hammer2 - Revamp flush and xopq mechanism, stabilization

[dragonfly.git] / sys / vfs / hammer2 / hammer2_io.c

/*
 * Copyright (c) 2013-2014 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.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.
 * 3. Neither the name of The DragonFly Project 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 COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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 "hammer2.h"

/*
 * Implements an abstraction layer for synchronous and asynchronous
 * buffered device I/O.  Can be used for OS-abstraction but the main
 * purpose is to allow larger buffers to be used against hammer2_chain's
 * using smaller allocations, without causing deadlocks.
 *
 */
static int hammer2_io_cleanup_callback(hammer2_io_t *dio, void *arg);
static void dio_write_stats_update(hammer2_io_t *dio);

static int
hammer2_io_cmp(hammer2_io_t *io1, hammer2_io_t *io2)
{
        if (io1->pbase < io2->pbase)
                return(-1);
        if (io1->pbase > io2->pbase)
                return(1);
        return(0);
}

RB_PROTOTYPE2(hammer2_io_tree, hammer2_io, rbnode, hammer2_io_cmp, off_t);
RB_GENERATE2(hammer2_io_tree, hammer2_io, rbnode, hammer2_io_cmp,
                off_t, pbase);

struct hammer2_cleanupcb_info {
        struct hammer2_io_tree tmptree;
        int     count;
};

static __inline
uint64_t
hammer2_io_mask(hammer2_io_t *dio, hammer2_off_t off, u_int bytes)
{
        uint64_t mask;
        int i;

        if (bytes < 1024)       /* smaller chunks not supported */
                return 0;

        /*
         * Calculate crc check mask for larger chunks
         */
        i = (((off & ~HAMMER2_OFF_MASK_RADIX) - dio->pbase) &
             HAMMER2_PBUFMASK) >> 10;
        if (i == 0 && bytes == HAMMER2_PBUFSIZE)
                return((uint64_t)-1);
        mask = ((uint64_t)1U << (bytes >> 10)) - 1;
        mask <<= i;

        return mask;
}

#define HAMMER2_GETBLK_GOOD     0
#define HAMMER2_GETBLK_QUEUED   1
#define HAMMER2_GETBLK_OWNED    2

/*
 * Allocate/Locate the requested dio, reference it, issue or queue iocb.
 */
void
hammer2_io_getblk(hammer2_dev_t *hmp, off_t lbase, int lsize,
                  hammer2_iocb_t *iocb)
{
        hammer2_io_t *dio;
        hammer2_io_t *xio;
        off_t pbase;
        off_t pmask;
        /*
         * XXX after free, buffer reuse case w/ different size can clash
         * with dio cache.  Lets avoid it for now.  Ultimate we need to
         * invalidate the dio cache when freeing blocks to allow a mix
         * of 16KB and 64KB block sizes).
         */
        /*int psize = hammer2_devblksize(lsize);*/
        int psize = HAMMER2_PBUFSIZE;
        uint64_t refs;

        pmask = ~(hammer2_off_t)(psize - 1);

        KKASSERT((1 << (int)(lbase & HAMMER2_OFF_MASK_RADIX)) == lsize);
        lbase &= ~HAMMER2_OFF_MASK_RADIX;
        pbase = lbase & pmask;
        if (pbase == 0 || ((lbase + lsize - 1) & pmask) != pbase) {
                kprintf("Illegal: %016jx %016jx+%08x / %016jx\n",
                        pbase, lbase, lsize, pmask);
        }
        KKASSERT(pbase != 0 && ((lbase + lsize - 1) & pmask) == pbase);

        /*
         * Access/Allocate the DIO, bump dio->refs to prevent destruction.
         */
        hammer2_spin_sh(&hmp->io_spin);
        dio = RB_LOOKUP(hammer2_io_tree, &hmp->iotree, pbase);
        if (dio) {
                if ((atomic_fetchadd_64(&dio->refs, 1) &
                     HAMMER2_DIO_MASK) == 0) {
                        atomic_add_int(&dio->hmp->iofree_count, -1);
                }
                hammer2_spin_unsh(&hmp->io_spin);
        } else {
                hammer2_spin_unsh(&hmp->io_spin);
                dio = kmalloc(sizeof(*dio), M_HAMMER2, M_INTWAIT | M_ZERO);
                dio->hmp = hmp;
                dio->pbase = pbase;
                dio->psize = psize;
                dio->btype = iocb->btype;
                dio->refs = 1;
                hammer2_spin_init(&dio->spin, "h2dio");
                TAILQ_INIT(&dio->iocbq);
                hammer2_spin_ex(&hmp->io_spin);
                xio = RB_INSERT(hammer2_io_tree, &hmp->iotree, dio);
                if (xio == NULL) {
                        atomic_add_int(&hammer2_dio_count, 1);
                        hammer2_spin_unex(&hmp->io_spin);
                } else {
                        if ((atomic_fetchadd_64(&xio->refs, 1) &
                             HAMMER2_DIO_MASK) == 0) {
                                atomic_add_int(&xio->hmp->iofree_count, -1);
                        }
                        hammer2_spin_unex(&hmp->io_spin);
                        kfree(dio, M_HAMMER2);
                        dio = xio;
                }
        }

