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/*
* s3backer - FUSE-based single file backing store via Amazon S3
*
* Copyright 2008-2011 Archie L. Cobbs <archie@dellroad.org>
*
* 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; either 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., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* In addition, as a special exception, the copyright holders give
* permission to link the code of portions of this program with the
* OpenSSL library under certain conditions as described in each
* individual source file, and distribute linked combinations including
* the two.
*
* You must obey the GNU General Public License in all respects for all
* of the code used other than OpenSSL. If you modify file(s) with this
* exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do
* so, delete this exception statement from your version. If you delete
* this exception statement from all source files in the program, then
* also delete it here.
*/
#include "s3backer.h"
#include "block_cache.h"
#include "dcache.h"
#include "hash.h"
/*
* This file implements a simple block cache that acts as a "layer" on top
* of an underlying s3backer_store.
*
* Blocks in the cache are in one of these states:
*
* CLEAN Data is consistent with underlying s3backer_store
* CLEAN2 Data is belived consistent with underlying s3backer_store, but need to verify MD5
* DIRTY Data is inconsistent with underlying s3backer_store (needs writing)
* READING Data is being read from the underlying s3backer_store
* READING2 Data is being read/verified from the underlying s3backer_store
* WRITING Data is being written to underlying s3backer_store
* WRITING2 Same as WRITING, but a subsequent write has stored new data
*
* Blocks in the CLEAN and CLEAN2 states are linked in a list in order from least recently
* used to most recently used (where 'used' means either read or written). CLEAN2 is the
* same as CLEAN except that the data must be MD5 verified before being used.
*
* Blocks in the DIRTY state are linked in a list in the order they should be written.
* A pool of worker threads picks them off and writes them through to the underlying
* s3backer_store; while being written they are in state WRITING, or WRITING2 if another
* write to the same block happens during that time. If the write is unsuccessful, the
* block goes back to DIRTY and to the head of the DIRTY list: the result is that failed
* writes of DIRTY blocks will retry indefinitely. If the write is successful, the
* block moves to CLEAN if still in state WRITING, or DIRTY if in WRITING2.
*
* Because we allow writes to update the data in a block while that block is being
* written, the worker threads always write from the original buffer, and a new buffer
* will get created on demand when a block moves to state WRITING2. When it completes
* its write attempt, the worker thread then checks for this condition and, if indeed
* the block has changed to WRITING2, it knows to free the original buffer.
*
* Blocks in the READING, WRITING and WRITING2 states are not in either list.
*
* Only CLEAN and CLEAN2 blocks are eligible to be evicted from the cache. We evict entries
* either when they timeout or the cache is full and we need to add a new entry to it.
*/
/* Cache entry states */
#define CLEAN 0
#define CLEAN2 1
#define DIRTY 2
#define READING 3
#define READING2 4
#define WRITING 5
#define WRITING2 6
/*
* One cache entry. In order to keep this structure as small as possible, we do
* two size optimizations:
*
* 1. We use the low-order bit of '_data' as the dirty flag (we assume all valid
* pointers are aligned to an even address).
* 2. When not linked into either list (i.e., in WRITING state), we set link.tqe_prev
* to NULL to indicate this; this is safe because link.tqe_prev is always non-NULL
* when the structure is linked into a list.
*
* Invariants:
*
* State ENTRY_IN_LIST()? dirty? timeout == -1 verify dcache
* ----- ---------------- ------ ------------- ------ ------
*
* CLEAN YES: priv->cleans NO ? 0 recorded
* CLEAN2 YES: priv->cleans NO ? 1 recorded
* READING NO NO YES 0 allocated
* READING2 NO NO YES 1 allocated
* DIRTY YES: priv->dirties YES ? ? allocated
* WRITING NO NO NO ? allocated
* WRITING2 NO YES NO ? allocated
*
* Timeouts: we track time in units of TIME_UNIT_MILLIS milliseconds from when we start.
* This is so we can jam them into 30 bits instead of 64. It's possible for the time value
* to wrap after about two years; the effect would be mis-timed writes and evictions.
*
* In state CLEAN2 only, the MD5 to verify immediately follows the structure.
*/
struct cache_entry {
s3b_block_t block_num; // block number - MUST BE FIRST
u_int dirty:1; // indicates state DIRTY or WRITING2
u_int verify:1; // data should be verified first
uint32_t timeout:30; // when to evict (CLEAN[2]) or write (DIRTY)
TAILQ_ENTRY(cache_entry) link; // next in list (cleans or dirties)
union {
void *data; // data buffer in memory
u_int dslot; // disk cache data slot
} u;
u_char md5[0]; // MD5 checksum (CLEAN2)
};
#define ENTRY_IN_LIST(entry) ((entry)->link.tqe_prev != NULL)
#define ENTRY_RESET_LINK(entry) do { (entry)->link.tqe_prev = NULL; } while (0)
#define ENTRY_GET_STATE(entry) (ENTRY_IN_LIST(entry) ? \
((entry)->dirty ? DIRTY : \
((entry)->verify ? CLEAN2 : CLEAN)) : \
((entry)->timeout == READING_TIMEOUT ? \
((entry)->verify ? READING2 : READING) : \
(entry)->dirty ? WRITING2 : WRITING))
/* One time unit in milliseconds */
#define TIME_UNIT_MILLIS 64
/* The dirty ratio at which we want to be writing out dirty blocks immediately */
#define DIRTY_RATIO_WRITE_ASAP 0.90 // 90%
/* Special timeout value for entries in state READING and READING2 */
#define READING_TIMEOUT ((uint32_t)0x3fffffff)
/* Private data */
struct block_cache_private {
struct block_cache_conf *config; // configuration
struct s3backer_store *inner; // underlying s3backer store
struct block_cache_stats stats; // statistics
TAILQ_HEAD(, cache_entry) cleans; // list of clean blocks (LRU order)
TAILQ_HEAD(, cache_entry) dirties; // list of dirty blocks (write order)
struct s3b_hash *hashtable; // hashtable of all cached blocks
struct s3b_dcache *dcache; // on-disk persistent cache
u_int num_cleans; // length of the 'cleans' list
u_int num_dirties; // # blocks that are DIRTY, WRITING, or WRITING2
