From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C64F606A327 for ; Mon, 26 Oct 2026 23:20:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=J9ZCe2L9; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=k3l8wKJU DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=QYsoVGWHtkw2Et3oC6m6nwjVDwbfipWvq0mSAbdveQ8=; b=J9ZCe2L9nOFFAV 9WndMUDCKz7I/LTd/MwsfO4AkyzbBT5kKNjRdsS8Ms5K3FNPIvsC2D72BorDdgur5UxqZPHlPypfQ CQ+DaJ4kf7Fi64LdZa3Y311f858I5Zi0l3Zj5FK0X9G8erqrgw+ucL1nuvCI8Or+ru/UDteN+EFAm UNMdYJj4Dc8w3N/NwVQ34hNV0SNq/Uuyjprvb9kg8fALynR3ZpGUq8HfegzPwPFc7zr3PzwerqNyQ Wy0bZIRcozW++9ZLcDXCiLkftKzneXunkXqX2ctBHST0wIPZyF9983OdzQIkqMec9hSNWDodPjOIQ ZzsNOXzDiH6uDANbJAWQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLTz5-00000003PLw-43dq; Mon, 26 Oct 2026 23:20:07 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLTz4-00000003PLp-3Sk4 for kexec@lists.infradead.org; Mon, 26 Oct 2026 23:20:06 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 458F5601EF; Mon, 26 Oct 2026 23:20:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A727F1F01825; Mon, 26 Oct 2026 23:19:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793056806; bh=QYsoVGWHtkw2Et3oC6m6nwjVDwbfipWvq0mSAbdveQ8=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=k3l8wKJUPoLuBGJhtUSrracjfjSgaR01/bX2LZmIh3c4sbgMmZhLpWd33Xnee7CFH eUNbDLr0zx54SOLCoUXJffQTOXAE48jWy0melTLiUWPZYrXpGfyW4gtylg1ZrpqNk4 tAqVUCS9P3zOuTzRW0zV6rxJdwAMnEz9sqZoEKhdn0nlQGxhuXj+pL6EoNoKyDXXnL ANyz/IY2YvRZ17k9m1vlaYARKC4L77al7sh0EEJ/I/Tet+XrmOZhTpKwG7wL65w2nz HCoGo/QKW6LyjEQxXookQg+D/15sIGcbWDPeXv24ecDgdjdxn+jHi6McygfzLLbHCR pqvdTr16YPXgA== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:27 +0100 Subject: [PATCH 07/46] mm/filemap: don't lose a folio lock wakeup to a signal X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261027-fixes_core-v1-7-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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=2175; i=david@kernel.org; h=from:subject:message-id; bh=Enq14m+9WKyv+oFe+xM7f34ozLLSwL77LPK+FMBugx8=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu359s5eS+49Spvoe8HVNr1wfK+bz+aOrRZTFxf2iJk IJzRKp7RykLgxgHg6yYIktQ8H2Dly/X1Va78THDzGFlAhnCwMUpABPxKWf4X3rz4dQJizbNz9j0 LP24XsGx/l6WivwJlzpu5D1zPys33Zjhf4XwVJ8bFss+nJ54IPb5q18X5G8c+75huei+w11JzjY 1XNwA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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 ] 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