/*      $NetBSD: mpool.c,v 1.23 2016/09/24 21:31:25 christos Exp $      */

/*-
 * Copyright (c) 1990, 1993, 1994
 *      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.
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
__RCSID("$NetBSD: mpool.c,v 1.23 2016/09/24 21:31:25 christos Exp $");

#include "namespace.h"
#include <sys/queue.h>
#include <sys/stat.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <db.h>

#define __MPOOLINTERFACE_PRIVATE
#include <mpool.h>

#ifdef __weak_alias
__weak_alias(mpool_close,_mpool_close)
__weak_alias(mpool_filter,_mpool_filter)
__weak_alias(mpool_get,_mpool_get)
__weak_alias(mpool_new,_mpool_new)
__weak_alias(mpool_newf,_mpool_newf)
__weak_alias(mpool_open,_mpool_open)
__weak_alias(mpool_put,_mpool_put)
__weak_alias(mpool_sync,_mpool_sync)
#endif

static BKT *mpool_bkt(MPOOL *);
static BKT *mpool_look(MPOOL *, pgno_t);
static int  mpool_write(MPOOL *, BKT *);

/*
 * mpool_open --
 *      Initialize a memory pool.
 */
/*ARGSUSED*/
MPOOL *
mpool_open(void *key, int fd, pgno_t pagesize, pgno_t maxcache)
{
        struct stat sb;
        MPOOL *mp;
        int entry;

        /*
         * Get information about the file.
         *
         * XXX
         * We don't currently handle pipes, although we should.
         */
        if (fstat(fd, &sb))
                return NULL;
        if (!S_ISREG(sb.st_mode)) {
                errno = ESPIPE;
                return NULL;
        }

        /* Allocate and initialize the MPOOL cookie. */
        if ((mp = calloc(1, sizeof(*mp))) == NULL)
                return (NULL);
        TAILQ_INIT(&mp->lqh);
        for (entry = 0; entry < HASHSIZE; ++entry)
                TAILQ_INIT(&mp->hqh[entry]);
        mp->maxcache = maxcache;
        mp->npages = (pgno_t)(sb.st_size / pagesize);
        mp->pagesize = pagesize;
        mp->fd = fd;
        return mp;
}

/*
 * mpool_filter --
 *      Initialize input/output filters.
 */
void
mpool_filter(MPOOL *mp, void (*pgin)(void *, pgno_t, void *),
    void (*pgout)(void *, pgno_t, void *), void *pgcookie)
{
        mp->pgin = pgin;
        mp->pgout = pgout;
        mp->pgcookie = pgcookie;
}
        
/*
 * mpool_new --
 *      Get a new page of memory.
 */
void *
mpool_newf(MPOOL *mp, pgno_t *pgnoaddr, unsigned int flags)
{
        struct _hqh *head;
        BKT *bp;

        if (mp->npages == MAX_PAGE_NUMBER) {
                (void)fprintf(stderr, "mpool_new: page allocation overflow.\n");
                abort();
        }
#ifdef STATISTICS
        ++mp->pagenew;
#endif
        /*
         * Get a BKT from the cache.  Assign a new page number, attach
         * it to the head of the hash chain, the tail of the lru chain,
         * and return.
         */
        if ((bp = mpool_bkt(mp)) == NULL)
                return NULL;

        if (flags == MPOOL_PAGE_REQUEST) {
                mp->npages++;
                bp->pgno = *pgnoaddr;
        } else
                bp->pgno = *pgnoaddr = mp->npages++;

        bp->flags = MPOOL_PINNED | MPOOL_INUSE;

        head = &mp->hqh[HASHKEY(bp->pgno)];
        TAILQ_INSERT_HEAD(head, bp, hq);
        TAILQ_INSERT_TAIL(&mp->lqh, bp, q);
        return bp->page;
}

void *
mpool_new(MPOOL *mp, pgno_t *pgnoaddr)
{
        return mpool_newf(mp, pgnoaddr, 0);
}

int
mpool_delete(MPOOL *mp, void *page)
{
        struct _hqh *head;
        BKT *bp;

        bp = (void *)((char *)page - sizeof(BKT));

#ifdef DEBUG
        if (!(bp->flags & MPOOL_PINNED)) {
               (void)fprintf(stderr,
                   "%s: page %d not pinned\n", __func__, bp->pgno);
               abort();
        }
#endif

        /* Remove from the hash and lru queues. */
        head = &mp->hqh[HASHKEY(bp->pgno)];
        TAILQ_REMOVE(head, bp, hq);
        TAILQ_REMOVE(&mp->lqh, bp, q);

        free(bp);
        return RET_SUCCESS;
}

/*
 * mpool_get
 *      Get a page.
 */
/*ARGSUSED*/
void *
mpool_get(MPOOL *mp, pgno_t pgno, unsigned int flags)
{
        struct _hqh *head;
        BKT *bp;
        off_t off;
        ssize_t nr;

