// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#include "xfs_platform.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_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_btree.h"
#include "xfs_rmap_btree.h"
#include "xfs_trace.h"
#include "xfs_rmap.h"
#include "xfs_alloc.h"
#include "xfs_bit.h"
#include <linux/fsmap.h>
#include "xfs_fsmap.h"
#include "xfs_refcount.h"
#include "xfs_refcount_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_rtbitmap.h"
#include "xfs_ag.h"
#include "xfs_rtgroup.h"
#include "xfs_rtrmap_btree.h"
#include "xfs_rtrefcount_btree.h"

/* Convert an xfs_fsmap to an fsmap. */
static void
xfs_fsmap_from_internal(
        struct fsmap            *dest,
        struct xfs_fsmap        *src)
{
        dest->fmr_device = src->fmr_device;
        dest->fmr_flags = src->fmr_flags;
        dest->fmr_physical = BBTOB(src->fmr_physical);
        dest->fmr_owner = src->fmr_owner;
        dest->fmr_offset = BBTOB(src->fmr_offset);
        dest->fmr_length = BBTOB(src->fmr_length);
        dest->fmr_reserved[0] = 0;
        dest->fmr_reserved[1] = 0;
        dest->fmr_reserved[2] = 0;
}

/* Convert an fsmap to an xfs_fsmap. */
static void
xfs_fsmap_to_internal(
        struct xfs_fsmap        *dest,
        struct fsmap            *src)
{
        dest->fmr_device = src->fmr_device;
        dest->fmr_flags = src->fmr_flags;
        dest->fmr_physical = BTOBBT(src->fmr_physical);
        dest->fmr_owner = src->fmr_owner;
        dest->fmr_offset = BTOBBT(src->fmr_offset);
        dest->fmr_length = BTOBBT(src->fmr_length);
}

/* Convert an fsmap owner into an rmapbt owner. */
static int
xfs_fsmap_owner_to_rmap(
        struct xfs_rmap_irec    *dest,
        const struct xfs_fsmap  *src)
{
        if (!(src->fmr_flags & FMR_OF_SPECIAL_OWNER)) {
                dest->rm_owner = src->fmr_owner;
                return 0;
        }

        switch (src->fmr_owner) {
        case 0:                 /* "lowest owner id possible" */
        case -1ULL:             /* "highest owner id possible" */
                dest->rm_owner = src->fmr_owner;
                break;
        case XFS_FMR_OWN_FREE:
                dest->rm_owner = XFS_RMAP_OWN_NULL;
                break;
        case XFS_FMR_OWN_UNKNOWN:
                dest->rm_owner = XFS_RMAP_OWN_UNKNOWN;
                break;
        case XFS_FMR_OWN_FS:
                dest->rm_owner = XFS_RMAP_OWN_FS;
                break;
        case XFS_FMR_OWN_LOG:
                dest->rm_owner = XFS_RMAP_OWN_LOG;
                break;
        case XFS_FMR_OWN_AG:
                dest->rm_owner = XFS_RMAP_OWN_AG;
                break;
        case XFS_FMR_OWN_INOBT:
                dest->rm_owner = XFS_RMAP_OWN_INOBT;
                break;
        case XFS_FMR_OWN_INODES:
                dest->rm_owner = XFS_RMAP_OWN_INODES;
                break;
        case XFS_FMR_OWN_REFC:
                dest->rm_owner = XFS_RMAP_OWN_REFC;
                break;
        case XFS_FMR_OWN_COW:
                dest->rm_owner = XFS_RMAP_OWN_COW;
                break;
        case XFS_FMR_OWN_DEFECTIVE:     /* not implemented */
                /* fall through */
        default:
                return -EINVAL;
        }
        return 0;
}

/* Convert an rmapbt owner into an fsmap owner. */
static int
xfs_fsmap_owner_from_frec(
        struct xfs_fsmap                *dest,
        const struct xfs_fsmap_irec     *frec)
{
        dest->fmr_flags = 0;
        if (!XFS_RMAP_NON_INODE_OWNER(frec->owner)) {
                dest->fmr_owner = frec->owner;
                return 0;
        }
        dest->fmr_flags |= FMR_OF_SPECIAL_OWNER;

        switch (frec->owner) {
        case XFS_RMAP_OWN_FS:
                dest->fmr_owner = XFS_FMR_OWN_FS;
                break;
        case XFS_RMAP_OWN_LOG:
                dest->fmr_owner = XFS_FMR_OWN_LOG;
                break;
        case XFS_RMAP_OWN_AG:
                dest->fmr_owner = XFS_FMR_OWN_AG;
                break;
        case XFS_RMAP_OWN_INOBT:
                dest->fmr_owner = XFS_FMR_OWN_INOBT;
                break;
        case XFS_RMAP_OWN_INODES:
                dest->fmr_owner = XFS_FMR_OWN_INODES;
                break;
        case XFS_RMAP_OWN_REFC:
                dest->fmr_owner = XFS_FMR_OWN_REFC;
                break;
        case XFS_RMAP_OWN_COW:
                dest->fmr_owner = XFS_FMR_OWN_COW;
                break;
        case XFS_RMAP_OWN_NULL: /* "free" */
                dest->fmr_owner = XFS_FMR_OWN_FREE;
                break;
        default:
                ASSERT(0);
                return -EFSCORRUPTED;
        }
        return 0;
}

/* getfsmap query state */
struct xfs_getfsmap_info {
        struct xfs_fsmap_head   *head;
        struct fsmap            *fsmap_recs;    /* mapping records */
        struct xfs_buf          *agf_bp;        /* AGF, for refcount queries */
        struct xfs_group        *group;         /* group info, if applicable */
        xfs_daddr_t             next_daddr;     /* next daddr we expect */
        /* daddr of low fsmap key when we're using the rtbitmap */
        xfs_daddr_t             low_daddr;
        /* daddr of high fsmap key, or the last daddr on the device */
        xfs_daddr_t             end_daddr;
        u64                     missing_owner;  /* owner of holes */
        u32                     dev;            /* device id */
        /*
         * Low rmap key for the query.  If low.rm_blockcount is nonzero, this
         * is the second (or later) call to retrieve the recordset in pieces.
         * xfs_getfsmap_rec_before_start will compare all records retrieved
         * by the rmapbt query to filter out any records that start before
         * the last record.
         */
        struct xfs_rmap_irec    low;
        struct xfs_rmap_irec    high;           /* high rmap key */
        bool                    last;           /* last extent? */
};

