFS_I(ip);
        xfs_off_t               rounding, start, end;
        int                     error;

        rounding = max_t(xfs_off_t, 1 << mp->m_sb.sb_blocklog, PAGE_SIZE);
        start = round_down(offset, rounding);
        end = round_up(offset + len, rounding) - 1;

        error = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (error)
                return error;
        truncate_pagecache_range(inode, start, end);
        return 0;
}

int
xfs_free_file_space(
        struct xfs_inode        *ip,
        xfs_off_t               offset,
        xfs_off_t               len)
{
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fileoff_t           startoffset_fsb;
        xfs_fileoff_t           endoffset_fsb;
        int                     done = 0, error;

        trace_xfs_free_file_space(ip);

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

        if (len <= 0)   /* if nothing being freed */
                return 0;

        startoffset_fsb = XFS_B_TO_FSB(mp, offset);
        endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len);

        /*
         * Need to zero the stuff we're not freeing, on disk.
         */
        if (endoffset_fsb > startoffset_fsb) {
                while (!done) {
                        error = xfs_unmap_extent(ip, startoffset_fsb,
                                        endoffset_fsb - startoffset_fsb, &done);
                        if (error)
                                return error;
                }
        }

        /*
         * Now that we've unmap all full blocks we'll have to zero out any
         * partial block at the beginning and/or end.  iomap_zero_range is smart
         * enough to skip any holes, including those we just created, but we
         * must take care not to zero beyond EOF and enlarge i_size.
         */
        if (offset >= XFS_ISIZE(ip))
                return 0;
        if (offset + len > XFS_ISIZE(ip))
                len = XFS_ISIZE(ip) - offset;
        error = iomap_zero_range(VFS_I(ip), offset, len, NULL,
                        &xfs_buffered_write_iomap_ops);
        if (error)
                return error;

        /*
         * If we zeroed right up to EOF and EOF straddles a page boundary we
         * must make sure that the post-EOF area is also zeroed because the
         * page could be mmap'd and iomap_zero_range doesn't do that for us.
         * Writeback of the eof page will do this, albeit clumsily.
         */
        if (offset + len >= XFS_ISIZE(ip) && offset_in_page(offset + len) > 0) {
                error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
                                round_down(offset + len, PAGE_SIZE), LLONG_MAX);
        }

        return error;
}

static int
xfs_prepare_shift(
        struct xfs_inode        *ip,
        loff_t                  offset)
{
        struct xfs_mount        *mp = ip->i_mount;
        int                     error;

        /*
         * 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(ip);
                if (error)
                        return error;
        }

        /*
         * Shift operations must stabilize the start block offset boundary along
         * with the full range of the operation. If we don't, a COW writeback
         * completion could race with an insert, front merge with the start
         * extent (after split) during the shift and corrupt the file. Start
         * with the block just prior to the start to stabilize the boundary.
         */
        offset = round_down(offset, 1 << mp->m_sb.sb_blocklog);
        if (offset)
                offset -= (1 << mp->m_sb.sb_blocklog);

        /*
         * Writeback and invalidate cache for the remainder of the file as we're
         * about to shift down every extent from offset to EOF.
         */
        error = xfs_flush_unmap_range(ip, offset, XFS_ISIZE(ip));
        if (error)
                return error;

        /*
         * Clean out anything hanging around in the cow fork now that
         * we've flushed all the dirty data out to disk to avoid having
         * CoW extents at the wrong offsets.
         */
        if (xfs_inode_has_cow_data(ip)) {
                error = xfs_reflink_cancel_cow_range(ip, offset, NULLFILEOFF,
                                true);
                if (error)
                        return error;
        }

        return 0;
}

/*
 * 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)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;
        xfs_fileoff_t           next_fsb = XFS_B_TO_FSB(mp, offset + len);
        xfs_fileoff_t           shift_fsb = XFS_B_TO_FSB(mp, len);
        bool                    done = false;

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

        trace_xfs_collapse_file_space(ip);

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

        error = xfs_prepare_shift(ip, offset);
        if (error)
                return error;

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

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

        while (!done) {
                error = xfs_bmap_collapse_extents(tp, ip, &next_fsb, shift_fsb,
                                &done);
                if (error)
                        goto out_trans_cancel;
                if (done)
                        break;

