Update.

[glibc.git] / db2 / mp / mp_sync.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  All rights reserved.
 */
#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)mp_sync.c     10.25 (Sleepycat) 4/26/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#endif

#include "db_int.h"
#include "shqueue.h"
#include "db_shash.h"
#include "mp.h"
#include "common_ext.h"

static int __bhcmp __P((const void *, const void *));
static int __memp_fsync __P((DB_MPOOLFILE *));

/*
 * memp_sync --
 *      Mpool sync function.
 */
int
memp_sync(dbmp, lsnp)
        DB_MPOOL *dbmp;
        DB_LSN *lsnp;
{
        BH *bhp, **bharray;
        DB_ENV *dbenv;
        MPOOL *mp;
        MPOOLFILE *mfp;
        int ar_cnt, cnt, nalloc, next, ret, wrote;

        dbenv = dbmp->dbenv;

        if (dbenv->lg_info == NULL) {
                __db_err(dbenv, "memp_sync: requires logging");
                return (EINVAL);
        }

        /*
         * We try and write the buffers in page order so that the underlying
         * filesystem doesn't have to seek and can write contiguous blocks,
         * plus, we don't want to hold the region lock while we write the
         * buffers.  Get memory to hold the buffer pointers.  Get a good-size
         * block, too, because we realloc while holding the region lock if we
         * run out.
         */
        if ((bharray =
            (BH **)__db_malloc((nalloc = 1024) * sizeof(BH *))) == NULL)
                return (ENOMEM);

        LOCKREGION(dbmp);

        /*
         * If the application is asking about a previous call to memp_sync(),
         * and we haven't found any buffers that the application holding the
         * pin couldn't write, return yes or no based on the current count.
         * Note, if the application is asking about a LSN *smaller* than one
         * we've already handled or are currently handling, then we return a
         * result based on the count for the larger LSN.
         */
        mp = dbmp->mp;
        if (!F_ISSET(mp, MP_LSN_RETRY) && log_compare(lsnp, &mp->lsn) <= 0) {
                if (mp->lsn_cnt == 0) {
                        *lsnp = mp->lsn;
                        ret = 0;
                } else
                        ret = DB_INCOMPLETE;
                goto done;
        }

        /* Else, it's a new checkpoint. */
        F_CLR(mp, MP_LSN_RETRY);

        /*
         * Save the LSN.  We know that it's a new LSN or larger than the one
         * for which we were already doing a checkpoint.  (BTW, I don't expect
         * to see multiple LSN's from the same or multiple processes, but You
         * Just Never Know.  Responding as if they all called with the largest
         * of the LSNs specified makes everything work.)
         *
         * We don't currently use the LSN we save.  We could potentially save
         * the last-written LSN in each buffer header and use it to determine
         * what buffers need to be written.  The problem with this is that it's
         * sizeof(LSN) more bytes of buffer header.  We currently write all the
         * dirty buffers instead.
         *
         * Walk the list of shared memory segments clearing the count of
         * buffers waiting to be written.
         */
        mp->lsn = *lsnp;
        mp->lsn_cnt = 0;
        for (mfp = SH_TAILQ_FIRST(&dbmp->mp->mpfq, __mpoolfile);
            mfp != NULL; mfp = SH_TAILQ_NEXT(mfp, q, __mpoolfile))
                mfp->lsn_cnt = 0;

        /*
         * Walk the list of buffers and mark all dirty buffers to be written
         * and all pinned buffers to be potentially written (we can't know if
         * we'll need to write them until the holding process returns them to
         * the cache).  We do this in one pass while holding the region locked
         * so that processes can't make new buffers dirty, causing us to never
         * finish.  Since the application may have restarted the sync, clear
         * any BH_WRITE flags that appear to be left over from previous calls.
         *
         * Keep a count of the total number of buffers we need to write in
         * MPOOL->lsn_cnt, and for each file, in MPOOLFILE->lsn_count.
         */
        ar_cnt = 0;
        for (bhp = SH_TAILQ_FIRST(&mp->bhq, __bh);
            bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, q, __bh))
                if (F_ISSET(bhp, BH_DIRTY) || bhp->ref != 0) {
                        F_SET(bhp, BH_WRITE);

