glibc/nscd/mem.c

/* Cache memory handling.
   Copyright (C) 2004, 2005, 2006, 2008 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published
   by the Free Software Foundation; version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include <assert.h>
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <inttypes.h>
#include <libintl.h>
#include <limits.h>
#include <obstack.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/param.h>

#include "dbg_log.h"
#include "nscd.h"


/* Wrapper functions with error checking for standard functions.  */
extern void *xmalloc (size_t n);
extern void *xcalloc (size_t n, size_t s);


static int
sort_he (const void *p1, const void *p2)
{
  struct hashentry *h1 = *(struct hashentry **) p1;
  struct hashentry *h2 = *(struct hashentry **) p2;

  if (h1 < h2)
    return -1;
  if (h1 > h2)
    return 1;
  return 0;
}


static int
sort_he_data (const void *p1, const void *p2)
{
  struct hashentry *h1 = *(struct hashentry **) p1;
  struct hashentry *h2 = *(struct hashentry **) p2;

  if (h1->packet < h2->packet)
    return -1;
  if (h1->packet > h2->packet)
    return 1;
  return 0;
}


/* Basic definitions for the bitmap implementation.  Only BITMAP_T
   needs to be changed to choose a different word size.  */
#define BITMAP_T uint8_t
#define BITS (CHAR_BIT * sizeof (BITMAP_T))
#define ALLBITS ((((BITMAP_T) 1) << BITS) - 1)
#define HIGHBIT (((BITMAP_T) 1) << (BITS - 1))


static void
markrange (BITMAP_T *mark, ref_t start, size_t len)
{
  /* Adjust parameters for block alignment.  */
  assert ((start & BLOCK_ALIGN_M1) == 0);
  start /= BLOCK_ALIGN;
  len = (len + BLOCK_ALIGN_M1) / BLOCK_ALIGN;

  size_t elem = start / BITS;

  if (start % BITS != 0)
    {
      if (start % BITS + len <= BITS)
	{
	  /* All fits in the partial byte.  */
	  mark[elem] |= (ALLBITS >> (BITS - len)) << (start % BITS);
	  return;
	}

      mark[elem++] |= ALLBITS << (start % BITS);
      len -= BITS - (start % BITS);
    }

  while (len >= BITS)
    {
      mark[elem++] = ALLBITS;
      len -= BITS;
    }

  if (len > 0)
    mark[elem] |= ALLBITS >> (BITS - len);
}


void
gc (struct database_dyn *db)
{
  /* We need write access.  */
  pthread_rwlock_wrlock (&db->lock);

  /* And the memory handling lock.  */
  pthread_mutex_lock (&db->memlock);

  /* We need an array representing the data area.  All memory
     allocation is BLOCK_ALIGN aligned so this is the level at which
     we have to look at the memory.  We use a mark and sweep algorithm
     where the marks are placed in this array.  */
  assert (db->head->first_free % BLOCK_ALIGN == 0);

  BITMAP_T *mark;
  bool mark_use_malloc;
  /* In prune_cache we are also using a dynamically allocated array.
     If the array in the caller is too large we have malloc'ed it.  */
  size_t stack_used = sizeof (bool) * db->head->module;
  if (__builtin_expect (stack_used > MAX_STACK_USE, 0))
    stack_used = 0;
  size_t nmark = (db->head->first_free / BLOCK_ALIGN + BITS - 1) / BITS;
  size_t memory_needed = nmark * sizeof (BITMAP_T);
  if (stack_used + memory_needed <= MAX_STACK_USE)
    {
      mark = (BITMAP_T *) alloca (memory_needed);
      mark_use_malloc = false;
      memset (mark, '\0', memory_needed);
      stack_used += memory_needed;
    }
  else
    {
      mark = (BITMAP_T *) xcalloc (1, memory_needed);
      mark_use_malloc = true;
    }

  /* Create an array which can hold pointer to all the entries in hash
     entries.  */
  memory_needed = 2 * db->head->nentries * sizeof (struct hashentry *);
  struct hashentry **he;
  struct hashentry **he_data;
  bool he_use_malloc;
  if (stack_used + memory_needed <= MAX_STACK_USE)
    {
      he = alloca (db->head->nentries * sizeof (struct hashentry *));
      he_data = alloca (db->head->nentries * sizeof (struct hashentry *));
      he_use_malloc = false;
      stack_used += memory_needed;
    }
  else
    {
      he = xmalloc (memory_needed);
      he_data = &he[db->head->nentries * sizeof (struct hashentry *)];
      he_use_malloc = true;
    }

  size_t cnt = 0;
  for (size_t idx = 0; idx < db->head->module; ++idx)
    {
      ref_t *prevp = &db->head->array[idx];
      ref_t run = *prevp;

      while (run != ENDREF)
	{
	  assert (cnt < db->head->nentries);
	  he[cnt] = (struct hashentry *) (db->data + run);

	  he[cnt]->prevp = prevp;
	  prevp = &he[cnt]->next;