/* Associate a device with a getfsmap handler. */
struct xfs_getfsmap_dev {
        u32                     dev;
        int                     (*fn)(struct xfs_trans *tp,
                                      const struct xfs_fsmap *keys,
                                      struct xfs_getfsmap_info *info);
        sector_t                nr_sectors;
};

/* Compare two getfsmap device handlers. */
static int
xfs_getfsmap_dev_compare(
        const void                      *p1,
        const void                      *p2)
{
        const struct xfs_getfsmap_dev   *d1 = p1;
        const struct xfs_getfsmap_dev   *d2 = p2;

        return d1->dev - d2->dev;
}

/* Decide if this mapping is shared. */
STATIC int
xfs_getfsmap_is_shared(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        const struct xfs_fsmap_irec     *frec,
        bool                            *stat)
{
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_btree_cur            *cur;
        xfs_agblock_t                   fbno;
        xfs_extlen_t                    flen = 0;
        int                             error;

        *stat = false;
        if (!xfs_has_reflink(mp) || !info->group)
                return 0;

        if (info->group->xg_type == XG_TYPE_RTG)
                cur = xfs_rtrefcountbt_init_cursor(tp, to_rtg(info->group));
        else
                cur = xfs_refcountbt_init_cursor(mp, tp, info->agf_bp,
                                to_perag(info->group));

        /* Are there any shared blocks here? */
        error = xfs_refcount_find_shared(cur, frec->rec_key,
                        XFS_BB_TO_FSBT(mp, frec->len_daddr), &fbno, &flen,
                        false);

        xfs_btree_del_cursor(cur, error);
        if (error)
                return error;

        *stat = flen > 0;
        return 0;
}

static inline void
xfs_getfsmap_format(
        struct xfs_mount                *mp,
        struct xfs_fsmap                *xfm,
        struct xfs_getfsmap_info        *info)
{
        struct fsmap                    *rec;

        trace_xfs_getfsmap_mapping(mp, xfm);

        rec = &info->fsmap_recs[info->head->fmh_entries++];
        xfs_fsmap_from_internal(rec, xfm);
}

static inline bool
xfs_getfsmap_frec_before_start(
        struct xfs_getfsmap_info        *info,
        const struct xfs_fsmap_irec     *frec)
{
        if (info->low_daddr != XFS_BUF_DADDR_NULL)
                return frec->start_daddr < info->low_daddr;
        if (info->low.rm_blockcount) {
                struct xfs_rmap_irec    rec = {
                        .rm_startblock  = frec->rec_key,
                        .rm_owner       = frec->owner,
                        .rm_flags       = frec->rm_flags,
                };

                return xfs_rmap_compare(&rec, &info->low) < 0;
        }

        return false;
}

/*
 * Format a reverse mapping for getfsmap, having translated rm_startblock
 * into the appropriate daddr units.  Pass in a nonzero @len_daddr if the
 * length could be larger than rm_blockcount in struct xfs_rmap_irec.
 */
STATIC int
xfs_getfsmap_helper(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        const struct xfs_fsmap_irec     *frec)
{
        struct xfs_fsmap                fmr;
        struct xfs_mount                *mp = tp->t_mountp;
        bool                            shared;
        int                             error = 0;

        if (fatal_signal_pending(current))
                return -EINTR;

        /*
         * Filter out records that start before our startpoint, if the
         * caller requested that.
         */
        if (xfs_getfsmap_frec_before_start(info, frec))
                goto out;

        /* Are we just counting mappings? */
        if (info->head->fmh_count == 0) {
                if (info->head->fmh_entries == UINT_MAX)
                        return -ECANCELED;

                if (frec->start_daddr > info->next_daddr)
                        info->head->fmh_entries++;

                if (info->last)
                        return 0;

                info->head->fmh_entries++;
                goto out;
        }

        /*
         * If the record starts past the last physical block we saw,
         * then we've found a gap.  Report the gap as being owned by
         * whatever the caller specified is the missing owner.
         */
        if (frec->start_daddr > info->next_daddr) {
                if (info->head->fmh_entries >= info->head->fmh_count)
                        return -ECANCELED;

                fmr.fmr_device = info->dev;
                fmr.fmr_physical = info->next_daddr;
                fmr.fmr_owner = info->missing_owner;
                fmr.fmr_offset = 0;
                fmr.fmr_length = frec->start_daddr - info->next_daddr;
                fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
                xfs_getfsmap_format(mp, &fmr, info);
        }

        if (info->last)
                goto out;

        /* Fill out the extent we found */
        if (info->head->fmh_entries >= info->head->fmh_count)
                return -ECANCELED;

        trace_xfs_fsmap_mapping(mp, info->dev,
                        info->group ? info->group->xg_gno : NULLAGNUMBER,
                        frec);

        fmr.fmr_device = info->dev;
        fmr.fmr_physical = frec->start_daddr;
        error = xfs_fsmap_owner_from_frec(&fmr, frec);
        if (error)
                return error;
        fmr.fmr_offset = XFS_FSB_TO_BB(mp, frec->offset);
        fmr.fmr_length = frec->len_daddr;
        if (frec->rm_flags & XFS_RMAP_UNWRITTEN)
                fmr.fmr_flags |= FMR_OF_PREALLOC;
        if (frec->rm_flags & XFS_RMAP_ATTR_FORK)
                fmr.fmr_flags |= FMR_OF_ATTR_FORK;
        if (frec->rm_flags & XFS_RMAP_BMBT_BLOCK)
                fmr.fmr_flags |= FMR_OF_EXTENT_MAP;
        if (fmr.fmr_flags == 0) {
                error = xfs_getfsmap_is_shared(tp, info, frec, &shared);
                if (error)
                        return error;
                if (shared)
                        fmr.fmr_flags |= FMR_OF_SHARED;
        }

        xfs_getfsmap_format(mp, &fmr, info);
out:
        info->next_daddr = max(info->next_daddr,
                               frec->start_daddr + frec->len_daddr);
        return 0;
}

static inline int
xfs_getfsmap_group_helper(
        struct xfs_getfsmap_info        *info,
        struct xfs_trans                *tp,
        struct xfs_group                *xg,
        xfs_agblock_t                   startblock,
        xfs_extlen_t                    blockcount,
        struct xfs_fsmap_irec           *frec)
{
        /*
         * For an info->last query, we're looking for a gap between the last
         * mapping emitted and the high key specified by userspace.  If the
         * user's query spans less than 1 fsblock, then info->high and
         * info->low will have the same rm_startblock, which causes rec_daddr
         * and next_daddr to be the same.  Therefore, use the end_daddr that
         * we calculated from userspace's high key to synthesize the record.
         * Note that if the btree query found a mapping, there won't be a gap.
         */
        if (info->last)
                frec->start_daddr = info->end_daddr + 1;
        else
                frec->start_daddr = xfs_gbno_to_daddr(xg, startblock);

        frec->len_daddr = XFS_FSB_TO_BB(xg->xg_mount, blockcount);
        return xfs_getfsmap_helper(tp, info, frec);
}