                        ++mp->lsn_cnt;

                        mfp = R_ADDR(dbmp, bhp->mf_offset);
                        ++mfp->lsn_cnt;

                        /*
                         * If the buffer isn't in use, we should be able to
                         * write it immediately, so save a reference to it.
                         */
                        if (bhp->ref == 0) {
                                if (ar_cnt == nalloc) {
                                        nalloc *= 2;
                                        if ((bharray =
                                            (BH **)__db_realloc(bharray,
                                            nalloc * sizeof(BH *))) == NULL) {
                                                ret = ENOMEM;
                                                goto err;
                                        }
                                }
                                bharray[ar_cnt++] = bhp;
                        }
                } else
                        if (F_ISSET(bhp, BH_WRITE))
                                F_CLR(bhp, BH_WRITE);

        /* If there no buffers we can write immediately, we're done. */
        if (ar_cnt == 0) {
                ret = mp->lsn_cnt ? DB_INCOMPLETE : 0;
                goto done;
        }

        /* Lock down the buffers and their contents. */
        for (cnt = 0; cnt < ar_cnt; ++cnt)
                ++bharray[cnt]->ref;

        UNLOCKREGION(dbmp);

        /* Sort the buffers we're going to write. */
        qsort(bharray, ar_cnt, sizeof(BH *), __bhcmp);

        LOCKREGION(dbmp);

        /* Walk the array, writing buffers. */
        for (next = 0; next < ar_cnt; ++next) {
                /*
                 * It's possible for a thread to have gotten the buffer since
                 * we listed it for writing.  If the reference count is still
                 * 1, we're the only ones using the buffer, go ahead and write.
                 * If it's >1, then skip the buffer and assume that it will be
                 * written when it's returned to the cache.
                 */
                if (bharray[next]->ref > 1) {
                        --bharray[next]->ref;
                        continue;
                }

                /* Write the buffer. */
                mfp = R_ADDR(dbmp, bharray[next]->mf_offset);
                ret = __memp_bhwrite(dbmp, mfp, bharray[next], NULL, &wrote);

                /* Release the buffer. */
                --bharray[next]->ref;

                /* If there's an error, release the rest of the buffers. */
                if (ret != 0 || !wrote) {
                        /*
                         * Any process syncing the shared memory buffer pool
                         * had better be able to write to any underlying file.
                         * Be understanding, but firm, on this point.
                         */
                        if (ret == 0) {
                                __db_err(dbenv, "%s: unable to flush page: %lu",
                                    __memp_fns(dbmp, mfp),
                                    (u_long)bharray[next]->pgno);
                                ret = EPERM;
                        }

                        while (++next < ar_cnt)
                                --bharray[next]->ref;
                        goto err;
                }
        }
        ret = mp->lsn_cnt ? DB_INCOMPLETE : 0;

done:
        if (0) {
err:            /*
                 * On error, clear:
                 *      MPOOL->lsn_cnt (the total sync count)
                 *      MPOOLFILE->lsn_cnt (the per-file sync count)
                 *      BH_WRITE flag (the scheduled for writing flag)
                 */
                mp->lsn_cnt = 0;
                for (mfp = SH_TAILQ_FIRST(&dbmp->mp->mpfq, __mpoolfile);
                    mfp != NULL; mfp = SH_TAILQ_NEXT(mfp, q, __mpoolfile))
                        mfp->lsn_cnt = 0;
                for (bhp = SH_TAILQ_FIRST(&mp->bhq, __bh);
                    bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, q, __bh))
                        F_CLR(bhp, BH_WRITE);
        }
        UNLOCKREGION(dbmp);
        __db_free(bharray);
        return (ret);
}

/*
 * memp_fsync --
 *      Mpool file sync function.
 */
int
memp_fsync(dbmfp)
        DB_MPOOLFILE *dbmfp;
{
        DB_MPOOL *dbmp;
        int is_tmp;

        dbmp = dbmfp->dbmp;

        /*
         * If this handle doesn't have a file descriptor that's open for
         * writing, or if the file is a temporary, there's no reason to
         * proceed further.
         */
        if (F_ISSET(dbmfp, MP_READONLY))
                return (0);

