xfs_rtalloc.c

Go to the documentation of this file.

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_rtalloc.h"
#include "xfs_fsops.h"
#include "xfs_error.h"
#include "xfs_inode_item.h"
#include "xfs_trans_space.h"
#include "xfs_utils.h"
#include "xfs_trace.h"
#include "xfs_buf.h"


/*
 * Prototypes for internal functions.
 */


STATIC int xfs_rtallocate_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
        xfs_extlen_t, xfs_buf_t **, xfs_fsblock_t *);
STATIC int xfs_rtany_summary(xfs_mount_t *, xfs_trans_t *, int, int,
        xfs_rtblock_t, xfs_buf_t **, xfs_fsblock_t *, int *);
STATIC int xfs_rtcheck_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
        xfs_extlen_t, int, xfs_rtblock_t *, int *);
STATIC int xfs_rtfind_back(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
        xfs_rtblock_t, xfs_rtblock_t *);
STATIC int xfs_rtfind_forw(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
        xfs_rtblock_t, xfs_rtblock_t *);
STATIC int xfs_rtget_summary( xfs_mount_t *, xfs_trans_t *, int,
        xfs_rtblock_t, xfs_buf_t **, xfs_fsblock_t *, xfs_suminfo_t *);
STATIC int xfs_rtmodify_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
        xfs_extlen_t, int);
STATIC int xfs_rtmodify_summary(xfs_mount_t *, xfs_trans_t *, int,
        xfs_rtblock_t, int, xfs_buf_t **, xfs_fsblock_t *);

/*
 * Internal functions.
 */

/*
 * Allocate space to the bitmap or summary file, and zero it, for growfs.
 */
STATIC int              /* error */
xfs_growfs_rt_alloc(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_extlen_t    oblocks,    /* old count of blocks */
    xfs_extlen_t    nblocks,    /* new count of blocks */
    xfs_inode_t *ip)        /* inode (bitmap/summary) */
{
    xfs_fileoff_t   bno;        /* block number in file */
    xfs_buf_t   *bp;        /* temporary buffer for zeroing */
    int     committed;  /* transaction committed flag */
    xfs_daddr_t d;      /* disk block address */
    int     error;      /* error return value */
    xfs_fsblock_t   firstblock; /* first block allocated in xaction */
    xfs_bmap_free_t flist;      /* list of freed blocks */
    xfs_fsblock_t   fsbno;      /* filesystem block for bno */
    xfs_bmbt_irec_t map;        /* block map output */
    int     nmap;       /* number of block maps */
    int     resblks;    /* space reservation */

    /*
     * Allocate space to the file, as necessary.
     */
    while (oblocks < nblocks) {
        int     cancelflags = 0;
        xfs_trans_t *tp;

        tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFSRT_ALLOC);
        resblks = XFS_GROWFSRT_SPACE_RES(mp, nblocks - oblocks);
        /*
         * Reserve space & log for one extent added to the file.
         */
        if ((error = xfs_trans_reserve(tp, resblks,
                XFS_GROWRTALLOC_LOG_RES(mp), 0,
                XFS_TRANS_PERM_LOG_RES,
                XFS_DEFAULT_PERM_LOG_COUNT)))
            goto error_cancel;
        cancelflags = XFS_TRANS_RELEASE_LOG_RES;
        /*
         * Lock the inode.
         */
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

        xfs_bmap_init(&flist, &firstblock);
        /*
         * Allocate blocks to the bitmap file.
         */
        nmap = 1;
        cancelflags |= XFS_TRANS_ABORT;
        error = xfs_bmapi_write(tp, ip, oblocks, nblocks - oblocks,
                    XFS_BMAPI_METADATA, &firstblock,
                    resblks, &map, &nmap, &flist);
        if (!error && nmap < 1)
            error = XFS_ERROR(ENOSPC);
        if (error)
            goto error_cancel;
        /*
         * Free any blocks freed up in the transaction, then commit.
         */
        error = xfs_bmap_finish(&tp, &flist, &committed);
        if (error)
            goto error_cancel;
        error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
        if (error)
            goto error;
        /*
         * Now we need to clear the allocated blocks.
         * Do this one block per transaction, to keep it simple.
         */
        cancelflags = 0;
        for (bno = map.br_startoff, fsbno = map.br_startblock;
             bno < map.br_startoff + map.br_blockcount;
             bno++, fsbno++) {
            tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFSRT_ZERO);
            /*
             * Reserve log for one block zeroing.
             */
            if ((error = xfs_trans_reserve(tp, 0,
                    XFS_GROWRTZERO_LOG_RES(mp), 0, 0, 0)))
                goto error_cancel;
            /*
             * Lock the bitmap inode.
             */
            xfs_ilock(ip, XFS_ILOCK_EXCL);
            xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
            /*
             * Get a buffer for the block.
             */
            d = XFS_FSB_TO_DADDR(mp, fsbno);
            bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
                mp->m_bsize, 0);
            if (bp == NULL) {
                error = XFS_ERROR(EIO);
error_cancel:
                xfs_trans_cancel(tp, cancelflags);
                goto error;
            }
            memset(bp->b_addr, 0, mp->m_sb.sb_blocksize);
            xfs_trans_log_buf(tp, bp, 0, mp->m_sb.sb_blocksize - 1);
            /*
             * Commit the transaction.
             */
            error = xfs_trans_commit(tp, 0);
            if (error)
                goto error;
        }
        /*
         * Go on to the next extent, if any.
         */
        oblocks = map.br_startoff + map.br_blockcount;
    }
    return 0;

error:
    return error;
}

/*
 * Attempt to allocate an extent minlen<=len<=maxlen starting from
 * bitmap block bbno.  If we don't get maxlen then use prod to trim
 * the length, if given.  Returns error; returns starting block in *rtblock.
 * The lengths are all in rtextents.
 */
STATIC int              /* error */
xfs_rtallocate_extent_block(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bbno,       /* bitmap block number */
    xfs_extlen_t    minlen,     /* minimum length to allocate */
    xfs_extlen_t    maxlen,     /* maximum length to allocate */
    xfs_extlen_t    *len,       /* out: actual length allocated */
    xfs_rtblock_t   *nextp,     /* out: next block to try */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    xfs_extlen_t    prod,       /* extent product factor */
    xfs_rtblock_t   *rtblock)   /* out: start block allocated */
{
    xfs_rtblock_t   besti;      /* best rtblock found so far */
    xfs_rtblock_t   bestlen;    /* best length found so far */
    xfs_rtblock_t   end;        /* last rtblock in chunk */
    int     error;      /* error value */
    xfs_rtblock_t   i;      /* current rtblock trying */
    xfs_rtblock_t   next;       /* next rtblock to try */
    int     stat;       /* status from internal calls */

    /*
     * Loop over all the extents starting in this bitmap block,
     * looking for one that's long enough.
     */
    for (i = XFS_BLOCKTOBIT(mp, bbno), besti = -1, bestlen = 0,
        end = XFS_BLOCKTOBIT(mp, bbno + 1) - 1;
         i <= end;
         i++) {
        /*
         * See if there's a free extent of maxlen starting at i.
         * If it's not so then next will contain the first non-free.
         */
        error = xfs_rtcheck_range(mp, tp, i, maxlen, 1, &next, &stat);
        if (error) {
            return error;
        }
        if (stat) {
            /*
             * i for maxlen is all free, allocate and return that.
             */
            error = xfs_rtallocate_range(mp, tp, i, maxlen, rbpp,
                rsb);
            if (error) {
                return error;
            }
            *len = maxlen;
            *rtblock = i;
            return 0;
        }
        /*
         * In the case where we have a variable-sized allocation
         * request, figure out how big this free piece is,
         * and if it's big enough for the minimum, and the best
         * so far, remember it.
         */
        if (minlen < maxlen) {
            xfs_rtblock_t   thislen;    /* this extent size */

            thislen = next - i;
            if (thislen >= minlen && thislen > bestlen) {
                besti = i;
                bestlen = thislen;
            }
        }
        /*
         * If not done yet, find the start of the next free space.
         */
        if (next < end) {
            error = xfs_rtfind_forw(mp, tp, next, end, &i);
            if (error) {
                return error;
            }
        } else
            break;
    }
    /*
     * Searched the whole thing & didn't find a maxlen free extent.
     */
    if (minlen < maxlen && besti != -1) {
        xfs_extlen_t    p;  /* amount to trim length by */