/* Transform a rmapbt irec into a fsmap */
STATIC int
xfs_getfsmap_rmapbt_helper(
        struct xfs_btree_cur            *cur,
        const struct xfs_rmap_irec      *rec,
        void                            *priv)
{
        struct xfs_fsmap_irec           frec = {
                .owner                  = rec->rm_owner,
                .offset                 = rec->rm_offset,
                .rm_flags               = rec->rm_flags,
                .rec_key                = rec->rm_startblock,
        };
        struct xfs_getfsmap_info        *info = priv;

        return xfs_getfsmap_group_helper(info, cur->bc_tp, cur->bc_group,
                        rec->rm_startblock, rec->rm_blockcount, &frec);
}

/* Transform a bnobt irec into a fsmap */
STATIC int
xfs_getfsmap_datadev_bnobt_helper(
        struct xfs_btree_cur            *cur,
        const struct xfs_alloc_rec_incore *rec,
        void                            *priv)
{
        struct xfs_fsmap_irec           frec = {
                .owner                  = XFS_RMAP_OWN_NULL, /* "free" */
                .rec_key                = rec->ar_startblock,
        };
        struct xfs_getfsmap_info        *info = priv;

        return xfs_getfsmap_group_helper(info, cur->bc_tp, cur->bc_group,
                        rec->ar_startblock, rec->ar_blockcount, &frec);
}

/* Set rmap flags based on the getfsmap flags */
static void
xfs_getfsmap_set_irec_flags(
        struct xfs_rmap_irec    *irec,
        const struct xfs_fsmap  *fmr)
{
        irec->rm_flags = 0;
        if (fmr->fmr_flags & FMR_OF_ATTR_FORK)
                irec->rm_flags |= XFS_RMAP_ATTR_FORK;
        if (fmr->fmr_flags & FMR_OF_EXTENT_MAP)
                irec->rm_flags |= XFS_RMAP_BMBT_BLOCK;
        if (fmr->fmr_flags & FMR_OF_PREALLOC)
                irec->rm_flags |= XFS_RMAP_UNWRITTEN;
}

static inline bool
rmap_not_shareable(struct xfs_mount *mp, const struct xfs_rmap_irec *r)
{
        if (!xfs_has_reflink(mp))
                return true;
        if (XFS_RMAP_NON_INODE_OWNER(r->rm_owner))
                return true;
        if (r->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK |
                           XFS_RMAP_UNWRITTEN))
                return true;
        return false;
}

/* Execute a getfsmap query against the regular data device. */
STATIC int
__xfs_getfsmap_datadev(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info,
        int                             (*query_fn)(struct xfs_trans *,
                                                    struct xfs_getfsmap_info *,
                                                    struct xfs_btree_cur **,
                                                    void *),
        void                            *priv)
{
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_perag                *pag = NULL;
        struct xfs_btree_cur            *bt_cur = NULL;
        xfs_fsblock_t                   start_fsb;
        xfs_fsblock_t                   end_fsb;
        xfs_agnumber_t                  start_ag, end_ag;
        uint64_t                        eofs;
        int                             error = 0;

        eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
        if (keys[0].fmr_physical >= eofs)
                return 0;
        start_fsb = XFS_DADDR_TO_FSB(mp, keys[0].fmr_physical);
        end_fsb = XFS_DADDR_TO_FSB(mp, min(eofs - 1, keys[1].fmr_physical));

        /*
         * Convert the fsmap low/high keys to AG based keys.  Initialize
         * low to the fsmap low key and max out the high key to the end
         * of the AG.
         */
        info->low.rm_offset = XFS_BB_TO_FSBT(mp, keys[0].fmr_offset);
        error = xfs_fsmap_owner_to_rmap(&info->low, &keys[0]);
        if (error)
                return error;
        info->low.rm_blockcount = XFS_BB_TO_FSBT(mp, keys[0].fmr_length);
        xfs_getfsmap_set_irec_flags(&info->low, &keys[0]);

        /* Adjust the low key if we are continuing from where we left off. */
        if (info->low.rm_blockcount == 0) {
                /* No previous record from which to continue */
        } else if (rmap_not_shareable(mp, &info->low)) {
                /* Last record seen was an unshareable extent */
                info->low.rm_owner = 0;
                info->low.rm_offset = 0;

                start_fsb += info->low.rm_blockcount;
                if (XFS_FSB_TO_DADDR(mp, start_fsb) >= eofs)
                        return 0;
        } else {
                /* Last record seen was a shareable file data extent */
                info->low.rm_offset += info->low.rm_blockcount;
        }
        info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);

        info->high.rm_startblock = -1U;
        info->high.rm_owner = ULLONG_MAX;
        info->high.rm_offset = ULLONG_MAX;
        info->high.rm_blockcount = 0;
        info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;

        start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
        end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);

        while ((pag = xfs_perag_next_range(mp, pag, start_ag, end_ag))) {
                /*
                 * Set the AG high key from the fsmap high key if this
                 * is the last AG that we're querying.
                 */
                info->group = pag_group(pag);
                if (pag_agno(pag) == end_ag) {
                        info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
                                        end_fsb);
                        info->high.rm_offset = XFS_BB_TO_FSBT(mp,
                                        keys[1].fmr_offset);
                        error = xfs_fsmap_owner_to_rmap(&info->high, &keys[1]);
                        if (error)
                                break;
                        xfs_getfsmap_set_irec_flags(&info->high, &keys[1]);
                }

                if (bt_cur) {
                        xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
                        bt_cur = NULL;
                        xfs_trans_brelse(tp, info->agf_bp);
                        info->agf_bp = NULL;
                }

                error = xfs_alloc_read_agf(pag, tp, 0, &info->agf_bp);
                if (error)
                        break;

                trace_xfs_fsmap_low_group_key(mp, info->dev, pag_agno(pag),
                                &info->low);
                trace_xfs_fsmap_high_group_key(mp, info->dev, pag_agno(pag),
                                &info->high);

                error = query_fn(tp, info, &bt_cur, priv);
                if (error)
                        break;