	  /* This is the hash entry itself.  */
	  markrange (mark, run, sizeof (struct hashentry));

	  /* Add the information for the data itself.  We do this
	     only for the one special entry marked with FIRST.  */
	  if (he[cnt]->first)
	    {
	      struct datahead *dh
		= (struct datahead *) (db->data + he[cnt]->packet);
	      markrange (mark, he[cnt]->packet, dh->allocsize);
	    }

	  run = he[cnt]->next;

	  ++cnt;
	}
    }
  assert (cnt == db->head->nentries);

  /* Go through the list of in-flight memory blocks.  */
  struct mem_in_flight *mrunp = mem_in_flight_list;
  while (mrunp != NULL)
    {
      /* NB: There can be no race between this test and another thread
        setting the field to the index we are looking for because
        this would require the other thread to also have the memlock
        for the database.

	NB2: we do not have to look at latter blocks (higher indices) if
	earlier blocks are not in flight.  They are always allocated in
	sequence.  */
      for (enum in_flight idx = IDX_result_data;
	   idx < IDX_last && mrunp->block[idx].dbidx == db - dbs; ++idx)
	{
	  assert (mrunp->block[idx].blockoff >= 0);
	  assert (mrunp->block[idx].blocklen < db->memsize);
	  assert (mrunp->block[idx].blockoff
		  + mrunp->block[0].blocklen <= db->memsize);
	  markrange (mark, mrunp->block[idx].blockoff,
		     mrunp->block[idx].blocklen);
	}

      mrunp = mrunp->next;
    }

  /* Sort the entries by the addresses of the referenced data.  All
     the entries pointing to the same DATAHEAD object will have the
     same key.  Stability of the sorting is unimportant.  */
  memcpy (he_data, he, cnt * sizeof (struct hashentry *));
  qsort (he_data, cnt, sizeof (struct hashentry *), sort_he_data);

  /* Sort the entries by their address.  */
  qsort (he, cnt, sizeof (struct hashentry *), sort_he);

  /* Determine the highest used address.  */
  size_t high = nmark;
  while (high > 0 && mark[high - 1] == 0)
    --high;

  /* No memory used.  */
  if (high == 0)
    {
      db->head->first_free = 0;
      goto out;
    }

  /* Determine the highest offset.  */
  BITMAP_T mask = HIGHBIT;
  ref_t highref = (high * BITS - 1) * BLOCK_ALIGN;
  while ((mark[high - 1] & mask) == 0)
    {
      mask >>= 1;
      highref -= BLOCK_ALIGN;
    }

  /* Now we can iterate over the MARK array and find bits which are not
     set.  These represent memory which can be recovered.  */
  size_t byte = 0;
  /* Find the first gap.  */
  while (byte < high && mark[byte] == ALLBITS)
    ++byte;

  if (byte == high
      || (byte == high - 1 && (mark[byte] & ~(mask | (mask - 1))) == 0))
    /* No gap.  */
    goto out;

  mask = 1;
  cnt = 0;
  while ((mark[byte] & mask) != 0)
    {
      ++cnt;
      mask <<= 1;
    }
  ref_t off_free = (byte * BITS + cnt) * BLOCK_ALIGN;
  assert (off_free <= db->head->first_free);

  struct hashentry **next_hash = he;
  struct hashentry **next_data = he_data;

  /* Skip over the hash entries in the first block which does not get
     moved.  */
  while (next_hash < &he[db->head->nentries]
	 && *next_hash < (struct hashentry *) (db->data + off_free))
    ++next_hash;

  while (next_data < &he_data[db->head->nentries]
	 && (*next_data)->packet < off_free)
    ++next_data;


  /* Now we start modifying the data.  Make sure all readers of the
     data are aware of this and temporarily don't use the data.  */
  ++db->head->gc_cycle;
  assert ((db->head->gc_cycle & 1) == 1);


  /* We do not perform the move operations right away since the
     he_data array is not sorted by the address of the data.  */
  struct moveinfo
  {
    void *from;
    void *to;
    size_t size;
    struct moveinfo *next;
  } *moves = NULL;
#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free
  struct obstack ob;
  obstack_init (&ob);

  while (byte < high)
    {
      /* Search for the next filled block.  BYTE is the index of the
	 entry in MARK, MASK is the bit, and CNT is the bit number.
	 OFF_FILLED is the corresponding offset.  */
      if ((mark[byte] & ~(mask - 1)) == 0)
	{
	  /* No other bit set in the same element of MARK.  Search in the
	     following memory.  */
	  do
	    ++byte;
	  while (byte < high && mark[byte] == 0);

	  if (byte == high)
	    /* That was it.  */
	    break;

	  mask = 1;
	  cnt = 0;
	}
      /* Find the exact bit.  */
      while ((mark[byte] & mask) == 0)
	{
	  ++cnt;
	  mask <<= 1;
	}

      ref_t off_alloc = (byte * BITS + cnt) * BLOCK_ALIGN;
      assert (off_alloc <= db->head->first_free);