u_int64_t start_time; // when we started
u_int32_t clean_timeout; // timeout for clean entries in time units
u_int32_t dirty_timeout; // timeout for dirty entries in time units
double max_dirty_ratio;// dirty ratio at which we write immediately
s3b_block_t seq_last; // last block read in sequence by upper layer
u_int seq_count; // # of blocks read in sequence by upper layer
u_int ra_count; // # of blocks of read-ahead initiated
u_int thread_id; // next thread id
u_int num_threads; // number of alive worker threads
int stopping; // signals worker threads to exit
pthread_mutex_t mutex; // my mutex
pthread_cond_t space_avail; // there is new space available in cache
pthread_cond_t end_reading; // some entry in state READING[2] changed state
pthread_cond_t worker_work; // there is new work for worker thread(s)
pthread_cond_t worker_exit; // a worker thread has exited
pthread_cond_t write_complete; // a write has completed
};
/* Callback info */
struct cbinfo {
block_list_func_t *callback;
void *arg;
};
/* s3backer_store functions */
static int block_cache_meta_data(struct s3backer_store *s3b, off_t *file_sizep, u_int *block_sizep);
static int block_cache_set_mounted(struct s3backer_store *s3b, int *old_valuep, int new_value);
static int block_cache_read_block(struct s3backer_store *s3b, s3b_block_t block_num, void *dest,
u_char *actual_md5, const u_char *expect_md5, int strict);
static int block_cache_write_block(struct s3backer_store *s3b, s3b_block_t block_num, const void *src, u_char *md5,
check_cancel_t *check_cancel, void *check_cancel_arg);
static int block_cache_read_block_part(struct s3backer_store *s3b, s3b_block_t block_num, u_int off, u_int len, void *dest);
static int block_cache_write_block_part(struct s3backer_store *s3b, s3b_block_t block_num, u_int off, u_int len, const void *src);
static int block_cache_list_blocks(struct s3backer_store *s3b, block_list_func_t *callback, void *arg);
static int block_cache_flush(struct s3backer_store *s3b);
static void block_cache_destroy(struct s3backer_store *s3b);
/* Other functions */
static s3b_dcache_visit_t block_cache_dcache_load;
static int block_cache_read(struct block_cache_private *priv, s3b_block_t block_num, u_int off, u_int len, void *dest);
static int block_cache_do_read(struct block_cache_private *priv, s3b_block_t block_num, u_int off, u_int len, void *dest, int stats);
static int block_cache_write(struct block_cache_private *priv, s3b_block_t block_num, u_int off, u_int len, const void *src);
static void *block_cache_worker_main(void *arg);
static int block_cache_check_cancel(void *arg, s3b_block_t block_num);
static int block_cache_get_entry(struct block_cache_private *priv, struct cache_entry **entryp, void **datap);
static void block_cache_free_entry(struct block_cache_private *priv, struct cache_entry **entryp);
static void block_cache_free_one(void *arg, void *value);
static struct cache_entry *block_cache_verified(struct block_cache_private *priv, struct cache_entry *entry);
static void block_cache_dirty_callback(void *arg, void *value);
static double block_cache_dirty_ratio(struct block_cache_private *priv);
static void block_cache_worker_wait(struct block_cache_private *priv, struct cache_entry *entry);
static uint32_t block_cache_get_time(struct block_cache_private *priv);
static uint64_t block_cache_get_time_millis(void);
static int block_cache_read_data(struct block_cache_private *priv, struct cache_entry *entry, void *dest, u_int off, u_int len);
static int block_cache_write_data(struct block_cache_private *priv, struct cache_entry *entry, const void *src, u_int off,
u_int len);
/* Invariants checking */
#ifndef NDEBUG
static void block_cache_check_invariants(struct block_cache_private *priv);
static void block_cache_check_one(void *arg, void *value);
#define S3BCACHE_CHECK_INVARIANTS(priv) block_cache_check_invariants(priv)
#else
#define S3BCACHE_CHECK_INVARIANTS(priv) do { } while (0)
#endif
/*
* Wrap an underlying s3backer store with a block cache. Invoking the
* destroy method will destroy both this and the inner s3backer store.
*
* Returns NULL and sets errno on failure.
*/
struct s3backer_store *
block_cache_create(struct block_cache_conf *config, struct s3backer_store *inner)
{
struct s3backer_store *s3b;
struct block_cache_private *priv;
struct cache_entry *entry;
pthread_t thread;
int r;
/* Initialize s3backer_store structure */
if ((s3b = calloc(1, sizeof(*s3b))) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "calloc(): %s", strerror(r));
goto fail0;
}
s3b->meta_data = block_cache_meta_data;
s3b->set_mounted = block_cache_set_mounted;
s3b->read_block = block_cache_read_block;
s3b->write_block = block_cache_write_block;
s3b->read_block_part = block_cache_read_block_part;
s3b->write_block_part = block_cache_write_block_part;
s3b->list_blocks = block_cache_list_blocks;
s3b->flush = block_cache_flush;
s3b->destroy = block_cache_destroy;
/* Initialize block_cache_private structure */
if ((priv = calloc(1, sizeof(*priv))) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "calloc(): %s", strerror(r));
goto fail1;
}
priv->config = config;
priv->inner = inner;
priv->start_time = block_cache_get_time_millis();
priv->clean_timeout = (config->timeout + TIME_UNIT_MILLIS - 1) / TIME_UNIT_MILLIS;
priv->dirty_timeout = (config->write_delay + TIME_UNIT_MILLIS - 1) / TIME_UNIT_MILLIS;
if ((r = pthread_mutex_init(&priv->mutex, NULL)) != 0)
goto fail2;
if ((r = pthread_cond_init(&priv->space_avail, NULL)) != 0)
goto fail3;
if ((r = pthread_cond_init(&priv->end_reading, NULL)) != 0)
goto fail4;
if ((r = pthread_cond_init(&priv->worker_work, NULL)) != 0)
goto fail5;
if ((r = pthread_cond_init(&priv->worker_exit, NULL)) != 0)
goto fail6;
if ((r = pthread_cond_init(&priv->write_complete, NULL)) != 0)
goto fail7;
TAILQ_INIT(&priv->cleans);
TAILQ_INIT(&priv->dirties);
if ((r = s3b_hash_create(&priv->hashtable, config->cache_size)) != 0)
goto fail8;
s3b->data = priv;
/* Compute dirty ratio at which we will be writing immediately */
priv->max_dirty_ratio = (double)(config->max_dirty != 0 ? config->max_dirty : config->cache_size) / (double)config->cache_size;
if (priv->max_dirty_ratio > DIRTY_RATIO_WRITE_ASAP)
priv->max_dirty_ratio = DIRTY_RATIO_WRITE_ASAP;
/* Initialize on-disk cache and read in directory */
if (config->cache_file != NULL) {
