fscache: Implement cache registration
Implement a register of caches and provide functions to manage it.
Two functions are provided for the cache backend to use:
(1) Acquire a cache cookie:
struct fscache_cache *fscache_acquire_cache(const char *name)
This gets the cache cookie for a cache of the specified name and moves
it to the preparation state. If a nameless cache cookie exists, that
will be given this name and used.
(2) Relinquish a cache cookie:
void fscache_relinquish_cache(struct fscache_cache *cache);
This relinquishes a cache cookie, cleans it and makes it available if
it's still referenced by a network filesystem.
Note that network filesystems don't deal with cache cookies directly, but
rather go straight to the volume registration.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819587157.215744.13523139317322503286.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906889665.143852.10378009165231294456.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967085081.1823006.2218944206363626210.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021494847.640689.10109692261640524343.stgit@warthog.procyon.org.uk/ # v4
This commit is contained in:
David Howells
parent
e8a07c9d22
commit
9549332df4
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@ -4,6 +4,7 @@
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#
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fscache-y := \
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cache.o \
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main.o
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fscache-$(CONFIG_PROC_FS) += proc.o
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@ -0,0 +1,274 @@
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// SPDX-License-Identifier: GPL-2.0-or-later
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/* FS-Cache cache handling
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define FSCACHE_DEBUG_LEVEL CACHE
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#include <linux/export.h>
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#include <linux/slab.h>
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#include "internal.h"
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static LIST_HEAD(fscache_caches);
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DECLARE_RWSEM(fscache_addremove_sem);
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EXPORT_SYMBOL(fscache_addremove_sem);
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static atomic_t fscache_cache_debug_id;
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/*
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* Allocate a cache cookie.
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*/
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static struct fscache_cache *fscache_alloc_cache(const char *name)
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{
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struct fscache_cache *cache;
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cache = kzalloc(sizeof(*cache), GFP_KERNEL);
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if (cache) {
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if (name) {
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cache->name = kstrdup(name, GFP_KERNEL);
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if (!cache->name) {
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kfree(cache);
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return NULL;
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}
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}
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refcount_set(&cache->ref, 1);
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INIT_LIST_HEAD(&cache->cache_link);
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cache->debug_id = atomic_inc_return(&fscache_cache_debug_id);
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}
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return cache;
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}
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static bool fscache_get_cache_maybe(struct fscache_cache *cache,
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enum fscache_cache_trace where)
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{
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bool success;
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int ref;
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success = __refcount_inc_not_zero(&cache->ref, &ref);
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if (success)
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trace_fscache_cache(cache->debug_id, ref + 1, where);
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return success;
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}
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/*
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* Look up a cache cookie.
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*/
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struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache)
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{
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struct fscache_cache *candidate, *cache, *unnamed = NULL;
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/* firstly check for the existence of the cache under read lock */
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down_read(&fscache_addremove_sem);
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list_for_each_entry(cache, &fscache_caches, cache_link) {
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if (cache->name && name && strcmp(cache->name, name) == 0 &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_r;
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if (!cache->name && !name &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_r;
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}
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if (!name) {
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list_for_each_entry(cache, &fscache_caches, cache_link) {
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if (cache->name &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_r;
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}
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}
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up_read(&fscache_addremove_sem);
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/* the cache does not exist - create a candidate */
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candidate = fscache_alloc_cache(name);
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if (!candidate)
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return ERR_PTR(-ENOMEM);
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/* write lock, search again and add if still not present */
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down_write(&fscache_addremove_sem);
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list_for_each_entry(cache, &fscache_caches, cache_link) {
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if (cache->name && name && strcmp(cache->name, name) == 0 &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_w;
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if (!cache->name) {
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unnamed = cache;
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if (!name &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_w;
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}
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}
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if (unnamed && is_cache &&
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fscache_get_cache_maybe(unnamed, fscache_cache_get_acquire))
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goto use_unnamed_cache;
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if (!name) {
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list_for_each_entry(cache, &fscache_caches, cache_link) {
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if (cache->name &&
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fscache_get_cache_maybe(cache, fscache_cache_get_acquire))
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goto got_cache_w;
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}
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}
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list_add_tail(&candidate->cache_link, &fscache_caches);
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trace_fscache_cache(candidate->debug_id,
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refcount_read(&candidate->ref),
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fscache_cache_new_acquire);
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up_write(&fscache_addremove_sem);
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return candidate;
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got_cache_r:
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up_read(&fscache_addremove_sem);
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return cache;
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use_unnamed_cache:
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cache = unnamed;
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cache->name = candidate->name;
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candidate->name = NULL;
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got_cache_w:
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up_write(&fscache_addremove_sem);
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kfree(candidate->name);
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kfree(candidate);
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return cache;
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}
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/**
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* fscache_acquire_cache - Acquire a cache-level cookie.
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* @name: The name of the cache.
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*
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* Get a cookie to represent an actual cache. If a name is given and there is
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* a nameless cache record available, this will acquire that and set its name,
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* directing all the volumes using it to this cache.
