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ufs_dirhash.c

/*-
 * Copyright (c) 2001, 2002 Ian Dowse.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

/*
 * This implements a hash-based lookup scheme for UFS directories.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/ufs/ufs/ufs_dirhash.c,v 1.23 2005/10/31 15:41:28 rwatson Exp $");

#include "opt_ufs.h"

#ifdef UFS_DIRHASH

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/fnv_hash.h>
#include <sys/proc.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <vm/uma.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/dir.h>
#include <ufs/ufs/dirhash.h>
#include <ufs/ufs/extattr.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/ufs_extern.h>

#define WRAPINCR(val, limit)  (((val) + 1 == (limit)) ? 0 : ((val) + 1))
#define WRAPDECR(val, limit)  (((val) == 0) ? ((limit) - 1) : ((val) - 1))
#define OFSFMT(vp)            ((vp)->v_mount->mnt_maxsymlinklen <= 0)
#define BLKFREE2IDX(n)        ((n) > DH_NFSTATS ? DH_NFSTATS : (n))

static MALLOC_DEFINE(M_DIRHASH, "ufs_dirhash", "UFS directory hash tables");

static SYSCTL_NODE(_vfs, OID_AUTO, ufs, CTLFLAG_RD, 0, "UFS filesystem");

static int ufs_mindirhashsize = DIRBLKSIZ * 5;
SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_minsize, CTLFLAG_RW,
    &ufs_mindirhashsize,
    0, "minimum directory size in bytes for which to use hashed lookup");
static int ufs_dirhashmaxmem = 2 * 1024 * 1024;
SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_maxmem, CTLFLAG_RW, &ufs_dirhashmaxmem,
    0, "maximum allowed dirhash memory usage");
static int ufs_dirhashmem;
SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_mem, CTLFLAG_RD, &ufs_dirhashmem,
    0, "current dirhash memory usage");
static int ufs_dirhashcheck = 0;
SYSCTL_INT(_vfs_ufs, OID_AUTO, dirhash_docheck, CTLFLAG_RW, &ufs_dirhashcheck,
    0, "enable extra sanity tests");


static int ufsdirhash_hash(struct dirhash *dh, char *name, int namelen);
static void ufsdirhash_adjfree(struct dirhash *dh, doff_t offset, int diff);
static void ufsdirhash_delslot(struct dirhash *dh, int slot);
static int ufsdirhash_findslot(struct dirhash *dh, char *name, int namelen,
         doff_t offset);
static doff_t ufsdirhash_getprev(struct direct *dp, doff_t offset);
static int ufsdirhash_recycle(int wanted);

static uma_zone_t ufsdirhash_zone;

#define DIRHASHLIST_LOCK()          mtx_lock(&ufsdirhash_mtx)
#define DIRHASHLIST_UNLOCK()        mtx_unlock(&ufsdirhash_mtx)
#define DIRHASH_LOCK(dh)            mtx_lock(&(dh)->dh_mtx)
#define DIRHASH_UNLOCK(dh)          mtx_unlock(&(dh)->dh_mtx)
#define DIRHASH_BLKALLOC_WAITOK()   uma_zalloc(ufsdirhash_zone, M_WAITOK)
#define DIRHASH_BLKFREE(ptr)        uma_zfree(ufsdirhash_zone, (ptr))

/* Dirhash list; recently-used entries are near the tail. */
static TAILQ_HEAD(, dirhash) ufsdirhash_list;

/* Protects: ufsdirhash_list, `dh_list' field, ufs_dirhashmem. */
static struct mtx ufsdirhash_mtx;

/*
 * Locking order:
 *    ufsdirhash_mtx
 *    dh_mtx
 *
 * The dh_mtx mutex should be acquired either via the inode lock, or via
 * ufsdirhash_mtx. Only the owner of the inode may free the associated
 * dirhash, but anything can steal its memory and set dh_hash to NULL.
 */

/*
 * Attempt to build up a hash table for the directory contents in
 * inode 'ip'. Returns 0 on success, or -1 of the operation failed.
 */
int
ufsdirhash_build(struct inode *ip)
{
      struct dirhash *dh;
      struct buf *bp = NULL;
      struct direct *ep;
      struct vnode *vp;
      doff_t bmask, pos;
      int dirblocks, i, j, memreqd, nblocks, narrays, nslots, slot;

      /* Check if we can/should use dirhash. */
      if (ip->i_dirhash == NULL) {
            if (ip->i_size < ufs_mindirhashsize || OFSFMT(ip->i_vnode))
                  return (-1);
      } else {
            /* Hash exists, but sysctls could have changed. */
            if (ip->i_size < ufs_mindirhashsize ||
                ufs_dirhashmem > ufs_dirhashmaxmem) {
                  ufsdirhash_free(ip);
                  return (-1);
            }
            /* Check if hash exists and is intact (note: unlocked read). */
            if (ip->i_dirhash->dh_hash != NULL)
                  return (0);
            /* Free the old, recycled hash and build a new one. */
            ufsdirhash_free(ip);
      }

