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/* mmc.c - mmap cache |
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** |
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** Copyright © 1998,2001 by Jef Poskanzer <jef@acme.com>. |
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** All rights reserved. |
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** |
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** Redistribution and use in source and binary forms, with or without |
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** modification, are permitted provided that the following conditions |
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** are met: |
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** 1. Redistributions of source code must retain the above copyright |
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** notice, this list of conditions and the following disclaimer. |
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** 2. Redistributions in binary form must reproduce the above copyright |
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** notice, this list of conditions and the following disclaimer in the |
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** documentation and/or other materials provided with the distribution. |
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** |
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** THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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** ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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** SUCH DAMAGE. |
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*/ |
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#include <sys/types.h> |
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#include <sys/stat.h> |
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#include <sys/time.h> |
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#include <stdlib.h> |
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#include <unistd.h> |
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#include <fcntl.h> |
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#include <syslog.h> |
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#ifdef HAVE_MMAP |
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#include <sys/mman.h> |
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#endif /* HAVE_MMAP */ |
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#include "mmc.h" |
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/* Defines. */ |
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#ifndef DEFAULT_EXPIRE_AGE |
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#define DEFAULT_EXPIRE_AGE 600 |
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#endif |
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#ifndef DESIRED_FREE_COUNT |
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#define DESIRED_FREE_COUNT 100 |
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#endif |
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#ifndef DESIRED_MAX_MAPPED_FILES |
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#define DESIRED_MAX_MAPPED_FILES 2000 |
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#endif |
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#ifndef INITIAL_HASH_SIZE |
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#define INITIAL_HASH_SIZE (1 << 10) |
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#endif |
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#define max(a,b) ((a)>(b)?(a):(b)) |
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#define min(a,b) ((a)<(b)?(a):(b)) |
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/* The Map struct. */ |
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typedef struct MapStruct { |
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ino_t ino; |
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dev_t dev; |
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off_t size; |
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time_t ctime; |
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int refcount; |
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time_t reftime; |
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void* addr; |
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unsigned int hash; |
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int hash_idx; |
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struct MapStruct* next; |
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} Map; |
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/* Globals. */ |
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static Map* maps = (Map*) 0; |
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static Map* free_maps = (Map*) 0; |
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static int alloc_count = 0, map_count = 0, free_count = 0; |
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static Map** hash_table = (Map**) 0; |
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static int hash_size; |
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static unsigned int hash_mask; |
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static time_t expire_age = DEFAULT_EXPIRE_AGE; |
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/* Forwards. */ |
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static void really_unmap( Map** mm ); |
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static int check_hash_size( void ); |
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static int add_hash( Map* m ); |
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static Map* find_hash( ino_t ino, dev_t dev, off_t size, time_t ctime ); |
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static unsigned int hash( ino_t ino, dev_t dev, off_t size, time_t ctime ); |
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void* |
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mmc_map( char* filename, struct stat* sbP, struct timeval* nowP ) |
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{ |
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time_t now; |
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struct stat sb; |
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Map* m; |
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int fd; |
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/* Stat the file, if necessary. */ |
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if ( sbP != (struct stat*) 0 ) |
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sb = *sbP; |
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else |
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{ |
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if ( stat( filename, &sb ) != 0 ) |
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{ |
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syslog( LOG_ERR, "stat - %m" ); |
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return (void*) 0; |
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} |
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} |
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/* Get the current time, if necessary. */ |
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if ( nowP != (struct timeval*) 0 ) |
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now = nowP->tv_sec; |
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else |
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now = time( (time_t*) 0 ); |
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/* See if we have it mapped already, via the hash table. */ |
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if ( check_hash_size() < 0 ) |
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{ |
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syslog( LOG_ERR, "check_hash_size() failure" ); |
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return (void*) 0; |
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} |
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m = find_hash( sb.st_ino, sb.st_dev, sb.st_size, sb.st_ctime ); |
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if ( m != (Map*) 0 ) |
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{ |
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/* Yep. Just return the existing map */ |
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++m->refcount; |
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m->reftime = now; |
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return m->addr; |
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} |
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/* Open the file. */ |
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fd = open( filename, O_RDONLY ); |
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if ( fd < 0 ) |
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{ |
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syslog( LOG_ERR, "open - %m" ); |
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return (void*) 0; |
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} |
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/* Find a free Map entry or make a new one. */ |
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if ( free_maps != (Map*) 0 ) |
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{ |
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m = free_maps; |
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free_maps = m->next; |
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--free_count; |
