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[minix.git] / sys / ufs / lfs / lfs_rfw.c

/*      $NetBSD: lfs_rfw.c,v 1.32 2015/10/03 08:27:55 dholland Exp $    */

/*-
 * Copyright (c) 1999, 2000, 2001, 2002, 2003 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Konrad E. Schroder <perseant@hhhh.org>.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: lfs_rfw.c,v 1.32 2015/10/03 08:27:55 dholland Exp $");

#if defined(_KERNEL_OPT)
#include "opt_quota.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/kthread.h>
#include <sys/buf.h>
#include <sys/device.h>
#include <sys/mbuf.h>
#include <sys/file.h>
#include <sys/disklabel.h>
#include <sys/ioctl.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <uvm/uvm_extern.h>
#include <sys/sysctl.h>
#include <sys/conf.h>
#include <sys/kauth.h>

#include <miscfs/specfs/specdev.h>

#include <ufs/lfs/ulfs_quotacommon.h>
#include <ufs/lfs/ulfs_inode.h>
#include <ufs/lfs/ulfsmount.h>
#include <ufs/lfs/ulfs_extern.h>

#include <uvm/uvm.h>
#include <uvm/uvm_stat.h>
#include <uvm/uvm_pager.h>
#include <uvm/uvm_pdaemon.h>

#include <ufs/lfs/lfs.h>
#include <ufs/lfs/lfs_accessors.h>
#include <ufs/lfs/lfs_kernel.h>
#include <ufs/lfs/lfs_extern.h>

#include <miscfs/genfs/genfs.h>
#include <miscfs/genfs/genfs_node.h>

/*
 * Roll-forward code.
 */
static daddr_t check_segsum(struct lfs *, daddr_t, u_int64_t,
    kauth_cred_t, int, int *, struct lwp *);

extern int lfs_do_rfw;

/*
 * Allocate a particular inode with a particular version number, freeing
 * any previous versions of this inode that may have gone before.
 * Used by the roll-forward code.
 *
 * XXX this function does not have appropriate locking to be used on a live fs;
 * XXX but something similar could probably be used for an "undelete" call.
 *
 * Called with the Ifile inode locked.
 */
int
lfs_rf_valloc(struct lfs *fs, ino_t ino, int vers, struct lwp *l,
              struct vnode **vpp)
{
        struct vattr va;
        struct vnode *vp;
        struct inode *ip;
        int error;

        ASSERT_SEGLOCK(fs); /* XXX it doesn't, really */

        /*
         * First, just try a vget. If the version number is the one we want,
         * we don't have to do anything else.  If the version number is wrong,
         * take appropriate action.
         */
        error = VFS_VGET(fs->lfs_ivnode->v_mount, ino, &vp);
        if (error == 0) {
                DLOG((DLOG_RF, "lfs_rf_valloc[1]: ino %d vp %p\n", ino, vp));

                *vpp = vp;
                ip = VTOI(vp);
                if (ip->i_gen == vers)
                        return 0;
                else if (ip->i_gen < vers) {
                        lfs_truncate(vp, (off_t)0, 0, NOCRED);
                        ip->i_gen = vers;
                        lfs_dino_setgen(fs, ip->i_din, vers);
                        LFS_SET_UINO(ip, IN_CHANGE | IN_UPDATE);
                        return 0;
                } else {
                        DLOG((DLOG_RF, "ino %d: sought version %d, got %d\n",
                               ino, vers, lfs_dino_getgen(fs, ip->i_din)));
                        vput(vp);
                        *vpp = NULLVP;
                        return EEXIST;
                }
        }

        /* Not found, create as regular file. */
        vattr_null(&va);
        va.va_type = VREG;
        va.va_mode = 0;
        va.va_fileid = ino;
        va.va_gen = vers;
        error = vcache_new(fs->lfs_ivnode->v_mount, NULL, &va, NOCRED, &vp);
        if (error)
                return error;
        error = vn_lock(vp, LK_EXCLUSIVE);
        if (error) {
                vrele(vp);
                *vpp = NULLVP;
                return error;
        }
        ip = VTOI(vp);
        ip->i_nlink = 1;
        lfs_dino_setnlink(fs, ip->i_din, 1);
        *vpp = vp;
        return 0;
}