      /* Don't hash removed directories. */
      if (ip->i_effnlink == 0)
            return (-1);

      vp = ip->i_vnode;
      /* Allocate 50% more entries than this dir size could ever need. */
      KASSERT(ip->i_size >= DIRBLKSIZ, ("ufsdirhash_build size"));
      nslots = ip->i_size / DIRECTSIZ(1);
      nslots = (nslots * 3 + 1) / 2;
      narrays = howmany(nslots, DH_NBLKOFF);
      nslots = narrays * DH_NBLKOFF;
      dirblocks = howmany(ip->i_size, DIRBLKSIZ);
      nblocks = (dirblocks * 3 + 1) / 2;

      memreqd = sizeof(*dh) + narrays * sizeof(*dh->dh_hash) +
          narrays * DH_NBLKOFF * sizeof(**dh->dh_hash) +
          nblocks * sizeof(*dh->dh_blkfree);
      DIRHASHLIST_LOCK();
      if (memreqd + ufs_dirhashmem > ufs_dirhashmaxmem) {
            DIRHASHLIST_UNLOCK();
            if (memreqd > ufs_dirhashmaxmem / 2)
                  return (-1);

            /* Try to free some space. */
            if (ufsdirhash_recycle(memreqd) != 0)
                  return (-1);
            /* Enough was freed, and list has been locked. */
      }
      ufs_dirhashmem += memreqd;
      DIRHASHLIST_UNLOCK();

      /*
       * Use non-blocking mallocs so that we will revert to a linear
       * lookup on failure rather than potentially blocking forever.
       */
      MALLOC(dh, struct dirhash *, sizeof *dh, M_DIRHASH, M_NOWAIT | M_ZERO);
      if (dh == NULL) {
            DIRHASHLIST_LOCK();
            ufs_dirhashmem -= memreqd;
            DIRHASHLIST_UNLOCK();
            return (-1);
      }
      mtx_init(&dh->dh_mtx, "dirhash", NULL, MTX_DEF);
      MALLOC(dh->dh_hash, doff_t **, narrays * sizeof(dh->dh_hash[0]),
          M_DIRHASH, M_NOWAIT | M_ZERO);
      MALLOC(dh->dh_blkfree, u_int8_t *, nblocks * sizeof(dh->dh_blkfree[0]),
          M_DIRHASH, M_NOWAIT);
      if (dh->dh_hash == NULL || dh->dh_blkfree == NULL)
            goto fail;
      for (i = 0; i < narrays; i++) {
            if ((dh->dh_hash[i] = DIRHASH_BLKALLOC_WAITOK()) == NULL)
                  goto fail;
            for (j = 0; j < DH_NBLKOFF; j++)
                  dh->dh_hash[i][j] = DIRHASH_EMPTY;
      }

      /* Initialise the hash table and block statistics. */
      dh->dh_narrays = narrays;
      dh->dh_hlen = nslots;
      dh->dh_nblk = nblocks;
      dh->dh_dirblks = dirblocks;
      for (i = 0; i < dirblocks; i++)
            dh->dh_blkfree[i] = DIRBLKSIZ / DIRALIGN;
      for (i = 0; i < DH_NFSTATS; i++)
            dh->dh_firstfree[i] = -1;
      dh->dh_firstfree[DH_NFSTATS] = 0;
      dh->dh_seqopt = 0;
      dh->dh_seqoff = 0;
      dh->dh_score = DH_SCOREINIT;
      ip->i_dirhash = dh;

      bmask = VFSTOUFS(vp->v_mount)->um_mountp->mnt_stat.f_iosize - 1;
      pos = 0;
      while (pos < ip->i_size) {
            /* If necessary, get the next directory block. */
            if ((pos & bmask) == 0) {
                  if (bp != NULL)
                        brelse(bp);
                  if (UFS_BLKATOFF(vp, (off_t)pos, NULL, &bp) != 0)
                        goto fail;
            }