        /*
         * If size should be a multiple of prod, make that so.
         */
        if (prod > 1 && (p = do_mod(bestlen, prod)))
            bestlen -= p;
        /*
         * Allocate besti for bestlen & return that.
         */
        error = xfs_rtallocate_range(mp, tp, besti, bestlen, rbpp, rsb);
        if (error) {
            return error;
        }
        *len = bestlen;
        *rtblock = besti;
        return 0;
    }
    /*
     * Allocation failed.  Set *nextp to the next block to try.
     */
    *nextp = next;
    *rtblock = NULLRTBLOCK;
    return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, starting at block
 * bno.  If we don't get maxlen then use prod to trim the length, if given.
 * Returns error; returns starting block in *rtblock.
 * The lengths are all in rtextents.
 */
STATIC int              /* error */
xfs_rtallocate_extent_exact(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bno,        /* starting block number to allocate */
    xfs_extlen_t    minlen,     /* minimum length to allocate */
    xfs_extlen_t    maxlen,     /* maximum length to allocate */
    xfs_extlen_t    *len,       /* out: actual length allocated */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    xfs_extlen_t    prod,       /* extent product factor */
    xfs_rtblock_t   *rtblock)   /* out: start block allocated */
{
    int     error;      /* error value */
    xfs_extlen_t    i;      /* extent length trimmed due to prod */
    int     isfree;     /* extent is free */
    xfs_rtblock_t   next;       /* next block to try (dummy) */

    ASSERT(minlen % prod == 0 && maxlen % prod == 0);
    /*
     * Check if the range in question (for maxlen) is free.
     */
    error = xfs_rtcheck_range(mp, tp, bno, maxlen, 1, &next, &isfree);
    if (error) {
        return error;
    }
    if (isfree) {
        /*
         * If it is, allocate it and return success.
         */
        error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
        if (error) {
            return error;
        }
        *len = maxlen;
        *rtblock = bno;
        return 0;
    }
    /*
     * If not, allocate what there is, if it's at least minlen.
     */
    maxlen = next - bno;
    if (maxlen < minlen) {
        /*
         * Failed, return failure status.
         */
        *rtblock = NULLRTBLOCK;
        return 0;
    }
    /*
     * Trim off tail of extent, if prod is specified.
     */
    if (prod > 1 && (i = maxlen % prod)) {
        maxlen -= i;
        if (maxlen < minlen) {
            /*
             * Now we can't do it, return failure status.
             */
            *rtblock = NULLRTBLOCK;
            return 0;
        }
    }
    /*
     * Allocate what we can and return it.
     */
    error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
    if (error) {
        return error;
    }
    *len = maxlen;
    *rtblock = bno;
    return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, starting as near
 * to bno as possible.  If we don't get maxlen then use prod to trim
 * the length, if given.  The lengths are all in rtextents.
 */
STATIC int              /* error */
xfs_rtallocate_extent_near(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bno,        /* starting block number to allocate */
    xfs_extlen_t    minlen,     /* minimum length to allocate */
    xfs_extlen_t    maxlen,     /* maximum length to allocate */
    xfs_extlen_t    *len,       /* out: actual length allocated */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    xfs_extlen_t    prod,       /* extent product factor */
    xfs_rtblock_t   *rtblock)   /* out: start block allocated */
{
    int     any;        /* any useful extents from summary */
    xfs_rtblock_t   bbno;       /* bitmap block number */
    int     error;      /* error value */
    int     i;      /* bitmap block offset (loop control) */
    int     j;      /* secondary loop control */
    int     log2len;    /* log2 of minlen */
    xfs_rtblock_t   n;      /* next block to try */
    xfs_rtblock_t   r;      /* result block */

    ASSERT(minlen % prod == 0 && maxlen % prod == 0);
    /*
     * If the block number given is off the end, silently set it to
     * the last block.
     */
    if (bno >= mp->m_sb.sb_rextents)
        bno = mp->m_sb.sb_rextents - 1;
    /*
     * Try the exact allocation first.
     */
    error = xfs_rtallocate_extent_exact(mp, tp, bno, minlen, maxlen, len,
        rbpp, rsb, prod, &r);
    if (error) {
        return error;
    }
    /*
     * If the exact allocation worked, return that.
     */
    if (r != NULLRTBLOCK) {
        *rtblock = r;
        return 0;
    }
    bbno = XFS_BITTOBLOCK(mp, bno);
    i = 0;
    ASSERT(minlen != 0);
    log2len = xfs_highbit32(minlen);
    /*
     * Loop over all bitmap blocks (bbno + i is current block).
     */
    for (;;) {
        /*
         * Get summary information of extents of all useful levels
         * starting in this bitmap block.
         */
        error = xfs_rtany_summary(mp, tp, log2len, mp->m_rsumlevels - 1,
            bbno + i, rbpp, rsb, &any);
        if (error) {
            return error;
        }
        /*
         * If there are any useful extents starting here, try
         * allocating one.
         */
        if (any) {
            /*
             * On the positive side of the starting location.
             */
            if (i >= 0) {
                /*
                 * Try to allocate an extent starting in
                 * this block.
                 */
                error = xfs_rtallocate_extent_block(mp, tp,
                    bbno + i, minlen, maxlen, len, &n, rbpp,
                    rsb, prod, &r);
                if (error) {
                    return error;
                }
                /*
                 * If it worked, return it.
                 */
                if (r != NULLRTBLOCK) {
                    *rtblock = r;
                    return 0;
                }
            }
            /*
             * On the negative side of the starting location.
             */
            else {      /* i < 0 */
                /*
                 * Loop backwards through the bitmap blocks from
                 * the starting point-1 up to where we are now.
                 * There should be an extent which ends in this
                 * bitmap block and is long enough.
                 */
                for (j = -1; j > i; j--) {
                    /*
                     * Grab the summary information for
                     * this bitmap block.
                     */
                    error = xfs_rtany_summary(mp, tp,
                        log2len, mp->m_rsumlevels - 1,
                        bbno + j, rbpp, rsb, &any);
                    if (error) {
                        return error;
                    }
                    /*
                     * If there's no extent given in the
                     * summary that means the extent we
                     * found must carry over from an
                     * earlier block.  If there is an
                     * extent given, we've already tried
                     * that allocation, don't do it again.
                     */
                    if (any)
                        continue;
                    error = xfs_rtallocate_extent_block(mp,
                        tp, bbno + j, minlen, maxlen,
                        len, &n, rbpp, rsb, prod, &r);
                    if (error) {
                        return error;
                    }
                    /*
                     * If it works, return the extent.
                     */
                    if (r != NULLRTBLOCK) {
                        *rtblock = r;
                        return 0;
                    }
                }
                /*
                 * There weren't intervening bitmap blocks
                 * with a long enough extent, or the
                 * allocation didn't work for some reason
                 * (i.e. it's a little * too short).
                 * Try to allocate from the summary block
                 * that we found.
                 */
                error = xfs_rtallocate_extent_block(mp, tp,
                    bbno + i, minlen, maxlen, len, &n, rbpp,
                    rsb, prod, &r);
                if (error) {
                    return error;
                }
                /*
                 * If it works, return the extent.
                 */
                if (r != NULLRTBLOCK) {
                    *rtblock = r;
                    return 0;
                }
            }
        }
        /*
         * Loop control.  If we were on the positive side, and there's
         * still more blocks on the negative side, go there.
         */
        if (i > 0 && (int)bbno - i >= 0)
            i = -i;
        /*
         * If positive, and no more negative, but there are more
         * positive, go there.
         */
        else if (i > 0 && (int)bbno + i < mp->m_sb.sb_rbmblocks - 1)
            i++;
        /*
         * If negative or 0 (just started), and there are positive
         * blocks to go, go there.  The 0 case moves to block 1.
         */
        else if (i <= 0 && (int)bbno - i < mp->m_sb.sb_rbmblocks - 1)
            i = 1 - i;
        /*
         * If negative or 0 and there are more negative blocks,
         * go there.
         */
        else if (i <= 0 && (int)bbno + i > 0)
            i--;
        /*
         * Must be done.  Return failure.
         */
        else
            break;
    }
    *rtblock = NULLRTBLOCK;
    return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, with no position
 * specified.  If we don't get maxlen then use prod to trim
 * the length, if given.  The lengths are all in rtextents.
 */
STATIC int              /* error */
xfs_rtallocate_extent_size(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_extlen_t    minlen,     /* minimum length to allocate */
    xfs_extlen_t    maxlen,     /* maximum length to allocate */
    xfs_extlen_t    *len,       /* out: actual length allocated */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    xfs_extlen_t    prod,       /* extent product factor */
    xfs_rtblock_t   *rtblock)   /* out: start block allocated */
{
    int     error;      /* error value */
    int     i;      /* bitmap block number */
    int     l;      /* level number (loop control) */
    xfs_rtblock_t   n;      /* next block to be tried */
    xfs_rtblock_t   r;      /* result block number */
    xfs_suminfo_t   sum;        /* summary information for extents */