/*
 * Load the appropriate indirect block, and change the appropriate pointer.
 * Mark the block dirty.  Do segment and avail accounting.
 */
static int
update_meta(struct lfs *fs, ino_t ino, int vers, daddr_t lbn,
            daddr_t ndaddr, size_t size, struct lwp *l)
{
        int error;
        struct vnode *vp;
        struct inode *ip;
#ifdef DEBUG
        daddr_t odaddr;
        struct indir a[ULFS_NIADDR];
        int num;
        int i;
#endif /* DEBUG */
        struct buf *bp;
        SEGUSE *sup;

        KASSERT(lbn >= 0);      /* no indirect blocks */

        if ((error = lfs_rf_valloc(fs, ino, vers, l, &vp)) != 0) {
                DLOG((DLOG_RF, "update_meta: ino %d: lfs_rf_valloc"
                      " returned %d\n", ino, error));
                return error;
        }

        if ((error = lfs_balloc(vp, (lbn << lfs_sb_getbshift(fs)), size,
                                NOCRED, 0, &bp)) != 0) {
                vput(vp);
                return (error);
        }
        /* No need to write, the block is already on disk */
        if (bp->b_oflags & BO_DELWRI) {
                LFS_UNLOCK_BUF(bp);
                lfs_sb_addavail(fs, lfs_btofsb(fs, bp->b_bcount));
                /* XXX should this wake up fs->lfs_availsleep? */
        }
        brelse(bp, BC_INVAL);

        /*
         * Extend the file, if it is not large enough already.
         * XXX this is not exactly right, we don't know how much of the
         * XXX last block is actually used.  We hope that an inode will
         * XXX appear later to give the correct size.
         */
        ip = VTOI(vp);
        if (ip->i_size <= (lbn << lfs_sb_getbshift(fs))) {
                u_int64_t newsize;

                if (lbn < ULFS_NDADDR) {
                        newsize = (lbn << lfs_sb_getbshift(fs)) +
                                (size - lfs_sb_getfsize(fs)) + 1;
                } else {
                        newsize = (lbn << lfs_sb_getbshift(fs)) + 1;
                }
                lfs_dino_setsize(fs, ip->i_din, newsize);

                if (ip->i_size < newsize) {
                        ip->i_size = newsize;
                        /*
                         * tell vm our new size for the case the inode won't
                         * appear later.
                         */
                        uvm_vnp_setsize(vp, newsize);
                }
        }

        lfs_update_single(fs, NULL, vp, lbn, ndaddr, size);

        LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, ndaddr), bp);
        sup->su_nbytes += size;
        LFS_WRITESEGENTRY(sup, fs, lfs_dtosn(fs, ndaddr), bp);

        /* differences here should be due to UNWRITTEN indirect blocks. */
        KASSERT((lfs_lblkno(fs, ip->i_size) > ULFS_NDADDR &&
            ip->i_lfs_effnblks == lfs_dino_getblocks(fs, ip->i_din)) ||
            ip->i_lfs_effnblks >= lfs_dino_getblocks(fs, ip->i_din));

#ifdef DEBUG
        /* Now look again to make sure it worked */
        ulfs_bmaparray(vp, lbn, &odaddr, &a[0], &num, NULL, NULL);
        for (i = num; i > 0; i--) {
                if (!a[i].in_exists)
                        panic("update_meta: absent %d lv indirect block", i);
        }
        if (LFS_DBTOFSB(fs, odaddr) != ndaddr)
                DLOG((DLOG_RF, "update_meta: failed setting ino %d lbn %"
                      PRId64 " to %" PRId64 "\n", ino, lbn, ndaddr));
#endif /* DEBUG */
        vput(vp);
        return 0;
}