            /* Add this entry to the hash. */
            ep = (struct direct *)((char *)bp->b_data + (pos & bmask));
            if (ep->d_reclen == 0 || ep->d_reclen >
                DIRBLKSIZ - (pos & (DIRBLKSIZ - 1))) {
                  /* Corrupted directory. */
                  brelse(bp);
                  goto fail;
            }
            if (ep->d_ino != 0) {
                  /* Add the entry (simplified ufsdirhash_add). */
                  slot = ufsdirhash_hash(dh, ep->d_name, ep->d_namlen);
                  while (DH_ENTRY(dh, slot) != DIRHASH_EMPTY)
                        slot = WRAPINCR(slot, dh->dh_hlen);
                  dh->dh_hused++;
                  DH_ENTRY(dh, slot) = pos;
                  ufsdirhash_adjfree(dh, pos, -DIRSIZ(0, ep));
            }
            pos += ep->d_reclen;
      }

      if (bp != NULL)
            brelse(bp);
      DIRHASHLIST_LOCK();
      TAILQ_INSERT_TAIL(&ufsdirhash_list, dh, dh_list);
      dh->dh_onlist = 1;
      DIRHASHLIST_UNLOCK();
      return (0);

fail:
      if (dh->dh_hash != NULL) {
            for (i = 0; i < narrays; i++)
                  if (dh->dh_hash[i] != NULL)
                        DIRHASH_BLKFREE(dh->dh_hash[i]);
            FREE(dh->dh_hash, M_DIRHASH);
      }
      if (dh->dh_blkfree != NULL)
            FREE(dh->dh_blkfree, M_DIRHASH);
      mtx_destroy(&dh->dh_mtx);
      FREE(dh, M_DIRHASH);
      ip->i_dirhash = NULL;
      DIRHASHLIST_LOCK();
      ufs_dirhashmem -= memreqd;
      DIRHASHLIST_UNLOCK();
      return (-1);
}

/*
 * Free any hash table associated with inode 'ip'.
 */
void
ufsdirhash_free(struct inode *ip)
{
      struct dirhash *dh;
      int i, mem;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASHLIST_LOCK();
      DIRHASH_LOCK(dh);
      if (dh->dh_onlist)
            TAILQ_REMOVE(&ufsdirhash_list, dh, dh_list);
      DIRHASH_UNLOCK(dh);
      DIRHASHLIST_UNLOCK();

      /* The dirhash pointed to by 'dh' is exclusively ours now. */

      mem = sizeof(*dh);
      if (dh->dh_hash != NULL) {
            for (i = 0; i < dh->dh_narrays; i++)
                  DIRHASH_BLKFREE(dh->dh_hash[i]);
            FREE(dh->dh_hash, M_DIRHASH);
            FREE(dh->dh_blkfree, M_DIRHASH);
            mem += dh->dh_narrays * sizeof(*dh->dh_hash) +
                dh->dh_narrays * DH_NBLKOFF * sizeof(**dh->dh_hash) +
                dh->dh_nblk * sizeof(*dh->dh_blkfree);
      }
      mtx_destroy(&dh->dh_mtx);
      FREE(dh, M_DIRHASH);
      ip->i_dirhash = NULL;

      DIRHASHLIST_LOCK();
      ufs_dirhashmem -= mem;
      DIRHASHLIST_UNLOCK();
}

/*
 * Find the offset of the specified name within the given inode.
 * Returns 0 on success, ENOENT if the entry does not exist, or
 * EJUSTRETURN if the caller should revert to a linear search.
 *
 * If successful, the directory offset is stored in *offp, and a
 * pointer to a struct buf containing the entry is stored in *bpp. If
 * prevoffp is non-NULL, the offset of the previous entry within
 * the DIRBLKSIZ-sized block is stored in *prevoffp (if the entry
 * is the first in a block, the start of the block is used).
 */
int
ufsdirhash_lookup(struct inode *ip, char *name, int namelen, doff_t *offp,
    struct buf **bpp, doff_t *prevoffp)
{
      struct dirhash *dh, *dh_next;
      struct direct *dp;
      struct vnode *vp;
      struct buf *bp;
      doff_t blkoff, bmask, offset, prevoff;
      int i, slot;

      if ((dh = ip->i_dirhash) == NULL)
            return (EJUSTRETURN);
      /*
       * Move this dirhash towards the end of the list if it has a
       * score higher than the next entry, and acquire the dh_mtx.
       * Optimise the case where it's already the last by performing
       * an unlocked read of the TAILQ_NEXT pointer.
       *
       * In both cases, end up holding just dh_mtx.
       */
      if (TAILQ_NEXT(dh, dh_list) != NULL) {
            DIRHASHLIST_LOCK();
            DIRHASH_LOCK(dh);
            /*
             * If the new score will be greater than that of the next
             * entry, then move this entry past it. With both mutexes
             * held, dh_next won't go away, but its dh_score could
             * change; that's not important since it is just a hint.
             */
            if (dh->dh_hash != NULL &&
                (dh_next = TAILQ_NEXT(dh, dh_list)) != NULL &&
                dh->dh_score >= dh_next->dh_score) {
                  KASSERT(dh->dh_onlist, ("dirhash: not on list"));
                  TAILQ_REMOVE(&ufsdirhash_list, dh, dh_list);
                  TAILQ_INSERT_AFTER(&ufsdirhash_list, dh_next, dh,
                      dh_list);
            }
            DIRHASHLIST_UNLOCK();
      } else {
            /* Already the last, though that could change as we wait. */
            DIRHASH_LOCK(dh);
      }
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return (EJUSTRETURN);
      }