                /* finish any deferred frees and roll the transaction */
                error = xfs_defer_finish(&tp);
                if (error)
                        goto out_trans_cancel;
        }

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

out_trans_cancel:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * 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)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;
        xfs_fileoff_t           stop_fsb = XFS_B_TO_FSB(mp, offset);
        xfs_fileoff_t           next_fsb = NULLFSBLOCK;
        xfs_fileoff_t           shift_fsb = XFS_B_TO_FSB(mp, len);
        bool                    done = false;

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

        trace_xfs_insert_file_space(ip);

        error = xfs_bmap_can_insert_extents(ip, stop_fsb, shift_fsb);
        if (error)
                return error;

        error = xfs_prepare_shift(ip, offset);
        if (error)
                return error;

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write,
                        XFS_DIOSTRAT_SPACE_RES(mp, 0), 0, 0, &tp);
        if (error)
                return error;

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

        /*
         * The extent shifting 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.
         */
        error = xfs_bmap_split_extent(tp, ip, stop_fsb);
        if (error)
                goto out_trans_cancel;

        do {
                error = xfs_defer_finish(&tp);
                if (error)
                        goto out_trans_cancel;

                error = xfs_bmap_insert_extents(tp, ip, &next_fsb, shift_fsb,
                                &done, stop_fsb);
                if (error)
                        goto out_trans_cancel;
        } while (!done);

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

out_trans_cancel:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * 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(
        struct xfs_inode        *ip,    /* target inode */
        struct xfs_inode        *tip)   /* tmp inode */
{
        struct xfs_ifork        *ifp = &ip->i_df;
        struct xfs_ifork        *tifp = &tip->i_df;

        /* User/group/project quota ids must match if quotas are enforced. */
        if (XFS_IS_QUOTA_ON(ip->i_mount) &&
            (!uid_eq(VFS_I(ip)->i_uid, VFS_I(tip)->i_uid) ||
             !gid_eq(VFS_I(ip)->i_gid, VFS_I(tip)->i_gid) ||
             ip->i_d.di_projid != tip->i_d.di_projid))
                return -EINVAL;

        /* Should never get a local format */
        if (ifp->if_format == XFS_DINODE_FMT_LOCAL ||
            tifp->if_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 (ifp->if_nextents < tifp->if_nextents)
                return -EINVAL;

        /*
         * If we have to use the (expensive) rmap swap method, we can
         * handle any number of extents and any format.
         */
        if (xfs_sb_version_hasrmapbt(&ip->i_mount->m_sb))
                return 0;

        /*
         * 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 (ifp->if_format == XFS_DINODE_FMT_EXTENTS &&
            tifp->if_format == XFS_DINODE_FMT_BTREE)
                return -EINVAL;

        /* Check temp in extent form to max in target */
        if (tifp->if_format == XFS_DINODE_FMT_EXTENTS &&
            tifp->if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK))
                return -EINVAL;

        /* Check target in extent form to max in temp */
        if (ifp->if_format == XFS_DINODE_FMT_EXTENTS &&
            ifp->if_nextents > 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 (tifp->if_format == XFS_DINODE_FMT_BTREE) {
                if (XFS_IFORK_Q(ip) &&
                    XFS_BMAP_BMDR_SPACE(tifp->if_broot) > XFS_IFORK_BOFF(ip))
                        return -EINVAL;
                if (tifp->if_nextents <= XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK))
                        return -EINVAL;
        }

        /* Reciprocal target->temp btree format checks */
        if (ifp->if_format == XFS_DINODE_FMT_BTREE) {
                if (XFS_IFORK_Q(tip) &&
                    XFS_BMAP_BMDR_SPACE(ip->i_df.if_broot) > XFS_IFORK_BOFF(tip))
                        return -EINVAL;
                if (ifp->if_nextents <= 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;
}

/*
 * Move extents from one file to another, when rmap is enabled.
 */
STATIC int
xfs_swap_extent_rmap(
        struct xfs_trans                **tpp,
        struct xfs_inode                *ip,
        struct xfs_inode                *tip)
{
        struct xfs_trans                *tp = *tpp;
        struct xfs_bmbt_irec            irec;
        struct xfs_bmbt_irec            uirec;
        struct xfs_bmbt_irec            tirec;
        xfs_fileoff_t                   offset_fsb;
        xfs_fileoff_t                   end_fsb;
        xfs_filblks_t                   count_fsb;
        int                             error;
        xfs_filblks_t                   ilen;
        xfs_filblks_t                   rlen;
        int                             nimaps;
        uint64_t                        tip_flags2;