if ((r = s3b_dcache_open(&priv->dcache, config->log, config->cache_file, config->block_size,
config->cache_size, block_cache_dcache_load, priv)) != 0)
goto fail9;
priv->stats.initial_size = priv->num_cleans;
}
/* Grab lock */
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Create threads */
for (priv->num_threads = 0; priv->num_threads < config->num_threads; priv->num_threads++) {
if ((r = pthread_create(&thread, NULL, block_cache_worker_main, priv)) != 0)
goto fail10;
}
/* Done */
pthread_mutex_unlock(&priv->mutex);
return s3b;
fail10:
priv->stopping = 1;
while (priv->num_threads > 0) {
pthread_cond_broadcast(&priv->worker_work);
pthread_cond_wait(&priv->worker_exit, &priv->mutex);
}
if (config->cache_file != NULL) {
while ((entry = TAILQ_FIRST(&priv->cleans)) != NULL) {
TAILQ_REMOVE(&priv->cleans, entry, link);
free(entry);
}
s3b_dcache_close(priv->dcache);
}
fail9:
s3b_hash_destroy(priv->hashtable);
fail8:
pthread_cond_destroy(&priv->write_complete);
fail7:
pthread_cond_destroy(&priv->worker_exit);
fail6:
pthread_cond_destroy(&priv->worker_work);
fail5:
pthread_cond_destroy(&priv->end_reading);
fail4:
pthread_cond_destroy(&priv->space_avail);
fail3:
pthread_mutex_destroy(&priv->mutex);
fail2:
free(priv);
fail1:
free(s3b);
fail0:
(*config->log)(LOG_ERR, "block_cache creation failed: %s", strerror(r));
errno = r;
return NULL;
}
/*
* Callback function to pre-load the cache from a pre-existing cache file.
*/
static int
block_cache_dcache_load(void *arg, s3b_block_t dslot, s3b_block_t block_num, const u_char *md5)
{
struct block_cache_private *const priv = arg;
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
int r;
/* Sanity check */
assert(config->cache_file != NULL);
/* Sanity check a block is not listed twice */
if ((entry = s3b_hash_get(priv->hashtable, block_num)) != NULL) {
(*config->log)(LOG_ERR, "corrupted cache file: block 0x%0*jx listed twice (in dslots %ju and %ju)",
S3B_BLOCK_NUM_DIGITS, (uintmax_t)block_num, (uintmax_t)entry->u.dslot, (uintmax_t)dslot);
return EINVAL;
}
/* Create a new cache entry in state CLEAN[2] */
assert(config->cache_file != NULL);
if ((entry = calloc(1, sizeof(*entry) + (!config->no_verify ? MD5_DIGEST_LENGTH : 0))) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "can't allocate block cache entry: %s", strerror(r));
priv->stats.out_of_memory_errors++;
return r;
}
entry->block_num = block_num;
entry->verify = !config->no_verify;
entry->timeout = block_cache_get_time(priv) + priv->clean_timeout;
if (entry->verify)
memcpy(&entry->md5, md5, MD5_DIGEST_LENGTH);
entry->u.dslot = dslot;
TAILQ_INSERT_TAIL(&priv->cleans, entry, link);
priv->num_cleans++;
s3b_hash_put_new(priv->hashtable, entry);
assert(ENTRY_GET_STATE(entry) == (config->no_verify ? CLEAN : CLEAN2));
return 0;
}
static int
block_cache_meta_data(struct s3backer_store *s3b, off_t *file_sizep, u_int *block_sizep)
{
struct block_cache_private *const priv = s3b->data;
return (*priv->inner->meta_data)(priv->inner, file_sizep, block_sizep);
}
static int
block_cache_set_mounted(struct s3backer_store *s3b, int *old_valuep, int new_value)
{
struct block_cache_private *const priv = s3b->data;
return (*priv->inner->set_mounted)(priv->inner, old_valuep, new_value);
}
static int
block_cache_flush(struct s3backer_store *const s3b)
{
struct block_cache_private *const priv = s3b->data;
/* Grab lock and sanity check */
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Wait for all dirty blocks to be written and all worker threads to exit */
priv->stopping = 1;
while (TAILQ_FIRST(&priv->dirties) != NULL || priv->num_threads > 0) {
pthread_cond_broadcast(&priv->worker_work);
pthread_cond_wait(&priv->worker_exit, &priv->mutex);
}
/* Release lock */
pthread_mutex_unlock(&priv->mutex);
return 0;
}
static void
block_cache_destroy(struct s3backer_store *const s3b)
{
struct block_cache_private *const priv = s3b->data;
struct block_cache_conf *const config = priv->config;
/* Grab lock and sanity check */
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Wait for all dirty blocks to be written and all worker threads to exit */
priv->stopping = 1;
while (TAILQ_FIRST(&priv->dirties) != NULL || priv->num_threads > 0) {
pthread_cond_broadcast(&priv->worker_work);
pthread_cond_wait(&priv->worker_exit, &priv->mutex);
}
/* Destroy inner store */
(*priv->inner->destroy)(priv->inner);
/* Free structures */
if (config->cache_file != NULL)
s3b_dcache_close(priv->dcache);
s3b_hash_foreach(priv->hashtable, block_cache_free_one, priv);
s3b_hash_destroy(priv->hashtable);
pthread_cond_destroy(&priv->write_complete);
pthread_cond_destroy(&priv->worker_exit);
pthread_cond_destroy(&priv->worker_work);
pthread_cond_destroy(&priv->end_reading);
pthread_cond_destroy(&priv->space_avail);
pthread_mutex_destroy(&priv->mutex);
free(priv);
free(s3b);
}
void
block_cache_get_stats(struct s3backer_store *s3b, struct block_cache_stats *stats)
{
struct block_cache_private *const priv = s3b->data;
pthread_mutex_lock(&priv->mutex);
memcpy(stats, &priv->stats, sizeof(*stats));
stats->current_size = s3b_hash_size(priv->hashtable);
stats->dirty_ratio = block_cache_dirty_ratio(priv);
pthread_mutex_unlock(&priv->mutex);
}
static int
block_cache_list_blocks(struct s3backer_store *s3b, block_list_func_t *callback, void *arg)
{
struct block_cache_private *const priv = s3b->data;
struct cbinfo cbinfo;
int r;
if ((r = (*priv->inner->list_blocks)(priv->inner, callback, arg)) != 0)
return r;
cbinfo.callback = callback;
cbinfo.arg = arg;
pthread_mutex_lock(&priv->mutex);
s3b_hash_foreach(priv->hashtable, block_cache_dirty_callback, &cbinfo);
pthread_mutex_unlock(&priv->mutex);
return 0;
}
static int
block_cache_read_block(struct s3backer_store *const s3b, s3b_block_t block_num, void *dest,
u_char *actual_md5, const u_char *expect_md5, int strict)
{
struct block_cache_private *const priv = s3b->data;
struct block_cache_conf *const config = priv->config;
assert(expect_md5 == NULL);
assert(actual_md5 == NULL);
return block_cache_read(priv, block_num, 0, config->block_size, dest);
}
static int
block_cache_read_block_part(struct s3backer_store *s3b, s3b_block_t block_num, u_int off, u_int len, void *dest)
{
struct block_cache_private *const priv = s3b->data;
return block_cache_read(priv, block_num, off, len, dest);
}
/*
* Read a block, and trigger read-ahead if necessary.