      /* Update the score. */
      if (dh->dh_score < DH_SCOREMAX)
            dh->dh_score++;

      vp = ip->i_vnode;
      bmask = VFSTOUFS(vp->v_mount)->um_mountp->mnt_stat.f_iosize - 1;
      blkoff = -1;
      bp = NULL;
restart:
      slot = ufsdirhash_hash(dh, name, namelen);

      if (dh->dh_seqopt) {
            /*
             * Sequential access optimisation. dh_seqoff contains the
             * offset of the directory entry immediately following
             * the last entry that was looked up. Check if this offset
             * appears in the hash chain for the name we are looking for.
             */
            for (i = slot; (offset = DH_ENTRY(dh, i)) != DIRHASH_EMPTY;
                i = WRAPINCR(i, dh->dh_hlen))
                  if (offset == dh->dh_seqoff)
                        break;
            if (offset == dh->dh_seqoff) {
                  /*
                   * We found an entry with the expected offset. This
                   * is probably the entry we want, but if not, the
                   * code below will turn off seqopt and retry.
                   */ 
                  slot = i;
            } else 
                  dh->dh_seqopt = 0;
      }

      for (; (offset = DH_ENTRY(dh, slot)) != DIRHASH_EMPTY;
          slot = WRAPINCR(slot, dh->dh_hlen)) {
            if (offset == DIRHASH_DEL)
                  continue;
            DIRHASH_UNLOCK(dh);

            if (offset < 0 || offset >= ip->i_size)
                  panic("ufsdirhash_lookup: bad offset in hash array");
            if ((offset & ~bmask) != blkoff) {
                  if (bp != NULL)
                        brelse(bp);
                  blkoff = offset & ~bmask;
                  if (UFS_BLKATOFF(vp, (off_t)blkoff, NULL, &bp) != 0)
                        return (EJUSTRETURN);
            }
            dp = (struct direct *)(bp->b_data + (offset & bmask));
            if (dp->d_reclen == 0 || dp->d_reclen >
                DIRBLKSIZ - (offset & (DIRBLKSIZ - 1))) {
                  /* Corrupted directory. */
                  brelse(bp);
                  return (EJUSTRETURN);
            }
            if (dp->d_namlen == namelen &&
                bcmp(dp->d_name, name, namelen) == 0) {
                  /* Found. Get the prev offset if needed. */
                  if (prevoffp != NULL) {
                        if (offset & (DIRBLKSIZ - 1)) {
                              prevoff = ufsdirhash_getprev(dp,
                                  offset);
                              if (prevoff == -1) {
                                    brelse(bp);
                                    return (EJUSTRETURN);
                              }
                        } else
                              prevoff = offset;
                        *prevoffp = prevoff;
                  }

                  /* Check for sequential access, and update offset. */
                  if (dh->dh_seqopt == 0 && dh->dh_seqoff == offset)
                        dh->dh_seqopt = 1;
                  dh->dh_seqoff = offset + DIRSIZ(0, dp);

                  *bpp = bp;
                  *offp = offset;
                  return (0);
            }

            DIRHASH_LOCK(dh);
            if (dh->dh_hash == NULL) {
                  DIRHASH_UNLOCK(dh);
                  if (bp != NULL)
                        brelse(bp);
                  ufsdirhash_free(ip);
                  return (EJUSTRETURN);
            }
            /*
             * When the name doesn't match in the seqopt case, go back
             * and search normally.
             */
            if (dh->dh_seqopt) {
                  dh->dh_seqopt = 0;
                  goto restart;
            }
      }
      DIRHASH_UNLOCK(dh);
      if (bp != NULL)
            brelse(bp);
      return (ENOENT);
}

/*
 * Find a directory block with room for 'slotneeded' bytes. Returns
 * the offset of the directory entry that begins the free space.
 * This will either be the offset of an existing entry that has free
 * space at the end, or the offset of an entry with d_ino == 0 at
 * the start of a DIRBLKSIZ block.
 *
 * To use the space, the caller may need to compact existing entries in
 * the directory. The total number of bytes in all of the entries involved
 * in the compaction is stored in *slotsize. In other words, all of
 * the entries that must be compacted are exactly contained in the
 * region beginning at the returned offset and spanning *slotsize bytes.
 *
 * Returns -1 if no space was found, indicating that the directory
 * must be extended.
 */
doff_t
ufsdirhash_findfree(struct inode *ip, int slotneeded, int *slotsize)
{
      struct direct *dp;
      struct dirhash *dh;
      struct buf *bp;
      doff_t pos, slotstart;
      int dirblock, error, freebytes, i;

      if ((dh = ip->i_dirhash) == NULL)
            return (-1);
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return (-1);
      }

