xfs: convert xfs_sb_version_has checks to use mount features

[mirror_ubuntu-jammy-kernel.git] / fs / xfs / xfs_fsmap.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#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_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_rtalloc.h"
#include "xfs_ag.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. */
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 = 0;
                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_rmap(
        struct xfs_fsmap                *dest,
        const struct xfs_rmap_irec      *src)
{
        dest->fmr_flags = 0;
        if (!XFS_RMAP_NON_INODE_OWNER(src->rm_owner)) {
                dest->fmr_owner = src->rm_owner;
                return 0;
        }
        dest->fmr_flags |= FMR_OF_SPECIAL_OWNER;

        switch (src->rm_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_perag        *pag;           /* AG info, if applicable */
        xfs_daddr_t             next_daddr;     /* next daddr we expect */
        u64                     missing_owner;  /* owner of holes */
        u32                     dev;            /* device id */
        struct xfs_rmap_irec    low;            /* low rmap key */
        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);
};

/* 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_rmap_irec      *rec,
        bool                            *stat)
{
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_btree_cur            *cur;
        xfs_agblock_t                   fbno;
        xfs_extlen_t                    flen;
        int                             error;

        *stat = false;
        if (!xfs_has_reflink(mp))
                return 0;
        /* rt files will have no perag structure */
        if (!info->pag)
                return 0;

        /* Are there any shared blocks here? */
        flen = 0;
        cur = xfs_refcountbt_init_cursor(mp, tp, info->agf_bp, info->pag);

        error = xfs_refcount_find_shared(cur, rec->rm_startblock,
                        rec->rm_blockcount, &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);
}

/*
 * Format a reverse mapping for getfsmap, having translated rm_startblock
 * into the appropriate daddr units.
 */
STATIC int
xfs_getfsmap_helper(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info,
        const struct xfs_rmap_irec      *rec,
        xfs_daddr_t                     rec_daddr)
{
        struct xfs_fsmap                fmr;
        struct xfs_mount                *mp = tp->t_mountp;
        bool                            shared;
        int                             error;

        if (fatal_signal_pending(current))
                return -EINTR;

        /*
         * Filter out records that start before our startpoint, if the
         * caller requested that.
         */
        if (xfs_rmap_compare(rec, &info->low) < 0) {
                rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
                if (info->next_daddr < rec_daddr)
                        info->next_daddr = rec_daddr;
                return 0;
        }

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

                if (rec_daddr > info->next_daddr)
                        info->head->fmh_entries++;

                if (info->last)
                        return 0;

                info->head->fmh_entries++;

                rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
                if (info->next_daddr < rec_daddr)
                        info->next_daddr = rec_daddr;
                return 0;
        }

        /*
         * 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 (rec_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 = rec_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->pag ? info->pag->pag_agno : NULLAGNUMBER, rec);

        fmr.fmr_device = info->dev;
        fmr.fmr_physical = rec_daddr;
        error = xfs_fsmap_owner_from_rmap(&fmr, rec);
        if (error)
                return error;
        fmr.fmr_offset = XFS_FSB_TO_BB(mp, rec->rm_offset);
        fmr.fmr_length = XFS_FSB_TO_BB(mp, rec->rm_blockcount);
        if (rec->rm_flags & XFS_RMAP_UNWRITTEN)
                fmr.fmr_flags |= FMR_OF_PREALLOC;
        if (rec->rm_flags & XFS_RMAP_ATTR_FORK)
                fmr.fmr_flags |= FMR_OF_ATTR_FORK;
        if (rec->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, rec, &shared);
                if (error)
                        return error;
                if (shared)
                        fmr.fmr_flags |= FMR_OF_SHARED;
        }

        xfs_getfsmap_format(mp, &fmr, info);
out:
        rec_daddr += XFS_FSB_TO_BB(mp, rec->rm_blockcount);
        if (info->next_daddr < rec_daddr)
                info->next_daddr = rec_daddr;
        return 0;
}

/* Transform a rmapbt irec into a fsmap */
STATIC int
xfs_getfsmap_datadev_helper(
        struct xfs_btree_cur            *cur,
        const struct xfs_rmap_irec      *rec,
        void                            *priv)
{
        struct xfs_mount                *mp = cur->bc_mp;
        struct xfs_getfsmap_info        *info = priv;
        xfs_fsblock_t                   fsb;
        xfs_daddr_t                     rec_daddr;

        fsb = XFS_AGB_TO_FSB(mp, cur->bc_ag.pag->pag_agno, rec->rm_startblock);
        rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);

        return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
}

/* 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_mount                *mp = cur->bc_mp;
        struct xfs_getfsmap_info        *info = priv;
        struct xfs_rmap_irec            irec;
        xfs_daddr_t                     rec_daddr;

        rec_daddr = XFS_AGB_TO_DADDR(mp, cur->bc_ag.pag->pag_agno,
                        rec->ar_startblock);

        irec.rm_startblock = rec->ar_startblock;
        irec.rm_blockcount = rec->ar_blockcount;
        irec.rm_owner = XFS_RMAP_OWN_NULL;      /* "free" */
        irec.rm_offset = 0;
        irec.rm_flags = 0;

        return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
}

/* 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;
}

/* 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_mount                *mp = tp->t_mountp;
        struct xfs_rmap_irec            rmap;
        int                             error;