        /*
         * Obtain/Validate the buffer.
         */
        iocb->dio = dio;

        if (dio->act < 5)       /* SMP race ok */
                ++dio->act;

        for (;;) {
                refs = dio->refs;
                cpu_ccfence();

                /*
                 * Issue the iocb immediately if the buffer is already good.
                 * Once set GOOD cannot be cleared until refs drops to 0.
                 *
                 * lfence required because dio's are not interlocked for
                 * the DIO_GOOD test.
                 */
                if (refs & HAMMER2_DIO_GOOD) {
                        cpu_lfence();
                        iocb->callback(iocb);
                        break;
                }

                /*
                 * Try to own the DIO by setting INPROG so we can issue
                 * I/O on it.
                 */
                if (refs & HAMMER2_DIO_INPROG) {
                        /*
                         * If DIO_INPROG is already set then set WAITING and
                         * queue the iocb.
                         */
                        hammer2_spin_ex(&dio->spin);
                        if (atomic_cmpset_64(&dio->refs, refs,
                                              refs | HAMMER2_DIO_WAITING)) {
                                iocb->flags |= HAMMER2_IOCB_ONQ |
                                               HAMMER2_IOCB_INPROG;
                                TAILQ_INSERT_TAIL(&dio->iocbq, iocb, entry);
                                hammer2_spin_unex(&dio->spin);
                                break;
                        }
                        hammer2_spin_unex(&dio->spin);
                        /* retry */
                } else {
                        /*
                         * If DIO_INPROG is not set then set it and issue the
                         * callback immediately to start I/O.
                         */
                        if (atomic_cmpset_64(&dio->refs, refs,
                                              refs | HAMMER2_DIO_INPROG)) {
                                iocb->flags |= HAMMER2_IOCB_INPROG;
                                iocb->callback(iocb);
                                break;
                        }
                        /* retry */
                }
                /* retry */
        }
}

/*
 * Quickly obtain a good DIO buffer, return NULL if the system no longer
 * caches the data.
 */
hammer2_io_t *
hammer2_io_getquick(hammer2_dev_t *hmp, off_t lbase, int lsize)
{
        hammer2_iocb_t iocb;
        hammer2_io_t *dio;
        struct buf *bp;
        off_t pbase;
        off_t pmask;
        int psize = HAMMER2_PBUFSIZE;
        uint64_t orefs;
        uint64_t nrefs;

        pmask = ~(hammer2_off_t)(psize - 1);

        KKASSERT((1 << (int)(lbase & HAMMER2_OFF_MASK_RADIX)) == lsize);
        lbase &= ~HAMMER2_OFF_MASK_RADIX;
        pbase = lbase & pmask;
        if (pbase == 0 || ((lbase + lsize - 1) & pmask) != pbase) {
                kprintf("Illegal: %016jx %016jx+%08x / %016jx\n",
                        pbase, lbase, lsize, pmask);
        }
        KKASSERT(pbase != 0 && ((lbase + lsize - 1) & pmask) == pbase);

        /*
         * Access/Allocate the DIO, bump dio->refs to prevent destruction.
         */
        hammer2_spin_sh(&hmp->io_spin);
        dio = RB_LOOKUP(hammer2_io_tree, &hmp->iotree, pbase);
        if (dio == NULL) {
                hammer2_spin_unsh(&hmp->io_spin);
                return NULL;
        }

        if ((atomic_fetchadd_64(&dio->refs, 1) & HAMMER2_DIO_MASK) == 0)
                atomic_add_int(&dio->hmp->iofree_count, -1);
        hammer2_spin_unsh(&hmp->io_spin);

        if (dio->act < 5)       /* SMP race ok */
                ++dio->act;

        /*
         * Obtain/validate the buffer.  Do NOT issue I/O.  Discard if
         * the system does not have the data already cached.
         */
        nrefs = (uint64_t)-1;
        for (;;) {
                orefs = dio->refs;
                cpu_ccfence();

                /*
                 * Issue the iocb immediately if the buffer is already good.
                 * Once set GOOD cannot be cleared until refs drops to 0.
                 *
                 * lfence required because dio is not interlockedf for
                 * the DIO_GOOD test.
                 */
                if (orefs & HAMMER2_DIO_GOOD) {
                        cpu_lfence();
                        break;
                }