      /* Find a directory block with the desired free space. */
      dirblock = -1;
      for (i = howmany(slotneeded, DIRALIGN); i <= DH_NFSTATS; i++)
            if ((dirblock = dh->dh_firstfree[i]) != -1)
                  break;
      if (dirblock == -1) {
            DIRHASH_UNLOCK(dh);
            return (-1);
      }

      KASSERT(dirblock < dh->dh_nblk &&
          dh->dh_blkfree[dirblock] >= howmany(slotneeded, DIRALIGN),
          ("ufsdirhash_findfree: bad stats"));
      DIRHASH_UNLOCK(dh);
      pos = dirblock * DIRBLKSIZ;
      error = UFS_BLKATOFF(ip->i_vnode, (off_t)pos, (char **)&dp, &bp);
      if (error)
            return (-1);

      /* Find the first entry with free space. */
      for (i = 0; i < DIRBLKSIZ; ) {
            if (dp->d_reclen == 0) {
                  brelse(bp);
                  return (-1);
            }
            if (dp->d_ino == 0 || dp->d_reclen > DIRSIZ(0, dp))
                  break;
            i += dp->d_reclen;
            dp = (struct direct *)((char *)dp + dp->d_reclen);
      }
      if (i > DIRBLKSIZ) {
            brelse(bp);
            return (-1);
      }
      slotstart = pos + i;

      /* Find the range of entries needed to get enough space */
      freebytes = 0;
      while (i < DIRBLKSIZ && freebytes < slotneeded) {
            freebytes += dp->d_reclen;
            if (dp->d_ino != 0)
                  freebytes -= DIRSIZ(0, dp);
            if (dp->d_reclen == 0) {
                  brelse(bp);
                  return (-1);
            }
            i += dp->d_reclen;
            dp = (struct direct *)((char *)dp + dp->d_reclen);
      }
      if (i > DIRBLKSIZ) {
            brelse(bp);
            return (-1);
      }
      if (freebytes < slotneeded)
            panic("ufsdirhash_findfree: free mismatch");
      brelse(bp);
      *slotsize = pos + i - slotstart;
      return (slotstart);
}

/*
 * Return the start of the unused space at the end of a directory, or
 * -1 if there are no trailing unused blocks.
 */
doff_t
ufsdirhash_enduseful(struct inode *ip)
{

      struct dirhash *dh;
      int i;

      if ((dh = ip->i_dirhash) == NULL)
            return (-1);
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return (-1);
      }

      if (dh->dh_blkfree[dh->dh_dirblks - 1] != DIRBLKSIZ / DIRALIGN) {
            DIRHASH_UNLOCK(dh);
            return (-1);
      }

      for (i = dh->dh_dirblks - 1; i >= 0; i--)
            if (dh->dh_blkfree[i] != DIRBLKSIZ / DIRALIGN)
                  break;
      DIRHASH_UNLOCK(dh);
      return ((doff_t)(i + 1) * DIRBLKSIZ);
}

/*
 * Insert information into the hash about a new directory entry. dirp
 * points to a struct direct containing the entry, and offset specifies
 * the offset of this entry.
 */
void
ufsdirhash_add(struct inode *ip, struct direct *dirp, doff_t offset)
{
      struct dirhash *dh;
      int slot;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      KASSERT(offset < dh->dh_dirblks * DIRBLKSIZ,
          ("ufsdirhash_add: bad offset"));
      /*
       * Normal hash usage is < 66%. If the usage gets too high then
       * remove the hash entirely and let it be rebuilt later.
       */
      if (dh->dh_hused >= (dh->dh_hlen * 3) / 4) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      /* Find a free hash slot (empty or deleted), and add the entry. */
      slot = ufsdirhash_hash(dh, dirp->d_name, dirp->d_namlen);
      while (DH_ENTRY(dh, slot) >= 0)
            slot = WRAPINCR(slot, dh->dh_hlen);
      if (DH_ENTRY(dh, slot) == DIRHASH_EMPTY)
            dh->dh_hused++;
      DH_ENTRY(dh, slot) = offset;

      /* Update the per-block summary info. */
      ufsdirhash_adjfree(dh, offset, -DIRSIZ(0, dirp));
      DIRHASH_UNLOCK(dh);
}

/*
 * Remove the specified directory entry from the hash. The entry to remove
 * is defined by the name in `dirp', which must exist at the specified
 * `offset' within the directory.
 */
void
ufsdirhash_remove(struct inode *ip, struct direct *dirp, doff_t offset)
{
      struct dirhash *dh;
      int slot;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      KASSERT(offset < dh->dh_dirblks * DIRBLKSIZ,
          ("ufsdirhash_remove: bad offset"));
      /* Find the entry */
      slot = ufsdirhash_findslot(dh, dirp->d_name, dirp->d_namlen, offset);