        /* Check for attempt to retrieve a non-existent page. */
        if (pgno >= mp->npages) {
                errno = EINVAL;
                return NULL;
        }

#ifdef STATISTICS
        ++mp->pageget;
#endif

        /* Check for a page that is cached. */
        if ((bp = mpool_look(mp, pgno)) != NULL) {
#ifdef DEBUG
                if (!(flags & MPOOL_IGNOREPIN) && bp->flags & MPOOL_PINNED) {
                        (void)fprintf(stderr,
                            "mpool_get: page %d already pinned\n", bp->pgno);
                        abort();
                }
#endif
                /*
                 * Move the page to the head of the hash chain and the tail
                 * of the lru chain.
                 */
                head = &mp->hqh[HASHKEY(bp->pgno)];
                TAILQ_REMOVE(head, bp, hq);
                TAILQ_INSERT_HEAD(head, bp, hq);
                TAILQ_REMOVE(&mp->lqh, bp, q);
                TAILQ_INSERT_TAIL(&mp->lqh, bp, q);

                /* Return a pinned page. */
                if (!(flags & MPOOL_IGNOREPIN))
                        bp->flags |= MPOOL_PINNED;
                return bp->page;
        }

        /* Get a page from the cache. */
        if ((bp = mpool_bkt(mp)) == NULL)
                return NULL;

        /* Read in the contents. */
#ifdef STATISTICS
        ++mp->pageread;
#endif
        off = mp->pagesize * pgno;
        if (off / mp->pagesize != pgno) {
                /* Run past the end of the file, or at least the part we
                   can address without large-file support?  */
                errno = E2BIG;
                return NULL;
        }

        if ((nr = pread(mp->fd, bp->page, (size_t)mp->pagesize, off)) != (int)mp->pagesize) {
                if (nr > 0) {
                        errno = EFTYPE;
                        return NULL;
                } else if (nr == 0) {
                        /*
                         * A zero-length reads, means you need to create a
                         * new page.
                         */
                        memset(bp->page, 0, mp->pagesize);
                } else
                        return NULL;
        }

        /* Set the page number, pin the page. */
        bp->pgno = pgno;
        if (!(flags & MPOOL_IGNOREPIN))
                bp->flags = MPOOL_PINNED;
bp->flags |= MPOOL_INUSE;

        /*
         * Add the page to the head of the hash chain and the tail
         * of the lru chain.
         */
        head = &mp->hqh[HASHKEY(bp->pgno)];
        TAILQ_INSERT_HEAD(head, bp, hq);
        TAILQ_INSERT_TAIL(&mp->lqh, bp, q);

        /* Run through the user's filter. */
        if (mp->pgin != NULL)
                (mp->pgin)(mp->pgcookie, bp->pgno, bp->page);

        return bp->page;
}

/*
 * mpool_put
 *      Return a page.
 */
/*ARGSUSED*/
int
mpool_put(MPOOL *mp, void *page, u_int flags)
{
        BKT *bp;

#ifdef STATISTICS
        ++mp->pageput;
#endif
        bp = (void *)((intptr_t)page - sizeof(BKT));
#ifdef DEBUG
        if (!(bp->flags & MPOOL_PINNED)) {
                (void)fprintf(stderr,
                    "mpool_put: page %d not pinned\n", bp->pgno);
                abort();
        }
#endif
        bp->flags &= ~MPOOL_PINNED;
        if (flags & MPOOL_DIRTY)
                bp->flags |= flags & MPOOL_DIRTY;
        return (RET_SUCCESS);
}

/*
 * mpool_close
 *      Close the buffer pool.
 */
int
mpool_close(MPOOL *mp)
{
        BKT *bp;

        /* Free up any space allocated to the lru pages. */
        while (!TAILQ_EMPTY(&mp->lqh)) {
                bp = TAILQ_FIRST(&mp->lqh);
                TAILQ_REMOVE(&mp->lqh, bp, q);
                free(bp);
        }

        /* Free the MPOOL cookie. */
        free(mp);
        return RET_SUCCESS;
}

/*
 * mpool_sync
 *      Sync the pool to disk.
 */
int
mpool_sync(MPOOL *mp)
{
        BKT *bp;

        /* Walk the lru chain, flushing any dirty pages to disk. */
        TAILQ_FOREACH(bp, &mp->lqh, q)
                if (bp->flags & MPOOL_DIRTY &&
                    mpool_write(mp, bp) == RET_ERROR)
                        return RET_ERROR;

        /* Sync the file descriptor. */
        return fsync(mp->fd) ? RET_ERROR : RET_SUCCESS;
}

/*
 * mpool_bkt
 *      Get a page from the cache (or create one).
 */
static BKT *
mpool_bkt(MPOOL *mp)
{
        struct _hqh *head;
        BKT *bp;

        /* If under the max cached, always create a new page. */
        if (mp->curcache < mp->maxcache)
                goto new;