/*
 * Copy some the fields of the dinode as needed by update_inoblk().
 */
static void
update_inoblk_copy_dinode(struct lfs *fs,
    union lfs_dinode *dstu, const union lfs_dinode *srcu)
{
        if (fs->lfs_is64) {
                struct lfs64_dinode *dst = &dstu->u_64;
                const struct lfs64_dinode *src = &srcu->u_64;
                unsigned i;

                /*
                 * Copy everything but the block pointers and di_blocks.
                 * XXX what about di_extb?
                 */
                dst->di_mode = src->di_mode;
                dst->di_nlink = src->di_nlink;
                dst->di_uid = src->di_uid;
                dst->di_gid = src->di_gid;
                dst->di_blksize = src->di_blksize;
                dst->di_size = src->di_size;
                dst->di_atime = src->di_atime;
                dst->di_mtime = src->di_mtime;
                dst->di_ctime = src->di_ctime;
                dst->di_birthtime = src->di_birthtime;
                dst->di_mtimensec = src->di_mtimensec;
                dst->di_atimensec = src->di_atimensec;
                dst->di_ctimensec = src->di_ctimensec;
                dst->di_birthnsec = src->di_birthnsec;
                dst->di_gen = src->di_gen;
                dst->di_kernflags = src->di_kernflags;
                dst->di_flags = src->di_flags;
                dst->di_extsize = src->di_extsize;
                dst->di_modrev = src->di_modrev;
                dst->di_inumber = src->di_inumber;
                for (i = 0; i < __arraycount(src->di_spare); i++) {
                        dst->di_spare[i] = src->di_spare[i];
                }
        } else {
                struct lfs32_dinode *dst = &dstu->u_32;
                const struct lfs32_dinode *src = &srcu->u_32;

                /* Get mode, link count, size, and times */
                memcpy(dst, src, offsetof(struct lfs32_dinode, di_db[0]));

                /* Then the rest, except di_blocks */
                dst->di_flags = src->di_flags;
                dst->di_gen = src->di_gen;
                dst->di_uid = src->di_uid;
                dst->di_gid = src->di_gid;
                dst->di_modrev = src->di_modrev;
        }
}

static int
update_inoblk(struct lfs *fs, daddr_t offset, kauth_cred_t cred,
              struct lwp *l)
{
        struct vnode *devvp, *vp;
        struct inode *ip;
        union lfs_dinode *dip;
        struct buf *dbp, *ibp;
        int error;
        daddr_t daddr;
        IFILE *ifp;
        SEGUSE *sup;
        unsigned i, num;

        devvp = VTOI(fs->lfs_ivnode)->i_devvp;

        /*
         * Get the inode, update times and perms.
         * DO NOT update disk blocks, we do that separately.
         */
        error = bread(devvp, LFS_FSBTODB(fs, offset), lfs_sb_getibsize(fs),
            0, &dbp);
        if (error) {
                DLOG((DLOG_RF, "update_inoblk: bread returned %d\n", error));
                return error;
        }
        num = LFS_INOPB(fs);
        for (i = num; i-- > 0; ) {
                dip = DINO_IN_BLOCK(fs, dbp->b_data, i);
                if (lfs_dino_getinumber(fs, dip) > LFS_IFILE_INUM) {
                        error = lfs_rf_valloc(fs, lfs_dino_getinumber(fs, dip),
                                              lfs_dino_getgen(fs, dip),
                                              l, &vp);
                        if (error) {
                                DLOG((DLOG_RF, "update_inoblk: lfs_rf_valloc"
                                      " returned %d\n", error));
                                continue;
                        }
                        ip = VTOI(vp);
                        if (lfs_dino_getsize(fs, dip) != ip->i_size)
                                lfs_truncate(vp, lfs_dino_getsize(fs, dip), 0,
                                             NOCRED);
                        update_inoblk_copy_dinode(fs, ip->i_din, dip);

                        ip->i_flags = lfs_dino_getflags(fs, dip);
                        ip->i_gen = lfs_dino_getgen(fs, dip);
                        ip->i_uid = lfs_dino_getuid(fs, dip);
                        ip->i_gid = lfs_dino_getgid(fs, dip);

