/*      $NetBSD: lfs_bio.c,v 1.153 2025/12/02 01:23:09 perseant Exp $   */

/*-
 * Copyright (c) 1999, 2000, 2001, 2002, 2003, 2008 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.
 */
/*
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      @(#)lfs_bio.c   8.10 (Berkeley) 6/10/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: lfs_bio.c,v 1.153 2025/12/02 01:23:09 perseant Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/resourcevar.h>
#include <sys/mount.h>
#include <sys/kernel.h>
#include <sys/kauth.h>

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

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

#include <uvm/uvm_extern.h>

/*
 * LFS block write function.
 *
 * XXX
 * No write cost accounting is done.
 * This is almost certainly wrong for synchronous operations and NFS.
 *
 * protected by lfs_lock.
 */
int     locked_queue_count   = 0;       /* Count of locked-down buffers. */
long    locked_queue_bytes   = 0L;      /* Total size of locked buffers. */
int     lfs_subsys_pages     = 0L;      /* Total number LFS-written pages */
int     lfs_fs_pagetrip      = 0;       /* # of pages to trip per-fs write */
int     lfs_writing          = 0;       /* Set if already kicked off a writer
                                           because of buffer space */
int     locked_queue_waiters = 0;       /* Number of processes waiting on lq */

/* Lock and condition variables for above. */
kcondvar_t      locked_queue_cv;
kcondvar_t      lfs_writing_cv;
kmutex_t        lfs_lock;
extern kcondvar_t lfs_writerd_cv;

extern int lfs_dostats;

/*
 * reserved number/bytes of locked buffers
 */
int locked_queue_rcount = 0;
long locked_queue_rbytes = 0L;

static int lfs_fits_buf(struct lfs *, int, int);
static int lfs_reservebuf(struct lfs *, struct vnode *vp, struct vnode *vp2,
    int, int);
static int lfs_reserveavail(struct lfs *, struct vnode *vp, struct vnode *vp2,
    int);

static int
lfs_fits_buf(struct lfs *fs, int n, int bytes)
{
        int count_fit, bytes_fit;

        ASSERT_NO_SEGLOCK(fs);
        KASSERT(mutex_owned(&lfs_lock));

        count_fit =
            (locked_queue_count + locked_queue_rcount + n <= LFS_WAIT_BUFS);
        bytes_fit =
            (locked_queue_bytes + locked_queue_rbytes + bytes <= LFS_WAIT_BYTES);

#ifdef DEBUG
        if (!count_fit) {
                DLOG((DLOG_AVAIL, "lfs_fits_buf: no fit count: %d + %d + %d >= %d\n",
                      locked_queue_count, locked_queue_rcount,
                      n, LFS_WAIT_BUFS));
        }
        if (!bytes_fit) {
                DLOG((DLOG_AVAIL, "lfs_fits_buf: no fit bytes: %ld + %ld + %d >= %ld\n",
                      locked_queue_bytes, locked_queue_rbytes,
                      bytes, LFS_WAIT_BYTES));
        }
#endif /* DEBUG */

        return (count_fit && bytes_fit);
}

/* ARGSUSED */
static int
lfs_reservebuf(struct lfs *fs, struct vnode *vp,
    struct vnode *vp2, int n, int bytes)
{
        int cantwait;

        ASSERT_MAYBE_SEGLOCK(fs);
        KASSERT(locked_queue_rcount >= 0);
        KASSERT(locked_queue_rbytes >= 0);

        cantwait = (VTOI(vp)->i_state & IN_ADIROP) || fs->lfs_unlockvp == vp;
        mutex_enter(&lfs_lock);
        while (!cantwait && n > 0 && !lfs_fits_buf(fs, n, bytes)) {
                int error;

                DLOG((DLOG_FLUSH, "lfs_reservebuf: flush filesystem %p with checkpoint\n", fs));
                lfs_flush(fs, SEGM_CKP, 0);