    ASSERT(minlen % prod == 0 && maxlen % prod == 0);
    ASSERT(maxlen != 0);

    /*
     * Loop over all the levels starting with maxlen.
     * At each level, look at all the bitmap blocks, to see if there
     * are extents starting there that are long enough (>= maxlen).
     * Note, only on the initial level can the allocation fail if
     * the summary says there's an extent.
     */
    for (l = xfs_highbit32(maxlen); l < mp->m_rsumlevels; l++) {
        /*
         * Loop over all the bitmap blocks.
         */
        for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
            /*
             * Get the summary for this level/block.
             */
            error = xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
                &sum);
            if (error) {
                return error;
            }
            /*
             * Nothing there, on to the next block.
             */
            if (!sum)
                continue;
            /*
             * Try allocating the extent.
             */
            error = xfs_rtallocate_extent_block(mp, tp, i, maxlen,
                maxlen, len, &n, rbpp, rsb, prod, &r);
            if (error) {
                return error;
            }
            /*
             * If it worked, return that.
             */
            if (r != NULLRTBLOCK) {
                *rtblock = r;
                return 0;
            }
            /*
             * If the "next block to try" returned from the
             * allocator is beyond the next bitmap block,
             * skip to that bitmap block.
             */
            if (XFS_BITTOBLOCK(mp, n) > i + 1)
                i = XFS_BITTOBLOCK(mp, n) - 1;
        }
    }
    /*
     * Didn't find any maxlen blocks.  Try smaller ones, unless
     * we're asking for a fixed size extent.
     */
    if (minlen > --maxlen) {
        *rtblock = NULLRTBLOCK;
        return 0;
    }
    ASSERT(minlen != 0);
    ASSERT(maxlen != 0);

    /*
     * Loop over sizes, from maxlen down to minlen.
     * This time, when we do the allocations, allow smaller ones
     * to succeed.
     */
    for (l = xfs_highbit32(maxlen); l >= xfs_highbit32(minlen); l--) {
        /*
         * Loop over all the bitmap blocks, try an allocation
         * starting in that block.
         */
        for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
            /*
             * Get the summary information for this level/block.
             */
            error = xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
                          &sum);
            if (error) {
                return error;
            }
            /*
             * If nothing there, go on to next.
             */
            if (!sum)
                continue;
            /*
             * Try the allocation.  Make sure the specified
             * minlen/maxlen are in the possible range for
             * this summary level.
             */
            error = xfs_rtallocate_extent_block(mp, tp, i,
                    XFS_RTMAX(minlen, 1 << l),
                    XFS_RTMIN(maxlen, (1 << (l + 1)) - 1),
                    len, &n, rbpp, rsb, prod, &r);
            if (error) {
                return error;
            }
            /*
             * If it worked, return that extent.
             */
            if (r != NULLRTBLOCK) {
                *rtblock = r;
                return 0;
            }
            /*
             * If the "next block to try" returned from the
             * allocator is beyond the next bitmap block,
             * skip to that bitmap block.
             */
            if (XFS_BITTOBLOCK(mp, n) > i + 1)
                i = XFS_BITTOBLOCK(mp, n) - 1;
        }
    }
    /*
     * Got nothing, return failure.
     */
    *rtblock = NULLRTBLOCK;
    return 0;
}

/*
 * Mark an extent specified by start and len allocated.
 * Updates all the summary information as well as the bitmap.
 */
STATIC int              /* error */
xfs_rtallocate_range(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* start block to allocate */
    xfs_extlen_t    len,        /* length to allocate */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb)       /* in/out: summary block number */
{
    xfs_rtblock_t   end;        /* end of the allocated extent */
    int     error;      /* error value */
    xfs_rtblock_t   postblock;  /* first block allocated > end */
    xfs_rtblock_t   preblock;   /* first block allocated < start */

    end = start + len - 1;
    /*
     * Assume we're allocating out of the middle of a free extent.
     * We need to find the beginning and end of the extent so we can
     * properly update the summary.
     */
    error = xfs_rtfind_back(mp, tp, start, 0, &preblock);
    if (error) {
        return error;
    }
    /*
     * Find the next allocated block (end of free extent).
     */
    error = xfs_rtfind_forw(mp, tp, end, mp->m_sb.sb_rextents - 1,
        &postblock);
    if (error) {
        return error;
    }
    /*
     * Decrement the summary information corresponding to the entire
     * (old) free extent.
     */
    error = xfs_rtmodify_summary(mp, tp,
        XFS_RTBLOCKLOG(postblock + 1 - preblock),
        XFS_BITTOBLOCK(mp, preblock), -1, rbpp, rsb);
    if (error) {
        return error;
    }
    /*
     * If there are blocks not being allocated at the front of the
     * old extent, add summary data for them to be free.
     */
    if (preblock < start) {
        error = xfs_rtmodify_summary(mp, tp,
            XFS_RTBLOCKLOG(start - preblock),
            XFS_BITTOBLOCK(mp, preblock), 1, rbpp, rsb);
        if (error) {
            return error;
        }
    }
    /*
     * If there are blocks not being allocated at the end of the
     * old extent, add summary data for them to be free.
     */
    if (postblock > end) {
        error = xfs_rtmodify_summary(mp, tp,
            XFS_RTBLOCKLOG(postblock - end),
            XFS_BITTOBLOCK(mp, end + 1), 1, rbpp, rsb);
        if (error) {
            return error;
        }
    }
    /*
     * Modify the bitmap to mark this extent allocated.
     */
    error = xfs_rtmodify_range(mp, tp, start, len, 0);
    return error;
}

/*
 * Return whether there are any free extents in the size range given
 * by low and high, for the bitmap block bbno.
 */
STATIC int              /* error */
xfs_rtany_summary(
    xfs_mount_t *mp,        /* file system mount structure */
    xfs_trans_t *tp,        /* transaction pointer */
    int     low,        /* low log2 extent size */
    int     high,       /* high log2 extent size */
    xfs_rtblock_t   bbno,       /* bitmap block number */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    int     *stat)      /* out: any good extents here? */
{
    int     error;      /* error value */
    int     log;        /* loop counter, log2 of ext. size */
    xfs_suminfo_t   sum;        /* summary data */

    /*
     * Loop over logs of extent sizes.  Order is irrelevant.
     */
    for (log = low; log <= high; log++) {
        /*
         * Get one summary datum.
         */
        error = xfs_rtget_summary(mp, tp, log, bbno, rbpp, rsb, &sum);
        if (error) {
            return error;
        }
        /*
         * If there are any, return success.
         */
        if (sum) {
            *stat = 1;
            return 0;
        }
    }
    /*
     * Found nothing, return failure.
     */
    *stat = 0;
    return 0;
}

/*
 * Get a buffer for the bitmap or summary file block specified.
 * The buffer is returned read and locked.
 */
STATIC int              /* error */
xfs_rtbuf_get(
    xfs_mount_t *mp,        /* file system mount structure */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   block,      /* block number in bitmap or summary */
    int     issum,      /* is summary not bitmap */
    xfs_buf_t   **bpp)      /* output: buffer for the block */
{
    xfs_buf_t   *bp;        /* block buffer, result */
    xfs_inode_t *ip;        /* bitmap or summary inode */
    xfs_bmbt_irec_t map;
    int     nmap = 1;
    int     error;      /* error value */

    ip = issum ? mp->m_rsumip : mp->m_rbmip;

    error = xfs_bmapi_read(ip, block, 1, &map, &nmap, XFS_DATA_FORK);
    if (error)
        return error;