                        ip->i_mode = lfs_dino_getmode(fs, dip);
                        ip->i_nlink = lfs_dino_getnlink(fs, dip);
                        ip->i_size = lfs_dino_getsize(fs, dip);

                        LFS_SET_UINO(ip, IN_CHANGE | IN_UPDATE);

                        /* Re-initialize to get type right */
                        ulfs_vinit(vp->v_mount, lfs_specop_p, lfs_fifoop_p,
                                  &vp);
                        vput(vp);

                        /* Record change in location */
                        LFS_IENTRY(ifp, fs, lfs_dino_getinumber(fs, dip), ibp);
                        daddr = lfs_if_getdaddr(fs, ifp);
                        lfs_if_setdaddr(fs, ifp, LFS_DBTOFSB(fs, dbp->b_blkno));
                        error = LFS_BWRITE_LOG(ibp); /* Ifile */
                        /* And do segment accounting */
                        if (lfs_dtosn(fs, daddr) != lfs_dtosn(fs, LFS_DBTOFSB(fs, dbp->b_blkno))) {
                                if (daddr > 0) {
                                        LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, daddr),
                                                     ibp);
                                        sup->su_nbytes -= DINOSIZE(fs);
                                        LFS_WRITESEGENTRY(sup, fs,
                                                          lfs_dtosn(fs, daddr),
                                                          ibp);
                                }
                                LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, LFS_DBTOFSB(fs, dbp->b_blkno)),
                                             ibp);
                                sup->su_nbytes += DINOSIZE(fs);
                                LFS_WRITESEGENTRY(sup, fs,
                                                  lfs_dtosn(fs, LFS_DBTOFSB(fs, dbp->b_blkno)),
                                                  ibp);
                        }
                }
        }
        brelse(dbp, BC_AGE);

        return 0;
}

#define CHECK_CKSUM   0x0001  /* Check the checksum to make sure it's valid */
#define CHECK_UPDATE  0x0002  /* Update Ifile for new data blocks / inodes */

static daddr_t
check_segsum(struct lfs *fs, daddr_t offset, u_int64_t nextserial,
             kauth_cred_t cred, int flags, int *pseg_flags, struct lwp *l)
{
        struct vnode *devvp;
        struct buf *bp, *dbp;
        int error, nblocks = 0, ninos, i, j; /* XXX: gcc */
        SEGSUM *ssp;
        u_long *dp = NULL, *datap = NULL; /* XXX u_int32_t */
        daddr_t oldoffset;
        IINFO *iip;
        FINFO *fip;
        SEGUSE *sup;
        size_t size;
        uint32_t datasum, foundsum;

        devvp = VTOI(fs->lfs_ivnode)->i_devvp;
        /*
         * If the segment has a superblock and we're at the top
         * of the segment, skip the superblock.
         */
        if (lfs_sntod(fs, lfs_dtosn(fs, offset)) == offset) {
                LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, offset), bp);
                if (sup->su_flags & SEGUSE_SUPERBLOCK)
                        offset += lfs_btofsb(fs, LFS_SBPAD);
                brelse(bp, 0);
        }

        /* Read in the segment summary */
        error = bread(devvp, LFS_FSBTODB(fs, offset), lfs_sb_getsumsize(fs),
            0, &bp);
        if (error)
                return -1;

        /* Check summary checksum */
        ssp = (SEGSUM *)bp->b_data;
        if (flags & CHECK_CKSUM) {
                size_t sumstart;

