From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- fs/btrfs/lru_cache.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 fs/btrfs/lru_cache.h (limited to 'fs/btrfs/lru_cache.h') diff --git a/fs/btrfs/lru_cache.h b/fs/btrfs/lru_cache.h new file mode 100644 index 000000000..07f1bb1c6 --- /dev/null +++ b/fs/btrfs/lru_cache.h @@ -0,0 +1,71 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef BTRFS_LRU_CACHE_H +#define BTRFS_LRU_CACHE_H + +#include +#include +#include + +/* + * A cache entry. This is meant to be embedded in a structure of a user of + * this module. Similar to how struct list_head and struct rb_node are used. + * + * Note: it should be embedded as the first element in a struct (offset 0), and + * this module assumes it was allocated with kmalloc(), so it calls kfree() when + * it needs to free an entry. + */ +struct btrfs_lru_cache_entry { + struct list_head lru_list; + u64 key; + /* + * Optional generation associated to a key. Use 0 if not needed/used. + * Entries with the same key and different generations are stored in a + * linked list, so use this only for cases where there's a small number + * of different generations. + */ + u64 gen; + /* + * The maple tree uses unsigned long type for the keys, which is 32 bits + * on 32 bits systems, and 64 bits on 64 bits systems. So if we want to + * use something like inode numbers as keys, which are always a u64, we + * have to deal with this in a special way - we store the key in the + * entry itself, as a u64, and the values inserted into the maple tree + * are linked lists of entries - so in case we are on a 64 bits system, + * that list always has a single entry, while on 32 bits systems it + * may have more than one, with each entry having the same value for + * their lower 32 bits of the u64 key. + */ + struct list_head list; +}; + +struct btrfs_lru_cache { + struct list_head lru_list; + struct maple_tree entries; + /* Number of entries stored in the cache. */ + unsigned int size; + /* Maximum number of entries the cache can have. */ + unsigned int max_size; +}; + +#define btrfs_lru_cache_for_each_entry_safe(cache, entry, tmp) \ + list_for_each_entry_safe_reverse((entry), (tmp), &(cache)->lru_list, lru_list) + +static inline struct btrfs_lru_cache_entry *btrfs_lru_cache_lru_entry( + struct btrfs_lru_cache *cache) +{ + return list_first_entry_or_null(&cache->lru_list, + struct btrfs_lru_cache_entry, lru_list); +} + +void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size); +struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache, + u64 key, u64 gen); +int btrfs_lru_cache_store(struct btrfs_lru_cache *cache, + struct btrfs_lru_cache_entry *new_entry, + gfp_t gfp); +void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache, + struct btrfs_lru_cache_entry *entry); +void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache); + +#endif -- cgit v1.3.1