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Add a 'consensus cache' type on top of storagedir.
Every file in the cache is labeled. The labels are held in memory; the bodies are mapped on demand.
This commit is contained in:
Nick Mathewson
@@ -0,0 +1,487 @@
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/* Copyright (c) 2017, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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#include "or.h"
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#include "config.h"
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#include "conscache.h"
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#include "storagedir.h"
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#define CCE_MAGIC 0x17162253
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/**
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* A consensus_cache_entry_t is a reference-counted handle to an
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* item in a consensus_cache_t. It can be mmapped into RAM, or not,
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* depending whether it's currently in use.
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*/
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struct consensus_cache_entry_t {
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uint32_t magic; /**< Must be set to CCE_MAGIC */
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int32_t refcnt; /**< Reference count. */
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unsigned can_remove : 1; /**< If true, we want to delete this file. */
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/** If true, we intend to unmap this file as soon as we're done with it. */
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unsigned release_aggressively : 1;
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/** Filename for this object within the storage_dir_t */
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char *fname;
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/** Labels associated with this object. Immutable once the object
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* is created. */
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config_line_t *labels;
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/** Pointer to the cache that includes this entry (if any). */
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consensus_cache_t *in_cache;
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/** Since what time has this object been mapped into RAM, but with the cache
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* being the only having a reference to it? */
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time_t unused_since;
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/** mmaped contents of the underlying file. May be NULL */
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tor_mmap_t *map;
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/** Length of the body within <b>map</b>. */
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size_t bodylen;
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/** Pointer to the body within <b>map</b>. */
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const uint8_t *body;
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};
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/**
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* A consensus_cache_t holds a directory full of labeled items.
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*/
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struct consensus_cache_t {
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/** Underling storage_dir_t to handle persistence */
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storage_dir_t *dir;
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/** List of all the entries in the directory. */
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smartlist_t *entries;
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};
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static void consensus_cache_clear(consensus_cache_t *cache);
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static void consensus_cache_rescan(consensus_cache_t *);
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static void consensus_cache_entry_map(consensus_cache_t *,
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consensus_cache_entry_t *);
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static void consensus_cache_entry_unmap(consensus_cache_entry_t *ent);
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/**
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* Helper: Open a consensus cache in subdirectory <b>subdir</b> of the
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* data directory, to hold up to <b>max_entries</b> of data.
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*/
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consensus_cache_t *
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consensus_cache_open(const char *subdir, int max_entries)
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{
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consensus_cache_t *cache = tor_malloc_zero(sizeof(consensus_cache_t));
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char *directory = get_datadir_fname(subdir);
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cache->dir = storage_dir_new(directory, max_entries);
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tor_free(directory);
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if (!cache->dir) {
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tor_free(cache);
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return NULL;
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}
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consensus_cache_rescan(cache);
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return cache;
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}
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/**
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* Helper: clear all entries from <b>cache</b> (but do not delete
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* any that aren't marked for removal
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*/
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static void
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consensus_cache_clear(consensus_cache_t *cache)
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{
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consensus_cache_delete_pending(cache);
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SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
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ent->in_cache = NULL;
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consensus_cache_entry_decref(ent);
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} SMARTLIST_FOREACH_END(ent);
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smartlist_free(cache->entries);
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cache->entries = NULL;
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}
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/**
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* Drop all storage held by <b>cache</b>.
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*/
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void
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consensus_cache_free(consensus_cache_t *cache)
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{
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if (! cache)
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return;
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if (cache->entries) {
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consensus_cache_clear(cache);
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}
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storage_dir_free(cache->dir);
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tor_free(cache);
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}
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/**
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* Write <b>datalen</b> bytes of data at <b>data</b> into the <b>cache</b>,
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* labeling that data with <b>labels</b>. On failure, return NULL. On
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* success, return a newly created consensus_cache_entry_t.
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*
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* The returned value will be owned by the cache, and you will have a
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* reference to it. Call consensus_cache_entry_decref() when you are
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* done with it.
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*
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* The provided <b>labels</b> MUST have distinct keys: if they don't,
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* this API does not specify which values (if any) for the duplicate keys
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* will be considered.
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*/
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consensus_cache_entry_t *
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consensus_cache_add(consensus_cache_t *cache,
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const config_line_t *labels,
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const uint8_t *data,
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size_t datalen)
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{
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char *fname = NULL;
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int r = storage_dir_save_labeled_to_file(cache->dir,
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labels, data, datalen, &fname);
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if (r < 0 || fname == NULL) {
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return NULL;
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}
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consensus_cache_entry_t *ent =
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tor_malloc_zero(sizeof(consensus_cache_entry_t));
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ent->magic = CCE_MAGIC;
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ent->fname = fname;
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ent->labels = config_lines_dup(labels);
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ent->in_cache = cache;
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ent->unused_since = TIME_MAX;
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smartlist_add(cache->entries, ent);
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/* Start the reference count at 2: the caller owns one copy, and the
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* cache owns another.
