From fa3595523d72d13508befd28cf2ca642cafc69f7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 22 Jan 2025 20:00:57 -0700 Subject: io_uring: get rid of alloc cache init_once handling init_once is called when an object doesn't come from the cache, and hence needs initial clearing of certain members. While the whole struct could get cleared by memset() in that case, a few of the cache members are large enough that this may cause unnecessary overhead if the caches used aren't large enough to satisfy the workload. For those cases, some churn of kmalloc+kfree is to be expected. Ensure that the 3 users that need clearing put the members they need cleared at the start of the struct, and wrap the rest of the struct in a struct group so the offset is known. While at it, improve the interaction with KASAN such that when/if KASAN writes to members inside the struct that should be retained over caching, it won't trip over itself. For rw and net, the retaining of the iovec over caching is disabled if KASAN is enabled. A helper will free and clear those members in that case. Signed-off-by: Jens Axboe --- io_uring/alloc_cache.h | 43 ++++++++++++++++++++++++++++++++++--------- 1 file changed, 34 insertions(+), 9 deletions(-) (limited to 'io_uring/alloc_cache.h') diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h index a3a8cfec32ce..cca96aff3277 100644 --- a/io_uring/alloc_cache.h +++ b/io_uring/alloc_cache.h @@ -6,6 +6,19 @@ */ #define IO_ALLOC_CACHE_MAX 128 +#if defined(CONFIG_KASAN) +static inline void io_alloc_cache_kasan(struct iovec **iov, int *nr) +{ + kfree(*iov); + *iov = NULL; + *nr = 0; +} +#else +static inline void io_alloc_cache_kasan(struct iovec **iov, int *nr) +{ +} +#endif + static inline bool io_alloc_cache_put(struct io_alloc_cache *cache, void *entry) { @@ -23,35 +36,47 @@ static inline void *io_alloc_cache_get(struct io_alloc_cache *cache) if (cache->nr_cached) { void *entry = cache->entries[--cache->nr_cached]; + /* + * If KASAN is enabled, always clear the initial bytes that + * must be zeroed post alloc, in case any of them overlap + * with KASAN storage. + */ +#if defined(CONFIG_KASAN) kasan_mempool_unpoison_object(entry, cache->elem_size); + if (cache->init_clear) + memset(entry, 0, cache->init_clear); +#endif return entry; } return NULL; } -static inline void *io_cache_alloc(struct io_alloc_cache *cache, gfp_t gfp, - void (*init_once)(void *obj)) +static inline void *io_cache_alloc(struct io_alloc_cache *cache, gfp_t gfp) { - if (unlikely(!cache->nr_cached)) { - void *obj = kmalloc(cache->elem_size, gfp); + void *obj; - if (obj && init_once) - init_once(obj); + obj = io_alloc_cache_get(cache); + if (obj) return obj; - } - return io_alloc_cache_get(cache); + + obj = kmalloc(cache->elem_size, gfp); + if (obj && cache->init_clear) + memset(obj, 0, cache->init_clear); + return obj; } /* returns false if the cache was initialized properly */ static inline bool io_alloc_cache_init(struct io_alloc_cache *cache, - unsigned max_nr, size_t size) + unsigned max_nr, unsigned int size, + unsigned int init_bytes) { cache->entries = kvmalloc_array(max_nr, sizeof(void *), GFP_KERNEL); if (cache->entries) { cache->nr_cached = 0; cache->max_cached = max_nr; cache->elem_size = size; + cache->init_clear = init_bytes; return false; } return true; -- cgit v1.2.3