                /*
                 * Try to own the DIO by setting INPROG so we can issue
                 * I/O on it.  INPROG might already be set, in which case
                 * there is no way we can do this non-blocking so we punt.
                 */
                if ((orefs & HAMMER2_DIO_INPROG))
                        break;
                nrefs = orefs | HAMMER2_DIO_INPROG;
                if (atomic_cmpset_64(&dio->refs, orefs, nrefs) == 0)
                        continue;

                /*
                 * We own DIO_INPROG, try to set DIO_GOOD.
                 *
                 * For now do not use GETBLK_NOWAIT because 
                 */
                bp = dio->bp;
                dio->bp = NULL;
                if (bp == NULL) {
#if 0
                        bp = getblk(hmp->devvp, dio->pbase, dio->psize, 0, 0);
#endif
                        bread(hmp->devvp, dio->pbase, dio->psize, &bp);
                }

                /*
                 * System buffer must also have remained cached.
                 */
                if (bp) {
                        if ((bp->b_flags & B_ERROR) == 0 &&
                            (bp->b_flags & B_CACHE)) {
                                dio->bp = bp;   /* assign BEFORE setting flag */
                                atomic_set_64(&dio->refs, HAMMER2_DIO_GOOD);
                        } else {
                                bqrelse(bp);
                                bp = NULL;
                        }
                }

                /*
                 * Clear DIO_INPROG.
                 *
                 * This is actually a bit complicated, see
                 * hammer2_io_complete() for more information.
                 */
                iocb.dio = dio;
                iocb.flags = HAMMER2_IOCB_INPROG;
                hammer2_io_complete(&iocb);
                break;
        }

        /*
         * Only return the dio if its buffer is good.  If the buffer is not
         * good be sure to clear INVALOK, meaning that invalidation is no
         * longer acceptable
         */
        if ((dio->refs & HAMMER2_DIO_GOOD) == 0) {
                hammer2_io_putblk(&dio);
        }
        return dio;
}

/*
 * Make sure that INVALOK is cleared on the dio associated with the specified
 * data offset.  Called from bulkfree when a block becomes reusable.
 */
void
hammer2_io_resetinval(hammer2_dev_t *hmp, off_t data_off)
{
        hammer2_io_t *dio;

        data_off &= ~HAMMER2_PBUFMASK64;
        hammer2_spin_sh(&hmp->io_spin);
        dio = RB_LOOKUP(hammer2_io_tree, &hmp->iotree, data_off);
        if (dio)
                atomic_clear_64(&dio->refs, HAMMER2_DIO_INVALOK);
        hammer2_spin_unsh(&hmp->io_spin);
}

/*
 * The originator of the iocb is finished with it.
 */
void
hammer2_io_complete(hammer2_iocb_t *iocb)
{
        hammer2_io_t *dio = iocb->dio;
        hammer2_iocb_t *cbtmp;
        uint64_t orefs;
        uint64_t nrefs;
        uint32_t oflags;
        uint32_t nflags;

        /*
         * If IOCB_INPROG was not set completion is synchronous due to the
         * buffer already being good.  We can simply set IOCB_DONE and return.
         *
         * In this situation DIO_INPROG is not set and we have no visibility
         * on dio->bp.  We should not try to mess with dio->bp because another
         * thread may be finishing up its processing.  dio->bp should already
         * be set to BUF_KERNPROC()!
         */
        if ((iocb->flags & HAMMER2_IOCB_INPROG) == 0) {
                atomic_set_int(&iocb->flags, HAMMER2_IOCB_DONE);
                return;
        }

        /*
         * The iocb was queued, obtained DIO_INPROG, and its callback was
         * made.  The callback is now complete.  We still own DIO_INPROG.
         *
         * We can set DIO_GOOD if no error occurred, which gives certain
         * stability guarantees to dio->bp and allows other accessors to
         * short-cut access.  DIO_GOOD cannot be cleared until the last
         * ref is dropped.
         */
        KKASSERT(dio->refs & HAMMER2_DIO_INPROG);
        if (dio->bp) {
                BUF_KERNPROC(dio->bp);
                if ((dio->bp->b_flags & B_ERROR) == 0) {
                        KKASSERT(dio->bp->b_flags & B_CACHE);
                        atomic_set_64(&dio->refs, HAMMER2_DIO_GOOD);
                }
        }