        /* Set up search keys */
        info->low.rm_startblock = XFS_BB_TO_FSBT(mp, keys[0].fmr_physical);
        info->low.rm_offset = XFS_BB_TO_FSBT(mp, keys[0].fmr_offset);
        error = xfs_fsmap_owner_to_rmap(&info->low, keys);
        if (error)
                return error;
        info->low.rm_blockcount = 0;
        xfs_getfsmap_set_irec_flags(&info->low, &keys[0]);

        error = xfs_fsmap_owner_to_rmap(&info->high, keys + 1);
        if (error)
                return error;
        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;
        info->missing_owner = XFS_FMR_OWN_FREE;

        trace_xfs_fsmap_low_key(mp, info->dev, NULLAGNUMBER, &info->low);
        trace_xfs_fsmap_high_key(mp, info->dev, NULLAGNUMBER, &info->high);

        if (keys[0].fmr_physical > 0)
                return 0;

        /* Fabricate an rmap entry for the external log device. */
        rmap.rm_startblock = 0;
        rmap.rm_blockcount = mp->m_sb.sb_logblocks;
        rmap.rm_owner = XFS_RMAP_OWN_LOG;
        rmap.rm_offset = 0;
        rmap.rm_flags = 0;

        return xfs_getfsmap_helper(tp, info, &rmap, 0);
}

#ifdef CONFIG_XFS_RT
/* Transform a rtbitmap "record" into a fsmap */
STATIC int
xfs_getfsmap_rtdev_rtbitmap_helper(
        struct xfs_trans                *tp,
        const struct xfs_rtalloc_rec    *rec,
        void                            *priv)
{
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_getfsmap_info        *info = priv;
        struct xfs_rmap_irec            irec;
        xfs_daddr_t                     rec_daddr;

        irec.rm_startblock = rec->ar_startext * mp->m_sb.sb_rextsize;
        rec_daddr = XFS_FSB_TO_BB(mp, irec.rm_startblock);
        irec.rm_blockcount = rec->ar_extcount * mp->m_sb.sb_rextsize;
        irec.rm_owner = XFS_RMAP_OWN_NULL;      /* "free" */
        irec.rm_offset = 0;
        irec.rm_flags = 0;

        return xfs_getfsmap_helper(tp, info, &irec, rec_daddr);
}

/* Execute a getfsmap query against the realtime device. */
STATIC int
__xfs_getfsmap_rtdev(
        struct xfs_trans                *tp,
        const struct xfs_fsmap          *keys,
        int                             (*query_fn)(struct xfs_trans *,
                                                    struct xfs_getfsmap_info *),
        struct xfs_getfsmap_info        *info)
{
        struct xfs_mount                *mp = tp->t_mountp;
        xfs_fsblock_t                   start_fsb;
        xfs_fsblock_t                   end_fsb;
        uint64_t                        eofs;
        int                             error = 0;

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

        /* Set up search keys */
        info->low.rm_startblock = start_fsb;
        error = xfs_fsmap_owner_to_rmap(&info->low, &keys[0]);
        if (error)
                return error;
        info->low.rm_offset = XFS_BB_TO_FSBT(mp, keys[0].fmr_offset);
        info->low.rm_blockcount = 0;
        xfs_getfsmap_set_irec_flags(&info->low, &keys[0]);

        info->high.rm_startblock = end_fsb;
        error = xfs_fsmap_owner_to_rmap(&info->high, &keys[1]);
        if (error)
                return error;
        info->high.rm_offset = XFS_BB_TO_FSBT(mp, keys[1].fmr_offset);
        info->high.rm_blockcount = 0;
        xfs_getfsmap_set_irec_flags(&info->high, &keys[1]);

        trace_xfs_fsmap_low_key(mp, info->dev, NULLAGNUMBER, &info->low);
        trace_xfs_fsmap_high_key(mp, info->dev, NULLAGNUMBER, &info->high);

        return query_fn(tp, info);
}

/* Actually query the realtime bitmap. */
STATIC int
xfs_getfsmap_rtdev_rtbitmap_query(
        struct xfs_trans                *tp,
        struct xfs_getfsmap_info        *info)
{
        struct xfs_rtalloc_rec          alow = { 0 };
        struct xfs_rtalloc_rec          ahigh = { 0 };
        struct xfs_mount                *mp = tp->t_mountp;
        int                             error;

        xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED);

        /*
         * Set up query parameters to return free rtextents covering the range
         * we want.
         */
        alow.ar_startext = info->low.rm_startblock;
        ahigh.ar_startext = info->high.rm_startblock;
        do_div(alow.ar_startext, mp->m_sb.sb_rextsize);
        if (do_div(ahigh.ar_startext, mp->m_sb.sb_rextsize))
                ahigh.ar_startext++;
        error = xfs_rtalloc_query_range(tp, &alow, &ahigh,
                        xfs_getfsmap_rtdev_rtbitmap_helper, info);
        if (error)
                goto err;