                /*
                 * Set the AG low key to the start of the AG prior to
                 * moving on to the next AG.
                 */
                if (pag_agno(pag) == start_ag)
                        memset(&info->low, 0, sizeof(info->low));

                /*
                 * If this is the last AG, report any gap at the end of it
                 * before we drop the reference to the perag when the loop
                 * terminates.
                 */
                if (pag_agno(pag) == end_ag) {
                        info->last = true;
                        error = query_fn(tp, info, &bt_cur, priv);
                        if (error)
                                break;
                }
                info->group = NULL;
        }

        if (bt_cur)
                xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
                                                         XFS_BTREE_NOERROR);
        if (info->agf_bp) {
                xfs_trans_brelse(tp, info->agf_bp);
                info->agf_bp = NULL;
        }
        if (info->group) {
                xfs_perag_rele(pag);
                info->group = NULL;
        } else if (pag) {
                /* loop termination case */
                xfs_perag_rele(pag);
        }

        return error;
}

/* Actually query the rmap btree. */
STATIC int
xfs_getfsmap_datadev_rmapbt_query(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        struct xfs_btree_cur            **curpp,
        void                            *priv)
{
        /* Report any gap at the end of the last AG. */
        if (info->last)
                return xfs_getfsmap_rmapbt_helper(*curpp, &info->high, info);

        /* Allocate cursor for this AG and query_range it. */
        *curpp = xfs_rmapbt_init_cursor(tp->t_mountp, tp, info->agf_bp,
                        to_perag(info->group));
        return xfs_rmap_query_range(*curpp, &info->low, &info->high,
                        xfs_getfsmap_rmapbt_helper, info);
}

/* Execute a getfsmap query against the regular data device rmapbt. */
STATIC int
xfs_getfsmap_datadev_rmapbt(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
{
        info->missing_owner = XFS_FMR_OWN_FREE;
        return __xfs_getfsmap_datadev(tp, keys, info,
                        xfs_getfsmap_datadev_rmapbt_query, NULL);
}

/* Actually query the bno btree. */
STATIC int
xfs_getfsmap_datadev_bnobt_query(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        struct xfs_btree_cur            **curpp,
        void                            *priv)
{
        struct xfs_alloc_rec_incore     *key = priv;

        /* Report any gap at the end of the last AG. */
        if (info->last)
                return xfs_getfsmap_datadev_bnobt_helper(*curpp, &key[1], info);

        /* Allocate cursor for this AG and query_range it. */
        *curpp = xfs_bnobt_init_cursor(tp->t_mountp, tp, info->agf_bp,
                        to_perag(info->group));
        key->ar_startblock = info->low.rm_startblock;
        key[1].ar_startblock = info->high.rm_startblock;
        return xfs_alloc_query_range(*curpp, key, &key[1],
                        xfs_getfsmap_datadev_bnobt_helper, info);
}

/* Execute a getfsmap query against the regular data device's bnobt. */
STATIC int
xfs_getfsmap_datadev_bnobt(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
{
        struct xfs_alloc_rec_incore     akeys[2];

        memset(akeys, 0, sizeof(akeys));
        info->missing_owner = XFS_FMR_OWN_UNKNOWN;
        return __xfs_getfsmap_datadev(tp, keys, info,
                        xfs_getfsmap_datadev_bnobt_query, &akeys[0]);
}

/* Execute a getfsmap query against the log device. */
STATIC int
xfs_getfsmap_logdev(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
{
        struct xfs_fsmap_irec           frec = {
                .start_daddr            = 0,
                .rec_key                = 0,
                .owner                  = XFS_RMAP_OWN_LOG,
        };
        struct xfs_mount                *mp = tp->t_mountp;
        xfs_fsblock_t                   start_fsb, end_fsb;
        uint64_t                        eofs;

        eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks);
        if (keys[0].fmr_physical >= eofs)
                return 0;
        start_fsb = XFS_BB_TO_FSBT(mp,
                                keys[0].fmr_physical + keys[0].fmr_length);
        end_fsb = XFS_BB_TO_FSB(mp, min(eofs - 1, keys[1].fmr_physical));

        /* Adjust the low key if we are continuing from where we left off. */
        if (keys[0].fmr_length > 0)
                info->low_daddr = XFS_FSB_TO_BB(mp, start_fsb);

        trace_xfs_fsmap_low_linear_key(mp, info->dev, start_fsb);
        trace_xfs_fsmap_high_linear_key(mp, info->dev, end_fsb);

        if (start_fsb > 0)
                return 0;

        /* Fabricate an rmap entry for the external log device. */
        frec.len_daddr = XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks);
        return xfs_getfsmap_helper(tp, info, &frec);
}

#ifdef CONFIG_XFS_RT
/* Transform a rtbitmap "record" into a fsmap */
STATIC int
xfs_getfsmap_rtdev_rtbitmap_helper(
        struct xfs_rtgroup              *rtg,
        struct xfs_trans                *tp,
        const struct xfs_rtalloc_rec    *rec,
        void                            *priv)
{
        struct xfs_fsmap_irec           frec = {
                .owner                  = XFS_RMAP_OWN_NULL, /* "free" */
        };
        struct xfs_mount                *mp = rtg_mount(rtg);
        struct xfs_getfsmap_info        *info = priv;
        xfs_rtblock_t                   start_rtb =
                                xfs_rtx_to_rtb(rtg, rec->ar_startext);
        uint64_t                        rtbcount =
                                xfs_rtbxlen_to_blen(mp, rec->ar_extcount);

        /*
         * For an info->last query, we're looking for a gap between the last
         * mapping emitted and the high key specified by userspace.  If the
         * user's query spans less than 1 fsblock, then info->high and
         * info->low will have the same rm_startblock, which causes rec_daddr
         * and next_daddr to be the same.  Therefore, use the end_daddr that
         * we calculated from userspace's high key to synthesize the record.
         * Note that if the btree query found a mapping, there won't be a gap.
         */
        if (info->last)
                frec.start_daddr = info->end_daddr + 1;
        else
                frec.start_daddr = xfs_rtb_to_daddr(mp, start_rtb);

        frec.len_daddr = XFS_FSB_TO_BB(mp, rtbcount);
        return xfs_getfsmap_helper(tp, info, &frec);
}