        /*
         * Clean up the dio before marking the iocb as being done.  If another
         * iocb is pending we chain to it while leaving DIO_INPROG set (it
         * will call io completion and presumably clear DIO_INPROG).
         *
         * Otherwise if no other iocbs are pending we clear DIO_INPROG before
         * finishing up the cbio.  This means that DIO_INPROG is cleared at
         * the end of the chain before ANY of the cbios are marked done.
         *
         * NOTE: The TAILQ is not stable until the spin-lock is held.
         */
        for (;;) {
                orefs = dio->refs;
                nrefs = orefs & ~(HAMMER2_DIO_WAITING | HAMMER2_DIO_INPROG);

                if (orefs & HAMMER2_DIO_WAITING) {
                        hammer2_spin_ex(&dio->spin);
                        cbtmp = TAILQ_FIRST(&dio->iocbq);
                        if (cbtmp) {
                                /*
                                 * NOTE: flags not adjusted in this case.
                                 *       Flags will be adjusted by the last
                                 *       iocb.
                                 */
                                TAILQ_REMOVE(&dio->iocbq, cbtmp, entry);
                                hammer2_spin_unex(&dio->spin);
                                cbtmp->callback(cbtmp); /* chained */
                                break;
                        } else if (atomic_cmpset_64(&dio->refs, orefs, nrefs)) {
                                hammer2_spin_unex(&dio->spin);
                                break;
                        }
                        hammer2_spin_unex(&dio->spin);
                        /* retry */
                } else if (atomic_cmpset_64(&dio->refs, orefs, nrefs)) {
                        break;
                } /* else retry */
                /* retry */
        }

        /*
         * Mark the iocb as done and wakeup any waiters.  This is done after
         * all iocb chains have been called back and after DIO_INPROG has been
         * cleared.  This avoids races against ref count drops by the waiting
         * threads (a hard but not impossible SMP race) which might result in
         * a 1->0 transition of the refs while DIO_INPROG is still set.
         */
        for (;;) {
                oflags = iocb->flags;
                cpu_ccfence();
                nflags = oflags;
                nflags &= ~(HAMMER2_IOCB_WAKEUP | HAMMER2_IOCB_INPROG);
                nflags |= HAMMER2_IOCB_DONE;

                if (atomic_cmpset_int(&iocb->flags, oflags, nflags)) {
                        if (oflags & HAMMER2_IOCB_WAKEUP)
                                wakeup(iocb);
                        /* SMP: iocb is now stale */
                        break;
                }
                /* retry */
        }
        iocb = NULL;

}

/*
 * Wait for an iocb's I/O to finish.
 */
void
hammer2_iocb_wait(hammer2_iocb_t *iocb)
{
        uint32_t oflags;
        uint32_t nflags;

        for (;;) {
                oflags = iocb->flags;
                cpu_ccfence();
                nflags = oflags | HAMMER2_IOCB_WAKEUP;
                if (oflags & HAMMER2_IOCB_DONE)
                        break;
                tsleep_interlock(iocb, 0);
                if (atomic_cmpset_int(&iocb->flags, oflags, nflags)) {
                        tsleep(iocb, PINTERLOCKED, "h2iocb", hz);
                }
        }

}

/*
 * Release our ref on *diop.
 *
 * On the last ref we must atomically clear DIO_GOOD and set DIO_INPROG,
 * then dispose of the underlying buffer.
 */
void
hammer2_io_putblk(hammer2_io_t **diop)
{
        hammer2_dev_t *hmp;
        hammer2_io_t *dio;
        hammer2_iocb_t iocb;
        struct buf *bp;
        off_t peof;
        off_t pbase;
        int psize;
        uint64_t orefs;
        uint64_t nrefs;

        dio = *diop;
        *diop = NULL;
        hmp = dio->hmp;

        while (dio->unused01) {
                tsleep(&dio->unused01, 0, "h2DEBUG", hz);
        }

        /*
         * Drop refs.
         *
         * On the 1->0 transition clear flags and set INPROG.
         *
         * On the 1->0 transition if INPROG is already set, another thread
         * is in lastdrop and we can just return after the transition.
         *
         * On any other transition we can generally just return.
         */
        for (;;) {
                orefs = dio->refs;
                cpu_ccfence();
                nrefs = orefs - 1;

                if ((orefs & HAMMER2_DIO_MASK) == 1 &&
                    (orefs & HAMMER2_DIO_INPROG) == 0) {
                        /*
                         * Lastdrop case, INPROG can be set.
                         */
                        nrefs &= ~(HAMMER2_DIO_GOOD | HAMMER2_DIO_DIRTY);
                        nrefs &= ~(HAMMER2_DIO_INVAL);
                        nrefs |= HAMMER2_DIO_INPROG;
                        if (atomic_cmpset_64(&dio->refs, orefs, nrefs))
                                break;
                } else if ((orefs & HAMMER2_DIO_MASK) == 1) {
                        /*
                         * Lastdrop case, INPROG already set.
                         */
                        if (atomic_cmpset_64(&dio->refs, orefs, nrefs)) {
                                atomic_add_int(&hmp->iofree_count, 1);
                                return;
                        }
                } else {
                        /*
                         * Normal drop case.
                         */
                        if (atomic_cmpset_64(&dio->refs, orefs, nrefs))
                                return;
                }
                cpu_pause();
                /* retry */
        }