                DLOG((DLOG_AVAIL, "lfs_reservebuf: waiting: count=%d, bytes=%ld\n",
                      locked_queue_count, locked_queue_bytes));
                ++locked_queue_waiters;
                cv_broadcast(&lfs_writerd_cv);
                error = cv_timedwait_sig(&locked_queue_cv, &lfs_lock,
                    hz * LFS_BUFWAIT);
                --locked_queue_waiters;
                if (error && error != EWOULDBLOCK) {
                        mutex_exit(&lfs_lock);
                        return error;
                }
        }

        locked_queue_rcount += n;
        locked_queue_rbytes += bytes;

        if (n < 0 && locked_queue_waiters > 0) {
                DLOG((DLOG_AVAIL, "lfs_reservebuf: broadcast: count=%d, bytes=%ld\n",
                      locked_queue_count, locked_queue_bytes));
                cv_broadcast(&locked_queue_cv);
        }

        mutex_exit(&lfs_lock);

        KASSERT(locked_queue_rcount >= 0);
        KASSERT(locked_queue_rbytes >= 0);

        return 0;
}

/*
 * Try to reserve some blocks, prior to performing a sensitive operation that
 * requires the vnode lock to be honored.  If there is not enough space, wait
 * for the space to become available.
 *
 * Called with vp locked.  (Note nowever that if fsb < 0, vp is ignored.)
 */
static int
lfs_reserveavail(struct lfs *fs, struct vnode *vp,
    struct vnode *vp2, int fsb)
{
        CLEANERINFO *cip;
        struct buf *bp;
        int error, slept;
        int cantwait;

        ASSERT_MAYBE_SEGLOCK(fs);
        slept = 0;
        mutex_enter(&lfs_lock);
        cantwait = (VTOI(vp)->i_state & IN_ADIROP) || fs->lfs_unlockvp == vp;
        while (!cantwait && fsb > 0 &&
               !lfs_fits(fs, fsb + fs->lfs_ravail + fs->lfs_favail)) {
                mutex_exit(&lfs_lock);

                if (!slept) {
                        DLOG((DLOG_AVAIL, "lfs_reserve: waiting for %ld (bfree = %jd,"
                              " est_bfree = %jd)\n",
                              fsb + fs->lfs_ravail + fs->lfs_favail,
                              (intmax_t)lfs_sb_getbfree(fs),
                              (intmax_t)LFS_EST_BFREE(fs)));
                }
                ++slept;

                /* Wake up the cleaner */
                LFS_CLEANERINFO(cip, fs, bp);
                LFS_SYNC_CLEANERINFO(cip, fs, bp, 0);
                lfs_wakeup_cleaner(fs);

                mutex_enter(&lfs_lock);
                /* Cleaner might have run while we were reading, check again */
                if (lfs_fits(fs, fsb + fs->lfs_ravail + fs->lfs_favail))
                        break;

                error = mtsleep(&fs->lfs_availsleep, PCATCH | PUSER,
                                "lfs_reserve", 0, &lfs_lock);
                if (error) {
                        mutex_exit(&lfs_lock);
                        return error;
                }
        }
#ifdef DEBUG
        if (slept) {
                DLOG((DLOG_AVAIL, "lfs_reserve: woke up\n"));
        }
#endif
        fs->lfs_ravail += fsb;
        mutex_exit(&lfs_lock);

        return 0;
}

#ifdef DIAGNOSTIC
int lfs_rescount;
int lfs_rescountdirop;
#endif

int
lfs_reserve(struct lfs *fs, struct vnode *vp, struct vnode *vp2, int fsb)
{
        int error;

        ASSERT_MAYBE_SEGLOCK(fs);
        if (vp2) {
                /* Make sure we're not in the process of reclaiming vp2 */
                mutex_enter(&lfs_lock);
                while(fs->lfs_flags & LFS_UNDIROP) {
                        mtsleep(&fs->lfs_flags, PRIBIO + 1, "lfsrundirop", 0,
                            &lfs_lock);
                }
                mutex_exit(&lfs_lock);
        }