/* Execute a getfsmap query against the realtime device rtbitmap. */
STATIC int
xfs_getfsmap_rtdev_rtbitmap(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
{
        struct xfs_mount                *mp = tp->t_mountp;
        xfs_rtblock_t                   start_rtbno, end_rtbno;
        xfs_rtxnum_t                    start_rtx, end_rtx;
        xfs_rgnumber_t                  start_rgno, end_rgno;
        struct xfs_rtgroup              *rtg = NULL;
        uint64_t                        eofs;
        int                             error;

        eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
        if (keys[0].fmr_physical >= eofs)
                return 0;

        info->missing_owner = XFS_FMR_OWN_UNKNOWN;

        /* Adjust the low key if we are continuing from where we left off. */
        start_rtbno = xfs_daddr_to_rtb(mp,
                        keys[0].fmr_physical + keys[0].fmr_length);
        if (keys[0].fmr_length > 0) {
                info->low_daddr = xfs_rtb_to_daddr(mp, start_rtbno);
                if (info->low_daddr >= eofs)
                        return 0;
        }
        start_rtx = xfs_rtb_to_rtx(mp, start_rtbno);
        start_rgno = xfs_rtb_to_rgno(mp, start_rtbno);

        end_rtbno = xfs_daddr_to_rtb(mp, min(eofs - 1, keys[1].fmr_physical));
        end_rgno = xfs_rtb_to_rgno(mp, end_rtbno);

        trace_xfs_fsmap_low_linear_key(mp, info->dev, start_rtbno);
        trace_xfs_fsmap_high_linear_key(mp, info->dev, end_rtbno);

        end_rtx = -1ULL;

        while ((rtg = xfs_rtgroup_next_range(mp, rtg, start_rgno, end_rgno))) {
                if (rtg_rgno(rtg) == end_rgno)
                        end_rtx = xfs_rtb_to_rtx(mp,
                                        end_rtbno + mp->m_sb.sb_rextsize - 1);

                info->group = rtg_group(rtg);
                xfs_rtgroup_lock(rtg, XFS_RTGLOCK_BITMAP_SHARED);
                error = xfs_rtalloc_query_range(rtg, tp, start_rtx, end_rtx,
                                xfs_getfsmap_rtdev_rtbitmap_helper, info);
                if (error)
                        break;

                /*
                 * Report any gaps at the end of the rtbitmap by simulating a
                 * zero-length free extent starting at the rtx after the end
                 * of the query range.
                 */
                if (rtg_rgno(rtg) == end_rgno) {
                        struct xfs_rtalloc_rec  ahigh = {
                                .ar_startext    = min(end_rtx + 1,
                                                      rtg->rtg_extents),
                        };

                        info->last = true;
                        error = xfs_getfsmap_rtdev_rtbitmap_helper(rtg, tp,
                                        &ahigh, info);
                        if (error)
                                break;
                }

                xfs_rtgroup_unlock(rtg, XFS_RTGLOCK_BITMAP_SHARED);
                info->group = NULL;
                start_rtx = 0;
        }

        /* loop termination case */
        if (rtg) {
                if (info->group) {
                        xfs_rtgroup_unlock(rtg, XFS_RTGLOCK_BITMAP_SHARED);
                        info->group = NULL;
                }
                xfs_rtgroup_rele(rtg);
        }

        return error;
}

/* Transform a realtime rmapbt record into a fsmap */
STATIC int
xfs_getfsmap_rtdev_rmapbt_helper(
        struct xfs_btree_cur            *cur,
        const struct xfs_rmap_irec      *rec,
        void                            *priv)
{
        struct xfs_fsmap_irec           frec = {
                .owner                  = rec->rm_owner,
                .offset                 = rec->rm_offset,
                .rm_flags               = rec->rm_flags,
                .rec_key                = rec->rm_startblock,
        };
        struct xfs_getfsmap_info        *info = priv;

        return xfs_getfsmap_group_helper(info, cur->bc_tp, cur->bc_group,
                        rec->rm_startblock, rec->rm_blockcount, &frec);
}

/* Actually query the rtrmap btree. */
STATIC int
xfs_getfsmap_rtdev_rmapbt_query(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        struct xfs_btree_cur            **curpp)
{
        struct xfs_rtgroup              *rtg = to_rtg(info->group);

        /* Query the rtrmapbt */
        xfs_rtgroup_lock(rtg, XFS_RTGLOCK_RMAP | XFS_RTGLOCK_REFCOUNT);
        *curpp = xfs_rtrmapbt_init_cursor(tp, rtg);
        return xfs_rmap_query_range(*curpp, &info->low, &info->high,
                        xfs_getfsmap_rtdev_rmapbt_helper, info);
}

/* Execute a getfsmap query against the realtime device rmapbt. */
STATIC int
xfs_getfsmap_rtdev_rmapbt(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        struct xfs_getfsmap_info        *info)
{
        struct xfs_fsmap                key0 = *keys; /* struct copy */
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_rtgroup              *rtg = NULL;
        struct xfs_btree_cur            *bt_cur = NULL;
        xfs_daddr_t                     rtstart_daddr;
        xfs_rtblock_t                   start_rtb;
        xfs_rtblock_t                   end_rtb;
        xfs_rgnumber_t                  start_rg, end_rg;
        uint64_t                        eofs;
        int                             error = 0;

        eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rtstart + mp->m_sb.sb_rblocks);
        if (key0.fmr_physical >= eofs)
                return 0;

        /*
         * On zoned filesystems with an internal rt volume, the volume comes
         * immediately after the end of the data volume.  However, the
         * xfs_rtblock_t address space is relative to the start of the data
         * device, which means that the first @rtstart fsblocks do not actually
         * point anywhere.  If a fsmap query comes in with the low key starting
         * below @rtstart, report it as "owned by filesystem".
         */
        rtstart_daddr = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rtstart);
        if (xfs_has_zoned(mp) && key0.fmr_physical < rtstart_daddr) {
                struct xfs_fsmap_irec           frec = {
                        .owner                  = XFS_RMAP_OWN_FS,
                        .len_daddr              = rtstart_daddr,
                };