      /* Remove the hash entry. */
      ufsdirhash_delslot(dh, slot);

      /* Update the per-block summary info. */
      ufsdirhash_adjfree(dh, offset, DIRSIZ(0, dirp));
      DIRHASH_UNLOCK(dh);
}

/*
 * Change the offset associated with a directory entry in the hash. Used
 * when compacting directory blocks.
 */
void
ufsdirhash_move(struct inode *ip, struct direct *dirp, doff_t oldoff,
    doff_t newoff)
{
      struct dirhash *dh;
      int slot;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      KASSERT(oldoff < dh->dh_dirblks * DIRBLKSIZ &&
          newoff < dh->dh_dirblks * DIRBLKSIZ,
          ("ufsdirhash_move: bad offset"));
      /* Find the entry, and update the offset. */
      slot = ufsdirhash_findslot(dh, dirp->d_name, dirp->d_namlen, oldoff);
      DH_ENTRY(dh, slot) = newoff;
      DIRHASH_UNLOCK(dh);
}

/*
 * Inform dirhash that the directory has grown by one block that
 * begins at offset (i.e. the new length is offset + DIRBLKSIZ).
 */
void
ufsdirhash_newblk(struct inode *ip, doff_t offset)
{
      struct dirhash *dh;
      int block;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      KASSERT(offset == dh->dh_dirblks * DIRBLKSIZ,
          ("ufsdirhash_newblk: bad offset"));
      block = offset / DIRBLKSIZ;
      if (block >= dh->dh_nblk) {
            /* Out of space; must rebuild. */
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }
      dh->dh_dirblks = block + 1;

      /* Account for the new free block. */
      dh->dh_blkfree[block] = DIRBLKSIZ / DIRALIGN;
      if (dh->dh_firstfree[DH_NFSTATS] == -1)
            dh->dh_firstfree[DH_NFSTATS] = block;
      DIRHASH_UNLOCK(dh);
}

/*
 * Inform dirhash that the directory is being truncated.
 */
void
ufsdirhash_dirtrunc(struct inode *ip, doff_t offset)
{
      struct dirhash *dh;
      int block, i;

      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      KASSERT(offset <= dh->dh_dirblks * DIRBLKSIZ,
          ("ufsdirhash_dirtrunc: bad offset"));
      block = howmany(offset, DIRBLKSIZ);
      /*
       * If the directory shrinks to less than 1/8 of dh_nblk blocks
       * (about 20% of its original size due to the 50% extra added in
       * ufsdirhash_build) then free it, and let the caller rebuild
       * if necessary.
       */
      if (block < dh->dh_nblk / 8 && dh->dh_narrays > 1) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      /*
       * Remove any `first free' information pertaining to the
       * truncated blocks. All blocks we're removing should be
       * completely unused.
       */
      if (dh->dh_firstfree[DH_NFSTATS] >= block)
            dh->dh_firstfree[DH_NFSTATS] = -1;
      for (i = block; i < dh->dh_dirblks; i++)
            if (dh->dh_blkfree[i] != DIRBLKSIZ / DIRALIGN)
                  panic("ufsdirhash_dirtrunc: blocks in use");
      for (i = 0; i < DH_NFSTATS; i++)
            if (dh->dh_firstfree[i] >= block)
                  panic("ufsdirhash_dirtrunc: first free corrupt");
      dh->dh_dirblks = block;
      DIRHASH_UNLOCK(dh);
}

/*
 * Debugging function to check that the dirhash information about
 * a directory block matches its actual contents. Panics if a mismatch
 * is detected.
 *
 * On entry, `buf' should point to the start of an in-core
 * DIRBLKSIZ-sized directory block, and `offset' should contain the
 * offset from the start of the directory of that block.
 */
void
ufsdirhash_checkblock(struct inode *ip, char *buf, doff_t offset)
{
      struct dirhash *dh;
      struct direct *dp;
      int block, ffslot, i, nfree;

      if (!ufs_dirhashcheck)
            return;
      if ((dh = ip->i_dirhash) == NULL)
            return;
      DIRHASH_LOCK(dh);
      if (dh->dh_hash == NULL) {
            DIRHASH_UNLOCK(dh);
            ufsdirhash_free(ip);
            return;
      }

      block = offset / DIRBLKSIZ;
      if ((offset & (DIRBLKSIZ - 1)) != 0 || block >= dh->dh_dirblks)
            panic("ufsdirhash_checkblock: bad offset");

      nfree = 0;
      for (i = 0; i < DIRBLKSIZ; i += dp->d_reclen) {
            dp = (struct direct *)(buf + i);
            if (dp->d_reclen == 0 || i + dp->d_reclen > DIRBLKSIZ)
                  panic("ufsdirhash_checkblock: bad dir");

            if (dp->d_ino == 0) {
#if 0
                  /*
                   * XXX entries with d_ino == 0 should only occur
                   * at the start of a DIRBLKSIZ block. However the
                   * ufs code is tolerant of such entries at other
                   * offsets, and fsck does not fix them.
                   */
                  if (i != 0)
                        panic("ufsdirhash_checkblock: bad dir inode");
#endif
                  nfree += dp->d_reclen;
                  continue;
            }