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*
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* The cache will be switched over to the preparing state if not currently in
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* use, otherwise -EBUSY will be returned.
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*/
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struct fscache_cache *fscache_acquire_cache(const char *name)
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{
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struct fscache_cache *cache;
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ASSERT(name);
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cache = fscache_lookup_cache(name, true);
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if (IS_ERR(cache))
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return cache;
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if (!fscache_set_cache_state_maybe(cache,
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FSCACHE_CACHE_IS_NOT_PRESENT,
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FSCACHE_CACHE_IS_PREPARING)) {
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pr_warn("Cache tag %s in use\n", name);
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fscache_put_cache(cache, fscache_cache_put_cache);
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return ERR_PTR(-EBUSY);
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}
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return cache;
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}
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EXPORT_SYMBOL(fscache_acquire_cache);
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/**
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* fscache_put_cache - Release a cache-level cookie.
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* @cache: The cache cookie to be released
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* @where: An indication of where the release happened
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*
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* Release the caller's reference on a cache-level cookie. The @where
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* indication should give information about the circumstances in which the call
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* occurs and will be logged through a tracepoint.
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*/
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void fscache_put_cache(struct fscache_cache *cache,
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enum fscache_cache_trace where)
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{
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unsigned int debug_id = cache->debug_id;
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bool zero;
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int ref;
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if (IS_ERR_OR_NULL(cache))
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return;
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zero = __refcount_dec_and_test(&cache->ref, &ref);
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trace_fscache_cache(debug_id, ref - 1, where);
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if (zero) {
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down_write(&fscache_addremove_sem);
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list_del_init(&cache->cache_link);
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up_write(&fscache_addremove_sem);
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kfree(cache->name);
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kfree(cache);
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}
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}
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/**
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* fscache_relinquish_cache - Reset cache state and release cookie
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* @cache: The cache cookie to be released
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*
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* Reset the state of a cache and release the caller's reference on a cache
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* cookie.
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*/
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void fscache_relinquish_cache(struct fscache_cache *cache)
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{
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enum fscache_cache_trace where =
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(cache->state == FSCACHE_CACHE_IS_PREPARING) ?
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fscache_cache_put_prep_failed :
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fscache_cache_put_relinquish;
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cache->cache_priv = NULL;
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smp_store_release(&cache->state, FSCACHE_CACHE_IS_NOT_PRESENT);
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fscache_put_cache(cache, where);
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}
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EXPORT_SYMBOL(fscache_relinquish_cache);
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#ifdef CONFIG_PROC_FS
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static const char fscache_cache_states[NR__FSCACHE_CACHE_STATE] = "-PAEW";
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/*
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* Generate a list of caches in /proc/fs/fscache/caches
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*/
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static int fscache_caches_seq_show(struct seq_file *m, void *v)
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{
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struct fscache_cache *cache;
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if (v == &fscache_caches) {
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seq_puts(m,
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"CACHE REF VOLS OBJS ACCES S NAME\n"
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"======== ===== ===== ===== ===== = ===============\n"
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);
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return 0;
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}
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cache = list_entry(v, struct fscache_cache, cache_link);
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seq_printf(m,
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"%08x %5d %5d %5d %5d %c %s\n",
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cache->debug_id,
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refcount_read(&cache->ref),
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atomic_read(&cache->n_volumes),
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atomic_read(&cache->object_count),
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atomic_read(&cache->n_accesses),
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fscache_cache_states[cache->state],
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cache->name ?: "-");
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return 0;
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}
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static void *fscache_caches_seq_start(struct seq_file *m, loff_t *_pos)
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__acquires(fscache_addremove_sem)
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{
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down_read(&fscache_addremove_sem);
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return seq_list_start_head(&fscache_caches, *_pos);
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}
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static void *fscache_caches_seq_next(struct seq_file *m, void *v, loff_t *_pos)
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{
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return seq_list_next(v, &fscache_caches, _pos);
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}
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static void fscache_caches_seq_stop(struct seq_file *m, void *v)
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__releases(fscache_addremove_sem)
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{
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up_read(&fscache_addremove_sem);
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}
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const struct seq_operations fscache_caches_seq_ops = {
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.start = fscache_caches_seq_start,
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.next = fscache_caches_seq_next,
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.stop = fscache_caches_seq_stop,
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.show = fscache_caches_seq_show,
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};
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#endif /* CONFIG_PROC_FS */
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@ -17,6 +17,39 @@
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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/*
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* cache.c
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*/
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#ifdef CONFIG_PROC_FS
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extern const struct seq_operations fscache_caches_seq_ops;
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#endif
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struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache);
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void fscache_put_cache(struct fscache_cache *cache, enum fscache_cache_trace where);