                sumstart = lfs_ss_getsumstart(fs);
                if (lfs_ss_getsumsum(fs, ssp) !=
                    cksum((char *)ssp + sumstart,
                          lfs_sb_getsumsize(fs) - sumstart)) {
                        DLOG((DLOG_RF, "Sumsum error at 0x%" PRIx64 "\n", offset));
                        offset = -1;
                        goto err1;
                }
                if (lfs_ss_getnfinfo(fs, ssp) == 0 &&
                    lfs_ss_getninos(fs, ssp) == 0) {
                        DLOG((DLOG_RF, "Empty pseg at 0x%" PRIx64 "\n", offset));
                        offset = -1;
                        goto err1;
                }
                if (lfs_ss_getcreate(fs, ssp) < lfs_sb_gettstamp(fs)) {
                        DLOG((DLOG_RF, "Old data at 0x%" PRIx64 "\n", offset));
                        offset = -1;
                        goto err1;
                }
        }
        if (lfs_sb_getversion(fs) > 1) {
                if (lfs_ss_getserial(fs, ssp) != nextserial) {
                        DLOG((DLOG_RF, "Unexpected serial number at 0x%" PRIx64
                              "\n", offset));
                        offset = -1;
                        goto err1;
                }
                if (lfs_ss_getident(fs, ssp) != lfs_sb_getident(fs)) {
                        DLOG((DLOG_RF, "Incorrect fsid (0x%x vs 0x%x) at 0x%"
                              PRIx64 "\n", lfs_ss_getident(fs, ssp),
                              lfs_sb_getident(fs), offset));
                        offset = -1;
                        goto err1;
                }
        }
        if (pseg_flags)
                *pseg_flags = lfs_ss_getflags(fs, ssp);
        oldoffset = offset;
        offset += lfs_btofsb(fs, lfs_sb_getsumsize(fs));

        ninos = howmany(lfs_ss_getninos(fs, ssp), LFS_INOPB(fs));
        iip = SEGSUM_IINFOSTART(fs, bp->b_data);
        if (flags & CHECK_CKSUM) {
                /* Count blocks */
                nblocks = 0;
                fip = SEGSUM_FINFOBASE(fs, (SEGSUM *)bp->b_data);
                for (i = 0; i < lfs_ss_getnfinfo(fs, ssp); ++i) {
                        nblocks += lfs_fi_getnblocks(fs, fip);
                        if (lfs_fi_getnblocks(fs, fip) <= 0)
                                break;
                        fip = NEXT_FINFO(fs, fip);
                }
                nblocks += ninos;
                /* Create the sum array */
                datap = dp = malloc(nblocks * sizeof(u_long),
                                    M_SEGMENT, M_WAITOK);
        }

        /* Handle individual blocks */
        fip = SEGSUM_FINFOBASE(fs, (SEGSUM *)bp->b_data);
        for (i = 0; i < lfs_ss_getnfinfo(fs, ssp) || ninos; ++i) {
                /* Inode block? */
                if (ninos && lfs_ii_getblock(fs, iip) == offset) {
                        if (flags & CHECK_CKSUM) {
                                /* Read in the head and add to the buffer */
                                error = bread(devvp, LFS_FSBTODB(fs, offset), lfs_sb_getbsize(fs),
                                              0, &dbp);
                                if (error) {
                                        offset = -1;
                                        goto err2;
                                }
                                /* XXX this can't be right, on-disk u_long? */
                                (*dp++) = ((u_long *)(dbp->b_data))[0];
                                brelse(dbp, BC_AGE);
                        }
                        if (flags & CHECK_UPDATE) {
                                if ((error = update_inoblk(fs, offset, cred, l))
                                    != 0) {
                                        offset = -1;
                                        goto err2;
                                }
                        }
                        offset += lfs_btofsb(fs, lfs_sb_getibsize(fs));
                        iip = NEXTLOWER_IINFO(fs, iip);
                        --ninos;
                        --i; /* compensate for ++i in loop header */
                        continue;
                }
                size = lfs_sb_getbsize(fs);
                for (j = 0; j < lfs_fi_getnblocks(fs, fip); ++j) {
                        if (j == lfs_fi_getnblocks(fs, fip) - 1)
                                size = lfs_fi_getlastlength(fs, fip);
                        if (flags & CHECK_CKSUM) {
                                error = bread(devvp, LFS_FSBTODB(fs, offset), size,
                                    0, &dbp);
                                if (error) {
                                        offset = -1;
                                        goto err2;
                                }
                                (*dp++) = ((u_long *)(dbp->b_data))[0];
                                brelse(dbp, BC_AGE);
                        }
                        /* Account for and update any direct blocks */
                        if ((flags & CHECK_UPDATE) &&
                           lfs_fi_getino(fs, fip) > LFS_IFILE_INUM &&
                           lfs_fi_getblock(fs, fip, j) >= 0) {
                                update_meta(fs, lfs_fi_getino(fs, fip),
                                            lfs_fi_getversion(fs, fip),
                                            lfs_fi_getblock(fs, fip, j),
                                            offset, size, l);
                        }
                        offset += lfs_btofsb(fs, size);
                }
                fip = NEXT_FINFO(fs, fip);
        }
        /* Checksum the array, compare */
        datasum = lfs_ss_getdatasum(fs, ssp);
        foundsum = cksum(datap, nblocks * sizeof(u_long));
        if ((flags & CHECK_CKSUM) && datasum != foundsum) {
                DLOG((DLOG_RF, "Datasum error at 0x%" PRIx64
                      " (wanted %x got %x)\n",
                      offset, datasum, foundsum));
                offset = -1;
                goto err2;
        }