        KASSERT(fsb < 0 || VOP_ISLOCKED(vp));
        KASSERT(vp2 == NULL || fsb < 0 || VOP_ISLOCKED(vp2));
        KASSERT(vp2 == NULL || vp2 != fs->lfs_unlockvp);

#ifdef DIAGNOSTIC
        mutex_enter(&lfs_lock);
        if (fsb > 0)
                lfs_rescount++;
        else if (fsb < 0)
                lfs_rescount--;
        if (lfs_rescount < 0)
                panic("lfs_rescount");
        mutex_exit(&lfs_lock);
#endif

        error = lfs_reserveavail(fs, vp, vp2, fsb);
        if (error)
                return error;

        /*
         * XXX just a guess. should be more precise.
         */
        error = lfs_reservebuf(fs, vp, vp2, fsb, lfs_fsbtob(fs, fsb));
        if (error)
                lfs_reserveavail(fs, vp, vp2, -fsb);

        return error;
}

int
lfs_max_bufs(void)
{

        return LFS_MAX_RESOURCE(buf_nbuf(), 1);
}

int
lfs_wait_bufs(void)
{

        return LFS_WAIT_RESOURCE(buf_nbuf(), 1);
}

int
lfs_bwrite(void *v)
{
        struct vop_bwrite_args /* {
                struct vnode *a_vp;
                struct buf *a_bp;
        } */ *ap = v;
        struct buf *bp = ap->a_bp;

        KASSERTMSG((VTOI(bp->b_vp)->i_lfs->lfs_ronly ||
                !(bp->b_flags & B_ASYNC)),
            "bawrite LFS buffer");
        return lfs_bwrite_ext(bp, 0);
}

/*
 * Determine if there is enough room currently available to write fsb
 * blocks.  We need enough blocks for the new blocks, the current
 * inode blocks (including potentially the ifile inode), a summary block,
 * and the segment usage table, plus an ifile block.
 */
int
lfs_fits(struct lfs *fs, int fsb)
{
        int64_t needed;

        ASSERT_NO_SEGLOCK(fs);
        needed = fsb + lfs_btofsb(fs, lfs_sb_getsumsize(fs)) +
                 ((howmany(lfs_sb_getuinodes(fs) + 1, LFS_INOPB(fs)) +
                   lfs_sb_getsegtabsz(fs) +
                   1) << (lfs_sb_getbshift(fs) - lfs_sb_getffshift(fs)));

        if (needed >= lfs_sb_getavail(fs)) {
#ifdef DEBUG
                DLOG((DLOG_AVAIL, "lfs_fits: no fit: fsb = %ld, uinodes = %ld, "
                      "needed = %jd, avail = %jd\n",
                      (long)fsb, (long)lfs_sb_getuinodes(fs), (intmax_t)needed,
                      (intmax_t)lfs_sb_getavail(fs)));
#endif
                return 0;
        }
        return 1;
}

int
lfs_availwait(struct lfs *fs, int fsb)
{
        int error;
        CLEANERINFO *cip;
        struct buf *cbp;

        ASSERT_NO_SEGLOCK(fs);
        /* Push cleaner blocks through regardless */
        mutex_enter(&lfs_lock);
        if (LFS_SEGLOCK_HELD(fs) &&
            fs->lfs_sp->seg_flags & (SEGM_CLEAN | SEGM_FORCE_CKP)) {
                mutex_exit(&lfs_lock);
                return 0;
        }
        mutex_exit(&lfs_lock);

        while (!lfs_fits(fs, fsb)) {
                /*
                 * Out of space, need cleaner to run.
                 * Update the cleaner info, then wake it up.
                 * Note the cleanerinfo block is on the ifile
                 * so it CANT_WAIT.
                 */
                LFS_CLEANERINFO(cip, fs, cbp);
                LFS_SYNC_CLEANERINFO(cip, fs, cbp, 0);