            /* Check that the entry exists (will panic if it doesn't). */
            ufsdirhash_findslot(dh, dp->d_name, dp->d_namlen, offset + i);

            nfree += dp->d_reclen - DIRSIZ(0, dp);
      }
      if (i != DIRBLKSIZ)
            panic("ufsdirhash_checkblock: bad dir end");

      if (dh->dh_blkfree[block] * DIRALIGN != nfree)
            panic("ufsdirhash_checkblock: bad free count");

      ffslot = BLKFREE2IDX(nfree / DIRALIGN);
      for (i = 0; i <= DH_NFSTATS; i++)
            if (dh->dh_firstfree[i] == block && i != ffslot)
                  panic("ufsdirhash_checkblock: bad first-free");
      if (dh->dh_firstfree[ffslot] == -1)
            panic("ufsdirhash_checkblock: missing first-free entry");
      DIRHASH_UNLOCK(dh);
}

/*
 * Hash the specified filename into a dirhash slot.
 */
static int
ufsdirhash_hash(struct dirhash *dh, char *name, int namelen)
{
      u_int32_t hash;

      /*
       * We hash the name and then some other bit of data that is
       * invariant over the dirhash's lifetime. Otherwise names
       * differing only in the last byte are placed close to one
       * another in the table, which is bad for linear probing.
       */
      hash = fnv_32_buf(name, namelen, FNV1_32_INIT);
      hash = fnv_32_buf(&dh, sizeof(dh), hash);
      return (hash % dh->dh_hlen);
}

/*
 * Adjust the number of free bytes in the block containing `offset'
 * by the value specified by `diff'.
 *
 * The caller must ensure we have exclusive access to `dh'; normally
 * that means that dh_mtx should be held, but this is also called
 * from ufsdirhash_build() where exclusive access can be assumed.
 */
static void
ufsdirhash_adjfree(struct dirhash *dh, doff_t offset, int diff)
{
      int block, i, nfidx, ofidx;

      /* Update the per-block summary info. */
      block = offset / DIRBLKSIZ;
      KASSERT(block < dh->dh_nblk && block < dh->dh_dirblks,
           ("dirhash bad offset"));
      ofidx = BLKFREE2IDX(dh->dh_blkfree[block]);
      dh->dh_blkfree[block] = (int)dh->dh_blkfree[block] + (diff / DIRALIGN);
      nfidx = BLKFREE2IDX(dh->dh_blkfree[block]);

      /* Update the `first free' list if necessary. */
      if (ofidx != nfidx) {
            /* If removing, scan forward for the next block. */
            if (dh->dh_firstfree[ofidx] == block) {
                  for (i = block + 1; i < dh->dh_dirblks; i++)
                        if (BLKFREE2IDX(dh->dh_blkfree[i]) == ofidx)
                              break;
                  dh->dh_firstfree[ofidx] = (i < dh->dh_dirblks) ? i : -1;
            }

            /* Make this the new `first free' if necessary */
            if (dh->dh_firstfree[nfidx] > block ||
                dh->dh_firstfree[nfidx] == -1)
                  dh->dh_firstfree[nfidx] = block;
      }
}

/*
 * Find the specified name which should have the specified offset.
 * Returns a slot number, and panics on failure.
 *
 * `dh' must be locked on entry and remains so on return.
 */
static int
ufsdirhash_findslot(struct dirhash *dh, char *name, int namelen, doff_t offset)
{
      int slot;

      mtx_assert(&dh->dh_mtx, MA_OWNED);

      /* Find the entry. */
      KASSERT(dh->dh_hused < dh->dh_hlen, ("dirhash find full"));
      slot = ufsdirhash_hash(dh, name, namelen);
      while (DH_ENTRY(dh, slot) != offset &&
          DH_ENTRY(dh, slot) != DIRHASH_EMPTY)
            slot = WRAPINCR(slot, dh->dh_hlen);
      if (DH_ENTRY(dh, slot) != offset)
            panic("ufsdirhash_findslot: '%.*s' not found", namelen, name);

      return (slot);
}

/*
 * Remove the entry corresponding to the specified slot from the hash array.
 *
 * `dh' must be locked on entry and remains so on return.
 */
static void
ufsdirhash_delslot(struct dirhash *dh, int slot)
{
      int i;

      mtx_assert(&dh->dh_mtx, MA_OWNED);