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} |
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else |
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{ |
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m = (Map*) malloc( sizeof(Map) ); |
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if ( m == (Map*) 0 ) |
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{ |
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(void) close( fd ); |
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syslog( LOG_ERR, "out of memory allocating a Map" ); |
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return (void*) 0; |
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} |
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++alloc_count; |
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} |
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/* Fill in the Map entry. */ |
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m->ino = sb.st_ino; |
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m->dev = sb.st_dev; |
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m->size = sb.st_size; |
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m->ctime = sb.st_ctime; |
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m->refcount = 1; |
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m->reftime = now; |
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/* Avoid doing anything for zero-length files; some systems don't like |
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** to mmap them, other systems dislike mallocing zero bytes. |
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*/ |
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if ( m->size == 0 ) |
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m->addr = (void*) 1; /* arbitrary non-NULL address */ |
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else |
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{ |
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#ifdef HAVE_MMAP |
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/* Map the file into memory. */ |
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m->addr = mmap( 0, m->size, PROT_READ, MAP_SHARED, fd, 0 ); |
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if ( m->addr == (void*) -1 ) |
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{ |
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syslog( LOG_ERR, "mmap - %m" ); |
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(void) close( fd ); |
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free( (void*) m ); |
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--alloc_count; |
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return (void*) 0; |
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} |
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#else /* HAVE_MMAP */ |
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/* Read the file into memory. */ |
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m->addr = (void*) malloc( m->size ); |
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if ( m->addr == (void*) 0 ) |
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{ |
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syslog( LOG_ERR, "out of memory storing a file" ); |
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(void) close( fd ); |
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free( (void*) m ); |
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--alloc_count; |
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return (void*) 0; |
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} |
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if ( read( fd, m->addr, m->size ) != m->size ) |
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{ |
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syslog( LOG_ERR, "read - %m" ); |
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(void) close( fd ); |
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free( (void*) m ); |
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--alloc_count; |
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return (void*) 0; |
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} |
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#endif /* HAVE_MMAP */ |
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} |
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(void) close( fd ); |
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/* Put the Map into the hash table. */ |
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if ( add_hash( m ) < 0 ) |
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{ |
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syslog( LOG_ERR, "add_hash() failure" ); |
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free( (void*) m ); |
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--alloc_count; |
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return (void*) 0; |
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} |
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/* Put the Map on the active list. */ |
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m->next = maps; |
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maps = m; |
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++map_count; |
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/* And return the address. */ |
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return m->addr; |
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} |
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void |
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mmc_unmap( void* addr, struct stat* sbP, struct timeval* nowP ) |
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{ |
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Map* m = (Map*) 0; |
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/* Find the Map entry for this address. First try a hash. */ |
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if ( sbP != (struct stat*) 0 ) |
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{ |
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m = find_hash( sbP->st_ino, sbP->st_dev, sbP->st_size, sbP->st_ctime ); |
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if ( m != (Map*) 0 && m->addr != addr ) |
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m = (Map*) 0; |
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} |
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/* If that didn't work, try a full search. */ |
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if ( m == (Map*) 0 ) |
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for ( m = maps; m != (Map*) 0; m = m->next ) |
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if ( m->addr == addr ) |
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break; |
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if ( m == (Map*) 0 ) |
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syslog( LOG_ERR, "mmc_unmap failed to find entry!" ); |
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else if ( m->refcount <= 0 ) |
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syslog( LOG_ERR, "mmc_unmap found zero or negative refcount!" ); |
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else |
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{ |
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--m->refcount; |
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if ( nowP != (struct timeval*) 0 ) |
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m->reftime = nowP->tv_sec; |
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else |
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m->reftime = time( (time_t*) 0 ); |
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} |
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} |
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void |
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mmc_cleanup( struct timeval* nowP ) |
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{ |
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time_t now; |
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Map** mm; |
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Map* m; |
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/* Get the current time, if necessary. */ |
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if ( nowP != (struct timeval*) 0 ) |
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now = nowP->tv_sec; |
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else |
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now = time( (time_t*) 0 ); |
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/* Really unmap any unreferenced entries older than the age limit. */ |
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for ( mm = &maps; *mm != (Map*) 0; ) |
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{ |
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m = *mm; |
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if ( m->refcount == 0 && now - m->reftime >= expire_age ) |
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really_unmap( mm ); |
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else |
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mm = &(*mm)->next; |
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} |
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/* If there are still too many (or too few) maps, adjust the age limit. */ |
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if ( map_count > DESIRED_MAX_MAPPED_FILES ) |
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expire_age = max( ( expire_age * 2 ) / 3, DEFAULT_EXPIRE_AGE / 10 ); |