        LOCKREGION(dbmp);
        is_tmp = F_ISSET(dbmfp->mfp, MP_TEMP);
        UNLOCKREGION(dbmp);
        if (is_tmp)
                return (0);

        return (__memp_fsync(dbmfp));
}

/*
 * __mp_xxx_fd --
 *      Return a file descriptor for DB 1.85 compatibility locking.
 *
 * PUBLIC: int __mp_xxx_fd __P((DB_MPOOLFILE *, int *));
 */
int
__mp_xxx_fd(dbmfp, fdp)
        DB_MPOOLFILE *dbmfp;
        int *fdp;
{
        int ret;

        /*
         * This is a truly spectacular layering violation, intended ONLY to
         * support compatibility for the DB 1.85 DB->fd call.
         *
         * Sync the database file to disk, creating the file as necessary.
         *
         * We skip the MP_READONLY and MP_TEMP tests done by memp_fsync(3).
         * The MP_READONLY test isn't interesting because we will either
         * already have a file descriptor (we opened the database file for
         * reading) or we aren't readonly (we created the database which
         * requires write privileges).  The MP_TEMP test isn't interesting
         * because we want to write to the backing file regardless so that
         * we get a file descriptor to return.
         */
        ret = dbmfp->fd == -1 ? __memp_fsync(dbmfp) : 0;

        return ((*fdp = dbmfp->fd) == -1 ? ENOENT : ret);
}

/*
 * __memp_fsync --
 *      Mpool file internal sync function.
 */
static int
__memp_fsync(dbmfp)
        DB_MPOOLFILE *dbmfp;
{
        BH *bhp, **bharray;
        DB_MPOOL *dbmp;
        size_t mf_offset;
        int ar_cnt, cnt, nalloc, next, pincnt, ret, wrote;

        ret = 0;
        dbmp = dbmfp->dbmp;
        mf_offset = R_OFFSET(dbmp, dbmfp->mfp);

        /*
         * We try and write the buffers in page order so that the underlying
         * filesystem doesn't have to seek and can write contiguous blocks,
         * plus, we don't want to hold the region lock while we write the
         * buffers.  Get memory to hold the buffer pointers.  Get a good-size
         * block, too, because we realloc while holding the region lock if we
         * run out.
         */
        nalloc = 1024;
        if ((bharray =
            (BH **)__db_malloc((size_t)nalloc * sizeof(BH *))) == NULL)
                return (ENOMEM);

        LOCKREGION(dbmp);

        /*
         * Walk the LRU list of buffer headers, and get a list of buffers to
         * write for this MPOOLFILE.
         */
        ar_cnt = pincnt = 0;
        for (bhp = SH_TAILQ_FIRST(&dbmp->mp->bhq, __bh);
            bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, q, __bh)) {
                if (!F_ISSET(bhp, BH_DIRTY) || bhp->mf_offset != mf_offset)
                        continue;
                if (bhp->ref != 0 || F_ISSET(bhp, BH_LOCKED)) {
                        ++pincnt;
                        continue;
                }

                if (ar_cnt == nalloc) {
                        nalloc *= 2;
                        if ((bharray = (BH **)__db_realloc(bharray,
                            nalloc * sizeof(BH *))) == NULL) {
                                ret = ENOMEM;
                                goto err;
                        }
                }

                bharray[ar_cnt++] = bhp;
        }

        /* Lock down the buffers and their contents. */
        for (cnt = 0; cnt < ar_cnt; ++cnt)
                ++bharray[cnt]->ref;

        UNLOCKREGION(dbmp);

        /* Sort the buffers we're going to write. */
        qsort(bharray, ar_cnt, sizeof(BH *), __bhcmp);

        LOCKREGION(dbmp);

        /* Walk the array, writing buffers. */
        for (next = 0; next < ar_cnt; ++next) {
                /*
                 * It's possible for a thread to have gotten the buffer since
                 * we listed it for writing.  If the reference count is still
                 * 1, we're the only ones using the buffer, go ahead and write.
                 * If it's >1, then skip the buffer and assume that it will be
                 * written when it's returned to the cache.
                 */
                if (bharray[next]->ref > 1) {
                        ++pincnt;