    ASSERT(map.br_startblock != NULLFSBLOCK);
    error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                   XFS_FSB_TO_DADDR(mp, map.br_startblock),
                   mp->m_bsize, 0, &bp);
    if (error)
        return error;
    ASSERT(!xfs_buf_geterror(bp));
    *bpp = bp;
    return 0;
}

#ifdef DEBUG
/*
 * Check that the given extent (block range) is allocated already.
 */
STATIC int              /* error */
xfs_rtcheck_alloc_range(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bno,        /* starting block number of extent */
    xfs_extlen_t    len,        /* length of extent */
    int     *stat)      /* out: 1 for allocated, 0 for not */
{
    xfs_rtblock_t   new;        /* dummy for xfs_rtcheck_range */

    return xfs_rtcheck_range(mp, tp, bno, len, 0, &new, stat);
}
#endif

/*
 * Check that the given range is either all allocated (val = 0) or
 * all free (val = 1).
 */
STATIC int              /* error */
xfs_rtcheck_range(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* starting block number of extent */
    xfs_extlen_t    len,        /* length of extent */
    int     val,        /* 1 for free, 0 for allocated */
    xfs_rtblock_t   *new,       /* out: first block not matching */
    int     *stat)      /* out: 1 for matches, 0 for not */
{
    xfs_rtword_t    *b;     /* current word in buffer */
    int     bit;        /* bit number in the word */
    xfs_rtblock_t   block;      /* bitmap block number */
    xfs_buf_t   *bp;        /* buf for the block */
    xfs_rtword_t    *bufp;      /* starting word in buffer */
    int     error;      /* error value */
    xfs_rtblock_t   i;      /* current bit number rel. to start */
    xfs_rtblock_t   lastbit;    /* last useful bit in word */
    xfs_rtword_t    mask;       /* mask of relevant bits for value */
    xfs_rtword_t    wdiff;      /* difference from wanted value */
    int     word;       /* word number in the buffer */

    /*
     * Compute starting bitmap block number
     */
    block = XFS_BITTOBLOCK(mp, start);
    /*
     * Read the bitmap block.
     */
    error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
    if (error) {
        return error;
    }
    bufp = bp->b_addr;
    /*
     * Compute the starting word's address, and starting bit.
     */
    word = XFS_BITTOWORD(mp, start);
    b = &bufp[word];
    bit = (int)(start & (XFS_NBWORD - 1));
    /*
     * 0 (allocated) => all zero's; 1 (free) => all one's.
     */
    val = -val;
    /*
     * If not starting on a word boundary, deal with the first
     * (partial) word.
     */
    if (bit) {
        /*
         * Compute first bit not examined.
         */
        lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
        /*
         * Mask of relevant bits.
         */
        mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = (*b ^ val) & mask)) {
            /*
             * Different, compute first wrong bit and return.
             */
            xfs_trans_brelse(tp, bp);
            i = XFS_RTLOBIT(wdiff) - bit;
            *new = start + i;
            *stat = 0;
            return 0;
        }
        i = lastbit - bit;
        /*
         * Go on to next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * If done with this block, get the next one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the next word in the buffer.
             */
            b++;
        }
    } else {
        /*
         * Starting on a word boundary, no partial word.
         */
        i = 0;
    }
    /*
     * Loop over whole words in buffers.  When we use up one buffer
     * we move on to the next one.
     */
    while (len - i >= XFS_NBWORD) {
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = *b ^ val)) {
            /*
             * Different, compute first wrong bit and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_RTLOBIT(wdiff);
            *new = start + i;
            *stat = 0;
            return 0;
        }
        i += XFS_NBWORD;
        /*
         * Go on to next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * If done with this block, get the next one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the next word in the buffer.
             */
            b++;
        }
    }
    /*
     * If not ending on a word boundary, deal with the last
     * (partial) word.
     */
    if ((lastbit = len - i)) {
        /*
         * Mask of relevant bits.
         */
        mask = ((xfs_rtword_t)1 << lastbit) - 1;
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = (*b ^ val) & mask)) {
            /*
             * Different, compute first wrong bit and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_RTLOBIT(wdiff);
            *new = start + i;
            *stat = 0;
            return 0;
        } else
            i = len;
    }
    /*
     * Successful, return.
     */
    xfs_trans_brelse(tp, bp);
    *new = start + i;
    *stat = 1;
    return 0;
}

/*
 * Copy and transform the summary file, given the old and new
 * parameters in the mount structures.
 */
STATIC int              /* error */
xfs_rtcopy_summary(
    xfs_mount_t *omp,       /* old file system mount point */
    xfs_mount_t *nmp,       /* new file system mount point */
    xfs_trans_t *tp)        /* transaction pointer */
{
    xfs_rtblock_t   bbno;       /* bitmap block number */
    xfs_buf_t   *bp;        /* summary buffer */
    int     error;      /* error return value */
    int     log;        /* summary level number (log length) */
    xfs_suminfo_t   sum;        /* summary data */
    xfs_fsblock_t   sumbno;     /* summary block number */

    bp = NULL;
    for (log = omp->m_rsumlevels - 1; log >= 0; log--) {
        for (bbno = omp->m_sb.sb_rbmblocks - 1;
             (xfs_srtblock_t)bbno >= 0;
             bbno--) {
            error = xfs_rtget_summary(omp, tp, log, bbno, &bp,
                &sumbno, &sum);
            if (error)
                return error;
            if (sum == 0)
                continue;
            error = xfs_rtmodify_summary(omp, tp, log, bbno, -sum,
                &bp, &sumbno);
            if (error)
                return error;
            error = xfs_rtmodify_summary(nmp, tp, log, bbno, sum,
                &bp, &sumbno);
            if (error)
                return error;
            ASSERT(sum > 0);
        }
    }
    return 0;
}

/*
 * Searching backward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int              /* error */
xfs_rtfind_back(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* starting block to look at */
    xfs_rtblock_t   limit,      /* last block to look at */
    xfs_rtblock_t   *rtblock)   /* out: start block found */
{
    xfs_rtword_t    *b;     /* current word in buffer */
    int     bit;        /* bit number in the word */
    xfs_rtblock_t   block;      /* bitmap block number */
    xfs_buf_t   *bp;        /* buf for the block */
    xfs_rtword_t    *bufp;      /* starting word in buffer */
    int     error;      /* error value */
    xfs_rtblock_t   firstbit;   /* first useful bit in the word */
    xfs_rtblock_t   i;      /* current bit number rel. to start */
    xfs_rtblock_t   len;        /* length of inspected area */
    xfs_rtword_t    mask;       /* mask of relevant bits for value */
    xfs_rtword_t    want;       /* mask for "good" values */
    xfs_rtword_t    wdiff;      /* difference from wanted value */
    int     word;       /* word number in the buffer */

