xfs: implement the GETFSMAP ioctl (e89c0413) · Commits · EulixOS / Software / Kernel

fs/xfs/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,7 @@ xfs-y += xfs_aops.o \
		xfs_extent_busy.o \
		xfs_file.o \
		xfs_filestream.o \
		xfs_fsmap.o \
		xfs_fsops.o \
		xfs_globals.o \
		xfs_icache.o \

fs/xfs/libxfs/xfs_fs.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -92,6 +92,18 @@ struct getbmapx {
		#define BMV_OF_LAST 0x4 /* segment is the last in the file */
		#define BMV_OF_SHARED 0x8 /* segment shared with another file */

		/* fmr_owner special values for FS_IOC_GETFSMAP */
		#define XFS_FMR_OWN_FREE FMR_OWN_FREE /* free space */
		#define XFS_FMR_OWN_UNKNOWN FMR_OWN_UNKNOWN /* unknown owner */
		#define XFS_FMR_OWN_FS FMR_OWNER('X', 1) /* static fs metadata */
		#define XFS_FMR_OWN_LOG FMR_OWNER('X', 2) /* journalling log */
		#define XFS_FMR_OWN_AG FMR_OWNER('X', 3) /* per-AG metadata */
		#define XFS_FMR_OWN_INOBT FMR_OWNER('X', 4) /* inode btree blocks */
		#define XFS_FMR_OWN_INODES FMR_OWNER('X', 5) /* inodes */
		#define XFS_FMR_OWN_REFC FMR_OWNER('X', 6) /* refcount tree */
		#define XFS_FMR_OWN_COW FMR_OWNER('X', 7) /* cow staging */
		#define XFS_FMR_OWN_DEFECTIVE FMR_OWNER('X', 8) /* bad blocks */

		/*
		* Structure for XFS_IOC_FSSETDM.
		* For use by backup and restore programs to set the XFS on-disk inode
		@@ -502,6 +514,7 @@ typedef struct xfs_swapext
		#define XFS_IOC_GETBMAPX _IOWR('X', 56, struct getbmap)
		#define XFS_IOC_ZERO_RANGE _IOW ('X', 57, struct xfs_flock64)
		#define XFS_IOC_FREE_EOFBLOCKS _IOR ('X', 58, struct xfs_fs_eofblocks)
		/* XFS_IOC_GETFSMAP ------ hoisted 59 */

		/*
		* ioctl commands that replace IRIX syssgi()'s

fs/xfs/libxfs/xfs_rmap.c

+28 −0

Original line number	Diff line number	Diff line
		@@ -2305,3 +2305,31 @@ xfs_rmap_free_extent(
		return __xfs_rmap_add(mp, dfops, XFS_RMAP_FREE, owner,
		XFS_DATA_FORK, &bmap);
		}

		/* Compare rmap records. Returns -1 if a < b, 1 if a > b, and 0 if equal. */
		int
		xfs_rmap_compare(
		const struct xfs_rmap_irec *a,
		const struct xfs_rmap_irec *b)
		{
		__u64 oa;
		__u64 ob;

		oa = xfs_rmap_irec_offset_pack(a);
		ob = xfs_rmap_irec_offset_pack(b);

		if (a->rm_startblock < b->rm_startblock)
		return -1;
		else if (a->rm_startblock > b->rm_startblock)
		return 1;
		else if (a->rm_owner < b->rm_owner)
		return -1;
		else if (a->rm_owner > b->rm_owner)
		return 1;
		else if (oa < ob)
		return -1;
		else if (oa > ob)
		return 1;
		else
		return 0;
		}

fs/xfs/libxfs/xfs_rmap.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -214,5 +214,7 @@ int xfs_rmap_find_left_neighbor(struct xfs_btree_cur *cur, xfs_agblock_t bno,
		int xfs_rmap_lookup_le_range(struct xfs_btree_cur *cur, xfs_agblock_t bno,
		uint64_t owner, uint64_t offset, unsigned int flags,
		struct xfs_rmap_irec irec, int stat);
		int xfs_rmap_compare(const struct xfs_rmap_irec *a,
		const struct xfs_rmap_irec *b);

		#endif /* __XFS_RMAP_H__ */

fs/xfs/xfs_fsmap.c

0 → 100644

+756 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2017 Oracle. All Rights Reserved.
		*
		* Author: Darrick J. Wong <darrick.wong@oracle.com>
		*
		* This program is free software; you can redistribute it and/or
		* modify it under the terms of the GNU General Public License
		* as published by the Free Software Foundation; either version 2
		* of the License, or (at your option) any later version.
		*
		* This program is distributed in the hope that it would be useful,
		* but WITHOUT ANY WARRANTY; without even the implied warranty of
		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
		* GNU General Public License for more details.
		*
		* You should have received a copy of the GNU General Public License
		* along with this program; if not, write the Free Software Foundation,
		* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
		*/
		#include "xfs.h"
		#include "xfs_fs.h"
		#include "xfs_shared.h"
		#include "xfs_format.h"
		#include "xfs_log_format.h"
		#include "xfs_trans_resv.h"
		#include "xfs_sb.h"
		#include "xfs_mount.h"
		#include "xfs_defer.h"
		#include "xfs_inode.h"
		#include "xfs_trans.h"
		#include "xfs_error.h"
		#include "xfs_btree.h"
		#include "xfs_rmap_btree.h"
		#include "xfs_trace.h"
		#include "xfs_log.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"