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static inline enum fscache_cache_state fscache_cache_state(const struct fscache_cache *cache)
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{
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return smp_load_acquire(&cache->state);
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}
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static inline bool fscache_cache_is_live(const struct fscache_cache *cache)
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{
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return fscache_cache_state(cache) == FSCACHE_CACHE_IS_ACTIVE;
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}
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static inline void fscache_set_cache_state(struct fscache_cache *cache,
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enum fscache_cache_state new_state)
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{
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smp_store_release(&cache->state, new_state);
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}
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static inline bool fscache_set_cache_state_maybe(struct fscache_cache *cache,
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enum fscache_cache_state old_state,
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enum fscache_cache_state new_state)
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{
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return try_cmpxchg_release(&cache->state, &old_state, new_state);
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}
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/*
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* main.c
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*/
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@ -19,6 +19,10 @@ int __init fscache_proc_init(void)
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if (!proc_mkdir("fs/fscache", NULL))
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goto error_dir;
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if (!proc_create_seq("fs/fscache/caches", S_IFREG | 0444, NULL,
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&fscache_caches_seq_ops))
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goto error;
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#ifdef CONFIG_FSCACHE_STATS
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if (!proc_create_single("fs/fscache/stats", S_IFREG | 0444, NULL,
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fscache_stats_show))
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@ -16,6 +16,40 @@
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#include <linux/fscache.h>
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enum fscache_cache_trace;
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enum fscache_access_trace;
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enum fscache_cache_state {
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FSCACHE_CACHE_IS_NOT_PRESENT, /* No cache is present for this name */
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FSCACHE_CACHE_IS_PREPARING, /* A cache is preparing to come live */
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FSCACHE_CACHE_IS_ACTIVE, /* Attached cache is active and can be used */
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FSCACHE_CACHE_GOT_IOERROR, /* Attached cache stopped on I/O error */
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FSCACHE_CACHE_IS_WITHDRAWN, /* Attached cache is being withdrawn */
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#define NR__FSCACHE_CACHE_STATE (FSCACHE_CACHE_IS_WITHDRAWN + 1)
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};
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/*
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* Cache cookie.
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*/
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struct fscache_cache {
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struct list_head cache_link; /* Link in cache list */
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void *cache_priv; /* Private cache data (or NULL) */
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refcount_t ref;
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atomic_t n_volumes; /* Number of active volumes; */
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atomic_t n_accesses; /* Number of in-progress accesses on the cache */
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atomic_t object_count; /* no. of live objects in this cache */
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unsigned int debug_id;
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enum fscache_cache_state state;
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char *name;
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};
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extern struct workqueue_struct *fscache_wq;
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/*
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* out-of-line cache backend functions
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*/
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extern struct rw_semaphore fscache_addremove_sem;
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extern struct fscache_cache *fscache_acquire_cache(const char *name);
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extern void fscache_relinquish_cache(struct fscache_cache *cache);
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#endif /* _LINUX_FSCACHE_CACHE_H */
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@ -19,11 +19,27 @@
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#ifndef __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
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#define __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
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enum fscache_cache_trace {
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fscache_cache_collision,
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fscache_cache_get_acquire,
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fscache_cache_new_acquire,
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fscache_cache_put_cache,
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fscache_cache_put_prep_failed,
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fscache_cache_put_relinquish,
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};
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#endif
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/*
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* Declare tracing information enums and their string mappings for display.
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*/
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#define fscache_cache_traces \
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EM(fscache_cache_collision, "*COLLIDE*") \
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EM(fscache_cache_get_acquire, "GET acq ") \
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EM(fscache_cache_new_acquire, "NEW acq ") \
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EM(fscache_cache_put_cache, "PUT cache") \
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EM(fscache_cache_put_prep_failed, "PUT pfail") \
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E_(fscache_cache_put_relinquish, "PUT relnq")
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/*
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* Export enum symbols via userspace.
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@ -33,6 +49,8 @@
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#define EM(a, b) TRACE_DEFINE_ENUM(a);
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#define E_(a, b) TRACE_DEFINE_ENUM(a);
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fscache_cache_traces;
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/*
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* Now redefine the EM() and E_() macros to map the enums to the strings that
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* will be printed in the output.
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@ -43,6 +61,31 @@
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#define E_(a, b) { a, b }
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TRACE_EVENT(fscache_cache,
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TP_PROTO(unsigned int cache_debug_id,
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int usage,
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enum fscache_cache_trace where),
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TP_ARGS(cache_debug_id, usage, where),
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TP_STRUCT__entry(
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__field(unsigned int, cache )
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__field(int, usage )
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__field(enum fscache_cache_trace, where )
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),
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TP_fast_assign(
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__entry->cache = cache_debug_id;
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__entry->usage = usage;
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__entry->where = where;
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),
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TP_printk("C=%08x %s r=%d",
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__entry->cache,
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||||
__print_symbolic(__entry->where, fscache_cache_traces),
|
||||
__entry->usage)
|
||||
);
|
||||
|
||||
#endif /* _TRACE_FSCACHE_H */
|
||||
|
||||
/* This part must be outside protection */
|
||||
|
|
|
|||
Loading…
Reference in New Issue