*/
static int
block_cache_read(struct block_cache_private *const priv, s3b_block_t block_num, u_int off, u_int len, void *dest)
{
struct block_cache_conf *const config = priv->config;
int r = 0;
/* Grab lock */
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Update count of block(s) read sequentially by the upper layer */
if (block_num == priv->seq_last + 1) {
priv->seq_count++;
if (priv->ra_count > 0)
priv->ra_count--;
} else if (block_num != priv->seq_last) {
priv->seq_count = 1;
priv->ra_count = 0;
}
priv->seq_last = block_num;
/* Wakeup a worker thread to read the next read-ahead block if needed */
if (priv->seq_count >= config->read_ahead_trigger && priv->ra_count < config->read_ahead)
pthread_cond_signal(&priv->worker_work);
/* Peform the read */
r = block_cache_do_read(priv, block_num, off, len, dest, 1);
/* Release lock */
pthread_mutex_unlock(&priv->mutex);
return r;
}
/*
* Read a block or a portion thereof.
*
* Assumes the mutex is held.
*/
static int
block_cache_do_read(struct block_cache_private *const priv, s3b_block_t block_num, u_int off, u_int len, void *dest, int stats)
{
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
u_char md5[MD5_DIGEST_LENGTH];
int verified_but_not_read = 0;
void *data = NULL;
int r;
/* Sanity check */
assert(off <= priv->config->block_size);
assert(len <= priv->config->block_size);
assert(off + len <= priv->config->block_size);
again:
/* Check to see if a cache entry already exists */
if ((entry = s3b_hash_get(priv->hashtable, block_num)) != NULL) {
assert(entry->block_num == block_num);
switch (ENTRY_GET_STATE(entry)) {
case READING: /* Wait for other thread already reading this block to finish */
case READING2:
pthread_cond_wait(&priv->end_reading, &priv->mutex);
goto again;
case CLEAN2: /* Go into READING2 state to read/verify the data */
/* Allocate temporary buffer for reading the data if necessary */
if (config->cache_file != NULL) {
if ((data = malloc(config->block_size)) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "can't allocate block cache buffer: %s", strerror(r));
return r;
}
} else
data = entry->u.data;
/* Change from CLEAN2 to READING2 */
if (config->cache_file != NULL) {
if ((r = s3b_dcache_erase_block(priv->dcache, entry->u.dslot)) != 0)
(*config->log)(LOG_ERR, "can't erase cached block! %s", strerror(r));
}
TAILQ_REMOVE(&priv->cleans, entry, link);
ENTRY_RESET_LINK(entry);
priv->num_cleans--;
entry->timeout = READING_TIMEOUT;
assert(entry->verify);
assert(ENTRY_GET_STATE(entry) == READING2);
/* Now go read/verify the data */
goto read;
case CLEAN: /* Update timestamp and move to the end of the list to maintain LRU ordering */
TAILQ_REMOVE(&priv->cleans, entry, link);
TAILQ_INSERT_TAIL(&priv->cleans, entry, link);
entry->timeout = block_cache_get_time(priv) + priv->clean_timeout;
// FALLTHROUGH
case DIRTY: /* Copy the cached data */
case WRITING:
case WRITING2:
if ((r = block_cache_read_data(priv, entry, dest, off, len)) != 0)
return r;
break;
default:
assert(0);
break;
}
if (stats)
priv->stats.read_hits++;
return 0;
}
/* Create a new cache entry in state READING */
if ((r = block_cache_get_entry(priv, &entry, &data)) != 0)
return r;
if (entry == NULL) { /* no free entries right now */
pthread_cond_wait(&priv->space_avail, &priv->mutex);
goto again;
}
entry->block_num = block_num;
entry->dirty = 0;
entry->verify = 0;
entry->timeout = READING_TIMEOUT;
ENTRY_RESET_LINK(entry);
s3b_hash_put_new(priv->hashtable, entry);
assert(ENTRY_GET_STATE(entry) == READING);
/* Update stats */
if (stats)
priv->stats.read_misses++;
read:
/* Read the block from the underlying s3backer_store */
assert(ENTRY_GET_STATE(entry) == READING || ENTRY_GET_STATE(entry) == READING2);
pthread_mutex_unlock(&priv->mutex);
r = (*priv->inner->read_block)(priv->inner, block_num, data, md5, entry->verify ? entry->md5 : NULL, 0);
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* The entry should still exist and be in state READING[2] */
assert(s3b_hash_get(priv->hashtable, block_num) == entry);
assert(ENTRY_GET_STATE(entry) == READING || ENTRY_GET_STATE(entry) == READING2);
assert(config->cache_file != NULL || entry->u.data == data);
/*
* We know two things at this point: the state is going to
* change from READING[2] and we will create new available space
* in the cache. Wake up any threads waiting on those events.