    /*
     * Compute and read in starting bitmap block for starting block.
     */
    block = XFS_BITTOBLOCK(mp, start);
    error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
    if (error) {
        return error;
    }
    bufp = bp->b_addr;
    /*
     * Get the first word's index & point to it.
     */
    word = XFS_BITTOWORD(mp, start);
    b = &bufp[word];
    bit = (int)(start & (XFS_NBWORD - 1));
    len = start - limit + 1;
    /*
     * Compute match value, based on the bit at start: if 1 (free)
     * then all-ones, else all-zeroes.
     */
    want = (*b & ((xfs_rtword_t)1 << bit)) ? -1 : 0;
    /*
     * If the starting position is not word-aligned, deal with the
     * partial word.
     */
    if (bit < XFS_NBWORD - 1) {
        /*
         * Calculate first (leftmost) bit number to look at,
         * and mask for all the relevant bits in this word.
         */
        firstbit = XFS_RTMAX((xfs_srtblock_t)(bit - len + 1), 0);
        mask = (((xfs_rtword_t)1 << (bit - firstbit + 1)) - 1) <<
            firstbit;
        /*
         * Calculate the difference between the value there
         * and what we're looking for.
         */
        if ((wdiff = (*b ^ want) & mask)) {
            /*
             * Different.  Mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i = bit - XFS_RTHIBIT(wdiff);
            *rtblock = start - i + 1;
            return 0;
        }
        i = bit - firstbit + 1;
        /*
         * Go on to previous block if that's where the previous word is
         * and we need the previous word.
         */
        if (--word == -1 && i < len) {
            /*
             * If done with this block, get the previous one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, --block, 0, &bp);
            if (error) {
                return error;
            }
            bufp = bp->b_addr;
            word = XFS_BLOCKWMASK(mp);
            b = &bufp[word];
        } else {
            /*
             * Go on to the previous word in the buffer.
             */
            b--;
        }
    } else {
        /*
         * Starting on a word boundary, no partial word.
         */
        i = 0;
    }
    /*
     * Loop over whole words in buffers.  When we use up one buffer
     * we move on to the previous one.
     */
    while (len - i >= XFS_NBWORD) {
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = *b ^ want)) {
            /*
             * Different, mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
            *rtblock = start - i + 1;
            return 0;
        }
        i += XFS_NBWORD;
        /*
         * Go on to previous block if that's where the previous word is
         * and we need the previous word.
         */
        if (--word == -1 && i < len) {
            /*
             * If done with this block, get the previous one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, --block, 0, &bp);
            if (error) {
                return error;
            }
            bufp = bp->b_addr;
            word = XFS_BLOCKWMASK(mp);
            b = &bufp[word];
        } else {
            /*
             * Go on to the previous word in the buffer.
             */
            b--;
        }
    }
    /*
     * If not ending on a word boundary, deal with the last
     * (partial) word.
     */
    if (len - i) {
        /*
         * Calculate first (leftmost) bit number to look at,
         * and mask for all the relevant bits in this word.
         */
        firstbit = XFS_NBWORD - (len - i);
        mask = (((xfs_rtword_t)1 << (len - i)) - 1) << firstbit;
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = (*b ^ want) & mask)) {
            /*
             * Different, mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
            *rtblock = start - i + 1;
            return 0;
        } else
            i = len;
    }
    /*
     * No match, return that we scanned the whole area.
     */
    xfs_trans_brelse(tp, bp);
    *rtblock = start - i + 1;
    return 0;
}

/*
 * Searching forward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int              /* error */
xfs_rtfind_forw(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* starting block to look at */
    xfs_rtblock_t   limit,      /* last block to look at */
    xfs_rtblock_t   *rtblock)   /* out: start block found */
{
    xfs_rtword_t    *b;     /* current word in buffer */
    int     bit;        /* bit number in the word */
    xfs_rtblock_t   block;      /* bitmap block number */
    xfs_buf_t   *bp;        /* buf for the block */
    xfs_rtword_t    *bufp;      /* starting word in buffer */
    int     error;      /* error value */
    xfs_rtblock_t   i;      /* current bit number rel. to start */
    xfs_rtblock_t   lastbit;    /* last useful bit in the word */
    xfs_rtblock_t   len;        /* length of inspected area */
    xfs_rtword_t    mask;       /* mask of relevant bits for value */
    xfs_rtword_t    want;       /* mask for "good" values */
    xfs_rtword_t    wdiff;      /* difference from wanted value */
    int     word;       /* word number in the buffer */

    /*
     * Compute and read in starting bitmap block for starting block.
     */
    block = XFS_BITTOBLOCK(mp, start);
    error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
    if (error) {
        return error;
    }
    bufp = bp->b_addr;
    /*
     * Get the first word's index & point to it.
     */
    word = XFS_BITTOWORD(mp, start);
    b = &bufp[word];
    bit = (int)(start & (XFS_NBWORD - 1));
    len = limit - start + 1;
    /*
     * Compute match value, based on the bit at start: if 1 (free)
     * then all-ones, else all-zeroes.
     */
    want = (*b & ((xfs_rtword_t)1 << bit)) ? -1 : 0;
    /*
     * If the starting position is not word-aligned, deal with the
     * partial word.
     */
    if (bit) {
        /*
         * Calculate last (rightmost) bit number to look at,
         * and mask for all the relevant bits in this word.
         */
        lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
        mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
        /*
         * Calculate the difference between the value there
         * and what we're looking for.
         */
        if ((wdiff = (*b ^ want) & mask)) {
            /*
             * Different.  Mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i = XFS_RTLOBIT(wdiff) - bit;
            *rtblock = start + i - 1;
            return 0;
        }
        i = lastbit - bit;
        /*
         * Go on to next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * If done with this block, get the previous one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the previous word in the buffer.
             */
            b++;
        }
    } else {
        /*
         * Starting on a word boundary, no partial word.
         */
        i = 0;
    }
    /*
     * Loop over whole words in buffers.  When we use up one buffer
     * we move on to the next one.
     */
    while (len - i >= XFS_NBWORD) {
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = *b ^ want)) {
            /*
             * Different, mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_RTLOBIT(wdiff);
            *rtblock = start + i - 1;
            return 0;
        }
        i += XFS_NBWORD;
        /*
         * Go on to next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * If done with this block, get the next one.
             */
            xfs_trans_brelse(tp, bp);
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the next word in the buffer.
             */
            b++;
        }
    }
    /*
     * If not ending on a word boundary, deal with the last
     * (partial) word.
     */
    if ((lastbit = len - i)) {
        /*
         * Calculate mask for all the relevant bits in this word.
         */
        mask = ((xfs_rtword_t)1 << lastbit) - 1;
        /*
         * Compute difference between actual and desired value.
         */
        if ((wdiff = (*b ^ want) & mask)) {
            /*
             * Different, mark where we are and return.
             */
            xfs_trans_brelse(tp, bp);
            i += XFS_RTLOBIT(wdiff);
            *rtblock = start + i - 1;
            return 0;
        } else
            i = len;
    }
    /*
     * No match, return that we scanned the whole area.
     */
    xfs_trans_brelse(tp, bp);
    *rtblock = start + i - 1;
    return 0;
}

/*
 * Mark an extent specified by start and len freed.
 * Updates all the summary information as well as the bitmap.
 */
STATIC int              /* error */
xfs_rtfree_range(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* starting block to free */
    xfs_extlen_t    len,        /* length to free */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb)       /* in/out: summary block number */
{
    xfs_rtblock_t   end;        /* end of the freed extent */
    int     error;      /* error value */
    xfs_rtblock_t   postblock;  /* first block freed > end */
    xfs_rtblock_t   preblock;   /* first block freed < start */

    end = start + len - 1;
    /*
     * Modify the bitmap to mark this extent freed.
     */
    error = xfs_rtmodify_range(mp, tp, start, len, 1);
    if (error) {
        return error;
    }
    /*
     * Assume we're freeing out of the middle of an allocated extent.
     * We need to find the beginning and end of the extent so we can
     * properly update the summary.
     */
    error = xfs_rtfind_back(mp, tp, start, 0, &preblock);
    if (error) {
        return error;
    }
    /*
     * Find the next allocated block (end of allocated extent).
     */
    error = xfs_rtfind_forw(mp, tp, end, mp->m_sb.sb_rextents - 1,
        &postblock);
    if (error)
        return error;
    /*
     * If there are blocks not being freed at the front of the
     * old extent, add summary data for them to be allocated.
     */
    if (preblock < start) {
        error = xfs_rtmodify_summary(mp, tp,
            XFS_RTBLOCKLOG(start - preblock),
            XFS_BITTOBLOCK(mp, preblock), -1, rbpp, rsb);
        if (error) {
            return error;
        }
    }
    /*
     * If there are blocks not being freed at the end of the
     * old extent, add summary data for them to be allocated.
     */
    if (postblock > end) {
        error = xfs_rtmodify_summary(mp, tp,
            XFS_RTBLOCKLOG(postblock - end),
            XFS_BITTOBLOCK(mp, end + 1), -1, rbpp, rsb);
        if (error) {
            return error;
        }
    }
    /*
     * Increment the summary information corresponding to the entire
     * (new) free extent.
     */
    error = xfs_rtmodify_summary(mp, tp,
        XFS_RTBLOCKLOG(postblock + 1 - preblock),
        XFS_BITTOBLOCK(mp, preblock), 1, rbpp, rsb);
    return error;
}

/*
 * Read and return the summary information for a given extent size,
 * bitmap block combination.
 * Keeps track of a current summary block, so we don't keep reading
 * it from the buffer cache.
 */
STATIC int              /* error */
xfs_rtget_summary(
    xfs_mount_t *mp,        /* file system mount structure */
    xfs_trans_t *tp,        /* transaction pointer */
    int     log,        /* log2 of extent size */
    xfs_rtblock_t   bbno,       /* bitmap block number */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb,       /* in/out: summary block number */
    xfs_suminfo_t   *sum)       /* out: summary info for this block */
{
    xfs_buf_t   *bp;        /* buffer for summary block */
    int     error;      /* error value */
    xfs_fsblock_t   sb;     /* summary fsblock */
    int     so;     /* index into the summary file */
    xfs_suminfo_t   *sp;        /* pointer to returned data */