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*/
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ent->refcnt = 2;
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return ent;
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}
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/**
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* Given a <b>cache</b>, return some entry for which <b>key</b>=<b>value</b>.
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* Return NULL if no such entry exists.
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*
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* Does not adjust reference counts.
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*/
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consensus_cache_entry_t *
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consensus_cache_find_first(consensus_cache_t *cache,
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const char *key,
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const char *value)
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{
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smartlist_t *tmp = smartlist_new();
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consensus_cache_find_all(tmp, cache, key, value);
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consensus_cache_entry_t *ent = NULL;
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if (smartlist_len(tmp))
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ent = smartlist_get(tmp, 0);
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smartlist_free(tmp);
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return ent;
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}
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/**
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* Given a <b>cache</b>, add every entry to <b>out<b> for which
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* <b>key</b>=<b>value</b>. If <b>key</b> is NULL, add every entry.
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*
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* Does not adjust reference counts.
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*/
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void
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consensus_cache_find_all(smartlist_t *out,
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consensus_cache_t *cache,
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const char *key,
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const char *value)
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{
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if (! key) {
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smartlist_add_all(out, cache->entries);
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return;
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}
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SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
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const char *found_val = consensus_cache_entry_get_value(ent, key);
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if (found_val && !strcmp(value, found_val)) {
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smartlist_add(out, ent);
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}
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} SMARTLIST_FOREACH_END(ent);
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}
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/**
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* Given a list of consensus_cache_entry_t, remove all those entries
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* that do not have <b>key</b>=<b>value</b> in their labels.
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*
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* Does not adjust reference counts.
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*/
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void
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consensus_cache_filter_list(smartlist_t *lst,
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const char *key,
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const char *value)
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{
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if (BUG(lst == NULL))
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return; // LCOV_EXCL_LINE
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if (key == NULL)
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return;
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SMARTLIST_FOREACH_BEGIN(lst, consensus_cache_entry_t *, ent) {
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const char *found_val = consensus_cache_entry_get_value(ent, key);
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if (! found_val || strcmp(value, found_val)) {
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SMARTLIST_DEL_CURRENT(lst, ent);
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}
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} SMARTLIST_FOREACH_END(ent);
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}
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/**
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* If <b>ent</b> has a label with the given <b>key</b>, return its
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* value. Otherwise return NULL.
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*
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* The return value is only guaranteed to be valid for as long as you
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* hold a reference to <b>ent</b>.
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*/
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const char *
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consensus_cache_entry_get_value(const consensus_cache_entry_t *ent,
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const char *key)
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{
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const config_line_t *match = config_line_find(ent->labels, key);
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if (match)
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return match->value;
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else
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return NULL;
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}
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/**
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* Return a pointer to the labels in <b>ent</b>.
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*
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* This pointer is only guaranteed to be valid for as long as you
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* hold a reference to <b>ent</b>.
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*/
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const config_line_t *
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consensus_cache_entry_get_labels(const consensus_cache_entry_t *ent)
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{
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return ent->labels;
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}
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/**
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* Increase the reference count of <b>ent</b>.
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*/
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void
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consensus_cache_entry_incref(consensus_cache_entry_t *ent)
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{
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if (BUG(ent->magic != CCE_MAGIC))
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return; // LCOV_EXCL_LINE
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++ent->refcnt;
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ent->unused_since = TIME_MAX;
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}
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/**
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* Release a reference held to <b>ent</b>.
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*
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* If it was the last reference, ent will be freed. Therefore, you must not
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* use <b>ent</b> after calling this function.
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*/
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void
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consensus_cache_entry_decref(consensus_cache_entry_t *ent)
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{
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if (! ent)
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return;
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if (BUG(ent->refcnt <= 0))
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return; // LCOV_EXCL_LINE
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if (BUG(ent->magic != CCE_MAGIC))
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return; // LCOV_EXCL_LINE
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--ent->refcnt;
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if (ent->refcnt == 1 && ent->in_cache) {
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/* Only the cache has a reference: we don't need to keep the file
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* mapped */
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if (ent->map) {
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if (ent->release_aggressively) {
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consensus_cache_entry_unmap(ent);
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} else {
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ent->unused_since = approx_time();
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}
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}
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return;
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}
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if (ent->refcnt > 0)
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return;
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/* Refcount is zero; we can free it. */
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if (ent->map) {
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consensus_cache_entry_unmap(ent);
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}
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tor_free(ent->fname);
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config_free_lines(ent->labels);
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memwipe(ent, 0, sizeof(consensus_cache_entry_t));
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tor_free(ent);
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}
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/**
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* Mark <b>ent</b> for deletion from the cache. Deletion will not occur
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* until the cache is the only place that holds a reference to <b>ent</b>.