		/* Convert an xfs_fsmap to an fsmap. */
		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,
		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,
		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;
		default:
		return -EFSCORRUPTED;
		}
		return 0;
		}

		/* getfsmap query state */
		struct xfs_getfsmap_info {
		struct xfs_fsmap_head *head;
		xfs_fsmap_format_t formatter; /* formatting fn */
		void format_arg; / format buffer */
		struct xfs_buf agf_bp; / AGF, for refcount queries */
		xfs_daddr_t next_daddr; /* next daddr we expect */
		u64 missing_owner; /* owner of holes */
		u32 dev; /* device id */
		xfs_agnumber_t agno; /* AG number, if applicable */
		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,
		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,
		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_sb_version_hasreflink(&mp->m_sb))
		return 0;
		/* rt files will have agno set to NULLAGNUMBER */
		if (info->agno == NULLAGNUMBER)
		return 0;

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

		error = xfs_refcount_find_shared(cur, rec->rm_startblock,
		rec->rm_blockcount, &fbno, &flen, false);

		xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
		if (error)
		return error;

		*stat = flen > 0;
		return 0;
		}

		/*
		* 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,
		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 XFS_BTREE_QUERY_RANGE_CONTINUE;
		}

		/* Are we just counting mappings? */
		if (info->head->fmh_count == 0) {
		if (rec_daddr > info->next_daddr)
		info->head->fmh_entries++;

		if (info->last)
		return XFS_BTREE_QUERY_RANGE_CONTINUE;

		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 XFS_BTREE_QUERY_RANGE_CONTINUE;
		}

		/*
		* 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 XFS_BTREE_QUERY_RANGE_ABORT;

		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;
		error = info->formatter(&fmr, info->format_arg);
		if (error)
		return error;
		info->head->fmh_entries++;
		}

		if (info->last)
		goto out;

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

		trace_xfs_fsmap_mapping(mp, info->dev, info->agno, 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;
		}
		error = info->formatter(&fmr, info->format_arg);
		if (error)
		return error;
		info->head->fmh_entries++;

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

		/* Transform a rmapbt irec into a fsmap */
		STATIC int
		xfs_getfsmap_datadev_helper(
		struct xfs_btree_cur *cur,
		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_private.a.agno, rec->rm_startblock);
		rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);

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

		/* Set rmap flags based on the getfsmap flags */
		static void
		xfs_getfsmap_set_irec_flags(
		struct xfs_rmap_irec *irec,
		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,
		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, info->agno, &info->low);
		trace_xfs_fsmap_high_key(mp, info->dev, info->agno, &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);
		}

		/* Execute a getfsmap query against the regular data device. */
		STATIC int
		__xfs_getfsmap_datadev(
		struct xfs_trans *tp,
		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_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;
		xfs_daddr_t eofs;
		int error = 0;

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

		/* Query each AG */
		for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
		/*
		* Set the AG high key from the fsmap high key if this
		* is the last AG that we're querying.
		*/
		if (info->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)
		goto err;
		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, info->agno, 0,
		&info->agf_bp);
		if (error)
		goto err;

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

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

		/*
		* Set the AG low key to the start of the AG prior to
		* moving on to the next AG.
		*/
		if (info->agno == start_ag) {
		info->low.rm_startblock = 0;
		info->low.rm_owner = 0;
		info->low.rm_offset = 0;
		info->low.rm_flags = 0;
		}
		}

		/* Report any gap at the end of the AG */
		info->last = true;
		error = query_fn(tp, info, &bt_cur, priv);
		if (error)
		goto err;

		err:
		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;
		}

		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->agno);
		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,
		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);
		}

		/* 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;
		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;
		}

		#define XFS_GETFSMAP_DEVS 2
		/*
		* Get filesystem's extents as described in head, and format for
		* output. Calls formatter to fill the user's buffer until all
		* extents are mapped, until the passed-in head->fmh_count slots have
		* been filled, or until the formatter short-circuits the loop, if it
		* is tracking filled-in extents on its own.
		*
		* 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,
		xfs_fsmap_format_t formatter,
		void *arg)
		{
		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 = {0};
		int i;
		int error = 0;

		if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
		return -EOPNOTSUPP;
		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;

		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);
		handlers[0].fn = xfs_getfsmap_datadev_rmapbt;
		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;
		}

		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.formatter = formatter;
		info.format_arg = arg;
		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));

		error = xfs_trans_alloc_empty(mp, &tp);
		if (error)
		break;

		info.dev = handlers[i].dev;
		info.last = false;
		info.agno = NULLAGNUMBER;
		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;
		}