        /*
         * If the source file has shared blocks, we must flag the donor
         * file as having shared blocks so that we get the shared-block
         * rmap functions when we go to fix up the rmaps.  The flags
         * will be switch for reals later.
         */
        tip_flags2 = tip->i_d.di_flags2;
        if (ip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK)
                tip->i_d.di_flags2 |= XFS_DIFLAG2_REFLINK;

        offset_fsb = 0;
        end_fsb = XFS_B_TO_FSB(ip->i_mount, i_size_read(VFS_I(ip)));
        count_fsb = (xfs_filblks_t)(end_fsb - offset_fsb);

        while (count_fsb) {
                /* Read extent from the donor file */
                nimaps = 1;
                error = xfs_bmapi_read(tip, offset_fsb, count_fsb, &tirec,
                                &nimaps, 0);
                if (error)
                        goto out;
                ASSERT(nimaps == 1);
                ASSERT(tirec.br_startblock != DELAYSTARTBLOCK);

                trace_xfs_swap_extent_rmap_remap(tip, &tirec);
                ilen = tirec.br_blockcount;

                /* Unmap the old blocks in the source file. */
                while (tirec.br_blockcount) {
                        ASSERT(tp->t_firstblock == NULLFSBLOCK);
                        trace_xfs_swap_extent_rmap_remap_piece(tip, &tirec);

                        /* Read extent from the source file */
                        nimaps = 1;
                        error = xfs_bmapi_read(ip, tirec.br_startoff,
                                        tirec.br_blockcount, &irec,
                                        &nimaps, 0);
                        if (error)
                                goto out;
                        ASSERT(nimaps == 1);
                        ASSERT(tirec.br_startoff == irec.br_startoff);
                        trace_xfs_swap_extent_rmap_remap_piece(ip, &irec);

                        /* Trim the extent. */
                        uirec = tirec;
                        uirec.br_blockcount = rlen = min_t(xfs_filblks_t,
                                        tirec.br_blockcount,
                                        irec.br_blockcount);
                        trace_xfs_swap_extent_rmap_remap_piece(tip, &uirec);

                        /* Remove the mapping from the donor file. */
                        xfs_bmap_unmap_extent(tp, tip, &uirec);

                        /* Remove the mapping from the source file. */
                        xfs_bmap_unmap_extent(tp, ip, &irec);

                        /* Map the donor file's blocks into the source file. */
                        xfs_bmap_map_extent(tp, ip, &uirec);

                        /* Map the source file's blocks into the donor file. */
                        xfs_bmap_map_extent(tp, tip, &irec);

                        error = xfs_defer_finish(tpp);
                        tp = *tpp;
                        if (error)
                                goto out;

                        tirec.br_startoff += rlen;
                        if (tirec.br_startblock != HOLESTARTBLOCK &&
                            tirec.br_startblock != DELAYSTARTBLOCK)
                                tirec.br_startblock += rlen;
                        tirec.br_blockcount -= rlen;
                }

                /* Roll on... */
                count_fsb -= ilen;
                offset_fsb += ilen;
        }

        tip->i_d.di_flags2 = tip_flags2;
        return 0;

out:
        trace_xfs_swap_extent_rmap_error(ip, error, _RET_IP_);
        tip->i_d.di_flags2 = tip_flags2;
        return error;
}

/* Swap the extents of two files by swapping data forks. */
STATIC int
xfs_swap_extent_forks(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        struct xfs_inode        *tip,
        int                     *src_log_flags,
        int                     *target_log_flags)
{
        xfs_filblks_t           aforkblks = 0;
        xfs_filblks_t           taforkblks = 0;
        xfs_extnum_t            junk;
        uint64_t                tmp;
        int                     error;