        /*
         * Lastdrop (1->0 transition).  INPROG has been set, GOOD and DIRTY
         * have been cleared.
         *
         * We can now dispose of the buffer, and should do it before calling
         * io_complete() in case there's a race against a new reference
         * which causes io_complete() to chain and instantiate the bp again.
         */
        pbase = dio->pbase;
        psize = dio->psize;
        bp = dio->bp;
        dio->bp = NULL;

        if (orefs & HAMMER2_DIO_GOOD) {
                KKASSERT(bp != NULL);
#if 1
                if (hammer2_inval_enable &&
                    (orefs & HAMMER2_DIO_INVALBITS) == HAMMER2_DIO_INVALBITS) {
                        ++hammer2_iod_invals;
                        bp->b_flags |= B_INVAL | B_RELBUF;
                        brelse(bp);
                } else
#endif
                if (orefs & HAMMER2_DIO_DIRTY) {
                        int hce;

                        dio_write_stats_update(dio);
                        if ((hce = hammer2_cluster_write) > 0) {
                                /*
                                 * Allows write-behind to keep the buffer
                                 * cache sane.
                                 */
                                peof = (pbase + HAMMER2_SEGMASK64) &
                                       ~HAMMER2_SEGMASK64;
                                bp->b_flags |= B_CLUSTEROK;
                                cluster_write(bp, peof, psize, hce);
                        } else {
                                /*
                                 * Allows dirty buffers to accumulate and
                                 * possibly be canceled (e.g. by a 'rm'),
                                 * will burst-write later.
                                 */
                                bp->b_flags |= B_CLUSTEROK;
                                bdwrite(bp);
                        }
                } else if (bp->b_flags & (B_ERROR | B_INVAL | B_RELBUF)) {
                        brelse(bp);
                } else {
                        bqrelse(bp);
                }
        } else if (bp) {
#if 1
                if (hammer2_inval_enable &&
                    (orefs & HAMMER2_DIO_INVALBITS) == HAMMER2_DIO_INVALBITS) {
                        ++hammer2_iod_invals;
                        bp->b_flags |= B_INVAL | B_RELBUF;
                        brelse(bp);
                } else
#endif
                if (orefs & HAMMER2_DIO_DIRTY) {
                        dio_write_stats_update(dio);
                        bdwrite(bp);
                } else {
                        brelse(bp);
                }
        }

        /*
         * The instant we call io_complete dio is a free agent again and
         * can be ripped out from under us.
         *
         * we can cleanup our final DIO_INPROG by simulating an iocb
         * completion.
         */
        hmp = dio->hmp;                         /* extract fields */
        atomic_add_int(&hmp->iofree_count, 1);
        cpu_ccfence();

        iocb.dio = dio;
        iocb.flags = HAMMER2_IOCB_INPROG;
        hammer2_io_complete(&iocb);
        dio = NULL;                             /* dio stale */

        /*
         * We cache free buffers so re-use cases can use a shared lock, but
         * if too many build up we have to clean them out.
         */
        if (hmp->iofree_count > 65536) {
                struct hammer2_cleanupcb_info info;

                RB_INIT(&info.tmptree);
                hammer2_spin_ex(&hmp->io_spin);
                if (hmp->iofree_count > 65536) {
                        info.count = hmp->iofree_count / 4;
                        RB_SCAN(hammer2_io_tree, &hmp->iotree, NULL,
                                hammer2_io_cleanup_callback, &info);
                }
                hammer2_spin_unex(&hmp->io_spin);
                hammer2_io_cleanup(hmp, &info.tmptree);
        }
}

/*
 * Cleanup any dio's with (INPROG | refs) == 0.
 *
 * Called to clean up cached DIOs on umount after all activity has been
 * flushed.
 */
static
int
hammer2_io_cleanup_callback(hammer2_io_t *dio, void *arg)
{
        struct hammer2_cleanupcb_info *info = arg;
        hammer2_io_t *xio;

        if ((dio->refs & (HAMMER2_DIO_MASK | HAMMER2_DIO_INPROG)) == 0) {
                if (dio->act > 0) {
                        --dio->act;
                        return 0;
                }
                KKASSERT(dio->bp == NULL);
                RB_REMOVE(hammer2_io_tree, &dio->hmp->iotree, dio);
                xio = RB_INSERT(hammer2_io_tree, &info->tmptree, dio);
                KKASSERT(xio == NULL);
                if (--info->count <= 0) /* limit scan */
                        return(-1);
        }
        return 0;
}

void
hammer2_io_cleanup(hammer2_dev_t *hmp, struct hammer2_io_tree *tree)
{
        hammer2_io_t *dio;

        while ((dio = RB_ROOT(tree)) != NULL) {
                RB_REMOVE(hammer2_io_tree, tree, dio);
                KKASSERT(dio->bp == NULL &&
                    (dio->refs & (HAMMER2_DIO_MASK | HAMMER2_DIO_INPROG)) == 0);
                kfree(dio, M_HAMMER2);
                atomic_add_int(&hammer2_dio_count, -1);
                atomic_add_int(&hmp->iofree_count, -1);
        }
}