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else if ( map_count < DESIRED_MAX_MAPPED_FILES / 2 ) |
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expire_age = min( ( expire_age * 5 ) / 4, DEFAULT_EXPIRE_AGE * 3 ); |
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/* Really free excess blocks on the free list. */ |
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while ( free_count > DESIRED_FREE_COUNT ) |
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{ |
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m = free_maps; |
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free_maps = m->next; |
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--free_count; |
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free( (void*) m ); |
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--alloc_count; |
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} |
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} |
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static void |
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really_unmap( Map** mm ) |
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{ |
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Map* m; |
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m = *mm; |
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if ( m->size != 0 ) |
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{ |
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#ifdef HAVE_MMAP |
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if ( munmap( m->addr, m->size ) < 0 ) |
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syslog( LOG_ERR, "munmap - %m" ); |
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#else /* HAVE_MMAP */ |
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free( (void*) m->addr ); |
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#endif /* HAVE_MMAP */ |
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} |
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/* And move the Map to the free list. */ |
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*mm = m->next; |
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--map_count; |
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m->next = free_maps; |
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free_maps = m; |
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++free_count; |
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/* This will sometimes break hash chains, but that's harmless; the |
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** unmapping code that searches the hash table knows to keep searching. |
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*/ |
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hash_table[m->hash_idx] = (Map*) 0; |
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} |
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void |
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mmc_destroy( void ) |
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{ |
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Map* m; |
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while ( maps != (Map*) 0 ) |
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really_unmap( &maps ); |
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while ( free_maps != (Map*) 0 ) |
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{ |
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m = free_maps; |
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free_maps = m->next; |
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--free_count; |
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free( (void*) m ); |
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--alloc_count; |
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} |
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} |
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/* Make sure the hash table is big enough. */ |
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static int |
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check_hash_size( void ) |
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{ |
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int i; |
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Map* m; |
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/* Are we just starting out? */ |
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if ( hash_table == (Map**) 0 ) |
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{ |
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hash_size = INITIAL_HASH_SIZE; |
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hash_mask = hash_size - 1; |
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} |
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/* Is it at least three times bigger than the number of entries? */ |
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else if ( hash_size >= map_count * 3 ) |
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return 0; |
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else |
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{ |
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/* No, got to expand. */ |
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free( (void*) hash_table ); |
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/* Double the hash size until it's big enough. */ |
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do |
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{ |
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hash_size = hash_size << 1; |
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} |
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while ( hash_size < map_count * 6 ); |
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hash_mask = hash_size - 1; |
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} |
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/* Make the new table. */ |
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hash_table = (Map**) malloc( hash_size * sizeof(Map*) ); |
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if ( hash_table == (Map**) 0 ) |
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return -1; |
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/* Clear it. */ |
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for ( i = 0; i < hash_size; ++i ) |
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hash_table[i] = (Map*) 0; |
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/* And rehash all entries. */ |
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for ( m = maps; m != (Map*) 0; m = m->next ) |
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if ( add_hash( m ) < 0 ) |
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return -1; |
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return 0; |
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} |
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static int |
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add_hash( Map* m ) |
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{ |
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unsigned int h, he, i; |
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h = hash( m->ino, m->dev, m->size, m->ctime ); |
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he = ( h + hash_size - 1 ) & hash_mask; |
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for ( i = h; ; i = ( i + 1 ) & hash_mask ) |
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{ |
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if ( hash_table[i] == (Map*) 0 ) |
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{ |
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hash_table[i] = m; |
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m->hash = h; |
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m->hash_idx = i; |
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return 0; |
408 |
|
|
} |
409 |
|
|
if ( i == he ) |
410 |
|
|
break; |
411 |
|
|
} |
412 |
|
|
return -1; |
413 |
|
|
} |
414 |
|
|
|
415 |
|
|
|
416 |
|
|
static Map* |
417 |
|
|
find_hash( ino_t ino, dev_t dev, off_t size, time_t ctime ) |
418 |
|
|
{ |
419 |
|
|
unsigned int h, he, i; |
420 |
|
|
Map* m; |
421 |
|
|
|
422 |
|
|
h = hash( ino, dev, size, ctime ); |
423 |
|
|
he = ( h + hash_size - 1 ) & hash_mask; |
424 |
|
|
for ( i = h; ; i = ( i + 1 ) & hash_mask ) |
425 |
|
|
{ |
426 |
|
|
m = hash_table[i]; |
427 |
|
|
if ( m == (Map*) 0 ) |
428 |
|
|
break; |
429 |
|
|
if ( m->hash == h && m->ino == ino && m->dev == dev && |
430 |
|
|
m->size == size && m->ctime == ctime ) |
431 |
|
|
return m; |
432 |
|
|
if ( i == he ) |
433 |
|
|
break; |
434 |
|
|
} |
435 |
|
|
return (Map*) 0; |
436 |
|
|
} |
437 |
|
|
|
438 |
|
|
|
439 |
|
|
static unsigned int |
440 |
|
|
hash( ino_t ino, dev_t dev, off_t size, time_t ctime ) |
441 |
|
|
{ |
442 |
|
|
unsigned int h = 177573; |
443 |
|
|
|
444 |
|
|
h ^= ino; |
445 |
|
|
h += h << 5; |
446 |
|
|
h ^= dev; |
447 |
|
|
h += h << 5; |
448 |
|
|
h ^= size; |
449 |
|
|
h += h << 5; |
450 |
|
|
h ^= ctime; |
451 |
|
|
|
452 |
|
|
return h & hash_mask; |
453 |
|
|
} |
454 |
|
|
|
455 |
|
|
|
456 |
|
|
/* Generate debugging statistics syslog message. */ |
457 |
|
|
void |
458 |
|
|
mmc_logstats( long secs ) |
459 |
|
|
{ |
460 |
|
|
syslog( |
461 |
|
|
LOG_NOTICE, " map cache - %d allocated, %d active, %d free; hash size: %d; expire age: %ld", |
462 |
|
|
alloc_count, map_count, free_count, hash_size, expire_age ); |
463 |
|
|
if ( map_count + free_count != alloc_count ) |
464 |
|
|
syslog( LOG_ERR, "map counts don't add up!" ); |
465 |
|
|
} |