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[2003:dc:6f04:b700:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e5765152asm40025455e9.11.2026.09.10.11.22.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Sep 2026 11:22:06 -0700 (PDT) From: Max Kellermann To: dhowells@redhat.com, steved@redhat.com, viro@zeniv.linux.org.uk, netfs@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Max Kellermann , stable@vger.kernel.org Subject: [PATCH] cachefiles: pass a poll key when waking the daemon Date: Thu, 10 Sep 2026 20:22:00 +0200 Message-ID: <20260910182200.1272489-1-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: netfs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Keyless wakeups bypass epoll's event-mask filtering. With only `EPOLLOUT` registered, any cachefiles_state_changed() call will wake up the epoll_wait() system call, but will not return any events, causing a busy loop. Pass the relevant poll events with each wakeup so `epoll` can filter out unwanted notifications. Fixes: a5b3a80b899b ("CacheFiles: Provide read-and-reset release counters for cachefilesd") Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann --- Note: backports to older branches need to adjust ondemand.c as well like this: - wake_up_all(&cache->daemon_pollwq); + cachefiles_wake_poll(cache, EPOLLIN); --- fs/cachefiles/cache.c | 4 ++-- fs/cachefiles/internal.h | 15 +++++++++++++-- fs/cachefiles/namei.c | 2 +- 3 files changed, 16 insertions(+), 5 deletions(-) diff --git a/fs/cachefiles/cache.c b/fs/cachefiles/cache.c index 9fb06dc16520..08ca598618ac 100644 --- a/fs/cachefiles/cache.c +++ b/fs/cachefiles/cache.c @@ -255,7 +255,7 @@ int cachefiles_has_space(struct cachefiles_cache *cache, test_and_clear_bit(CACHEFILES_CULLING, &cache->flags) ) { _debug("cease culling"); - cachefiles_state_changed(cache); + cachefiles_state_changed(cache, EPOLLIN); } //_leave(" = 0"); @@ -275,7 +275,7 @@ int cachefiles_has_space(struct cachefiles_cache *cache, begin_cull: if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) { _debug("### CULL CACHE ###"); - cachefiles_state_changed(cache); + cachefiles_state_changed(cache, EPOLLIN | EPOLLOUT); } _leave(" = %d", ret); diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index c93324e0f98c..b8a5ea4a5ced 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -15,6 +15,7 @@ #include #include #include +#include #define CACHEFILES_DIO_BLOCK_SIZE 4096 @@ -117,13 +118,23 @@ struct cachefiles_object *cachefiles_cres_object(struct netfs_cache_resources *c return fscache_cres_cookie(cres)->cache_priv; } +/* + * Wake up the daemon polling on /dev/cachefiles. + */ +static inline void cachefiles_wake_poll(struct cachefiles_cache *cache, + __poll_t mask) +{ + __wake_up(&cache->daemon_pollwq, TASK_NORMAL, 0, poll_to_key(mask)); +} + /* * note change of state for daemon */ -static inline void cachefiles_state_changed(struct cachefiles_cache *cache) +static inline void cachefiles_state_changed(struct cachefiles_cache *cache, + __poll_t mask) { set_bit(CACHEFILES_STATE_CHANGED, &cache->flags); - wake_up_all(&cache->daemon_pollwq); + cachefiles_wake_poll(cache, mask); } /* diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c index 88955249a1a6..52eb227f07e8 100644 --- a/fs/cachefiles/namei.c +++ b/fs/cachefiles/namei.c @@ -74,7 +74,7 @@ void cachefiles_unmark_inode_in_use(struct cachefiles_object *object, if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) { atomic_long_add(inode->i_blocks, &cache->b_released); if (atomic_inc_return(&cache->f_released)) - cachefiles_state_changed(cache); + cachefiles_state_changed(cache, EPOLLIN); } } -- 2.47.3