        /*
         * If the cache is max'd out, walk the lru list for a buffer we
         * can flush.  If we find one, write it (if necessary) and take it
         * off any lists.  If we don't find anything we grow the cache anyway.
         * The cache never shrinks.
         */
        TAILQ_FOREACH(bp, &mp->lqh, q)
                if (!(bp->flags & MPOOL_PINNED)) {
                        /* Flush if dirty. */
                        if (bp->flags & MPOOL_DIRTY &&
                            mpool_write(mp, bp) == RET_ERROR)
                                return NULL;
#ifdef STATISTICS
                        ++mp->pageflush;
#endif
                        /* Remove from the hash and lru queues. */
                        head = &mp->hqh[HASHKEY(bp->pgno)];
                        TAILQ_REMOVE(head, bp, hq);
                        TAILQ_REMOVE(&mp->lqh, bp, q);
#ifdef DEBUG
                        {
                                void *spage = bp->page;
                                (void)memset(bp, 0xff,
                                    (size_t)(sizeof(BKT) + mp->pagesize));
                                bp->page = spage;
                        }
#endif
                        return bp;
                }

new:    if ((bp = calloc(1, (size_t)(sizeof(BKT) + mp->pagesize))) == NULL)
                return NULL;
#ifdef STATISTICS
        ++mp->pagealloc;
#endif
#if defined(DEBUG) || defined(PURIFY)
        (void)memset(bp, 0xff, (size_t)(sizeof(BKT) + mp->pagesize));
#endif
        bp->page = (void *)((intptr_t)bp + sizeof(BKT));
        ++mp->curcache;
        return bp;
}

/*
 * mpool_write
 *      Write a page to disk.
 */
static int
mpool_write(MPOOL *mp, BKT *bp)
{
        off_t off;

#ifdef STATISTICS
        ++mp->pagewrite;
#endif

        /* Run through the user's filter. */
        if (mp->pgout)
                (mp->pgout)(mp->pgcookie, bp->pgno, bp->page);

        off = mp->pagesize * bp->pgno;
        if (off / mp->pagesize != bp->pgno) {
                /* Run past the end of the file, or at least the part we
                   can address without large-file support?  */
                errno = E2BIG;
                return RET_ERROR;
        }

        if (pwrite(mp->fd, bp->page, (size_t)mp->pagesize, off) !=
            (ssize_t)mp->pagesize)
                return RET_ERROR;

        /*
         * Re-run through the input filter since this page may soon be
         * accessed via the cache, and whatever the user's output filter
         * did may screw things up if we don't let the input filter
         * restore the in-core copy.
         */
        if (mp->pgin)
                (mp->pgin)(mp->pgcookie, bp->pgno, bp->page);

        bp->flags &= ~MPOOL_DIRTY;
        return RET_SUCCESS;
}

/*
 * mpool_look
 *      Lookup a page in the cache.
 */
static BKT *
mpool_look(MPOOL *mp, pgno_t pgno)
{
        struct _hqh *head;
        BKT *bp;

        head = &mp->hqh[HASHKEY(pgno)];
        TAILQ_FOREACH(bp, head, hq)
                if (bp->pgno == pgno) {
#ifdef STATISTICS
                        ++mp->cachehit;
#endif
                        return bp;
                }
#ifdef STATISTICS
        ++mp->cachemiss;
#endif
        return NULL;
}

#ifdef STATISTICS
/*
 * mpool_stat
 *      Print out cache statistics.
 */
void
mpool_stat(mp)
        MPOOL *mp;
{
        BKT *bp;
        int cnt;
        const char *sep;

        (void)fprintf(stderr, "%lu pages in the file\n", (u_long)mp->npages);
        (void)fprintf(stderr,
            "page size %lu, cacheing %lu pages of %lu page max cache\n",
            (u_long)mp->pagesize, (u_long)mp->curcache, (u_long)mp->maxcache);
        (void)fprintf(stderr, "%lu page puts, %lu page gets, %lu page new\n",
            mp->pageput, mp->pageget, mp->pagenew);
        (void)fprintf(stderr, "%lu page allocs, %lu page flushes\n",
            mp->pagealloc, mp->pageflush);
        if (mp->cachehit + mp->cachemiss)
                (void)fprintf(stderr,
                    "%.0f%% cache hit rate (%lu hits, %lu misses)\n", 
                    ((double)mp->cachehit / (mp->cachehit + mp->cachemiss))
                    * 100, mp->cachehit, mp->cachemiss);
        (void)fprintf(stderr, "%lu page reads, %lu page writes\n",
            mp->pageread, mp->pagewrite);

        sep = "";
        cnt = 0;
        TAILQ_FOREACH(bp, &mp->lqh, q) {
                (void)fprintf(stderr, "%s%d", sep, bp->pgno);
                if (bp->flags & MPOOL_DIRTY)
                        (void)fprintf(stderr, "d");
                if (bp->flags & MPOOL_PINNED)
                        (void)fprintf(stderr, "P");
                if (++cnt == 10) {
                        sep = "\n";
                        cnt = 0;
                } else
                        sep = ", ";
                        
        }
        (void)fprintf(stderr, "\n");
}
#endif