#ifdef DEBUG
                DLOG((DLOG_AVAIL, "lfs_availwait: out of available space, "
                      "waiting on cleaner\n"));
#endif

                lfs_wakeup_cleaner(fs);
                KASSERTMSG(!LFS_SEGLOCK_HELD(fs), "lfs_availwait: deadlock");
                error = tsleep(&fs->lfs_availsleep, PCATCH | PUSER,
                               "cleaner", 0);
                if (error)
                        return (error);
        }
        return 0;
}

int
lfs_bwrite_ext(struct buf *bp, int flags)
{
        struct lfs *fs;
        struct inode *ip;
        struct vnode *vp;
        int fsb;

        vp = bp->b_vp;
        fs = VFSTOULFS(vp->v_mount)->um_lfs;

        ASSERT_MAYBE_SEGLOCK(fs);
        KASSERT(bp->b_cflags & BC_BUSY);
        KASSERT(flags & BW_CLEAN || !LFS_IS_MALLOC_BUF(bp));
        KASSERT((bp->b_flags & B_LOCKED) || !(bp->b_oflags & BO_DELWRI));
        KASSERT(!(flags & BW_CLEAN) || lfs_cleanerlock_held(fs));

        
        /*
         * Don't write *any* blocks if we're mounted read-only, or
         * if we are "already unmounted".
         *
         * In particular the cleaner can't write blocks either.
         */
        if (fs->lfs_ronly || (lfs_sb_getpflags(fs) & LFS_PF_CLEAN)) {
                bp->b_oflags &= ~BO_DELWRI;
                bp->b_flags |= B_READ; /* XXX is this right? --ks */
                bp->b_error = 0;
                mutex_enter(&bufcache_lock);
                LFS_UNLOCK_BUF(bp);
                if (LFS_IS_MALLOC_BUF(bp))
                        bp->b_cflags &= ~BC_BUSY;
                else
                        brelsel(bp, 0);
                mutex_exit(&bufcache_lock);
                return (fs->lfs_ronly ? EROFS : 0);
        }

        /*
         * Set the delayed write flag and use reassignbuf to move the buffer
         * from the clean list to the dirty one.
         *
         * Set the B_LOCKED flag and unlock the buffer, causing brelse to move
         * the buffer onto the LOCKED free list.  This is necessary, otherwise
         * getnewbuf() would try to reclaim the buffers using bawrite, which
         * isn't going to work.
         *
         * XXX we don't let meta-data writes run out of space because they can
         * come from the segment writer.  We need to make sure that there is
         * enough space reserved so that there's room to write meta-data
         * blocks.
         */
        if ((bp->b_flags & B_LOCKED) == 0) {
                fsb = lfs_numfrags(fs, bp->b_bcount);

                ip = VTOI(vp);
                if (flags & BW_CLEAN) {
                        lfs_setclean(fs, vp);
                } else {
                        mutex_enter(&lfs_lock);
                        LFS_SET_UINO(ip, IN_MODIFIED);
                        mutex_exit(&lfs_lock);
                }
                if ((bp->b_oflags & BO_DELWRI) == 0)
                        lfs_sb_subavail(fs, fsb);

                mutex_enter(&bufcache_lock);
                mutex_enter(vp->v_interlock);
                bp->b_oflags = (bp->b_oflags | BO_DELWRI) & ~BO_DONE;
                LFS_LOCK_BUF(bp);
                bp->b_flags &= ~B_READ;
                bp->b_error = 0;
                reassignbuf(bp, bp->b_vp);
                mutex_exit(vp->v_interlock);
        } else {
                mutex_enter(&bufcache_lock);
        }

        if (bp->b_iodone != NULL)
                bp->b_cflags &= ~BC_BUSY;
        else
                brelsel(bp, 0);
        mutex_exit(&bufcache_lock);

        return (0);
}

/*
 * Called and return with the lfs_lock held.
 */
void
lfs_flush_fs(struct lfs *fs, int flags)
{
        ASSERT_NO_SEGLOCK(fs);
        KASSERT(mutex_owned(&lfs_lock));
        if (fs->lfs_ronly)
                return;

        if (lfs_dostats)
                ++lfs_stats.flush_invoked;

        fs->lfs_pdflush = 0;
        mutex_exit(&lfs_lock);
        lfs_writer_enter(fs, "fldirop");
        lfs_segwrite(fs->lfs_ivnode->v_mount, flags);
        lfs_writer_leave(fs);
        mutex_enter(&lfs_lock);
        fs->lfs_favail = 0; /* XXX */
}