    /*
     * Compute entry number in the summary file.
     */
    so = XFS_SUMOFFS(mp, log, bbno);
    /*
     * Compute the block number in the summary file.
     */
    sb = XFS_SUMOFFSTOBLOCK(mp, so);
    /*
     * If we have an old buffer, and the block number matches, use that.
     */
    if (rbpp && *rbpp && *rsb == sb)
        bp = *rbpp;
    /*
     * Otherwise we have to get the buffer.
     */
    else {
        /*
         * If there was an old one, get rid of it first.
         */
        if (rbpp && *rbpp)
            xfs_trans_brelse(tp, *rbpp);
        error = xfs_rtbuf_get(mp, tp, sb, 1, &bp);
        if (error) {
            return error;
        }
        /*
         * Remember this buffer and block for the next call.
         */
        if (rbpp) {
            *rbpp = bp;
            *rsb = sb;
        }
    }
    /*
     * Point to the summary information & copy it out.
     */
    sp = XFS_SUMPTR(mp, bp, so);
    *sum = *sp;
    /*
     * Drop the buffer if we're not asked to remember it.
     */
    if (!rbpp)
        xfs_trans_brelse(tp, bp);
    return 0;
}

/*
 * Set the given range of bitmap bits to the given value.
 * Do whatever I/O and logging is required.
 */
STATIC int              /* error */
xfs_rtmodify_range(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   start,      /* starting block to modify */
    xfs_extlen_t    len,        /* length of extent to modify */
    int     val)        /* 1 for free, 0 for allocated */
{
    xfs_rtword_t    *b;     /* current word in buffer */
    int     bit;        /* bit number in the word */
    xfs_rtblock_t   block;      /* bitmap block number */
    xfs_buf_t   *bp;        /* buf for the block */
    xfs_rtword_t    *bufp;      /* starting word in buffer */
    int     error;      /* error value */
    xfs_rtword_t    *first;     /* first used word in the buffer */
    int     i;      /* current bit number rel. to start */
    int     lastbit;    /* last useful bit in word */
    xfs_rtword_t    mask;       /* mask o frelevant bits for value */
    int     word;       /* word number in the buffer */

    /*
     * Compute starting bitmap block number.
     */
    block = XFS_BITTOBLOCK(mp, start);
    /*
     * Read the bitmap block, and point to its data.
     */
    error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
    if (error) {
        return error;
    }
    bufp = bp->b_addr;
    /*
     * Compute the starting word's address, and starting bit.
     */
    word = XFS_BITTOWORD(mp, start);
    first = b = &bufp[word];
    bit = (int)(start & (XFS_NBWORD - 1));
    /*
     * 0 (allocated) => all zeroes; 1 (free) => all ones.
     */
    val = -val;
    /*
     * If not starting on a word boundary, deal with the first
     * (partial) word.
     */
    if (bit) {
        /*
         * Compute first bit not changed and mask of relevant bits.
         */
        lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
        mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
        /*
         * Set/clear the active bits.
         */
        if (val)
            *b |= mask;
        else
            *b &= ~mask;
        i = lastbit - bit;
        /*
         * Go on to the next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * Log the changed part of this block.
             * Get the next one.
             */
            xfs_trans_log_buf(tp, bp,
                (uint)((char *)first - (char *)bufp),
                (uint)((char *)b - (char *)bufp));
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            first = b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the next word in the buffer
             */
            b++;
        }
    } else {
        /*
         * Starting on a word boundary, no partial word.
         */
        i = 0;
    }
    /*
     * Loop over whole words in buffers.  When we use up one buffer
     * we move on to the next one.
     */
    while (len - i >= XFS_NBWORD) {
        /*
         * Set the word value correctly.
         */
        *b = val;
        i += XFS_NBWORD;
        /*
         * Go on to the next block if that's where the next word is
         * and we need the next word.
         */
        if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
            /*
             * Log the changed part of this block.
             * Get the next one.
             */
            xfs_trans_log_buf(tp, bp,
                (uint)((char *)first - (char *)bufp),
                (uint)((char *)b - (char *)bufp));
            error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
            if (error) {
                return error;
            }
            first = b = bufp = bp->b_addr;
            word = 0;
        } else {
            /*
             * Go on to the next word in the buffer
             */
            b++;
        }
    }
    /*
     * If not ending on a word boundary, deal with the last
     * (partial) word.
     */
    if ((lastbit = len - i)) {
        /*
         * Compute a mask of relevant bits.
         */
        bit = 0;
        mask = ((xfs_rtword_t)1 << lastbit) - 1;
        /*
         * Set/clear the active bits.
         */
        if (val)
            *b |= mask;
        else
            *b &= ~mask;
        b++;
    }
    /*
     * Log any remaining changed bytes.
     */
    if (b > first)
        xfs_trans_log_buf(tp, bp, (uint)((char *)first - (char *)bufp),
            (uint)((char *)b - (char *)bufp - 1));
    return 0;
}

/*
 * Read and modify the summary information for a given extent size,
 * bitmap block combination.
 * Keeps track of a current summary block, so we don't keep reading
 * it from the buffer cache.
 */
STATIC int              /* error */
xfs_rtmodify_summary(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    int     log,        /* log2 of extent size */
    xfs_rtblock_t   bbno,       /* bitmap block number */
    int     delta,      /* change to make to summary info */
    xfs_buf_t   **rbpp,     /* in/out: summary block buffer */
    xfs_fsblock_t   *rsb)       /* in/out: summary block number */
{
    xfs_buf_t   *bp;        /* buffer for the summary block */
    int     error;      /* error value */
    xfs_fsblock_t   sb;     /* summary fsblock */
    int     so;     /* index into the summary file */
    xfs_suminfo_t   *sp;        /* pointer to returned data */

    /*
     * Compute entry number in the summary file.
     */
    so = XFS_SUMOFFS(mp, log, bbno);
    /*
     * Compute the block number in the summary file.
     */
    sb = XFS_SUMOFFSTOBLOCK(mp, so);
    /*
     * If we have an old buffer, and the block number matches, use that.
     */
    if (rbpp && *rbpp && *rsb == sb)
        bp = *rbpp;
    /*
     * Otherwise we have to get the buffer.
     */
    else {
        /*
         * If there was an old one, get rid of it first.
         */
        if (rbpp && *rbpp)
            xfs_trans_brelse(tp, *rbpp);
        error = xfs_rtbuf_get(mp, tp, sb, 1, &bp);
        if (error) {
            return error;
        }
        /*
         * Remember this buffer and block for the next call.
         */
        if (rbpp) {
            *rbpp = bp;
            *rsb = sb;
        }
    }
    /*
     * Point to the summary information, modify and log it.
     */
    sp = XFS_SUMPTR(mp, bp, so);
    *sp += delta;
    xfs_trans_log_buf(tp, bp, (uint)((char *)sp - (char *)bp->b_addr),
        (uint)((char *)sp - (char *)bp->b_addr + sizeof(*sp) - 1));
    return 0;
}