        /*
         * Count the number of extended attribute blocks
         */
        if (XFS_IFORK_Q(ip) && ip->i_afp->if_nextents > 0 &&
            ip->i_afp->if_format != XFS_DINODE_FMT_LOCAL) {
                error = xfs_bmap_count_blocks(tp, ip, XFS_ATTR_FORK, &junk,
                                &aforkblks);
                if (error)
                        return error;
        }
        if (XFS_IFORK_Q(tip) && tip->i_afp->if_nextents > 0 &&
            tip->i_afp->if_format != XFS_DINODE_FMT_LOCAL) {
                error = xfs_bmap_count_blocks(tp, tip, XFS_ATTR_FORK, &junk,
                                &taforkblks);
                if (error)
                        return error;
        }

        /*
         * Btree format (v3) inodes have the inode number stamped in the bmbt
         * block headers. We can't start changing the bmbt blocks until the
         * inode owner change is logged so recovery does the right thing in the
         * event of a crash. Set the owner change log flags now and leave the
         * bmbt scan as the last step.
         */
        if (xfs_sb_version_has_v3inode(&ip->i_mount->m_sb)) {
                if (ip->i_df.if_format == XFS_DINODE_FMT_BTREE)
                        (*target_log_flags) |= XFS_ILOG_DOWNER;
                if (tip->i_df.if_format == XFS_DINODE_FMT_BTREE)
                        (*src_log_flags) |= XFS_ILOG_DOWNER;
        }

        /*
         * Swap the data forks of the inodes
         */
        swap(ip->i_df, tip->i_df);

        /*
         * 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;

        /*
         * 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_df.if_format) {
        case XFS_DINODE_FMT_EXTENTS:
                (*src_log_flags) |= XFS_ILOG_DEXT;
                break;
        case XFS_DINODE_FMT_BTREE:
                ASSERT(!xfs_sb_version_has_v3inode(&ip->i_mount->m_sb) ||
                       (*src_log_flags & XFS_ILOG_DOWNER));
                (*src_log_flags) |= XFS_ILOG_DBROOT;
                break;
        }

        switch (tip->i_df.if_format) {
        case XFS_DINODE_FMT_EXTENTS:
                (*target_log_flags) |= XFS_ILOG_DEXT;
                break;
        case XFS_DINODE_FMT_BTREE:
                (*target_log_flags) |= XFS_ILOG_DBROOT;
                ASSERT(!xfs_sb_version_has_v3inode(&ip->i_mount->m_sb) ||
                       (*target_log_flags & XFS_ILOG_DOWNER));
                break;
        }

        return 0;
}

/*
 * Fix up the owners of the bmbt blocks to refer to the current inode. The
 * change owner scan attempts to order all modified buffers in the current
 * transaction. In the event of ordered buffer failure, the offending buffer is
 * physically logged as a fallback and the scan returns -EAGAIN. We must roll
 * the transaction in this case to replenish the fallback log reservation and
 * restart the scan. This process repeats until the scan completes.
 */
static int
xfs_swap_change_owner(
        struct xfs_trans        **tpp,
        struct xfs_inode        *ip,
        struct xfs_inode        *tmpip)
{
        int                     error;
        struct xfs_trans        *tp = *tpp;

        do {
                error = xfs_bmbt_change_owner(tp, ip, XFS_DATA_FORK, ip->i_ino,
                                              NULL);
                /* success or fatal error */
                if (error != -EAGAIN)
                        break;

                error = xfs_trans_roll(tpp);
                if (error)
                        break;
                tp = *tpp;

                /*
                 * Redirty both inodes so they can relog and keep the log tail
                 * moving forward.
                 */
                xfs_trans_ijoin(tp, ip, 0);
                xfs_trans_ijoin(tp, tmpip, 0);
                xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
                xfs_trans_log_inode(tp, tmpip, XFS_ILOG_CORE);
        } while (true);

        return error;
}

int
xfs_swap_extents(
        struct xfs_inode        *ip,    /* target inode */
        struct xfs_inode        *tip,   /* tmp inode */
        struct xfs_swapext      *sxp)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        struct xfs_bstat        *sbp = &sxp->sx_stat;
        int                     src_log_flags, target_log_flags;
        int                     error = 0;
        int                     lock_flags;
        uint64_t                f;
        int                     resblks = 0;
        unsigned int            flags = 0;

        /*
         * 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_two_nondirectories(VFS_I(ip), VFS_I(tip));
        lock_flags = XFS_MMAPLOCK_EXCL;
        xfs_lock_two_inodes(ip, XFS_MMAPLOCK_EXCL, tip, XFS_MMAPLOCK_EXCL);