/*
 * This routine initiates segment writes when LFS is consuming too many
 * resources.  Ideally the pageout daemon would be able to direct LFS
 * more subtly.
 * XXX We have one static count of locked buffers;
 * XXX need to think more about the multiple filesystem case.
 *
 * Called and return with lfs_lock held.
 * If fs != NULL, we hold the segment lock for fs.
 */
void
lfs_flush(struct lfs *fs, int flags, int only_onefs)
{
        extern u_int64_t locked_fakequeue_count;
        mount_iterator_t *iter;
        struct mount *mp;
        struct lfs *tfs;

        KASSERT(mutex_owned(&lfs_lock));
        KDASSERT(fs == NULL || !LFS_SEGLOCK_HELD(fs));
        KASSERT(!(fs == NULL && only_onefs));

        if (lfs_dostats)
                ++lfs_stats.write_exceeded;
        if (lfs_writing && !(flags & (SEGM_SYNC|SEGM_CKP))) {
                DLOG((DLOG_FLUSH, "lfs_flush: not flushing because another flush is active\n"));
                return;
        }
        while (lfs_writing)
                cv_wait(&lfs_writing_cv, &lfs_lock);
        lfs_writing = 1;

        mutex_exit(&lfs_lock);

        if (fs != NULL) {
                if (!(fs->lfs_flags & LFS_NOTYET)
                        && vfs_busy(fs->lfs_ivnode->v_mount))
                        goto errout;
                mutex_enter(&lfs_lock);
                lfs_flush_fs(fs, flags);
                mutex_exit(&lfs_lock);
                if (!(fs->lfs_flags & LFS_NOTYET))
                        vfs_unbusy(fs->lfs_ivnode->v_mount);
        }
        if (!only_onefs) {
                locked_fakequeue_count = 0;
                mountlist_iterator_init(&iter);
                while ((mp = mountlist_iterator_next(iter)) != NULL) {
                        if (strncmp(&mp->mnt_stat.f_fstypename[0], MOUNT_LFS,
                            sizeof(mp->mnt_stat.f_fstypename)) == 0) {
                                tfs = VFSTOULFS(mp)->um_lfs;
                                if (tfs == fs)
                                        continue;
                                mutex_enter(&lfs_lock);
                                lfs_flush_fs(tfs, flags);
                                mutex_exit(&lfs_lock);
                        }
                }
                mountlist_iterator_destroy(iter);
        }
        wakeup(&lfs_subsys_pages);

    errout:
        mutex_enter(&lfs_lock);
        KASSERT(lfs_writing);
        lfs_writing = 0;
        wakeup(&lfs_writing);
}

#define INOCOUNT(fs) howmany(lfs_sb_getuinodes(fs), LFS_INOPB(fs))
#define INOBYTES(fs) (lfs_sb_getuinodes(fs) * DINOSIZE(fs))

/*
 * Determine whether this filesystem, or the global state,
 * needs to flush.
 */
int
lfs_needsflush(struct lfs *fs)
{
        if (locked_queue_count + INOCOUNT(fs) > LFS_MAX_BUFS)
                return 1;
        if (locked_queue_bytes + INOBYTES(fs) > LFS_MAX_BYTES)
                return 1;
        if (lfs_subsys_pages > LFS_MAX_PAGES)
                return 1;
        if (fs->lfs_dirvcount > LFS_MAX_FSDIROP(fs))
                return 1;
        if (lfs_dirvcount > LFS_MAX_DIROP)
                return 1;
        if (fs->lfs_diropwait > 0)
                return 1;