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*/
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void
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consensus_cache_entry_mark_for_removal(consensus_cache_entry_t *ent)
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{
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ent->can_remove = 1;
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}
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/**
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* Mark <b>ent</b> as the kind of entry that we don't need to keep mmap'd for
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* any longer than we're actually using it.
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*/
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void
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consensus_cache_entry_mark_for_aggressive_release(consensus_cache_entry_t *ent)
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{
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ent->release_aggressively = 1;
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}
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/**
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* Try to read the body of <b>ent</b> into memory if it isn't already
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* loaded. On success, set *<b>body_out</b> to the body, *<b>sz_out</b>
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* to its size, and return 0. On failure return -1.
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*
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* The resulting body pointer will only be valid for as long as you
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* hold a reference to <b>ent</b>.
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*/
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int
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consensus_cache_entry_get_body(const consensus_cache_entry_t *ent,
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const uint8_t **body_out,
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size_t *sz_out)
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{
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if (BUG(ent->magic != CCE_MAGIC))
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return -1; // LCOV_EXCL_LINE
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if (! ent->map) {
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if (! ent->in_cache)
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return -1;
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consensus_cache_entry_map((consensus_cache_t *)ent->in_cache,
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(consensus_cache_entry_t *)ent);
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if (! ent->map) {
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return -1;
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}
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}
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*body_out = ent->body;
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*sz_out = ent->bodylen;
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return 0;
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}
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/**
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* Unmap every mmap'd element of <b>cache</b> that has been unused
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* since <b>cutoff</b>.
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*/
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void
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consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff)
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{
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SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
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tor_assert_nonfatal(ent->in_cache == cache);
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if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
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/* Somebody is using this entry right now */
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continue;
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}
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if (ent->unused_since > cutoff) {
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/* Has been unused only for a little while */
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continue;
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}
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if (ent->map == NULL) {
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/* Not actually mapped. */
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continue;
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}
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consensus_cache_entry_unmap(ent);
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} SMARTLIST_FOREACH_END(ent);
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}
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/**
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* Delete every element of <b>cache</b> has been marked with
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* consensus_cache_entry_mark_for_removal, and which is not in use except by
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* the cache.
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*/
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void
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consensus_cache_delete_pending(consensus_cache_t *cache)
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{
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SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
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tor_assert_nonfatal(ent->in_cache == cache);
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if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
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/* Somebody is using this entry right now */
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continue;
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}
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if (ent->can_remove == 0) {
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/* Don't want to delete this. */
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continue;
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}
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if (BUG(ent->refcnt <= 0)) {
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continue; // LCOV_EXCL_LINE
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}
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SMARTLIST_DEL_CURRENT(cache->entries, ent);
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ent->in_cache = NULL;
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char *fname = tor_strdup(ent->fname); /* save a copy */
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consensus_cache_entry_decref(ent);
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storage_dir_remove_file(cache->dir, fname);
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tor_free(fname);
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} SMARTLIST_FOREACH_END(ent);
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}
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/**
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* Internal helper: rescan <b>cache</b> and rebuild its list of entries.
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*/
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static void
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consensus_cache_rescan(consensus_cache_t *cache)
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{
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if (cache->entries) {
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consensus_cache_clear(cache);
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}
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cache->entries = smartlist_new();
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const smartlist_t *fnames = storage_dir_list(cache->dir);
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SMARTLIST_FOREACH_BEGIN(fnames, const char *, fname) {
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tor_mmap_t *map = NULL;
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config_line_t *labels = NULL;
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const uint8_t *body;
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size_t bodylen;
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map = storage_dir_map_labeled(cache->dir, fname,
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&labels, &body, &bodylen);
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if (! map) {
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/* Can't load this; continue */
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log_warn(LD_FS, "Unable to map file %s from consensus cache: %s",
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escaped(fname), strerror(errno));
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continue;
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}
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consensus_cache_entry_t *ent =
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tor_malloc_zero(sizeof(consensus_cache_entry_t));
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ent->magic = CCE_MAGIC;
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ent->fname = tor_strdup(fname);
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ent->labels = labels;
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ent->refcnt = 1;
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ent->in_cache = cache;
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ent->unused_since = TIME_MAX;
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smartlist_add(cache->entries, ent);
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tor_munmap_file(map); /* don't actually need to keep this around */
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} SMARTLIST_FOREACH_END(fname);
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}
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/**
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* Make sure that <b>ent</b> is mapped into RAM.
