From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794591077; b=Ygrz04oSEMPv/B7/LGJWAZ3Qzfi6dt7C5nUoAPw/gmQt2idl27TWEmrE6aVCywnrUOqR lo1B+xJ/7g05Q4Trj+7v9KqMuPYrMXANMzlsUT4Dc1RbcWd0zx6ZZaau5KJe45MhlqGja KNyz9V1sUeUw1NxAc1cIymaoTm8gnE3kThpL0cSvNVX3Z6pYBedieMwjR86p781X4yepR nU+7TE6/SVxcS1R3jm72+IXU+OnKNttgjcwsyHugDCAzM8XvTDbRssYga+LEh4WgFMpYh xjt3ksK9bXH69vWoMME5pMtfdqPxIBYsRZf0NlgvMYlNDiMIuLc2YGAORwS4iZV77oQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591077; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=S2o8waxP5WWJPpwSBU45PxG+GhrtrmNhBml3nBHpPP8=; b=5ilis1M0cVFydgwAU6H7db5cdhGuDrfaT11PE+5VUT3lgWjXyOWFruwj2wwnU+v5df1Q b6Z+0NoxIPU5sWWUDyFz5k2JFR6Va29mut3m7epJHr2MXzRPla5ENntBaQ2xh/gSCGd1s 2+0OI+QJzCsgr+gzytD3hdvXE4jntbkwC3GLYNR5dHD/JhB6NiumzcSVOGioHpcp8V5F1 dweD9BRFhyYqt7d33KQZwMFEYYWxYd1hVG0P2cZWsismkhsf06jN/7Tl+2LRNsKW1HYKp rxzSAIGiTnYZmqQwSMOn3zZjYAtf+wVx08kEH45TVs3kQEk+XZTbhGA+h2ozRSV1VuQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ym3mQESO; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1905607321E; Fri, 13 Nov 2026 17:31:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ym3mQESO Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83FC51F000C4; Fri, 13 Nov 2026 17:31:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591077; bh=S2o8waxP5WWJPpwSBU45PxG+GhrtrmNhBml3nBHpPP8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ym3mQESOP6UJcwuDYvWBOtpnfPqDEKftZYujRhjzsLlekFPz2MOmQJg0jMcIQPfsq BQOkYbsAxOx7eONxsgTLqjh/+zAaXJz1PvvW5cMSxH40cVQnZDzGtanNIgeA5dkanJ TJWmd9/uwsgbtpO4QpZS0Tn+f2HZybXfJxzwbrSU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , Rik van Riel , Pedro Falcato , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.12 233/670] mm/filemap: dont lose a folio lock wakeup to a signal Date: Fri, 13 Nov 2026 10:46:37 -0500 Message-ID: <20261113153819.762733698@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josef Bacik [ Upstream commit 8ccb6ded6a47b59b4907ed4f8c293cf8122de889 ] An exclusive waiter in folio_wait_bit_common() can leave the wait loop because of a fatal signal, then be woken by folio_unlock() before finish_wait(). If the waker did not hand over the lock, the waiter returns -EINTR without trying to acquire it. folio_wake_bit() stops after waking the first exclusive waiter, so this loses the wakeup and can leave other waiters asleep indefinitely on an unlocked folio. After finish_wait(), let a waiter woken without a lock handoff try once more to acquire the lock. If successful, return success so the caller's eventual unlock wakes the next waiter. Otherwise, the current lock owner will do so. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 5ef64cc8987a ("mm: allow a controlled amount of unfairness in the page lock") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: clarify and simplify comment + description ] Reviewed-by: Rik van Riel Acked-by: Pedro Falcato Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-7-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/filemap.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 64c2325b92389..d7eab05b28f4b 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1346,10 +1346,22 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, * return value based on that state without races. * * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive - * waiter, but an exclusive one requires WQ_FLAG_DONE. + * waiter, but an exclusive one must also acquire the bit. */ - if (behavior == EXCLUSIVE) - return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR; + if (behavior == EXCLUSIVE) { + if (wait->flags & WQ_FLAG_DONE) + return 0; + /* + * We might have just been woken up and the waker will not + * wake up anybody else. If we ignore that now, the remaining + * waiters may not get woken up: take the bit now if it is + * still free. + */ + if ((wait->flags & WQ_FLAG_WOKEN) && + !test_and_set_bit(bit_nr, folio_flags(folio, 0))) + return 0; + return -EINTR; + } return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR; } -- 2.53.0