        return 0;
}

/*
 * As above, but needs to *wait*.
 */
int
lfs_needswait(struct lfs *fs)
{
        if (locked_queue_count + INOCOUNT(fs) > LFS_WAIT_BUFS)
                return 1;
        if (locked_queue_bytes + INOBYTES(fs) > LFS_WAIT_BYTES)
                return 1;
        if (lfs_subsys_pages > LFS_WAIT_PAGES)
                return 1;
        if (fs->lfs_dirvcount > LFS_MAX_FSDIROP(fs)) /* XXX */
                return 1;
        if (lfs_dirvcount > LFS_MAX_DIROP) /* XXX */
                return 1;
        if (fs->lfs_diropwait > 0)
                return 1;

        return 0;
}
                

/*
 * make sure that we don't have too many locked buffers.
 * flush buffers if needed.
 */
int
lfs_check(struct vnode *vp, daddr_t blkno, int flags)
{
        int error;
        struct lfs *fs;
        struct inode *ip;
        extern kcondvar_t lfs_writerd_cv;

        error = 0;
        ip = VTOI(vp);

        /* If out of buffers, wait on writer */
        /* XXX KS - if it's the Ifile, we're probably the cleaner! */
        if (ip->i_number == LFS_IFILE_INUM)
                return 0;
        /* If we're being called from inside a dirop, don't sleep */
        if (ip->i_state & IN_ADIROP)
                return 0;

        fs = ip->i_lfs;

        ASSERT_NO_SEGLOCK(fs);

        /*
         * If we would flush below, but dirops are active, sleep.
         * Note that a dirop cannot ever reach this code!
         */
        mutex_enter(&lfs_lock);
        while (fs->lfs_dirops > 0 && lfs_needswait(fs)) {
                ++fs->lfs_diropwait;
                mtsleep(&fs->lfs_writer, PRIBIO+1, "bufdirop", 0,
                        &lfs_lock);
                --fs->lfs_diropwait;
        }

#ifdef DEBUG
        if (locked_queue_count + INOCOUNT(fs) > LFS_MAX_BUFS)
                DLOG((DLOG_FLUSH, "lfs_check: lqc = %d, max %d\n",
                      locked_queue_count + INOCOUNT(fs), LFS_MAX_BUFS));
        if (locked_queue_bytes + INOBYTES(fs) > LFS_MAX_BYTES)
                DLOG((DLOG_FLUSH, "lfs_check: lqb = %ld, max %ld\n",
                      locked_queue_bytes + INOBYTES(fs), LFS_MAX_BYTES));
        if (lfs_subsys_pages > LFS_MAX_PAGES)
                DLOG((DLOG_FLUSH, "lfs_check: lssp = %d, max %d\n",
                      lfs_subsys_pages, LFS_MAX_PAGES));
        if (lfs_fs_pagetrip && fs->lfs_pages > lfs_fs_pagetrip)
                DLOG((DLOG_FLUSH, "lfs_check: fssp = %d, trip at %d\n",
                      fs->lfs_pages, lfs_fs_pagetrip));
        if (lfs_dirvcount > LFS_MAX_DIROP)
                DLOG((DLOG_FLUSH, "lfs_check: ldvc = %d, max %d\n",
                      lfs_dirvcount, LFS_MAX_DIROP));
        if (fs->lfs_dirvcount > LFS_MAX_FSDIROP(fs))
                DLOG((DLOG_FLUSH, "lfs_check: lfdvc = %d, max %d\n",
                      fs->lfs_dirvcount, LFS_MAX_FSDIROP(fs)));
        if (fs->lfs_diropwait > 0)
                DLOG((DLOG_FLUSH, "lfs_check: ldvw = %d\n",
                      fs->lfs_diropwait));
#endif