      /* Mark the entry as deleted. */
      DH_ENTRY(dh, slot) = DIRHASH_DEL;

      /* If this is the end of a chain of DIRHASH_DEL slots, remove them. */
      for (i = slot; DH_ENTRY(dh, i) == DIRHASH_DEL; )
            i = WRAPINCR(i, dh->dh_hlen);
      if (DH_ENTRY(dh, i) == DIRHASH_EMPTY) {
            i = WRAPDECR(i, dh->dh_hlen);
            while (DH_ENTRY(dh, i) == DIRHASH_DEL) {
                  DH_ENTRY(dh, i) = DIRHASH_EMPTY;
                  dh->dh_hused--;
                  i = WRAPDECR(i, dh->dh_hlen);
            }
            KASSERT(dh->dh_hused >= 0, ("ufsdirhash_delslot neg hlen"));
      }
}

/*
 * Given a directory entry and its offset, find the offset of the
 * previous entry in the same DIRBLKSIZ-sized block. Returns an
 * offset, or -1 if there is no previous entry in the block or some
 * other problem occurred.
 */
static doff_t
ufsdirhash_getprev(struct direct *dirp, doff_t offset)
{
      struct direct *dp;
      char *blkbuf;
      doff_t blkoff, prevoff;
      int entrypos, i;

      blkoff = offset & ~(DIRBLKSIZ - 1); /* offset of start of block */
      entrypos = offset & (DIRBLKSIZ - 1);      /* entry relative to block */
      blkbuf = (char *)dirp - entrypos;
      prevoff = blkoff;

      /* If `offset' is the start of a block, there is no previous entry. */
      if (entrypos == 0)
            return (-1);

      /* Scan from the start of the block until we get to the entry. */
      for (i = 0; i < entrypos; i += dp->d_reclen) {
            dp = (struct direct *)(blkbuf + i);
            if (dp->d_reclen == 0 || i + dp->d_reclen > entrypos)
                  return (-1);      /* Corrupted directory. */
            prevoff = blkoff + i;
      }
      return (prevoff);
}

/*
 * Try to free up `wanted' bytes by stealing memory from existing
 * dirhashes. Returns zero with list locked if successful.
 */
static int
ufsdirhash_recycle(int wanted)
{
      struct dirhash *dh;
      doff_t **hash;
      u_int8_t *blkfree;
      int i, mem, narrays;

      DIRHASHLIST_LOCK();
      while (wanted + ufs_dirhashmem > ufs_dirhashmaxmem) {
            /* Find a dirhash, and lock it. */
            if ((dh = TAILQ_FIRST(&ufsdirhash_list)) == NULL) {
                  DIRHASHLIST_UNLOCK();
                  return (-1);
            }
            DIRHASH_LOCK(dh);
            KASSERT(dh->dh_hash != NULL, ("dirhash: NULL hash on list"));

            /* Decrement the score; only recycle if it becomes zero. */
            if (--dh->dh_score > 0) {
                  DIRHASH_UNLOCK(dh);
                  DIRHASHLIST_UNLOCK();
                  return (-1);
            }

            /* Remove it from the list and detach its memory. */
            TAILQ_REMOVE(&ufsdirhash_list, dh, dh_list);
            dh->dh_onlist = 0;
            hash = dh->dh_hash;
            dh->dh_hash = NULL;
            blkfree = dh->dh_blkfree;
            dh->dh_blkfree = NULL;
            narrays = dh->dh_narrays;
            mem = narrays * sizeof(*dh->dh_hash) +
                narrays * DH_NBLKOFF * sizeof(**dh->dh_hash) +
                dh->dh_nblk * sizeof(*dh->dh_blkfree);

            /* Unlock everything, free the detached memory. */
            DIRHASH_UNLOCK(dh);
            DIRHASHLIST_UNLOCK();
            for (i = 0; i < narrays; i++)
                  DIRHASH_BLKFREE(hash[i]);
            FREE(hash, M_DIRHASH);
            FREE(blkfree, M_DIRHASH);

            /* Account for the returned memory, and repeat if necessary. */
            DIRHASHLIST_LOCK();
            ufs_dirhashmem -= mem;
      }
      /* Success; return with list locked. */
      return (0);
}


void
ufsdirhash_init()
{
      ufsdirhash_zone = uma_zcreate("DIRHASH", DH_NBLKOFF * sizeof(doff_t),
          NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
      mtx_init(&ufsdirhash_mtx, "dirhash list", NULL, MTX_DEF);
      TAILQ_INIT(&ufsdirhash_list);
}

void
ufsdirhash_uninit()
{
      KASSERT(TAILQ_EMPTY(&ufsdirhash_list), ("ufsdirhash_uninit"));
      uma_zdestroy(ufsdirhash_zone);
      mtx_destroy(&ufsdirhash_mtx);
}

#endif /* UFS_DIRHASH */

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