*/
pthread_cond_broadcast(&priv->end_reading);
pthread_cond_signal(&priv->space_avail);
/* Check for unexpected error from underlying s3backer_store */
if (r != 0 && !(entry->verify && r == EEXIST))
goto fail;
/* Handle READING2 blocks that were verified (revert to READING) */
if (entry->verify) {
if (r == EEXIST) { /* MD5 matched our expectation, download avoided */
priv->stats.read_hits++;
priv->stats.verified++;
verified_but_not_read = 1;
r = 0;
} else {
assert(r == 0);
priv->stats.read_misses++;
priv->stats.mismatch++;
}
entry = block_cache_verified(priv, entry);
assert(ENTRY_GET_STATE(entry) == READING);
}
/* Copy the block data's into the destination buffer */
if (!verified_but_not_read)
memcpy(dest, (char *)data + off, len);
/* Copy data into the disk cache and free temporary buffer (if necessary) */
if (config->cache_file != NULL) {
if (!verified_but_not_read) {
if ((r = s3b_dcache_write_block(priv->dcache, entry->u.dslot, data, 0, config->block_size)) != 0)
goto fail;
}
free(data);
}
/* Change entry from READING to CLEAN */
assert(ENTRY_GET_STATE(entry) == READING);
assert(!entry->verify);
if (config->cache_file != NULL) {
if ((r = s3b_dcache_record_block(priv->dcache, entry->u.dslot, entry->block_num, md5)) != 0)
(*config->log)(LOG_ERR, "can't record cached block! %s", strerror(r));
}
entry->timeout = block_cache_get_time(priv) + priv->clean_timeout;
TAILQ_INSERT_TAIL(&priv->cleans, entry, link);
priv->num_cleans++;
assert(ENTRY_GET_STATE(entry) == CLEAN);
/* If data was only verified, we have to actually go read it now */
if (verified_but_not_read)
goto again;
/* Done */
return 0;
fail:
assert(r != 0);
assert(ENTRY_GET_STATE(entry) == READING || ENTRY_GET_STATE(entry) == READING2);
if (config->cache_file != NULL)
s3b_dcache_free_block(priv->dcache, entry->u.dslot);
s3b_hash_remove(priv->hashtable, entry->block_num);
free(data);
free(entry);
return r;
}
static int
block_cache_write_block(struct s3backer_store *const s3b, s3b_block_t block_num, const void *src, u_char *md5,
check_cancel_t *check_cancel, void *check_cancel_arg)
{
struct block_cache_private *const priv = s3b->data;
struct block_cache_conf *const config = priv->config;
assert(md5 == NULL);
return block_cache_write(priv, block_num, 0, config->block_size, src);
}
static int
block_cache_write_block_part(struct s3backer_store *s3b, s3b_block_t block_num, u_int off, u_int len, const void *src)
{
struct block_cache_private *const priv = s3b->data;
return block_cache_write(priv, block_num, off, len, src);
}
/*
* Write a block or a portion thereof.
*/
static int
block_cache_write(struct block_cache_private *const priv, s3b_block_t block_num, u_int off, u_int len, const void *src)
{
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
int r;
/* Sanity check */
assert(off <= config->block_size);
assert(len <= config->block_size);
assert(off + len <= config->block_size);
/* Grab lock */
pthread_mutex_lock(&priv->mutex);
again:
/* Sanity check */
S3BCACHE_CHECK_INVARIANTS(priv);
/* Find cache entry */
if ((entry = s3b_hash_get(priv->hashtable, block_num)) != NULL) {
assert(entry->block_num == block_num);
switch (ENTRY_GET_STATE(entry)) {
case READING: /* wait for entry to leave READING */
case READING2:
pthread_cond_wait(&priv->end_reading, &priv->mutex);
goto again;
case CLEAN2: /* convert to CLEAN, then proceed */
entry = block_cache_verified(priv, entry);
// FALLTHROUGH
case CLEAN: /* update data, move to state DIRTY */
/* If there are too many dirty blocks, we have to wait */
if (config->max_dirty != 0 && priv->num_dirties >= config->max_dirty) {
pthread_cond_signal(&priv->worker_work);
pthread_cond_wait(&priv->write_complete, &priv->mutex);
goto again;
}
/* Invalidate disk cache entry */
if (config->cache_file != NULL) {
if ((r = s3b_dcache_erase_block(priv->dcache, entry->u.dslot)) != 0)
(*config->log)(LOG_ERR, "can't erase cached block! %s", strerror(r));
}
/* Change from CLEAN to DIRTY */
TAILQ_REMOVE(&priv->cleans, entry, link);
priv->num_cleans--;
TAILQ_INSERT_TAIL(&priv->dirties, entry, link);
priv->num_dirties++;
entry->timeout = block_cache_get_time(priv) + priv->dirty_timeout;
pthread_cond_signal(&priv->worker_work);
// FALLTHROUGH
case WRITING2: /* update data, stay in state WRITING2 */
case WRITING: /* update data, move to state WRITING2 */
case DIRTY: /* update data, stay in state DIRTY */
if ((r = block_cache_write_data(priv, entry, src, off, len)) != 0)
(*config->log)(LOG_ERR, "error updating dirty block! %s", strerror(r));
entry->dirty = 1;
priv->stats.write_hits++;
break;
default:
assert(0);
break;
}
goto success;
}
/*
* The block is not in the cache. If we're writing a partial block,
* we have to read it into the cache first.