                /*
                 * Adjust the start of the query range if we're picking up from
                 * a previous round, and only emit the record if we haven't
                 * already gone past.
                 */
                key0.fmr_physical += key0.fmr_length;
                if (key0.fmr_physical < rtstart_daddr) {
                        error = xfs_getfsmap_helper(tp, info, &frec);
                        if (error)
                                return error;

                        key0.fmr_physical = rtstart_daddr;
                }

                /* Zero the other fields to avoid further adjustments. */
                key0.fmr_owner = 0;
                key0.fmr_offset = 0;
                key0.fmr_length = 0;
        }

        start_rtb = xfs_daddr_to_rtb(mp, key0.fmr_physical);
        end_rtb = xfs_daddr_to_rtb(mp, min(eofs - 1, keys[1].fmr_physical));
        info->missing_owner = XFS_FMR_OWN_FREE;

        /*
         * Convert the fsmap low/high keys to rtgroup based keys.  Initialize
         * low to the fsmap low key and max out the high key to the end
         * of the rtgroup.
         */
        info->low.rm_offset = XFS_BB_TO_FSBT(mp, key0.fmr_offset);
        error = xfs_fsmap_owner_to_rmap(&info->low, &key0);
        if (error)
                return error;
        info->low.rm_blockcount = XFS_BB_TO_FSBT(mp, key0.fmr_length);
        xfs_getfsmap_set_irec_flags(&info->low, &key0);

        /* Adjust the low key if we are continuing from where we left off. */
        if (info->low.rm_blockcount == 0) {
                /* No previous record from which to continue */
        } else if (rmap_not_shareable(mp, &info->low)) {
                /* Last record seen was an unshareable extent */
                info->low.rm_owner = 0;
                info->low.rm_offset = 0;

                start_rtb += info->low.rm_blockcount;
                if (xfs_rtb_to_daddr(mp, start_rtb) >= eofs)
                        return 0;
        } else {
                /* Last record seen was a shareable file data extent */
                info->low.rm_offset += info->low.rm_blockcount;
        }
        info->low.rm_startblock = xfs_rtb_to_rgbno(mp, start_rtb);

        info->high.rm_startblock = -1U;
        info->high.rm_owner = ULLONG_MAX;
        info->high.rm_offset = ULLONG_MAX;
        info->high.rm_blockcount = 0;
        info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;

        start_rg = xfs_rtb_to_rgno(mp, start_rtb);
        end_rg = xfs_rtb_to_rgno(mp, end_rtb);

        while ((rtg = xfs_rtgroup_next_range(mp, rtg, start_rg, end_rg))) {
                /*
                 * Set the rtgroup high key from the fsmap high key if this
                 * is the last rtgroup that we're querying.
                 */
                info->group = rtg_group(rtg);
                if (rtg_rgno(rtg) == end_rg) {
                        info->high.rm_startblock =
                                xfs_rtb_to_rgbno(mp, end_rtb);
                        info->high.rm_offset =
                                XFS_BB_TO_FSBT(mp, keys[1].fmr_offset);
                        error = xfs_fsmap_owner_to_rmap(&info->high, &keys[1]);
                        if (error)
                                break;
                        xfs_getfsmap_set_irec_flags(&info->high, &keys[1]);
                }

                if (bt_cur) {
                        xfs_rtgroup_unlock(to_rtg(bt_cur->bc_group),
                                        XFS_RTGLOCK_RMAP |
                                        XFS_RTGLOCK_REFCOUNT);
                        xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
                        bt_cur = NULL;
                }

                trace_xfs_fsmap_low_group_key(mp, info->dev, rtg_rgno(rtg),
                                &info->low);
                trace_xfs_fsmap_high_group_key(mp, info->dev, rtg_rgno(rtg),
                                &info->high);

                error = xfs_getfsmap_rtdev_rmapbt_query(tp, info, &bt_cur);
                if (error)
                        break;

                /*
                 * Set the rtgroup low key to the start of the rtgroup prior to
                 * moving on to the next rtgroup.
                 */
                if (rtg_rgno(rtg) == start_rg)
                        memset(&info->low, 0, sizeof(info->low));

                /*
                 * If this is the last rtgroup, report any gap at the end of it
                 * before we drop the reference to the perag when the loop
                 * terminates.
                 */
                if (rtg_rgno(rtg) == end_rg) {
                        info->last = true;
                        error = xfs_getfsmap_rtdev_rmapbt_helper(bt_cur,
                                        &info->high, info);
                        if (error)
                                break;
                }
                info->group = NULL;
        }

        if (bt_cur) {
                xfs_rtgroup_unlock(to_rtg(bt_cur->bc_group),
                                XFS_RTGLOCK_RMAP | XFS_RTGLOCK_REFCOUNT);
                xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
                                                         XFS_BTREE_NOERROR);
        }

        /* loop termination case */
        if (rtg) {
                info->group = NULL;
                xfs_rtgroup_rele(rtg);
        }

        return error;
}
#endif /* CONFIG_XFS_RT */

static uint32_t
xfs_getfsmap_device(
        struct xfs_mount        *mp,
        enum xfs_device         dev)
{
        if (mp->m_sb.sb_rtstart)
                return dev;

        switch (dev) {
        case XFS_DEV_DATA:
                return new_encode_dev(mp->m_ddev_targp->bt_dev);
        case XFS_DEV_LOG:
                return new_encode_dev(mp->m_logdev_targp->bt_dev);
        case XFS_DEV_RT:
                if (!mp->m_rtdev_targp)
                        break;
                return new_encode_dev(mp->m_rtdev_targp->bt_dev);
        }

        return -1;
}

/* Do we recognize the device? */
STATIC bool
xfs_getfsmap_is_valid_device(
        struct xfs_mount        *mp,
        struct xfs_fsmap        *fm)
{
        return fm->fmr_device == 0 ||
                fm->fmr_device == UINT_MAX ||
                fm->fmr_device == xfs_getfsmap_device(mp, XFS_DEV_DATA) ||
                fm->fmr_device == xfs_getfsmap_device(mp, XFS_DEV_LOG) ||
                (mp->m_rtdev_targp &&
                 fm->fmr_device == xfs_getfsmap_device(mp, XFS_DEV_RT));
}