        /* If we're at the end of the segment, move to the next */
        if (lfs_dtosn(fs, offset + lfs_btofsb(fs, lfs_sb_getsumsize(fs) + lfs_sb_getbsize(fs))) !=
           lfs_dtosn(fs, offset)) {
                if (lfs_dtosn(fs, offset) == lfs_dtosn(fs, lfs_ss_getnext(fs, ssp))) {
                        offset = -1;
                        goto err2;
                }
                offset = lfs_ss_getnext(fs, ssp);
                DLOG((DLOG_RF, "LFS roll forward: moving to offset 0x%" PRIx64
                       " -> segment %d\n", offset, lfs_dtosn(fs,offset)));
        }

        if (flags & CHECK_UPDATE) {
                lfs_sb_subavail(fs, offset - oldoffset);
                /* Don't clog the buffer queue */
                mutex_enter(&lfs_lock);
                if (locked_queue_count > LFS_MAX_BUFS ||
                    locked_queue_bytes > LFS_MAX_BYTES) {
                        lfs_flush(fs, SEGM_CKP, 0);
                }
                mutex_exit(&lfs_lock);
        }

    err2:
        if (flags & CHECK_CKSUM)
                free(datap, M_SEGMENT);
    err1:
        brelse(bp, BC_AGE);

        /* XXX should we update the serial number even for bad psegs? */
        if ((flags & CHECK_UPDATE) && offset > 0 && lfs_sb_getversion(fs) > 1)
                lfs_sb_setserial(fs, nextserial);
        return offset;
}

void
lfs_roll_forward(struct lfs *fs, struct mount *mp, struct lwp *l)
{
        int flags, dirty;
        daddr_t offset, oldoffset, lastgoodpseg;
        int sn, curseg, do_rollforward;
        struct proc *p;
        kauth_cred_t cred;
        SEGUSE *sup;
        struct buf *bp;

        p = l ? l->l_proc : NULL;
        cred = p ? p->p_cred : NOCRED;