*/
if (off != 0 || len != config->block_size) {
if ((r = block_cache_do_read(priv, block_num, 0, 0, NULL, 0)) != 0)
goto fail;
goto again;
}
/* If there are too many dirty blocks, we have to wait */
if (config->max_dirty != 0 && priv->num_dirties >= config->max_dirty) {
pthread_cond_signal(&priv->worker_work);
pthread_cond_wait(&priv->write_complete, &priv->mutex);
goto again;
}
/* Get a cache entry, evicting a CLEAN[2] entry if necessary */
if ((r = block_cache_get_entry(priv, &entry, NULL)) != 0)
goto fail;
/* If cache is full, wait for an entry to go CLEAN[2] so we can evict it */
if (entry == NULL) {
pthread_cond_wait(&priv->space_avail, &priv->mutex);
goto again;
}
/* Record block data */
if ((r = block_cache_write_data(priv, entry, src, off, len)) != 0)
(*config->log)(LOG_ERR, "error updating dirty block! %s", strerror(r));
/* Initialize a new DIRTY cache entry */
priv->stats.write_misses++;
entry->block_num = block_num;
entry->timeout = block_cache_get_time(priv) + priv->dirty_timeout;
entry->dirty = 1;
assert(off == 0 && len == config->block_size);
s3b_hash_put_new(priv->hashtable, entry);
TAILQ_INSERT_TAIL(&priv->dirties, entry, link);
priv->num_dirties++;
assert(ENTRY_GET_STATE(entry) == DIRTY);
/* Wake up a worker thread to go write it */
pthread_cond_signal(&priv->worker_work);
success:
/* If doing synchronous writes, wait for write to complete */
if (config->synchronous) {
while (1) {
int state;
/* Wait for notification */
pthread_cond_wait(&priv->write_complete, &priv->mutex);
/* Sanity check */
S3BCACHE_CHECK_INVARIANTS(priv);
/* Find cache entry */
if ((entry = s3b_hash_get(priv->hashtable, block_num)) == NULL)
break;
/* See if it is now clean */
state = ENTRY_GET_STATE(entry);
if (state == CLEAN || state == CLEAN2 || state == READING || state == READING2)
break;
/* Not written yet, go back to sleep */
continue;
}
}
r = 0;
fail:
/* Done */
pthread_mutex_unlock(&priv->mutex);
return r;
}
/*
* Acquire a new cache entry. If the cache is full, and there is at least one
* CLEAN[2] entry, evict and return it (uninitialized). Otherwise, return NULL entry.
*
* On successful return, *datap will point to a malloc'd buffer for the data. If using
* the disk cache, this will be a temporary buffer, otherwise it's the in-memory buffer.
* If datap == NULL, then in the case of the disk cache only, no buffer is allocated.
*
* This assumes the mutex is held.
*
* Returns non-zero on error.
*/
static int
block_cache_get_entry(struct block_cache_private *priv, struct cache_entry **entryp, void **datap)
{
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
void *data = NULL;
int r;
again:
/*
* If cache is not full, allocate a new entry. We allocate the structure
* and the data separately in hopes that the malloc() implementation will
* put the data into its own page of virtual memory.
*
* If the cache is full, try to evict a clean entry.
*/
if (s3b_hash_size(priv->hashtable) < config->cache_size) {
if ((entry = calloc(1, sizeof(*entry))) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "can't allocate block cache entry: %s", strerror(r));
priv->stats.out_of_memory_errors++;
return r;
}
} else if ((entry = TAILQ_FIRST(&priv->cleans)) != NULL) {
block_cache_free_entry(priv, &entry);
goto again;
} else
goto done;
/* Get associated data buffer */
if (datap != NULL || config->cache_file == NULL) {
if ((data = malloc(config->block_size)) == NULL) {
r = errno;
(*config->log)(LOG_ERR, "can't allocate block cache buffer: %s", strerror(r));
priv->stats.out_of_memory_errors++;
free(entry);
return r;
}
}
/* Get permanent data buffer */
if (config->cache_file == NULL)
entry->u.data = data;
else if ((r = s3b_dcache_alloc_block(priv->dcache, &entry->u.dslot)) != 0) { /* should not happen */
(*config->log)(LOG_ERR, "can't alloc cached block! %s", strerror(r));
free(data); /* OK if NULL */
data = NULL;
free(entry);
entry = NULL;
goto done;
}
done:
/* Return what we got */
*entryp = entry;
if (datap != NULL)
*datap = data;
return 0;
}
/*
* Evict a CLEAN[2] entry.
*/
static void
block_cache_free_entry(struct block_cache_private *priv, struct cache_entry **entryp)
{
struct block_cache_conf *const config = priv->config;
struct cache_entry *const entry = *entryp;
int r;
/* Sanity check */
assert(ENTRY_GET_STATE(entry) == CLEAN || ENTRY_GET_STATE(entry) == CLEAN2);
/* Invalidate caller's pointer */
*entryp = NULL;
/* Free the data */
if (config->cache_file != NULL) {
if ((r = s3b_dcache_erase_block(priv->dcache, entry->u.dslot)) != 0)
(*config->log)(LOG_ERR, "can't erase cached block! %s", strerror(r));
if ((r = s3b_dcache_free_block(priv->dcache, entry->u.dslot)) != 0)
(*config->log)(LOG_ERR, "can't free cached block! %s", strerror(r));
} else
free(entry->u.data);
/* Remove entry from the clean list */
TAILQ_REMOVE(&priv->cleans, entry, link);
s3b_hash_remove(priv->hashtable, entry->block_num);
priv->num_cleans--;
/* Free the entry */
free(entry);
}
/*
* Worker thread main entry point.
*/
static void *
block_cache_worker_main(void *arg)
{
struct block_cache_private *const priv = arg;
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
struct cache_entry *clean_entry = NULL;
u_char md5[MD5_DIGEST_LENGTH];
uint32_t adjusted_now;
uint32_t now;
u_int thread_id;
void *buf;
int r;
/* Grab lock */
pthread_mutex_lock(&priv->mutex);
/* Assign myself a thread ID (for debugging purposes) */
thread_id = priv->thread_id++;
/*
* Allocate buffer for outgoing block data. We have to copy it before we send it in case
* another write to this block comes in and updates the data associated with the cache entry.
