Merge branch 'bcache-for-3.13' of git://evilpiepirate.org/~kent/linux-bcache into...

[mirror_ubuntu-bionic-kernel.git] / fs / xfs / xfs_rtalloc.c

/*
 * 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_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc.h"
#include "xfs_error.h"
#include "xfs_trans.h"
#include "xfs_trans_space.h"
#include "xfs_trace.h"
#include "xfs_buf.h"
#include "xfs_icache.h"
#include "xfs_dinode.h"
#include "xfs_rtalloc.h"


/*
 * 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;
}


/*
 * 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;
}


/*
 * 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;
}
/*
 * 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 = 0;  /* first block allocated > end */
        xfs_rtblock_t   preblock = 0;   /* 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;
}

/*
 * 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;
}

/*
 * 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.
                 */
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_growdata,
                                          resblks, 0);
                if (error)
                        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.
                         */
                        error = xfs_trans_reserve(tp, &M_RES(mp)->tr_growrtzero,
                                                  0, 0);
                        if (error)
                                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;
}

/*
 * 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, NULL);
        if (!bp)
                return EIO;
        if (bp->b_error) {
                error = bp->b_error;
                xfs_buf_relse(bp);
                return error;
        }
        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);
                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_growrtfree,
                                          0, 0);
                if (error)
                        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;
}

/*
 * 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, NULL);
        if (!bp || bp->b_error) {
                xfs_warn(mp, "realtime device size check failed");
                if (bp)
                        xfs_buf_relse(bp);
                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;
}