        /*
         * Roll forward.
         *
         * We don't roll forward for v1 filesystems, because
         * of the danger that the clock was turned back between the last
         * checkpoint and crash.  This would roll forward garbage.
         *
         * v2 filesystems don't have this problem because they use a
         * monotonically increasing serial number instead of a timestamp.
         */
        do_rollforward = (!(lfs_sb_getpflags(fs) & LFS_PF_CLEAN) &&
                          lfs_do_rfw && lfs_sb_getversion(fs) > 1 && p != NULL);
        if (do_rollforward) {
                u_int64_t nextserial;
                /*
                 * Phase I: Find the address of the last good partial
                 * segment that was written after the checkpoint.  Mark
                 * the segments in question dirty, so they won't be
                 * reallocated.
                 */
                lastgoodpseg = oldoffset = offset = lfs_sb_getoffset(fs);
                flags = 0x0;
                DLOG((DLOG_RF, "LFS roll forward phase 1: start at offset 0x%"
                      PRIx64 "\n", offset));
                LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, offset), bp);
                if (!(sup->su_flags & SEGUSE_DIRTY))
                        lfs_sb_subnclean(fs, 1);
                sup->su_flags |= SEGUSE_DIRTY;
                LFS_WRITESEGENTRY(sup, fs, lfs_dtosn(fs, offset), bp);
                nextserial = lfs_sb_getserial(fs) + 1;
                while ((offset = check_segsum(fs, offset, nextserial,
                    cred, CHECK_CKSUM, &flags, l)) > 0) {
                        nextserial++;
                        if (lfs_sntod(fs, oldoffset) != lfs_sntod(fs, offset)) {
                                LFS_SEGENTRY(sup, fs, lfs_dtosn(fs, oldoffset),
                                             bp);
                                if (!(sup->su_flags & SEGUSE_DIRTY))
                                        lfs_sb_subnclean(fs, 1);
                                sup->su_flags |= SEGUSE_DIRTY;
                                LFS_WRITESEGENTRY(sup, fs, lfs_dtosn(fs, oldoffset),
                                             bp);
                        }

                        DLOG((DLOG_RF, "LFS roll forward phase 1: offset=0x%"
                              PRIx64 "\n", offset));
                        if (flags & SS_DIROP) {
                                DLOG((DLOG_RF, "lfs_mountfs: dirops at 0x%"
                                      PRIx64 "\n", oldoffset));
                                if (!(flags & SS_CONT)) {
                                     DLOG((DLOG_RF, "lfs_mountfs: dirops end "
                                           "at 0x%" PRIx64 "\n", oldoffset));
                                }
                        }
                        if (!(flags & SS_CONT))
                                lastgoodpseg = offset;
                        oldoffset = offset;
                }
                if (flags & SS_CONT) {
                        DLOG((DLOG_RF, "LFS roll forward: warning: incomplete "
                              "dirops discarded\n"));
                }
                DLOG((DLOG_RF, "LFS roll forward phase 1: completed: "
                      "lastgoodpseg=0x%" PRIx64 "\n", lastgoodpseg));
                oldoffset = lfs_sb_getoffset(fs);
                if (lfs_sb_getoffset(fs) != lastgoodpseg) {
                        /* Don't overwrite what we're trying to preserve */
                        offset = lfs_sb_getoffset(fs);
                        lfs_sb_setoffset(fs, lastgoodpseg);
                        lfs_sb_setcurseg(fs, lfs_sntod(fs, lfs_dtosn(fs, lfs_sb_getoffset(fs))));
                        for (sn = curseg = lfs_dtosn(fs, lfs_sb_getcurseg(fs));;) {
                                sn = (sn + 1) % lfs_sb_getnseg(fs);
                                if (sn == curseg)
                                        panic("lfs_mountfs: no clean segments");
                                LFS_SEGENTRY(sup, fs, sn, bp);
                                dirty = (sup->su_flags & SEGUSE_DIRTY);
                                brelse(bp, 0);
                                if (!dirty)
                                        break;
                        }
                        lfs_sb_setnextseg(fs, lfs_sntod(fs, sn));

                        /*
                         * Phase II: Roll forward from the first superblock.
                         */
                        while (offset != lastgoodpseg) {
                                DLOG((DLOG_RF, "LFS roll forward phase 2: 0x%"
                                      PRIx64 "\n", offset));
                                offset = check_segsum(fs, offset,
                                    lfs_sb_getserial(fs) + 1, cred, CHECK_UPDATE,
                                    NULL, l);
                        }

                        /*
                         * Finish: flush our changes to disk.
                         */
                        lfs_segwrite(mp, SEGM_CKP | SEGM_SYNC);
                        DLOG((DLOG_RF, "lfs_mountfs: roll forward ",
                              "recovered %jd blocks\n",
                              (intmax_t)(lastgoodpseg - oldoffset)));
                }
                DLOG((DLOG_RF, "LFS roll forward complete\n"));
        }
}