*/
if ((buf = malloc(config->block_size)) == NULL) {
(*config->log)(LOG_ERR, "block_cache worker %u can't alloc buffer, exiting: %s", thread_id, strerror(errno));
goto done;
}
/* Repeatedly do stuff until told to stop */
while (1) {
/* Sanity check */
S3BCACHE_CHECK_INVARIANTS(priv);
/* Get current time */
now = block_cache_get_time(priv);
/* Evict any CLEAN[2] blocks that have timed out (if enabled) */
if (priv->clean_timeout != 0) {
while ((clean_entry = TAILQ_FIRST(&priv->cleans)) != NULL && now >= clean_entry->timeout) {
block_cache_free_entry(priv, &clean_entry);
pthread_cond_signal(&priv->space_avail);
}
}
/* As we approach our maximum dirty block limit, force earlier than planned writes */
adjusted_now = now + (uint32_t)(priv->dirty_timeout * (block_cache_dirty_ratio(priv) / priv->max_dirty_ratio));
/* See if there is a block that needs writing */
if ((entry = TAILQ_FIRST(&priv->dirties)) != NULL && (priv->stopping || adjusted_now >= entry->timeout)) {
/* If we are also supposed to do read-ahead, wake up a sibling to handle it */
if (priv->seq_count >= config->read_ahead_trigger && priv->ra_count < config->read_ahead)
pthread_cond_signal(&priv->worker_work);
/* Copy data to our private buffer; it may change while we're writing */
if ((r = block_cache_read_data(priv, entry, buf, 0, config->block_size)) != 0) {
(*config->log)(LOG_ERR, "error reading cached block! %s", strerror(r));
sleep(5);
continue;
}
/* Move to WRITING state */
assert(ENTRY_GET_STATE(entry) == DIRTY);
TAILQ_REMOVE(&priv->dirties, entry, link);
ENTRY_RESET_LINK(entry);
entry->dirty = 0;
entry->timeout = 0;
assert(ENTRY_GET_STATE(entry) == WRITING);
/* Attempt to write the block */
pthread_mutex_unlock(&priv->mutex);
r = (*priv->inner->write_block)(priv->inner, entry->block_num, buf, md5, block_cache_check_cancel, priv);
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Sanity checks */
assert(ENTRY_GET_STATE(entry) == WRITING || ENTRY_GET_STATE(entry) == WRITING2);
/* If write attempt failed (or we canceled it), go back to the DIRTY state and try again later */
if (r != 0) {
entry->dirty = 1;
TAILQ_INSERT_HEAD(&priv->dirties, entry, link);
continue;
}
/* If block was not modified while being written (WRITING), it is now CLEAN */
if (!entry->dirty) {
if (config->cache_file != NULL) {
if ((r = s3b_dcache_record_block(priv->dcache, entry->u.dslot, entry->block_num, md5)) != 0)
(*config->log)(LOG_ERR, "can't record cached block! %s", strerror(r));
}
priv->num_dirties--;
TAILQ_INSERT_TAIL(&priv->cleans, entry, link);
entry->verify = 0;
entry->timeout = block_cache_get_time(priv) + priv->clean_timeout;
priv->num_cleans++;
assert(ENTRY_GET_STATE(entry) == CLEAN);
pthread_cond_signal(&priv->space_avail);
pthread_cond_broadcast(&priv->write_complete);
continue;
}
/* Block was modified while being written (WRITING2), so it stays DIRTY */
TAILQ_INSERT_TAIL(&priv->dirties, entry, link);
entry->timeout = now + priv->dirty_timeout; /* update for 2nd write timing conservatively */
continue;
}
/* Are we supposed to stop? */
if (priv->stopping != 0)
break;
/* See if there is a read-ahead block that needs to be read */
if (priv->seq_count >= config->read_ahead_trigger && priv->ra_count < config->read_ahead) {
while (priv->ra_count < config->read_ahead) {
s3b_block_t ra_block;
/* We will handle read-ahead for the next read-ahead block; claim it now */
ra_block = priv->seq_last + ++priv->ra_count;
/* If block already exists in the cache, nothing needs to be done */
if (s3b_hash_get(priv->hashtable, ra_block) != NULL)
continue;
/* Perform a speculative read of the block so it will get stored in the cache */
(void)block_cache_do_read(priv, ra_block, 0, 0, NULL, 0);
break;
}
continue;
}
/* There is nothing to do at this time; sleep until there is something to do */
if (entry == NULL || (clean_entry != NULL && clean_entry->timeout < entry->timeout))
entry = clean_entry;
block_cache_worker_wait(priv, entry);
}
/* Decrement live worker thread count */
priv->num_threads--;
pthread_cond_signal(&priv->worker_exit);
done:
/* Done */
pthread_mutex_unlock(&priv->mutex);
free(buf);
return NULL;
}
/*
* See if we want to cancel the current write for the given block.
*/
static int
block_cache_check_cancel(void *arg, s3b_block_t block_num)
{
struct block_cache_private *const priv = arg;
struct cache_entry *entry;
int r;
/* Lock mutex */
pthread_mutex_lock(&priv->mutex);
S3BCACHE_CHECK_INVARIANTS(priv);
/* Find cache entry */
entry = s3b_hash_get(priv->hashtable, block_num);
/* Sanity check */
assert(entry != NULL);
assert(entry->block_num == block_num);
assert(ENTRY_GET_STATE(entry) == WRITING || ENTRY_GET_STATE(entry) == WRITING2);
/* If block is in the WRITING2 state, cancel the current (obsolete) write operation */
r = entry->dirty;
/* Unlock mutex */
pthread_mutex_unlock(&priv->mutex);
return r;
}
/*
* Sleep until either the 'worker_work' condition becomes true, or the
* entry (if any) times out.
*
* This assumes the mutex is held.
*/
static void
block_cache_worker_wait(struct block_cache_private *priv, struct cache_entry *entry)
{
uint64_t wake_time_millis;
struct timespec wake_time;
if (entry == NULL) {
pthread_cond_wait(&priv->worker_work, &priv->mutex);
return;
}
wake_time_millis = priv->start_time + ((uint64_t)entry->timeout * TIME_UNIT_MILLIS);
wake_time.tv_sec = wake_time_millis / 1000;
wake_time.tv_nsec = (wake_time_millis % 1000) * 1000000;
pthread_cond_timedwait(&priv->worker_work, &priv->mutex, &wake_time);
}
/*
* Return current time in units of TIME_UNIT_MILLIS milliseconds since startup.