        /* If there are too many pending dirops, we have to flush them. */
        if (fs->lfs_dirvcount > LFS_MAX_FSDIROP(fs) ||
            lfs_dirvcount > LFS_MAX_DIROP || fs->lfs_diropwait > 0) {
                KASSERT(fs->lfs_dirops == 0);
                fs->lfs_writer++;
                mutex_exit(&lfs_lock);
                lfs_flush_dirops(fs);
                mutex_enter(&lfs_lock);
                if (--fs->lfs_writer == 0)
                        cv_broadcast(&fs->lfs_diropscv);
                KASSERT(fs->lfs_dirops == 0);
        } else if (lfs_needsflush(fs)) {
                lfs_flush(fs, flags, 0);
        } else if (lfs_fs_pagetrip && fs->lfs_pages > lfs_fs_pagetrip) {
                /*
                 * If we didn't flush the whole thing, some filesystems
                 * still might want to be flushed.
                 */
                ++fs->lfs_pdflush;
                cv_broadcast(&lfs_writerd_cv);
        }

        while (lfs_needswait(fs)) {
                if (lfs_dostats)
                        ++lfs_stats.wait_exceeded;
                DLOG((DLOG_AVAIL, "lfs_check: waiting: count=%d, bytes=%ld\n",
                      locked_queue_count, locked_queue_bytes));
                ++locked_queue_waiters;
                cv_broadcast(&lfs_writerd_cv);
                error = cv_timedwait_sig(&locked_queue_cv, &lfs_lock,
                    hz * LFS_BUFWAIT);
                --locked_queue_waiters;
                if (error != EWOULDBLOCK)
                        break;

                /*
                 * lfs_flush might not flush all the buffers, if some of the
                 * inodes were locked or if most of them were Ifile blocks
                 * and we weren't asked to checkpoint.  Try flushing again
                 * after waiting, to keep us from blocking indefinitely.
                 */
                if (locked_queue_count + INOCOUNT(fs) >= LFS_MAX_BUFS ||
                    locked_queue_bytes + INOBYTES(fs) >= LFS_MAX_BYTES) {
                        lfs_flush(fs, flags | SEGM_CKP, 0);
                }
        }
        mutex_exit(&lfs_lock);
        return (error);
}

/*
 * Allocate a new buffer header.
 */
struct buf *
lfs_newbuf(struct lfs *fs, struct vnode *vp, daddr_t daddr, size_t size, int type)
{
        struct buf *bp;
        size_t nbytes;

        ASSERT_MAYBE_SEGLOCK(fs);
        nbytes = roundup(size, lfs_fsbtob(fs, 1));

        bp = getiobuf(NULL, true);
        if (nbytes) {
                bp->b_data = lfs_malloc(fs, nbytes, type);
                /* memset(bp->b_data, 0, nbytes); */
        }
        KASSERT(vp != NULL);
        KASSERT(bp != NULL);

        bp->b_bufsize = size;
        bp->b_bcount = size;
        bp->b_lblkno = daddr;
        bp->b_blkno = daddr;
        bp->b_error = 0;
        bp->b_resid = 0;
        bp->b_iodone = lfs_free_aiodone;
        bp->b_private = fs;

        mutex_enter(&bufcache_lock);
        bp->b_cflags |= BC_BUSY | BC_NOCACHE;
        mutex_enter(vp->v_interlock);
        bgetvp(vp, bp);
        mutex_exit(vp->v_interlock);
        mutex_exit(&bufcache_lock);

        return (bp);
}

void
lfs_freebuf(struct lfs *fs, struct buf *bp)
{
        struct vnode *vp;

        mutex_enter(&bufcache_lock);
        vp = bp->b_vp;
        mutex_enter(vp->v_interlock);
        if (vp != NULL)
                brelvp(bp);
        mutex_exit(vp->v_interlock);
        if (!(bp->b_cflags & BC_INVAL)) { /* BC_INVAL indicates a "fake" buffer */
                lfs_free(fs, bp->b_data, LFS_NB_UNKNOWN);
                bp->b_data = NULL;
        }
        mutex_exit(&bufcache_lock);
        putiobuf(bp);
}

int
lfs_wait_pages(void)
{
        int active, inactive;

        uvm_estimatepageable(&active, &inactive);
        return LFS_WAIT_RESOURCE(active + inactive + uvm_availmem(false), 1);
}

int
lfs_max_pages(void)
{
        int active, inactive;

        uvm_estimatepageable(&active, &inactive);
        return LFS_MAX_RESOURCE(active + inactive + uvm_availmem(false), 1);
}