      /* Find the end of the used area.  */
      if ((mark[byte] & ~(mask - 1)) == (BITMAP_T) ~(mask - 1))
	{
	  /* All other bits set.  Search the next bytes in MARK.  */
	  do
	    ++byte;
	  while (byte < high && mark[byte] == ALLBITS);

	  mask = 1;
	  cnt = 0;
	}
      if (byte < high)
	{
	  /* Find the exact bit.  */
	  while ((mark[byte] & mask) != 0)
	    {
	      ++cnt;
	      mask <<= 1;
	    }
	}

      ref_t off_allocend = (byte * BITS + cnt) * BLOCK_ALIGN;
      assert (off_allocend <= db->head->first_free);
      /* Now we know that we can copy the area from OFF_ALLOC to
	 OFF_ALLOCEND (not included) to the memory starting at
	 OFF_FREE.  First fix up all the entries for the
	 displacement.  */
      ref_t disp = off_alloc - off_free;

      struct moveinfo *new_move;
      if (stack_used + sizeof (*new_move) <= MAX_STACK_USE)
	{
	  new_move = alloca (sizeof (*new_move));
	  stack_used += sizeof (*new_move);
	}
      else
	new_move = obstack_alloc (&ob, sizeof (*new_move));
      new_move->from = db->data + off_alloc;
      new_move->to = db->data + off_free;
      new_move->size = off_allocend - off_alloc;
      /* Create a circular list to be always able to append at the end.  */
      if (moves == NULL)
	moves = new_move->next = new_move;
      else
	{
	  new_move->next = moves->next;
	  moves = moves->next = new_move;
	}

      /* The following loop will prepare to move this much data.  */
      off_free += off_allocend - off_alloc;

      while (off_alloc < off_allocend)
	{
	  /* Determine whether the next entry is for a hash entry or
	     the data.  */
	  if ((struct hashentry *) (db->data + off_alloc) == *next_hash)
	    {
	      /* Just correct the forward reference.  */
	      *(*next_hash++)->prevp -= disp;

	      off_alloc += ((sizeof (struct hashentry) + BLOCK_ALIGN_M1)
			    & ~BLOCK_ALIGN_M1);
	    }
	  else
	    {
	      assert (next_data < &he_data[db->head->nentries]);
	      assert ((*next_data)->packet == off_alloc);

	      struct datahead *dh = (struct datahead *) (db->data + off_alloc);
	      do
		{
		  assert ((*next_data)->key >= (*next_data)->packet);
		  assert ((*next_data)->key + (*next_data)->len
			  <= (*next_data)->packet + dh->allocsize);

		  (*next_data)->packet -= disp;
		  (*next_data)->key -= disp;
		  ++next_data;
		}
	      while (next_data < &he_data[db->head->nentries]
		     && (*next_data)->packet == off_alloc);

	      off_alloc += (dh->allocsize + BLOCK_ALIGN_M1) & ~BLOCK_ALIGN_M1;
	    }
	}
      assert (off_alloc == off_allocend);

      assert (off_alloc <= db->head->first_free);
      if (off_alloc == db->head->first_free)
	/* We are done, that was the last block.  */
	break;
    }
  assert (next_hash == &he[db->head->nentries]);
  assert (next_data == &he_data[db->head->nentries]);

  /* Now perform the actual moves.  */
  if (moves != NULL)
    {
      struct moveinfo *runp = moves->next;
      do
	{
	  assert ((char *) runp->to >= db->data);
	  assert ((char *) runp->to + runp->size
		  <= db->data  + db->head->first_free);
	  assert ((char *) runp->from >= db->data);
	  assert ((char *) runp->from + runp->size
		  <= db->data  + db->head->first_free);

	  /* The regions may overlap.  */
	  memmove (runp->to, runp->from, runp->size);
	  runp = runp->next;
	}
      while (runp != moves->next);

      if (__builtin_expect (debug_level >= 3, 0))
	dbg_log (_("freed %zu bytes in %s cache"),
		 db->head->first_free
		 - ((char *) moves->to + moves->size - db->data),
		 dbnames[db - dbs]);

      /* The byte past the end of the last copied block is the next
	 available byte.  */
      db->head->first_free = (char *) moves->to + moves->size - db->data;