*/
static uint32_t
block_cache_get_time(struct block_cache_private *priv)
{
uint64_t since_start;
since_start = block_cache_get_time_millis() - priv->start_time;
return (uint32_t)(since_start / TIME_UNIT_MILLIS);
}
/*
* Return current time in milliseconds.
*/
static uint64_t
block_cache_get_time_millis(void)
{
struct timeval tv;
gettimeofday(&tv, NULL);
return (uint64_t)tv.tv_sec * 1000 + (uint64_t)tv.tv_usec / 1000;
}
static void
block_cache_free_one(void *arg, void *value)
{
struct block_cache_private *const priv = arg;
struct block_cache_conf *const config = priv->config;
struct cache_entry *const entry = value;
if (config->cache_file == NULL)
free(entry->u.data);
free(entry);
}
/*
* Mark an entry verified and free the extra bytes we allocated for the MD5 checksum.
*/
static struct cache_entry *
block_cache_verified(struct block_cache_private *priv, struct cache_entry *entry)
{
struct cache_entry *new_entry;
/* Sanity check */
assert(entry->verify);
assert(ENTRY_GET_STATE(entry) == CLEAN2 || ENTRY_GET_STATE(entry) == READING2);
/* Give back some memory; if we can't no big deal */
if ((new_entry = realloc(entry, sizeof(*entry))) == NULL)
goto done;
/* Update all references that point to the entry */
s3b_hash_put(priv->hashtable, new_entry);
if (ENTRY_IN_LIST(entry)) {
TAILQ_REMOVE(&priv->cleans, entry, link);
TAILQ_INSERT_TAIL(&priv->cleans, new_entry, link);
}
entry = new_entry;
done:
/* Mark entry as verified */
entry->verify = 0;
return entry;
}
/*
* Read the data from a cached block into a buffer.
*/
static int
block_cache_read_data(struct block_cache_private *priv, struct cache_entry *entry, void *dest, u_int off, u_int len)
{
struct block_cache_conf *const config = priv->config;
/* Sanity check */
assert(off <= config->block_size);
assert(len <= config->block_size);
assert(off + len <= config->block_size);
/* Handle easy in-memory case */
if (config->cache_file == NULL) {
memcpy(dest, (char *)entry->u.data + off, len);
return 0;
}
/* Handle on-disk case */
return s3b_dcache_read_block(priv->dcache, entry->u.dslot, dest, off, len);
}
/*
* Write the data in a buffer to a cached block.
*/
static int
block_cache_write_data(struct block_cache_private *priv, struct cache_entry *entry, const void *src, u_int off, u_int len)
{
struct block_cache_conf *const config = priv->config;
/* Sanity check */
assert(off <= config->block_size);
assert(len <= config->block_size);
assert(off + len <= config->block_size);
/* Handle easy in-memory case */
if (config->cache_file == NULL) {
if (src == NULL)
memset((char *)entry->u.data + off, 0, len);
else
memcpy((char *)entry->u.data + off, src, len);
return 0;
}
/* Handle on-disk case */
return s3b_dcache_write_block(priv->dcache, entry->u.dslot, src, off, len);
}
/*
* Compute dirty ratio, i.e., percent of total cache space occupied by entries
* that are not CLEAN[2] or READING[2].
*/
static double
block_cache_dirty_ratio(struct block_cache_private *priv)
{
struct block_cache_conf *const config = priv->config;
return (double)priv->num_dirties / (double)config->cache_size;
}
static void
block_cache_dirty_callback(void *arg, void *value)
{
struct cbinfo *const cbinfo = arg;
struct cache_entry *const entry = value;
switch (ENTRY_GET_STATE(entry)) {
case CLEAN:
case CLEAN2:
case READING:
case READING2:
break;
case WRITING2:
case WRITING:
case DIRTY:
(*cbinfo->callback)(cbinfo->arg, entry->block_num);
break;
default:
assert(0);
break;
}
}
#ifndef NDEBUG
/* Accounting structure */
struct check_info {
u_int num_clean;
u_int num_dirty;
u_int num_reading;
u_int num_writing;
u_int num_writing2;
};
static void
block_cache_check_invariants(struct block_cache_private *priv)
{
struct block_cache_conf *const config = priv->config;
struct cache_entry *entry;
struct check_info info;
int clean_len = 0;
int dirty_len = 0;
/* Check CLEANs and CLEAN2s */
for (entry = TAILQ_FIRST(&priv->cleans); entry != NULL; entry = TAILQ_NEXT(entry, link)) {
assert(ENTRY_GET_STATE(entry) == CLEAN || ENTRY_GET_STATE(entry) == CLEAN2);
assert(s3b_hash_get(priv->hashtable, entry->block_num) == entry);
clean_len++;
}
assert(clean_len == priv->num_cleans);
/* Check DIRTYs */
for (entry = TAILQ_FIRST(&priv->dirties); entry != NULL; entry = TAILQ_NEXT(entry, link)) {
assert(ENTRY_GET_STATE(entry) == DIRTY);
assert(s3b_hash_get(priv->hashtable, entry->block_num) == entry);
dirty_len++;
}
/* Check hash table size */
assert(s3b_hash_size(priv->hashtable) <= config->cache_size);
/* Check hash table entries */
memset(&info, 0, sizeof(info));
s3b_hash_foreach(priv->hashtable, block_cache_check_one, &info);
/* Check agreement */
assert(info.num_clean == clean_len);
assert(info.num_dirty == dirty_len);
assert(info.num_clean + info.num_dirty + info.num_reading + info.num_writing + info.num_writing2
== s3b_hash_size(priv->hashtable));
assert(priv->num_dirties == info.num_dirty + info.num_writing + info.num_writing2);
/* Check read-ahead */
assert(priv->ra_count <= config->read_ahead);
}
static void
block_cache_check_one(void *arg, void *value)
{
struct cache_entry *const entry = value;
struct check_info *const info = arg;
assert(entry != NULL);
switch (ENTRY_GET_STATE(entry)) {
case CLEAN:
case CLEAN2:
info->num_clean++;
break;
case DIRTY:
info->num_dirty++;
break;
case READING:
case READING2:
assert(!entry->dirty);
info->num_reading++;
break;
case WRITING:
info->num_writing++;
break;
case WRITING2:
info->num_writing2++;
break;
default:
assert(0);
break;
}
}
#endif
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