/* Ensure that the low key is less than the high key. */
STATIC bool
xfs_getfsmap_check_keys(
        struct xfs_fsmap                *low_key,
        struct xfs_fsmap                *high_key)
{
        if (low_key->fmr_flags & (FMR_OF_SPECIAL_OWNER | FMR_OF_EXTENT_MAP)) {
                if (low_key->fmr_offset)
                        return false;
        }
        if (high_key->fmr_flags != -1U &&
            (high_key->fmr_flags & (FMR_OF_SPECIAL_OWNER |
                                    FMR_OF_EXTENT_MAP))) {
                if (high_key->fmr_offset && high_key->fmr_offset != -1ULL)
                        return false;
        }
        if (high_key->fmr_length && high_key->fmr_length != -1ULL)
                return false;

        if (low_key->fmr_device > high_key->fmr_device)
                return false;
        if (low_key->fmr_device < high_key->fmr_device)
                return true;

        if (low_key->fmr_physical > high_key->fmr_physical)
                return false;
        if (low_key->fmr_physical < high_key->fmr_physical)
                return true;

        if (low_key->fmr_owner > high_key->fmr_owner)
                return false;
        if (low_key->fmr_owner < high_key->fmr_owner)
                return true;

        if (low_key->fmr_offset > high_key->fmr_offset)
                return false;
        if (low_key->fmr_offset < high_key->fmr_offset)
                return true;

        return false;
}

/*
 * There are only two devices if we didn't configure RT devices at build time.
 */
#ifdef CONFIG_XFS_RT
#define XFS_GETFSMAP_DEVS       3
#else
#define XFS_GETFSMAP_DEVS       2
#endif /* CONFIG_XFS_RT */

/*
 * Get filesystem's extents as described in head, and format for output. Fills
 * in the supplied records array until there are no more reverse mappings to
 * return or head.fmh_entries == head.fmh_count.  In the second case, this
 * function returns -ECANCELED to indicate that more records would have been
 * returned.
 *
 * Key to Confusion
 * ----------------
 * There are multiple levels of keys and counters at work here:
 * xfs_fsmap_head.fmh_keys      -- low and high fsmap keys passed in;
 *                                 these reflect fs-wide sector addrs.
 * dkeys                        -- fmh_keys used to query each device;
 *                                 these are fmh_keys but w/ the low key
 *                                 bumped up by fmr_length.
 * xfs_getfsmap_info.next_daddr -- next disk addr we expect to see; this
 *                                 is how we detect gaps in the fsmap
                                   records and report them.
 * xfs_getfsmap_info.low/high   -- per-AG low/high keys computed from
 *                                 dkeys; used to query the metadata.
 */
STATIC int
xfs_getfsmap(
        struct xfs_mount                *mp,
        struct xfs_fsmap_head           *head,
        struct fsmap                    *fsmap_recs)
{
        struct xfs_trans                *tp = NULL;
        struct xfs_fsmap                dkeys[2];       /* per-dev keys */
        struct xfs_getfsmap_dev         handlers[XFS_GETFSMAP_DEVS];
        struct xfs_getfsmap_info        info = {
                .fsmap_recs             = fsmap_recs,
                .head                   = head,
        };
        bool                            use_rmap;
        int                             i;
        int                             error = 0;

        if (head->fmh_iflags & ~FMH_IF_VALID)
                return -EINVAL;
        if (!xfs_getfsmap_is_valid_device(mp, &head->fmh_keys[0]) ||
            !xfs_getfsmap_is_valid_device(mp, &head->fmh_keys[1]))
                return -EINVAL;
        if (!xfs_getfsmap_check_keys(&head->fmh_keys[0], &head->fmh_keys[1]))
                return -EINVAL;

        use_rmap = xfs_has_rmapbt(mp) &&
                   has_capability_noaudit(current, CAP_SYS_ADMIN);
        head->fmh_entries = 0;

        /* Set up our device handlers. */
        memset(handlers, 0, sizeof(handlers));
        handlers[0].nr_sectors = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
        handlers[0].dev = xfs_getfsmap_device(mp, XFS_DEV_DATA);
        if (use_rmap)
                handlers[0].fn = xfs_getfsmap_datadev_rmapbt;
        else
                handlers[0].fn = xfs_getfsmap_datadev_bnobt;
        if (mp->m_logdev_targp != mp->m_ddev_targp) {
                handlers[1].nr_sectors = XFS_FSB_TO_BB(mp,
                                                       mp->m_sb.sb_logblocks);
                handlers[1].dev = xfs_getfsmap_device(mp, XFS_DEV_LOG);
                handlers[1].fn = xfs_getfsmap_logdev;
        }
#ifdef CONFIG_XFS_RT
        /*
         * For zoned file systems there is no rtbitmap, so only support fsmap
         * if the callers is privileged enough to use the full rmap version.
         */
        if (mp->m_rtdev_targp && (use_rmap || !xfs_has_zoned(mp))) {
                handlers[2].nr_sectors = XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
                handlers[2].dev = xfs_getfsmap_device(mp, XFS_DEV_RT);
                if (use_rmap)
                        handlers[2].fn = xfs_getfsmap_rtdev_rmapbt;
                else
                        handlers[2].fn = xfs_getfsmap_rtdev_rtbitmap;
        }
#endif /* CONFIG_XFS_RT */

        xfs_sort(handlers, XFS_GETFSMAP_DEVS, sizeof(struct xfs_getfsmap_dev),
                        xfs_getfsmap_dev_compare);

        /*
         * To continue where we left off, we allow userspace to use the
         * last mapping from a previous call as the low key of the next.
         * This is identified by a non-zero length in the low key. We
         * have to increment the low key in this scenario to ensure we
         * don't return the same mapping again, and instead return the
         * very next mapping.
         *
         * If the low key mapping refers to file data, the same physical
         * blocks could be mapped to several other files/offsets.
         * According to rmapbt record ordering, the minimal next
         * possible record for the block range is the next starting
         * offset in the same inode. Therefore, each fsmap backend bumps
         * the file offset to continue the search appropriately.  For
         * all other low key mapping types (attr blocks, metadata), each
         * fsmap backend bumps the physical offset as there can be no
         * other mapping for the same physical block range.
         */
        dkeys[0] = head->fmh_keys[0];
        memset(&dkeys[1], 0xFF, sizeof(struct xfs_fsmap));

        info.next_daddr = head->fmh_keys[0].fmr_physical +
                          head->fmh_keys[0].fmr_length;

        /* For each device we support... */
        for (i = 0; i < XFS_GETFSMAP_DEVS; i++) {
                /* Is this device within the range the user asked for? */
                if (!handlers[i].fn)
                        continue;
                if (head->fmh_keys[0].fmr_device > handlers[i].dev)
                        continue;
                if (head->fmh_keys[1].fmr_device < handlers[i].dev)
                        break;

