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=1793306119; b=Z7dyLwzZRtmPrLIe5p/nyFTOisIWwUP+kMVag4/7Ug23SSnUtk/M1amZpXl++c2RPvYx JJvFtDyFcTrGM2YvnhO3JvxQRo5ocnh72iW6Ze7zr7O4vCwmyu1CYnySH5P0ikN8Tegb8 L9aWeWWbZyZckOAI88eh7kFovuNyGIHlPDBk4PKcca+1zYXAmQAiKMfP9n9Xgxo/wzkmV wt2xdZh2td4tOtF7TGecTQPDPZHwwKChiAykmiwBJN3ECRbiBSf7j4WHu3yKcDqMHae8r 7zXCNUOLy88bF6U1oWCWJf1tFoPhJlLjxAoRtR7Y9fLf0Ql8Tk7GC9UFaD+80wLCGdw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306119; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=kFAjWqVlFrIH7aRNsfEXW0cTwDAw9D8sfuZWY6alCX0=; b=YIsgluetqXDw+nU3n3fA4dcpLIoE1O14ffelW+qYWjZL1oIJ8A+RCDyt2Gnt5gWO1D+T KFShtjYQPYs5wrJs3cOWcnxNmfXUY5n5jm0XVRta+kzq5TkY8ZumDMN4Jtx/BEbYYlclG 48+mqPawA5vk8h2dlNvbJTKYXMVc/KqhlMcZvVv09kjaC7cpkxuIwjQacSbomDUIOLSn2 5vqjCHZYbd4RO4kYo2I+wcfhzEZo6bq+Gpr//v9wt/LbGsbTbhGP2/ngnvXFOWar5V2QM b2v4zM48qQEg9K69o379gMERl3kL0IRUaxfvwT3/WSqFeritTQ8IZxXrIVYN0J84irw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="XzOcSZ0/"; 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 41783606A31C; Thu, 29 Oct 2026 20:35:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XzOcSZ0/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26A761F01828; Thu, 29 Oct 2026 20:34:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306113; bh=kFAjWqVlFrIH7aRNsfEXW0cTwDAw9D8sfuZWY6alCX0=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XzOcSZ0/8EjfLSpO8K/HcuZSOJbmmXQkIY53mzRn59GBRxsAtfiTFEDVrcM1yLKl3 oBTrNqK7TdiI9gM7WJtE7zLxyjhZPpzV0WsUkCfYL/Zq7ZgrFgNEGdSxyxupO/nLIR Fs81prGpuyNkh4h18yqjW9N0cMlbxwMV3ALHT/84WBDoVJ05WlcrWo0o5AIcoX8Ql7 0AhvnXbjkE3P/WuPhUNmmNp4c7S4pWbHzyrQPQDz0y4hQDrEGq2WCt9sVPsDVsy6e6 zuX6cUOkjI5zZKKMpRFrRsGcZ9emk6B2GcItEG2PBmoGgzccnuLwaPMBL3pmdnj64+ bnSOphJYGh87A== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:02 +0100 Subject: [PATCH v2 07/47] mm/filemap: don't lose a folio lock wakeup to a signal X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-7-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Josef Bacik , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2263; i=david@kernel.org; h=from:subject:message-id; bh=7u0AsrX18I9QfeKreay7tXsWSgpaxn4U+CWR4qcEsEM=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer2291MuXbnXaLNMw/uX1tOZXcYnK+9aeVL/nlaF4h qdaO96jo5SFQYyDQVZMkSUo+L7By5fraqvd+Jhh5rAygQxh4OIUgIkcF2P4X16RdGbNIbGQ9tV/ VrRe9lk932Zp6z6/K2/elLFvtlF9HcjIcMTwqNbp+EmRTVN1f3YYHTcs7L35TMld5fmhDd/PyCm e4gcA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A From: Josef Bacik 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 Signed-off-by: David Hildenbrand (Arm) --- mm/filemap.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 906b013c11eb..6b5e1d866a9e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1373,10 +1373,22 @@ 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; } -- 2.43.0