/*
 * Returns a pointer to the requested data.
 */
char *
hammer2_io_data(hammer2_io_t *dio, off_t lbase)
{
        struct buf *bp;
        int off;

        bp = dio->bp;
        KKASSERT(bp != NULL);
        off = (lbase & ~HAMMER2_OFF_MASK_RADIX) - bp->b_loffset;
        KKASSERT(off >= 0 && off < bp->b_bufsize);
        return(bp->b_data + off);
}

#if 0
/*
 * Keep track of good CRCs in dio->good_crc_mask. XXX needs to be done
 * in the chain structure, but chain structure needs to be persistent as
 * well on refs=0 and it isn't.
 */
int
hammer2_io_crc_good(hammer2_chain_t *chain, uint64_t *maskp)
{
        hammer2_io_t *dio;
        uint64_t mask;

        if ((dio = chain->dio) != NULL && chain->bytes >= 1024) {
                mask = hammer2_io_mask(dio, chain->bref.data_off, chain->bytes);
                *maskp = mask;
                if ((dio->crc_good_mask & mask) == mask)
                        return 1;
                return 0;
        }
        *maskp = 0;

        return 0;
}

void
hammer2_io_crc_setmask(hammer2_io_t *dio, uint64_t mask)
{
        if (dio) {
                if (sizeof(long) == 8) {
                        atomic_set_long(&dio->crc_good_mask, mask);
                } else {
#if _BYTE_ORDER == _LITTLE_ENDIAN
                        atomic_set_int(&((int *)&dio->crc_good_mask)[0],
                                        (uint32_t)mask);
                        atomic_set_int(&((int *)&dio->crc_good_mask)[1],
                                        (uint32_t)(mask >> 32));
#else
                        atomic_set_int(&((int *)&dio->crc_good_mask)[0],
                                        (uint32_t)(mask >> 32));
                        atomic_set_int(&((int *)&dio->crc_good_mask)[1],
                                        (uint32_t)mask);
#endif
                }
        }
}

void
hammer2_io_crc_clrmask(hammer2_io_t *dio, uint64_t mask)
{
        if (dio) {
                if (sizeof(long) == 8) {
                        atomic_clear_long(&dio->crc_good_mask, mask);
                } else {
#if _BYTE_ORDER == _LITTLE_ENDIAN
                        atomic_clear_int(&((int *)&dio->crc_good_mask)[0],
                                        (uint32_t)mask);
                        atomic_clear_int(&((int *)&dio->crc_good_mask)[1],
                                        (uint32_t)(mask >> 32));
#else
                        atomic_clear_int(&((int *)&dio->crc_good_mask)[0],
                                        (uint32_t)(mask >> 32));
                        atomic_clear_int(&((int *)&dio->crc_good_mask)[1],
                                        (uint32_t)mask);
#endif
                }
        }
}
#endif

/*
 * Helpers for hammer2_io_new*() functions
 */
static
void
hammer2_iocb_new_callback(hammer2_iocb_t *iocb)
{
        hammer2_io_t *dio = iocb->dio;
        int gbctl = (iocb->flags & HAMMER2_IOCB_QUICK) ? GETBLK_NOWAIT : 0;

        /*
         * If IOCB_INPROG is not set the dio already has a good buffer and we
         * can't mess with it other than zero the requested range.
         *
         * If IOCB_INPROG is set we also own DIO_INPROG at this time and can
         * do what needs to be done with dio->bp.
         */
        if (iocb->flags & HAMMER2_IOCB_INPROG) {
                if ((iocb->flags & HAMMER2_IOCB_READ) == 0) {
                        if (iocb->lsize == dio->psize) {
                                /*
                                 * Fully covered buffer, try to optimize to
                                 * avoid any I/O.  We might already have the
                                 * buffer due to iocb chaining.
                                 */
                                if (dio->bp == NULL) {
                                        dio->bp = getblk(dio->hmp->devvp,
                                                         dio->pbase, dio->psize,
                                                         gbctl, 0);
                                }
                                if (dio->bp) {
                                        vfs_bio_clrbuf(dio->bp);
                                        dio->bp->b_flags |= B_CACHE;
                                }