        /* Verify that both files have the same format */
        if ((VFS_I(ip)->i_mode & S_IFMT) != (VFS_I(tip)->i_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_qm_dqattach(ip);
        if (error)
                goto out_unlock;

        error = xfs_qm_dqattach(tip);
        if (error)
                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;

        if (xfs_inode_has_cow_data(tip)) {
                error = xfs_reflink_cancel_cow_range(tip, 0, NULLFILEOFF, true);
                if (error)
                        goto out_unlock;
        }

        /*
         * Extent "swapping" with rmap requires a permanent reservation and
         * a block reservation because it's really just a remap operation
         * performed with log redo items!
         */
        if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
                int             w = XFS_DATA_FORK;
                uint32_t        ipnext = ip->i_df.if_nextents;
                uint32_t        tipnext = tip->i_df.if_nextents;

                /*
                 * Conceptually this shouldn't affect the shape of either bmbt,
                 * but since we atomically move extents one by one, we reserve
                 * enough space to rebuild both trees.
                 */
                resblks = XFS_SWAP_RMAP_SPACE_RES(mp, ipnext, w);
                resblks +=  XFS_SWAP_RMAP_SPACE_RES(mp, tipnext, w);

                /*
                 * If either inode straddles a bmapbt block allocation boundary,
                 * the rmapbt algorithm triggers repeated allocs and frees as
                 * extents are remapped. This can exhaust the block reservation
                 * prematurely and cause shutdown. Return freed blocks to the
                 * transaction reservation to counter this behavior.
                 */
                flags |= XFS_TRANS_RES_FDBLKS;
        }
        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, flags,
                                &tp);
        if (error)
                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, XFS_ILOCK_EXCL, tip, XFS_ILOCK_EXCL);
        lock_flags |= XFS_ILOCK_EXCL;
        xfs_trans_ijoin(tp, ip, 0);
        xfs_trans_ijoin(tp, tip, 0);


        /* 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;
        }

        /*
         * 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 (xfs_sb_version_hasrmapbt(&mp->m_sb))
                error = xfs_swap_extent_rmap(&tp, ip, tip);
        else
                error = xfs_swap_extent_forks(tp, ip, tip, &src_log_flags,
                                &target_log_flags);
        if (error)
                goto out_trans_cancel;

        /* Do we have to swap reflink flags? */
        if ((ip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK) ^
            (tip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK)) {
                f = ip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK;
                ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
                ip->i_d.di_flags2 |= tip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK;
                tip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
                tip->i_d.di_flags2 |= f & XFS_DIFLAG2_REFLINK;
        }

        /* Swap the cow forks. */
        if (xfs_sb_version_hasreflink(&mp->m_sb)) {
                ASSERT(!ip->i_cowfp ||
                       ip->i_cowfp->if_format == XFS_DINODE_FMT_EXTENTS);
                ASSERT(!tip->i_cowfp ||
                       tip->i_cowfp->if_format == XFS_DINODE_FMT_EXTENTS);

                swap(ip->i_cowfp, tip->i_cowfp);

                if (ip->i_cowfp && ip->i_cowfp->if_bytes)
                        xfs_inode_set_cowblocks_tag(ip);
                else
                        xfs_inode_clear_cowblocks_tag(ip);
                if (tip->i_cowfp && tip->i_cowfp->if_bytes)
                        xfs_inode_set_cowblocks_tag(tip);
                else
                        xfs_inode_clear_cowblocks_tag(tip);
        }

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

        /*
         * The extent forks have been swapped, but crc=1,rmapbt=0 filesystems
         * have inode number owner values in the bmbt blocks that still refer to
         * the old inode. Scan each bmbt to fix up the owner values with the
         * inode number of the current inode.
         */
        if (src_log_flags & XFS_ILOG_DOWNER) {
                error = xfs_swap_change_owner(&tp, ip, tip);
                if (error)
                        goto out_trans_cancel;
        }
        if (target_log_flags & XFS_ILOG_DOWNER) {
                error = xfs_swap_change_owner(&tp, tip, ip);
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * 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_unlock:
        xfs_iunlock(ip, lock_flags);
        xfs_iunlock(tip, lock_flags);
        unlock_two_nondirectories(VFS_I(ip), VFS_I(tip));
        return error;

out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out_unlock;
}