/*
 * Visible (exported) functions.
 */

/*
 * Grow the realtime area of the filesystem.
 */
int
xfs_growfs_rt(
    xfs_mount_t *mp,        /* mount point for filesystem */
    xfs_growfs_rt_t *in)        /* growfs rt input struct */
{
    xfs_rtblock_t   bmbno;      /* bitmap block number */
    xfs_buf_t   *bp;        /* temporary buffer */
    int     error;      /* error return value */
    xfs_mount_t *nmp;       /* new (fake) mount structure */
    xfs_drfsbno_t   nrblocks;   /* new number of realtime blocks */
    xfs_extlen_t    nrbmblocks; /* new number of rt bitmap blocks */
    xfs_drtbno_t    nrextents;  /* new number of realtime extents */
    uint8_t     nrextslog;  /* new log2 of sb_rextents */
    xfs_extlen_t    nrsumblocks;    /* new number of summary blocks */
    uint        nrsumlevels;    /* new rt summary levels */
    uint        nrsumsize;  /* new size of rt summary, bytes */
    xfs_sb_t    *nsbp;      /* new superblock */
    xfs_extlen_t    rbmblocks;  /* current number of rt bitmap blocks */
    xfs_extlen_t    rsumblocks; /* current number of rt summary blks */
    xfs_sb_t    *sbp;       /* old superblock */
    xfs_fsblock_t   sumbno;     /* summary block number */

    sbp = &mp->m_sb;
    /*
     * Initial error checking.
     */
    if (!capable(CAP_SYS_ADMIN))
        return XFS_ERROR(EPERM);
    if (mp->m_rtdev_targp == NULL || mp->m_rbmip == NULL ||
        (nrblocks = in->newblocks) <= sbp->sb_rblocks ||
        (sbp->sb_rblocks && (in->extsize != sbp->sb_rextsize)))
        return XFS_ERROR(EINVAL);
    if ((error = xfs_sb_validate_fsb_count(sbp, nrblocks)))
        return error;
    /*
     * Read in the last block of the device, make sure it exists.
     */
    bp = xfs_buf_read_uncached(mp->m_rtdev_targp,
                XFS_FSB_TO_BB(mp, nrblocks - 1),
                XFS_FSB_TO_BB(mp, 1), 0);
    if (!bp)
        return EIO;
    xfs_buf_relse(bp);

    /*
     * Calculate new parameters.  These are the final values to be reached.
     */
    nrextents = nrblocks;
    do_div(nrextents, in->extsize);
    nrbmblocks = howmany_64(nrextents, NBBY * sbp->sb_blocksize);
    nrextslog = xfs_highbit32(nrextents);
    nrsumlevels = nrextslog + 1;
    nrsumsize = (uint)sizeof(xfs_suminfo_t) * nrsumlevels * nrbmblocks;
    nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
    nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
    /*
     * New summary size can't be more than half the size of
     * the log.  This prevents us from getting a log overflow,
     * since we'll log basically the whole summary file at once.
     */
    if (nrsumblocks > (mp->m_sb.sb_logblocks >> 1))
        return XFS_ERROR(EINVAL);
    /*
     * Get the old block counts for bitmap and summary inodes.
     * These can't change since other growfs callers are locked out.
     */
    rbmblocks = XFS_B_TO_FSB(mp, mp->m_rbmip->i_d.di_size);
    rsumblocks = XFS_B_TO_FSB(mp, mp->m_rsumip->i_d.di_size);
    /*
     * Allocate space to the bitmap and summary files, as necessary.
     */
    error = xfs_growfs_rt_alloc(mp, rbmblocks, nrbmblocks, mp->m_rbmip);
    if (error)
        return error;
    error = xfs_growfs_rt_alloc(mp, rsumblocks, nrsumblocks, mp->m_rsumip);
    if (error)
        return error;
    /*
     * Allocate a new (fake) mount/sb.
     */
    nmp = kmem_alloc(sizeof(*nmp), KM_SLEEP);
    /*
     * Loop over the bitmap blocks.
     * We will do everything one bitmap block at a time.
     * Skip the current block if it is exactly full.
     * This also deals with the case where there were no rtextents before.
     */
    for (bmbno = sbp->sb_rbmblocks -
             ((sbp->sb_rextents & ((1 << mp->m_blkbit_log) - 1)) != 0);
         bmbno < nrbmblocks;
         bmbno++) {
        xfs_trans_t *tp;
        int     cancelflags = 0;

        *nmp = *mp;
        nsbp = &nmp->m_sb;
        /*
         * Calculate new sb and mount fields for this round.
         */
        nsbp->sb_rextsize = in->extsize;
        nsbp->sb_rbmblocks = bmbno + 1;
        nsbp->sb_rblocks =
            XFS_RTMIN(nrblocks,
                  nsbp->sb_rbmblocks * NBBY *
                  nsbp->sb_blocksize * nsbp->sb_rextsize);
        nsbp->sb_rextents = nsbp->sb_rblocks;
        do_div(nsbp->sb_rextents, nsbp->sb_rextsize);
        ASSERT(nsbp->sb_rextents != 0);
        nsbp->sb_rextslog = xfs_highbit32(nsbp->sb_rextents);
        nrsumlevels = nmp->m_rsumlevels = nsbp->sb_rextslog + 1;
        nrsumsize =
            (uint)sizeof(xfs_suminfo_t) * nrsumlevels *
            nsbp->sb_rbmblocks;
        nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
        nmp->m_rsumsize = nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
        /*
         * Start a transaction, get the log reservation.
         */
        tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFSRT_FREE);
        if ((error = xfs_trans_reserve(tp, 0,
                XFS_GROWRTFREE_LOG_RES(nmp), 0, 0, 0)))
            goto error_cancel;
        /*
         * Lock out other callers by grabbing the bitmap inode lock.
         */
        xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
        /*
         * Update the bitmap inode's size.
         */
        mp->m_rbmip->i_d.di_size =
            nsbp->sb_rbmblocks * nsbp->sb_blocksize;
        xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
        cancelflags |= XFS_TRANS_ABORT;
        /*
         * Get the summary inode into the transaction.
         */
        xfs_ilock(mp->m_rsumip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, mp->m_rsumip, XFS_ILOCK_EXCL);
        /*
         * Update the summary inode's size.
         */
        mp->m_rsumip->i_d.di_size = nmp->m_rsumsize;
        xfs_trans_log_inode(tp, mp->m_rsumip, XFS_ILOG_CORE);
        /*
         * Copy summary data from old to new sizes.
         * Do this when the real size (not block-aligned) changes.
         */
        if (sbp->sb_rbmblocks != nsbp->sb_rbmblocks ||
            mp->m_rsumlevels != nmp->m_rsumlevels) {
            error = xfs_rtcopy_summary(mp, nmp, tp);
            if (error)
                goto error_cancel;
        }
        /*
         * Update superblock fields.
         */
        if (nsbp->sb_rextsize != sbp->sb_rextsize)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSIZE,
                nsbp->sb_rextsize - sbp->sb_rextsize);
        if (nsbp->sb_rbmblocks != sbp->sb_rbmblocks)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBMBLOCKS,
                nsbp->sb_rbmblocks - sbp->sb_rbmblocks);
        if (nsbp->sb_rblocks != sbp->sb_rblocks)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBLOCKS,
                nsbp->sb_rblocks - sbp->sb_rblocks);
        if (nsbp->sb_rextents != sbp->sb_rextents)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTENTS,
                nsbp->sb_rextents - sbp->sb_rextents);
        if (nsbp->sb_rextslog != sbp->sb_rextslog)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSLOG,
                nsbp->sb_rextslog - sbp->sb_rextslog);
        /*
         * Free new extent.
         */
        bp = NULL;
        error = xfs_rtfree_range(nmp, tp, sbp->sb_rextents,
            nsbp->sb_rextents - sbp->sb_rextents, &bp, &sumbno);
        if (error) {
error_cancel:
            xfs_trans_cancel(tp, cancelflags);
            break;
        }
        /*
         * Mark more blocks free in the superblock.
         */
        xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS,
            nsbp->sb_rextents - sbp->sb_rextents);
        /*
         * Update mp values into the real mp structure.
         */
        mp->m_rsumlevels = nrsumlevels;
        mp->m_rsumsize = nrsumsize;

        error = xfs_trans_commit(tp, 0);
        if (error)
            break;
    }

    /*
     * Free the fake mp structure.
     */
    kmem_free(nmp);

    return error;
}

/*
 * Allocate an extent in the realtime subvolume, with the usual allocation
 * parameters.  The length units are all in realtime extents, as is the
 * result block number.
 */
int                 /* error */
xfs_rtallocate_extent(
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bno,        /* starting block number to allocate */
    xfs_extlen_t    minlen,     /* minimum length to allocate */
    xfs_extlen_t    maxlen,     /* maximum length to allocate */
    xfs_extlen_t    *len,       /* out: actual length allocated */
    xfs_alloctype_t type,       /* allocation type XFS_ALLOCTYPE... */
    int     wasdel,     /* was a delayed allocation extent */
    xfs_extlen_t    prod,       /* extent product factor */
    xfs_rtblock_t   *rtblock)   /* out: start block allocated */
{
    xfs_mount_t *mp = tp->t_mountp;
    int     error;      /* error value */
    xfs_rtblock_t   r;      /* result allocated block */
    xfs_fsblock_t   sb;     /* summary file block number */
    xfs_buf_t   *sumbp;     /* summary file block buffer */

    ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
    ASSERT(minlen > 0 && minlen <= maxlen);

    /*
     * If prod is set then figure out what to do to minlen and maxlen.
     */
    if (prod > 1) {
        xfs_extlen_t    i;

        if ((i = maxlen % prod))
            maxlen -= i;
        if ((i = minlen % prod))
            minlen += prod - i;
        if (maxlen < minlen) {
            *rtblock = NULLRTBLOCK;
            return 0;
        }
    }

    sumbp = NULL;
    /*
     * Allocate by size, or near another block, or exactly at some block.
     */
    switch (type) {
    case XFS_ALLOCTYPE_ANY_AG:
        error = xfs_rtallocate_extent_size(mp, tp, minlen, maxlen, len,
                &sumbp, &sb, prod, &r);
        break;
    case XFS_ALLOCTYPE_NEAR_BNO:
        error = xfs_rtallocate_extent_near(mp, tp, bno, minlen, maxlen,
                len, &sumbp, &sb, prod, &r);
        break;
    case XFS_ALLOCTYPE_THIS_BNO:
        error = xfs_rtallocate_extent_exact(mp, tp, bno, minlen, maxlen,
                len, &sumbp, &sb, prod, &r);
        break;
    default:
        error = EIO;
        ASSERT(0);
    }
    if (error)
        return error;

    /*
     * If it worked, update the superblock.
     */
    if (r != NULLRTBLOCK) {
        long    slen = (long)*len;

        ASSERT(*len >= minlen && *len <= maxlen);
        if (wasdel)
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FREXTENTS, -slen);
        else
            xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS, -slen);
    }
    *rtblock = r;
    return 0;
}

/*
 * Free an extent in the realtime subvolume.  Length is expressed in
 * realtime extents, as is the block number.
 */
int                 /* error */
xfs_rtfree_extent(
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_rtblock_t   bno,        /* starting block number to free */
    xfs_extlen_t    len)        /* length of extent freed */
{
    int     error;      /* error value */
    xfs_mount_t *mp;        /* file system mount structure */
    xfs_fsblock_t   sb;     /* summary file block number */
    xfs_buf_t   *sumbp;     /* summary file block buffer */

    mp = tp->t_mountp;

    ASSERT(mp->m_rbmip->i_itemp != NULL);
    ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));

#if defined(__KERNEL__) && defined(DEBUG)
    /*
     * Check to see that this whole range is currently allocated.
     */
    {
        int stat;       /* result from checking range */

        error = xfs_rtcheck_alloc_range(mp, tp, bno, len, &stat);
        if (error) {
            return error;
        }
        ASSERT(stat);
    }
#endif
    sumbp = NULL;
    /*
     * Free the range of realtime blocks.
     */
    error = xfs_rtfree_range(mp, tp, bno, len, &sumbp, &sb);
    if (error) {
        return error;
    }
    /*
     * Mark more blocks free in the superblock.
     */
    xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS, (long)len);
    /*
     * If we've now freed all the blocks, reset the file sequence
     * number to 0.
     */
    if (tp->t_frextents_delta + mp->m_sb.sb_frextents ==
        mp->m_sb.sb_rextents) {
        if (!(mp->m_rbmip->i_d.di_flags & XFS_DIFLAG_NEWRTBM))
            mp->m_rbmip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;
        *(__uint64_t *)&mp->m_rbmip->i_d.di_atime = 0;
        xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
    }
    return 0;
}

/*
 * Initialize realtime fields in the mount structure.
 */
int             /* error */
xfs_rtmount_init(
    xfs_mount_t *mp)    /* file system mount structure */
{
    xfs_buf_t   *bp;    /* buffer for last block of subvolume */
    xfs_daddr_t d;  /* address of last block of subvolume */
    xfs_sb_t    *sbp;   /* filesystem superblock copy in mount */

    sbp = &mp->m_sb;
    if (sbp->sb_rblocks == 0)
        return 0;
    if (mp->m_rtdev_targp == NULL) {
        xfs_warn(mp,
    "Filesystem has a realtime volume, use rtdev=device option");
        return XFS_ERROR(ENODEV);
    }
    mp->m_rsumlevels = sbp->sb_rextslog + 1;
    mp->m_rsumsize =
        (uint)sizeof(xfs_suminfo_t) * mp->m_rsumlevels *
        sbp->sb_rbmblocks;
    mp->m_rsumsize = roundup(mp->m_rsumsize, sbp->sb_blocksize);
    mp->m_rbmip = mp->m_rsumip = NULL;
    /*
     * Check that the realtime section is an ok size.
     */
    d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
    if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_rblocks) {
        xfs_warn(mp, "realtime mount -- %llu != %llu",
            (unsigned long long) XFS_BB_TO_FSB(mp, d),
            (unsigned long long) mp->m_sb.sb_rblocks);
        return XFS_ERROR(EFBIG);
    }
    bp = xfs_buf_read_uncached(mp->m_rtdev_targp,
                    d - XFS_FSB_TO_BB(mp, 1),
                    XFS_FSB_TO_BB(mp, 1), 0);
    if (!bp) {
        xfs_warn(mp, "realtime device size check failed");
        return EIO;
    }
    xfs_buf_relse(bp);
    return 0;
}

/*
 * Get the bitmap and summary inodes into the mount structure
 * at mount time.
 */
int                 /* error */
xfs_rtmount_inodes(
    xfs_mount_t *mp)        /* file system mount structure */
{
    int     error;      /* error return value */
    xfs_sb_t    *sbp;

    sbp = &mp->m_sb;
    if (sbp->sb_rbmino == NULLFSINO)
        return 0;
    error = xfs_iget(mp, NULL, sbp->sb_rbmino, 0, 0, &mp->m_rbmip);
    if (error)
        return error;
    ASSERT(mp->m_rbmip != NULL);
    ASSERT(sbp->sb_rsumino != NULLFSINO);
    error = xfs_iget(mp, NULL, sbp->sb_rsumino, 0, 0, &mp->m_rsumip);
    if (error) {
        IRELE(mp->m_rbmip);
        return error;
    }
    ASSERT(mp->m_rsumip != NULL);
    return 0;
}

void
xfs_rtunmount_inodes(
    struct xfs_mount    *mp)
{
    if (mp->m_rbmip)
        IRELE(mp->m_rbmip);
    if (mp->m_rsumip)
        IRELE(mp->m_rsumip);
}

/*
 * Pick an extent for allocation at the start of a new realtime file.
 * Use the sequence number stored in the atime field of the bitmap inode.
 * Translate this to a fraction of the rtextents, and return the product
 * of rtextents and the fraction.
 * The fraction sequence is 0, 1/2, 1/4, 3/4, 1/8, ..., 7/8, 1/16, ...
 */
int                 /* error */
xfs_rtpick_extent(
    xfs_mount_t *mp,        /* file system mount point */
    xfs_trans_t *tp,        /* transaction pointer */
    xfs_extlen_t    len,        /* allocation length (rtextents) */
    xfs_rtblock_t   *pick)      /* result rt extent */
{
    xfs_rtblock_t   b;      /* result block */
    int     log2;       /* log of sequence number */
    __uint64_t  resid;      /* residual after log removed */
    __uint64_t  seq;        /* sequence number of file creation */
    __uint64_t  *seqp;      /* pointer to seqno in inode */

    ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));

    seqp = (__uint64_t *)&mp->m_rbmip->i_d.di_atime;
    if (!(mp->m_rbmip->i_d.di_flags & XFS_DIFLAG_NEWRTBM)) {
        mp->m_rbmip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;
        *seqp = 0;
    }
    seq = *seqp;
    if ((log2 = xfs_highbit64(seq)) == -1)
        b = 0;
    else {
        resid = seq - (1ULL << log2);
        b = (mp->m_sb.sb_rextents * ((resid << 1) + 1ULL)) >>
            (log2 + 1);
        if (b >= mp->m_sb.sb_rextents)
            b = do_mod(b, mp->m_sb.sb_rextents);
        if (b + len > mp->m_sb.sb_rextents)
            b = mp->m_sb.sb_rextents - len;
    }
    *seqp = seq + 1;
    xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);
    *pick = b;
    return 0;
}