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*/
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static void
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consensus_cache_entry_map(consensus_cache_t *cache,
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consensus_cache_entry_t *ent)
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{
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if (ent->map)
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return;
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ent->map = storage_dir_map_labeled(cache->dir, ent->fname,
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NULL, &ent->body, &ent->bodylen);
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ent->unused_since = TIME_MAX;
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}
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/**
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* Unmap <b>ent</b> from RAM.
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*
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* Do not call this if something other than the cache is holding a reference
|
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* to <b>ent</b>
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*/
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static void
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consensus_cache_entry_unmap(consensus_cache_entry_t *ent)
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{
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ent->unused_since = TIME_MAX;
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if (!ent->map)
|
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return;
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tor_munmap_file(ent->map);
|
||||
ent->map = NULL;
|
||||
ent->body = NULL;
|
||||
ent->bodylen = 0;
|
||||
ent->unused_since = TIME_MAX;
|
||||
}
|
||||
|
||||
@@ -0,0 +1,48 @@
|
||||
/* Copyright (c) 2017, The Tor Project, Inc. */
|
||||
/* See LICENSE for licensing information */
|
||||
|
||||
#ifndef TOR_CONSCACHE_H
|
||||
#define TOR_CONSCACHE_H
|
||||
|
||||
typedef struct consensus_cache_entry_t consensus_cache_entry_t;
|
||||
typedef struct consensus_cache_t consensus_cache_t;
|
||||
|
||||
consensus_cache_t *consensus_cache_open(const char *subdir, int max_entries);
|
||||
void consensus_cache_free(consensus_cache_t *cache);
|
||||
void consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff);
|
||||
void consensus_cache_delete_pending(consensus_cache_t *cache);
|
||||
consensus_cache_entry_t *consensus_cache_add(consensus_cache_t *cache,
|
||||
const config_line_t *labels,
|
||||
const uint8_t *data,
|
||||
size_t datalen);
|
||||
|
||||
consensus_cache_entry_t *consensus_cache_find_first(
|
||||
consensus_cache_t *cache,
|
||||
const char *key,
|
||||
const char *value);
|
||||
|
||||
void consensus_cache_find_all(smartlist_t *out,
|
||||
consensus_cache_t *cache,
|
||||
const char *key,
|
||||
const char *value);
|
||||
void consensus_cache_filter_list(smartlist_t *lst,
|
||||
const char *key,
|
||||
const char *value);
|
||||
|
||||
const char *consensus_cache_entry_get_value(const consensus_cache_entry_t *ent,
|
||||
const char *key);
|
||||
const config_line_t *consensus_cache_entry_get_labels(
|
||||
const consensus_cache_entry_t *ent);
|
||||
|
||||
void consensus_cache_entry_incref(consensus_cache_entry_t *ent);
|
||||
void consensus_cache_entry_decref(consensus_cache_entry_t *ent);
|
||||
|
||||
void consensus_cache_entry_mark_for_removal(consensus_cache_entry_t *ent);
|
||||
void consensus_cache_entry_mark_for_aggressive_release(
|
||||
consensus_cache_entry_t *ent);
|
||||
int consensus_cache_entry_get_body(const consensus_cache_entry_t *ent,
|
||||
const uint8_t **body_out,
|
||||
size_t *sz_out);
|
||||
|
||||
#endif
|
||||
|
||||
@@ -36,6 +36,7 @@ LIBTOR_A_SOURCES = \
|
||||
src/or/connection.c \
|
||||
src/or/connection_edge.c \
|
||||
src/or/connection_or.c \
|
||||
src/or/conscache.c \
|
||||
src/or/consdiff.c \
|
||||
src/or/control.c \
|
||||
src/or/cpuworker.c \
|
||||
@@ -152,6 +153,7 @@ ORHEADERS = \
|
||||
src/or/connection.h \
|
||||
src/or/connection_edge.h \
|
||||
src/or/connection_or.h \
|
||||
src/or/conscache.h \
|
||||
src/or/consdiff.h \
|
||||
src/or/control.h \
|
||||
src/or/cpuworker.h \
|
||||
|
||||
Reference in New Issue
Block a user