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=1793439725; b=g1sgdFRNZGG7UMbhMNcedmf7QbBjdQGg9f4Y0oNfuWxTfrIBo7gnw7yt//UDRV1nzECk ui4maScXFAv9p5pUUN7cSQGayFboHer5VEQqkSegmH0o/MpXIbjeC/qv7zYuZRwcUEX3s bElad2fJW4v4E+nw3Xnd2++Ld2QLrzCm3ok1x+V2VPNKINOWHjzo/KDJxf1/otM91M65s QFxAO/pVqOeKbcwbWwGG5+SDM95zkf1Hamk5rJLx7goQa2ehHaIBjVFqS3p+8RHdI9Adn WKY/qe3dWhhKAkIed+gX9JHzSIhNaWnhJN+00DTvdQnSLJwDW2qc9vl99xrRda2R1XA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793439725; 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=IukBtRcm5JcTGqbT6M2HPOb7HGng0HF2onbt6cV1NiQ=; b=eO+UnYTyCnLyfUxZqQARcEIGd8oRw++ziJS+N+XSjqLi8c9chN9sAyCW5ZR93fzzeXOQ 1J/wXxiupwqjjPXmp1+QU/ih0L0SzdHVjQDcM2kqdEOpun5Bm70mdgmre9N1WSmKGDZHn xhJ7f3NXthHpwFZd63ldL1I7bvwTPZKjV9BdKj5C5Alop+ja6cnjMv8xyJJWbxdugp4bn 4YcA3zoOLnVSVynfGWp9N0EUua7Pm6/xj66rFu4fWNtLHEE306dKMyouvh7NwqkYasnTj oYcyO3af0AiHBMtc0sjroyj86TvoZc+mdotWTejN4M8VvFRIpjjP5hacbouIh9n9iPA== 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=WDvrQdG5; 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 C3E07606A31F; Sat, 31 Oct 2026 09:42:04 +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=WDvrQdG5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id E61251F000C1; Sat, 31 Oct 2026 09:41:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439724; bh=IukBtRcm5JcTGqbT6M2HPOb7HGng0HF2onbt6cV1NiQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WDvrQdG5hCiqqzMhtB/MzrVC9SfHJYmvsM+QeuMFIgZMDQPmyuobhUnHZ9+7hPQzi gVUJkZSIqfjU8K+snzcvUC7FhtT2BFPz5C0P5yt9u69tkrGqKiIu1uNXN9a3O/j54k bf8E1hUtM4jsYNl/HSzb0ag/8FNx8IkAabUZyF5mVVisr5bbYqhOGyFb9grd/xUASI +NL1vfWv5AjvaVU7Nof6g7QBNIZ1Uh0fOgswY9WBSfabF8TDyRD7azLgDW3fCSDgvf HIqjgwkJ0gsCYzWjXY6pntuKMlzjqSwb5WGm4jXkF8aCN2VCxTfPNUKpLLPVVKDUTW +dII6PS0SeO5g== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:36 +0100 Subject: [PATCH v3 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: <20261031-fixes_core-v3-7-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2320; i=david@kernel.org; h=from:subject:message-id; bh=vb6IUsg7QbXcDgoe07H04DrJ083jgsIHjnvhmRFBkeo=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk+VKpvXtEtgjfSyFg7bb8v4+ResXt4Z45c9Z0e5C ouLac2VjlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACYy/zsjw6tDMrHnJM9UGV58 27n4dF/5p226k2zXNjWKmfuVvY+b6Mnw31dyyZeEPUvLCkrS7r5lEBBXl1c7N5HvJwsTX7vOlim f+QE= 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 Tested-by: Muhammad Usama Anjum 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 906b013c11eb3..6b5e1d866a9e0 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