                /*
                 * If this device number matches the high key, we have to pass
                 * the high key to the handler to limit the query results, and
                 * set the end_daddr so that we can synthesize records at the
                 * end of the query range or device.
                 */
                if (handlers[i].dev == head->fmh_keys[1].fmr_device) {
                        dkeys[1] = head->fmh_keys[1];
                        info.end_daddr = min(handlers[i].nr_sectors - 1,
                                             dkeys[1].fmr_physical);
                } else {
                        info.end_daddr = handlers[i].nr_sectors - 1;
                }

                /*
                 * If the device number exceeds the low key, zero out the low
                 * key so that we get everything from the beginning.
                 */
                if (handlers[i].dev > head->fmh_keys[0].fmr_device)
                        memset(&dkeys[0], 0, sizeof(struct xfs_fsmap));

                /*
                 * Grab an empty transaction so that we can use its recursive
                 * buffer locking abilities to detect cycles in the rmapbt
                 * without deadlocking.
                 */
                tp = xfs_trans_alloc_empty(mp);

                info.dev = handlers[i].dev;
                info.last = false;
                info.group = NULL;
                info.low_daddr = XFS_BUF_DADDR_NULL;
                info.low.rm_blockcount = 0;
                error = handlers[i].fn(tp, dkeys, &info);
                if (error)
                        break;
                xfs_trans_cancel(tp);
                tp = NULL;
                info.next_daddr = 0;
        }

        if (tp)
                xfs_trans_cancel(tp);

        /*
         * For internal RT device we need to report different synthetic devices
         * for a single physical device, and thus can't report the actual dev_t.
         */
        if (!mp->m_sb.sb_rtstart)
                head->fmh_oflags = FMH_OF_DEV_T;
        return error;
}

int
xfs_ioc_getfsmap(
        struct xfs_inode        *ip,
        struct fsmap_head       __user *arg)
{
        struct xfs_fsmap_head   xhead = {0};
        struct fsmap_head       head;
        struct fsmap            *recs;
        unsigned int            count;
        __u32                   last_flags = 0;
        bool                    done = false;
        int                     error;

        if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
                return -EFAULT;
        if (memchr_inv(head.fmh_reserved, 0, sizeof(head.fmh_reserved)) ||
            memchr_inv(head.fmh_keys[0].fmr_reserved, 0,
                       sizeof(head.fmh_keys[0].fmr_reserved)) ||
            memchr_inv(head.fmh_keys[1].fmr_reserved, 0,
                       sizeof(head.fmh_keys[1].fmr_reserved)))
                return -EINVAL;

        /*
         * Use an internal memory buffer so that we don't have to copy fsmap
         * data to userspace while holding locks.  Start by trying to allocate
         * up to 128k for the buffer, but fall back to a single page if needed.
         */
        count = min_t(unsigned int, head.fmh_count,
                        131072 / sizeof(struct fsmap));
        recs = kvzalloc_objs(struct fsmap, count);
        if (!recs) {
                count = min_t(unsigned int, head.fmh_count,
                                PAGE_SIZE / sizeof(struct fsmap));
                recs = kvzalloc_objs(struct fsmap, count);
                if (!recs)
                        return -ENOMEM;
        }

        xhead.fmh_iflags = head.fmh_iflags;
        xfs_fsmap_to_internal(&xhead.fmh_keys[0], &head.fmh_keys[0]);
        xfs_fsmap_to_internal(&xhead.fmh_keys[1], &head.fmh_keys[1]);

        trace_xfs_getfsmap_low_key(ip->i_mount, &xhead.fmh_keys[0]);
        trace_xfs_getfsmap_high_key(ip->i_mount, &xhead.fmh_keys[1]);

        head.fmh_entries = 0;
        do {
                struct fsmap __user     *user_recs;
                struct fsmap            *last_rec;

                user_recs = &arg->fmh_recs[head.fmh_entries];
                xhead.fmh_entries = 0;
                xhead.fmh_count = min_t(unsigned int, count,
                                        head.fmh_count - head.fmh_entries);

                /* Run query, record how many entries we got. */
                error = xfs_getfsmap(ip->i_mount, &xhead, recs);
                switch (error) {
                case 0:
                        /*
                         * There are no more records in the result set.  Copy
                         * whatever we got to userspace and break out.
                         */
                        done = true;
                        break;
                case -ECANCELED:
                        /*
                         * The internal memory buffer is full.  Copy whatever
                         * records we got to userspace and go again if we have
                         * not yet filled the userspace buffer.
                         */
                        error = 0;
                        break;
                default:
                        goto out_free;
                }
                head.fmh_entries += xhead.fmh_entries;
                head.fmh_oflags = xhead.fmh_oflags;

                /*
                 * If the caller wanted a record count or there aren't any
                 * new records to return, we're done.
                 */
                if (head.fmh_count == 0 || xhead.fmh_entries == 0)
                        break;

                /* Copy all the records we got out to userspace. */
                if (copy_to_user(user_recs, recs,
                                 xhead.fmh_entries * sizeof(struct fsmap))) {
                        error = -EFAULT;
                        goto out_free;
                }

                /* Remember the last record flags we copied to userspace. */
                last_rec = &recs[xhead.fmh_entries - 1];
                last_flags = last_rec->fmr_flags;

                /* Set up the low key for the next iteration. */
                xfs_fsmap_to_internal(&xhead.fmh_keys[0], last_rec);
                trace_xfs_getfsmap_low_key(ip->i_mount, &xhead.fmh_keys[0]);
        } while (!done && head.fmh_entries < head.fmh_count);

        /*
         * If there are no more records in the query result set and we're not
         * in counting mode, mark the last record returned with the LAST flag.
         */
        if (done && head.fmh_count > 0 && head.fmh_entries > 0) {
                struct fsmap __user     *user_rec;

                last_flags |= FMR_OF_LAST;
                user_rec = &arg->fmh_recs[head.fmh_entries - 1];

                if (copy_to_user(&user_rec->fmr_flags, &last_flags,
                                        sizeof(last_flags))) {
                        error = -EFAULT;
                        goto out_free;
                }
        }

        /* copy back header */
        if (copy_to_user(arg, &head, sizeof(struct fsmap_head))) {
                error = -EFAULT;
                goto out_free;
        }

out_free:
        kvfree(recs);
        return error;
}