                                /*
                                 * Invalidation is ok on newly allocated
                                 * buffers which cover the entire buffer.
                                 * Flag will be cleared on use by the de-dup
                                 * code.
                                 *
                                 * hammer2_chain_modify() also checks this flag.
                                 *
                                 * QUICK mode is used by the freemap code to
                                 * pre-validate a junk buffer to prevent an
                                 * unnecessary read I/O.  We do NOT want
                                 * to set INVALOK in that situation as the
                                 * underlying allocations may be smaller.
                                 */
                                if ((iocb->flags & HAMMER2_IOCB_QUICK) == 0) {
                                        atomic_set_64(&dio->refs,
                                                      HAMMER2_DIO_INVALOK);
                                }
                        } else if (iocb->flags & HAMMER2_IOCB_QUICK) {
                                /*
                                 * Partial buffer, quick mode.  Do nothing.
                                 * Do not instantiate the buffer or try to
                                 * mark it B_CACHE because other portions of
                                 * the buffer might have to be read by other
                                 * accessors.
                                 */
                        } else if (dio->bp == NULL ||
                                   (dio->bp->b_flags & B_CACHE) == 0) {
                                /*
                                 * Partial buffer, normal mode, requires
                                 * read-before-write.  Chain the read.
                                 *
                                 * We might already have the buffer due to
                                 * iocb chaining.  XXX unclear if we really
                                 * need to write/release it and reacquire
                                 * in that case.
                                 *
                                 * QUEUE ASYNC I/O, IOCB IS NOT YET COMPLETE.
                                 */
                                if (dio->bp) {
                                        if (dio->refs & HAMMER2_DIO_DIRTY) {
                                                dio_write_stats_update(dio);
                                                bdwrite(dio->bp);
                                        } else {
                                                bqrelse(dio->bp);
                                        }
                                        dio->bp = NULL;
                                }
                                atomic_set_int(&iocb->flags, HAMMER2_IOCB_READ);
                                breadcb(dio->hmp->devvp,
                                        dio->pbase, dio->psize,
                                        hammer2_io_callback, iocb);
                                return;
                        } /* else buffer is good */
                } /* else callback from breadcb is complete */
        }
        if (dio->bp) {
                if (iocb->flags & HAMMER2_IOCB_ZERO)
                        bzero(hammer2_io_data(dio, iocb->lbase), iocb->lsize);
                atomic_set_64(&dio->refs, HAMMER2_DIO_DIRTY);
        }
        hammer2_io_complete(iocb);
}

static
int
_hammer2_io_new(hammer2_dev_t *hmp, int btype, off_t lbase, int lsize,
                hammer2_io_t **diop, int flags)
{
        hammer2_iocb_t iocb;

        iocb.callback = hammer2_iocb_new_callback;
        iocb.cluster = NULL;
        iocb.chain = NULL;
        iocb.ptr = NULL;
        iocb.lbase = lbase;
        iocb.lsize = lsize;
        iocb.flags = flags;
        iocb.btype = btype;
        iocb.error = 0;
        hammer2_io_getblk(hmp, lbase, lsize, &iocb);
        if ((iocb.flags & HAMMER2_IOCB_DONE) == 0)
                hammer2_iocb_wait(&iocb);
        *diop = iocb.dio;

        return (iocb.error);
}

int
hammer2_io_new(hammer2_dev_t *hmp, int btype, off_t lbase, int lsize,
               hammer2_io_t **diop)
{
        return(_hammer2_io_new(hmp, btype, lbase, lsize,
                               diop, HAMMER2_IOCB_ZERO));
}

int
hammer2_io_newnz(hammer2_dev_t *hmp, int btype, off_t lbase, int lsize,
                 hammer2_io_t **diop)
{
        return(_hammer2_io_new(hmp, btype, lbase, lsize, diop, 0));
}

/*
 * This is called from the freemap to pre-validate a full-sized buffer
 * whos contents we don't care about, in order to prevent an unnecessary
 * read-before-write.
 */
void
hammer2_io_newq(hammer2_dev_t *hmp, int btype, off_t lbase, int lsize)
{
        hammer2_io_t *dio = NULL;

        _hammer2_io_new(hmp, btype, lbase, lsize, &dio, HAMMER2_IOCB_QUICK);
        hammer2_io_bqrelse(&dio);
}

static
void
hammer2_iocb_bread_callback(hammer2_iocb_t *iocb)
{
        hammer2_io_t *dio = iocb->dio;
        off_t peof;
        int error;