        /*
         * Report any gaps at the end of the rtbitmap by simulating a null
         * rmap starting at the block after the end of the query range.
         */
        info->last = true;
        ahigh.ar_startext = min(mp->m_sb.sb_rextents, ahigh.ar_startext);

        error = xfs_getfsmap_rtdev_rtbitmap_helper(tp, &ahigh, info);
        if (error)
                goto err;
err:
        xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED);
        return error;
}

/* 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)
{
        info->missing_owner = XFS_FMR_OWN_UNKNOWN;
        return __xfs_getfsmap_rtdev(tp, keys, xfs_getfsmap_rtdev_rtbitmap_query,
                        info);
}
#endif /* CONFIG_XFS_RT */

/* 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;
        struct xfs_btree_cur            *bt_cur = NULL;
        xfs_fsblock_t                   start_fsb;
        xfs_fsblock_t                   end_fsb;
        xfs_agnumber_t                  start_ag;
        xfs_agnumber_t                  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_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
        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 = 0;
        xfs_getfsmap_set_irec_flags(&info->low, &keys[0]);

        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);

        for_each_perag_range(mp, start_ag, end_ag, pag) {
                /*
                 * Set the AG high key from the fsmap high key if this
                 * is the last AG that we're querying.
                 */
                info->pag = pag;
                if (pag->pag_agno == 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(mp, tp, pag->pag_agno, 0,
                                &info->agf_bp);
                if (error)
                        break;

                trace_xfs_fsmap_low_key(mp, info->dev, pag->pag_agno,
                                &info->low);
                trace_xfs_fsmap_high_key(mp, info->dev, pag->pag_agno,
                                &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->pag_agno == start_ag) {
                        info->low.rm_startblock = 0;
                        info->low.rm_owner = 0;
                        info->low.rm_offset = 0;
                        info->low.rm_flags = 0;
                }

                /*
                 * 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->pag_agno == end_ag) {
                        info->last = true;
                        error = query_fn(tp, info, &bt_cur, priv);
                        if (error)
                                break;
                }
                info->pag = 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->pag) {
                xfs_perag_put(info->pag);
                info->pag = NULL;
        } else if (pag) {
                /* loop termination case */
                xfs_perag_put(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_datadev_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,
                        info->pag);
        return xfs_rmap_query_range(*curpp, &info->low, &info->high,
                        xfs_getfsmap_datadev_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_allocbt_init_cursor(tp->t_mountp, tp, info->agf_bp,
                        info->pag, XFS_BTNUM_BNO);
        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];

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

/* Do we recognize the device? */
STATIC bool
xfs_getfsmap_is_valid_device(
        struct xfs_mount        *mp,
        struct xfs_fsmap        *fm)
{
        if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
            fm->fmr_device == new_encode_dev(mp->m_ddev_targp->bt_dev))
                return true;
        if (mp->m_logdev_targp &&
            fm->fmr_device == new_encode_dev(mp->m_logdev_targp->bt_dev))
                return true;
        if (mp->m_rtdev_targp &&
            fm->fmr_device == new_encode_dev(mp->m_rtdev_targp->bt_dev))
                return true;
        return false;
}

/* 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_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.
 */
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 = { NULL };
        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;

        use_rmap = capable(CAP_SYS_ADMIN) &&
                   xfs_has_rmapbt(mp);
        head->fmh_entries = 0;

        /* Set up our device handlers. */
        memset(handlers, 0, sizeof(handlers));
        handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
        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].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
                handlers[1].fn = xfs_getfsmap_logdev;
        }
#ifdef CONFIG_XFS_RT
        if (mp->m_rtdev_targp) {
                handlers[2].dev = new_encode_dev(mp->m_rtdev_targp->bt_dev);
                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, bump the file offset to
         * continue the search appropriately.  For all other low key
         * mapping types (attr blocks, metadata), bump the physical
         * offset as there can be no other mapping for the same physical
         * block range.
         */
        dkeys[0] = head->fmh_keys[0];
        if (dkeys[0].fmr_flags & (FMR_OF_SPECIAL_OWNER | FMR_OF_EXTENT_MAP)) {
                dkeys[0].fmr_physical += dkeys[0].fmr_length;
                dkeys[0].fmr_owner = 0;
                if (dkeys[0].fmr_offset)
                        return -EINVAL;
        } else
                dkeys[0].fmr_offset += dkeys[0].fmr_length;
        dkeys[0].fmr_length = 0;
        memset(&dkeys[1], 0xFF, sizeof(struct xfs_fsmap));

        if (!xfs_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
                return -EINVAL;

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

        /* 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.  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[1].fmr_device)
                        dkeys[1] = head->fmh_keys[1];
                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.
                 */
                error = xfs_trans_alloc_empty(mp, &tp);
                if (error)
                        break;

                info.dev = handlers[i].dev;
                info.last = false;
                info.pag = NULL;
                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);
        head->fmh_oflags = FMH_OF_DEV_T;
        return error;
}