                        --bharray[next]->ref;
                        continue;
                }

                /* Write the buffer. */
                ret = __memp_pgwrite(dbmfp, bharray[next], NULL, &wrote);

                /* Release the buffer. */
                --bharray[next]->ref;

                /* If there's an error, release the rest of the buffers. */
                if (ret != 0) {
                        while (++next < ar_cnt)
                                --bharray[next]->ref;
                        goto err;
                }
                if (!wrote)
                        ++pincnt;
        }

err:    UNLOCKREGION(dbmp);

        __db_free(bharray);

        /*
         * Sync the underlying file as the last thing we do, so that the OS
         * has maximal opportunity to flush buffers before we request it.
         *
         * XXX:
         * Don't lock the region around the sync, fsync(2) has no atomicity
         * issues.
         */
        if (ret == 0)
                return (pincnt == 0 ? __db_fsync(dbmfp->fd) : DB_INCOMPLETE);
        return (ret);
}

/*
 * memp_trickle --
 *      Keep a specified percentage of the buffers clean.
 */
int
memp_trickle(dbmp, pct, nwrotep)
        DB_MPOOL *dbmp;
        int pct, *nwrotep;
{
        BH *bhp;
        MPOOL *mp;
        MPOOLFILE *mfp;
        u_long total;
        int ret, wrote;

        mp = dbmp->mp;
        if (nwrotep != NULL)
                *nwrotep = 0;

        if (pct < 1 || pct > 100)
                return (EINVAL);

        LOCKREGION(dbmp);

        /*
         * If there are sufficient clean buffers, or no buffers or no dirty
         * buffers, we're done.
         *
         * XXX
         * Using st_page_clean and st_page_dirty is our only choice at the
         * moment, but it's not as correct as we might like in the presence
         * of pools with more than one buffer size, as a free 512-byte buffer
         * isn't the same as a free 8K buffer.
         */
loop:   total = mp->stat.st_page_clean + mp->stat.st_page_dirty;
        if (total == 0 || mp->stat.st_page_dirty == 0 ||
            (mp->stat.st_page_clean * 100) / total >= (u_long)pct) {
                UNLOCKREGION(dbmp);
                return (0);
        }

        /* Loop until we write a buffer. */
        for (bhp = SH_TAILQ_FIRST(&mp->bhq, __bh);
            bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, q, __bh)) {
                if (bhp->ref != 0 ||
                    !F_ISSET(bhp, BH_DIRTY) || F_ISSET(bhp, BH_LOCKED))
                        continue;

                mfp = R_ADDR(dbmp, bhp->mf_offset);

                /*
                 * We can't write to temporary files -- see the comment in
                 * mp_bh.c:__memp_bhwrite().
                 */
                if (F_ISSET(mfp, MP_TEMP))
                        continue;

                if ((ret = __memp_bhwrite(dbmp, mfp, bhp, NULL, &wrote)) != 0)
                        goto err;

                /*
                 * Any process syncing the shared memory buffer pool had better
                 * be able to write to any underlying file.  Be understanding,
                 * but firm, on this point.
                 */
                if (!wrote) {
                        __db_err(dbmp->dbenv, "%s: unable to flush page: %lu",
                            __memp_fns(dbmp, mfp), (u_long)bhp->pgno);
                        ret = EPERM;
                        goto err;
                }

                ++mp->stat.st_page_trickle;
                if (nwrotep != NULL)
                        ++*nwrotep;
                goto loop;
        }

        /* No more buffers to write. */
        return (0);

err:    UNLOCKREGION(dbmp);
        return (ret);
}

static int
__bhcmp(p1, p2)
        const void *p1, *p2;
{
        BH *bhp1, *bhp2;

        bhp1 = *(BH * const *)p1;
        bhp2 = *(BH * const *)p2;

        /* Sort by file (shared memory pool offset). */
        if (bhp1->mf_offset < bhp2->mf_offset)
                return (-1);
        if (bhp1->mf_offset > bhp2->mf_offset)
                return (1);

        /* Sort by page in file. */
        return (bhp1->pgno < bhp2->pgno ? -1 : 1);
}