        /*
         * If IOCB_INPROG is not set the dio already has a good buffer and we
         * can't mess with it other than zero the requested range.
         *
         * If IOCB_INPROG is set we also own DIO_INPROG at this time and can
         * do what needs to be done with dio->bp.
         */
        if (iocb->flags & HAMMER2_IOCB_INPROG) {
                int hce;

                if (dio->bp && (dio->bp->b_flags & B_CACHE)) {
                        /*
                         * Already good, likely due to being chained from
                         * another iocb.
                         */
                        error = 0;
                } else if ((hce = hammer2_cluster_read) > 0) {
                        /*
                         * Synchronous cluster I/O for now.
                         */
                        if (dio->bp) {
                                bqrelse(dio->bp);
                                dio->bp = NULL;
                        }
                        peof = (dio->pbase + HAMMER2_SEGMASK64) &
                               ~HAMMER2_SEGMASK64;
                        error = cluster_read(dio->hmp->devvp, peof, dio->pbase,
                                             dio->psize,
                                             dio->psize, HAMMER2_PBUFSIZE*hce,
                                             &dio->bp);
                } else {
                        /*
                         * Synchronous I/O for now.
                         */
                        if (dio->bp) {
                                bqrelse(dio->bp);
                                dio->bp = NULL;
                        }
                        error = bread(dio->hmp->devvp, dio->pbase,
                                      dio->psize, &dio->bp);
                }
                if (error) {
                        brelse(dio->bp);
                        dio->bp = NULL;
                }
        }
        hammer2_io_complete(iocb);
}

int
hammer2_io_bread(hammer2_dev_t *hmp, int btype, off_t lbase, int lsize,
                hammer2_io_t **diop)
{
        hammer2_iocb_t iocb;

        iocb.callback = hammer2_iocb_bread_callback;
        iocb.cluster = NULL;
        iocb.chain = NULL;
        iocb.ptr = NULL;
        iocb.lbase = lbase;
        iocb.lsize = lsize;
        iocb.btype = btype;
        iocb.flags = 0;
        iocb.error = 0;
        hammer2_io_getblk(hmp, lbase, lsize, &iocb);
        if ((iocb.flags & HAMMER2_IOCB_DONE) == 0)
                hammer2_iocb_wait(&iocb);
        *diop = iocb.dio;

        return (iocb.error);
}

/*
 * System buf/bio async callback extracts the iocb and chains
 * to the iocb callback.
 */
void
hammer2_io_callback(struct bio *bio)
{
        struct buf *dbp = bio->bio_buf;
        hammer2_iocb_t *iocb = bio->bio_caller_info1.ptr;
        hammer2_io_t *dio;

        dio = iocb->dio;
        if ((bio->bio_flags & BIO_DONE) == 0)
                bpdone(dbp, 0);
        bio->bio_flags &= ~(BIO_DONE | BIO_SYNC);
        dio->bp = bio->bio_buf;
        iocb->callback(iocb);
}

void
hammer2_io_bawrite(hammer2_io_t **diop)
{
        atomic_set_64(&(*diop)->refs, HAMMER2_DIO_DIRTY);
        hammer2_io_putblk(diop);
}

void
hammer2_io_bdwrite(hammer2_io_t **diop)
{
        atomic_set_64(&(*diop)->refs, HAMMER2_DIO_DIRTY);
        hammer2_io_putblk(diop);
}

int
hammer2_io_bwrite(hammer2_io_t **diop)
{
        atomic_set_64(&(*diop)->refs, HAMMER2_DIO_DIRTY);
        hammer2_io_putblk(diop);
        return (0);     /* XXX */
}

void
hammer2_io_setdirty(hammer2_io_t *dio)
{
        atomic_set_64(&dio->refs, HAMMER2_DIO_DIRTY);
}

/*
 * Request an invalidation.  The hammer2_io code will oblige only if
 * DIO_INVALOK is also set.  INVALOK is cleared if the dio is used
 * in a dedup lookup and prevents invalidation of the dirty buffer.
 */
void
hammer2_io_setinval(hammer2_io_t *dio, hammer2_off_t off, u_int bytes)
{
        if ((u_int)dio->psize == bytes)
                atomic_set_64(&dio->refs, HAMMER2_DIO_INVAL);
}

void
hammer2_io_brelse(hammer2_io_t **diop)
{
        hammer2_io_putblk(diop);
}

void
hammer2_io_bqrelse(hammer2_io_t **diop)
{
        hammer2_io_putblk(diop);
}

int
hammer2_io_isdirty(hammer2_io_t *dio)
{
        return((dio->refs & HAMMER2_DIO_DIRTY) != 0);
}

static
void
dio_write_stats_update(hammer2_io_t *dio)
{
        long *counterp;

        switch(dio->btype) {
        case 0:
                return;
        case HAMMER2_BREF_TYPE_DATA:
                counterp = &hammer2_iod_file_write;
                break;
        case HAMMER2_BREF_TYPE_INODE:
                counterp = &hammer2_iod_meta_write;
                break;
        case HAMMER2_BREF_TYPE_INDIRECT:
                counterp = &hammer2_iod_indr_write;
                break;
        case HAMMER2_BREF_TYPE_FREEMAP_NODE:
        case HAMMER2_BREF_TYPE_FREEMAP_LEAF:
                counterp = &hammer2_iod_fmap_write;
                break;
        default:
                counterp = &hammer2_iod_volu_write;
                break;
        }
        *counterp += dio->psize;
}