      /* Consistency check.  */
      if (__builtin_expect (debug_level >= 3, 0))
	{
	  for (size_t idx = 0; idx < db->head->module; ++idx)
	    {
	      ref_t run = db->head->array[idx];
	      size_t cnt = 0;

	      while (run != ENDREF)
		{
		  if (run + sizeof (struct hashentry) > db->head->first_free)
		    {
		      dbg_log ("entry %zu in hash bucket %zu out of bounds: "
			       "%" PRIu32 "+%zu > %zu\n",
			       cnt, idx, run, sizeof (struct hashentry),
			       (size_t) db->head->first_free);
		      break;
		    }

		  struct hashentry *he = (struct hashentry *) (db->data + run);

		  if (he->key + he->len > db->head->first_free)
		    dbg_log ("key of entry %zu in hash bucket %zu out of "
			     "bounds: %" PRIu32 "+%zu > %zu\n",
			     cnt, idx, he->key, (size_t) he->len,
			     (size_t) db->head->first_free);

		  if (he->packet + sizeof (struct datahead)
		      > db->head->first_free)
		    dbg_log ("packet of entry %zu in hash bucket %zu out of "
			     "bounds: %" PRIu32 "+%zu > %zu\n",
			     cnt, idx, he->packet, sizeof (struct datahead),
			     (size_t) db->head->first_free);
		  else
		    {
		      struct datahead *dh = (struct datahead *) (db->data
								 + he->packet);
		      if (he->packet + dh->allocsize
			  > db->head->first_free)
			dbg_log ("full key of entry %zu in hash bucket %zu "
				 "out of bounds: %" PRIu32 "+%zu > %zu",
				 cnt, idx, he->packet, (size_t) dh->allocsize,
				 (size_t) db->head->first_free);
		    }

		  run = he->next;
		  ++cnt;
		}
	    }
	}
    }

  /* Make sure the data on disk is updated.  */
  if (db->persistent)
    msync (db->head, db->data + db->head->first_free - (char *) db->head,
	   MS_ASYNC);


  /* Now we are done modifying the data.  */
  ++db->head->gc_cycle;
  assert ((db->head->gc_cycle & 1) == 0);

  /* We are done.  */
 out:
  pthread_mutex_unlock (&db->memlock);
  pthread_rwlock_unlock (&db->lock);

  if (he_use_malloc)
    free (he);
  if (mark_use_malloc)
    free (mark);

  obstack_free (&ob, NULL);
}


void *
mempool_alloc (struct database_dyn *db, size_t len, enum in_flight idx)
{
  /* Make sure LEN is a multiple of our maximum alignment so we can
     keep track of used memory is multiples of this alignment value.  */
  if ((len & BLOCK_ALIGN_M1) != 0)
    len += BLOCK_ALIGN - (len & BLOCK_ALIGN_M1);

  pthread_mutex_lock (&db->memlock);

  assert ((db->head->first_free & BLOCK_ALIGN_M1) == 0);

  bool tried_resize = false;
  void *res;
 retry:
  res = db->data + db->head->first_free;

  if (__builtin_expect (db->head->first_free + len > db->head->data_size, 0))
    {
      if (! tried_resize)
	{
	  /* Try to resize the database.  Grow size of 1/8th.  */
	  size_t oldtotal = (sizeof (struct database_pers_head)
			     + roundup (db->head->module * sizeof (ref_t),
					ALIGN)
			     + db->head->data_size);
	  size_t new_data_size = (db->head->data_size
				  + MAX (2 * len, db->head->data_size / 8));
	  size_t newtotal = (sizeof (struct database_pers_head)
			     + roundup (db->head->module * sizeof (ref_t), ALIGN)
			     + new_data_size);
	  if (newtotal > db->max_db_size)
	    {
	      new_data_size -= newtotal - db->max_db_size;
	      newtotal = db->max_db_size;
	    }

	  if (db->mmap_used && newtotal > oldtotal
	      /* We only have to adjust the file size.  The new pages
		 become magically available.  */
	      && TEMP_FAILURE_RETRY_VAL (posix_fallocate (db->wr_fd, oldtotal,
							  newtotal
							  - oldtotal)) == 0)
	    {
	      db->head->data_size = new_data_size;
	      tried_resize = true;
	      goto retry;
	    }
	}

      if (! db->last_alloc_failed)
	{
	  dbg_log (_("no more memory for database '%s'"), dbnames[db - dbs]);

	  db->last_alloc_failed = true;
	}

      /* No luck.  */
      res = NULL;
    }
  else
    {
      /* Remember that we have allocated this memory.  */
      assert (idx >= 0 && idx < IDX_last);
      mem_in_flight.block[idx].dbidx = db - dbs;
      mem_in_flight.block[idx].blocklen = len;
      mem_in_flight.block[idx].blockoff = db->head->first_free;

      db->head->first_free += len;

      db->last_alloc_failed = false;

    }

  pthread_mutex_unlock (&db->memlock);

  return res;
}