From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F1D9AC5B572 for ; Wed, 19 Aug 2026 23:11:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 974A66B00AF; Wed, 19 Aug 2026 19:11:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 94C6E6B00B0; Wed, 19 Aug 2026 19:11:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 862D86B00B1; Wed, 19 Aug 2026 19:11:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 5B5296B00AF for ; Wed, 19 Aug 2026 19:11:00 -0400 (EDT) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id DD2818040E for ; Wed, 19 Aug 2026 23:10:59 +0000 (UTC) X-FDA: 85119566238.25.D9504A1 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf28.hostedemail.com (Postfix) with ESMTP id 1E7B3C000A for ; Wed, 19 Aug 2026 23:10:57 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h7ly3cBX; spf=pass (imf28.hostedemail.com: domain of brauner@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=brauner@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787181058; b=JmyGzyx6ggoXm6G0i2yWLnlCrGc90bKVO/uWmc+aA3OBz3SiofkJX0ELm6xUQA9f8cGivV tERaEQwNOZPCqgfzhR/LgWrvrgn9FIl3375QDqWEH4MrrIA+8DTKadtXl0eriG1202nzJo 0g9+l09tbJLdxwhlBhzwEZVhmQUeUXI= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h7ly3cBX; spf=pass (imf28.hostedemail.com: domain of brauner@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=brauner@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787181058; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=dfXAgoL+9LBeM/3gsj9qXNECM/y7xKAoBOAjrqptYLA=; b=BS3dXPeFZKo1H44Tunr9Gsr1QQwK2dPSOeBWQJIyu61aTNv7azAsb8jgyaLV2E2/q0a549 yhTfJX/3Cf2lzTg3ZjsBDQw1G3absBh6nXUhAy2C/8uYQ+84JTl2j7qnfN97gBdgEY7q5B rV5qrJLQuOwBPGLYbXCNeRJyMCHxzks= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6CCB6439D9; Wed, 19 Aug 2026 23:10:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C17171F00A3D; Wed, 19 Aug 2026 23:10:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787181057; bh=dfXAgoL+9LBeM/3gsj9qXNECM/y7xKAoBOAjrqptYLA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=h7ly3cBXNdZl7hnrgTxPREaO8oFEfhc6DvRM7kPLZVg7S7AYOKvbSlD9lhr61Eply 6jOr4ONLrlIllToPvALfSQHXVeXm6QkRDJsyAJAwXh0P5oEm1qTk3f2Ur8CZH0XB31 QU++l1mZjfVPwqPjieBgTtwk3lSZCIwowoSOdYaXBlHHSg7sC04B1d8XT23AUS4xlr pg+jQwMlNP1UfKYn/aeN27+I0aDebskxj5YMCLCEG6QgxJeBSAKlu8gf8J/9gscEcQ WfK2J0wv1iUVT5UsUTnDaFTNMGeJE2I63alCUTI+iAxn3wJb323FOgOGRANuP8CQk2 RcEKGSk7x5o2A== From: Christian Brauner Date: Thu, 20 Aug 2026 01:09:28 +0200 Subject: [PATCH v2 11/22] coredump: always chunk writes MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260820-work-coredump-sparse-v2-11-ba32dd718c51@kernel.org> References: <20260820-work-coredump-sparse-v2-0-ba32dd718c51@kernel.org> In-Reply-To: <20260820-work-coredump-sparse-v2-0-ba32dd718c51@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Jacob Lalonde , Josef Bacik , Jann Horn , Alexander Viro , Jan Kara , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Omar Sandoval , Jacob Lalonde , Shuah Khan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "Christian Brauner (Amutable)" X-Mailer: b4 0.17-dev-362b8 X-Developer-Signature: v=1; a=openpgp-sha256; l=3072; i=brauner@kernel.org; h=from:subject:message-id; bh=6lmk01oIrCpLddgF34l1qNeK7azUHFnu6/y3MNvc9fs=; b=kA0DAAoWkcYbwGV43KIByyZiAGqGN7+jKg8nZ84IvdAkuVaAv3pB/3A8P2ohgfbcn0M9u/3qY 4h1BAAWCgAdFiEEQIc0Vx6nDHizMmkokcYbwGV43KIFAmqGN78ACgkQkcYbwGV43KIysgD/a+/5 REHHWLX+2VlcBK70uw4E+bPFY60zOkDXluZRbuoBAKZwJlYA6NSqs/oHBznLIQErTWGeszoobly JDQFMN1YJ X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Rspamd-Queue-Id: 1E7B3C000A X-Rspam-User: X-Stat-Signature: gop888qr89qoq94bqq4xm7qgrphq1jm1 X-Rspamd-Server: rspam06 X-HE-Tag: 1787181057-337497 X-HE-Meta: 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 9k4sDkWp khreyU5Cgcf4XGHSm/EmuZWOJUmrFZDqpn+xs/hwi4ywoR1Dhh9QUM3XXwNZ8SQssEHiOVMArsudH407bMXfZlDwSqZfqKKCwEWCBpEZSkxAp/M21+KajsfcdP4cz1E9qUANMuAwDBNsvV1LWAR3ns2VkhhrRhNfqEdrPoEJCha1aApwyrr5Q55yLzDwpK8izvTCOESXy4iLiVxvTDMG7C6k7JSSy05b6XVTGY4rVARqFPKDIhFFWp7B75g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Right now dump_emit() is the only coredump helper that writes buffers larger than a page in one call. For elf notes that can easily blow past PAGE_SIZE. That's annoying because neither pipes nor af_unix sockets take such writes in one piece. If a signal arrives while the writer is waiting they drop a short write. With the coredump records work coming up that means header and its data are desynchronized. A write that fits in one pipe buffer or one skb doesn't suffer from this. So split all writes up, including elf notes, and cap every write at a page. The coredump socket already raises sk_sndbuf far enough for a page to fit a single skb and pipes always work that way. That means dump_interrupted() is now checked once per page. So a large coredump stops earlier (good). An empty write no longer issues a zero-length write. The rlimit core check stays where it was. It continues refusing whole writes. Signed-off-by: Christian Brauner (Amutable) --- fs/coredump.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index d837819031ff..d61f36239f91 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -1215,19 +1215,21 @@ void vfs_coredump(const kernel_siginfo_t *siginfo) * do on a core-file: use only these functions to write out all the * necessary info. */ -static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) +/* One write, never more than a page. See __dump_emit(). */ +static bool dump_emit_chunk(struct coredump_params *cprm, const void *addr, + int nr) { struct file *file = cprm->file; loff_t pos = file->f_pos; ssize_t n; - if (cprm->written + nr > cprm->limit) - return false; if (dump_interrupted()) return false; + n = __kernel_write(file, addr, nr, &pos); if (n != nr) return false; + file->f_pos = pos; cprm->written += n; cprm->pos += n; @@ -1235,6 +1237,24 @@ static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) return true; } +static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) +{ + if (cprm->written + nr > cprm->limit) + return false; + + while (nr) { + int chunk = min_t(int, nr, PAGE_SIZE); + + if (!dump_emit_chunk(cprm, addr, chunk)) + return false; + + addr += chunk; + nr -= chunk; + } + + return true; +} + static bool __dump_skip(struct coredump_params *cprm, size_t nr) { static char zeroes[PAGE_SIZE]; @@ -1247,13 +1267,16 @@ static bool __dump_skip(struct coredump_params *cprm, size_t nr) return true; } - while (nr > PAGE_SIZE) { - if (!__dump_emit(cprm, zeroes, PAGE_SIZE)) + while (nr) { + size_t chunk = min_t(size_t, nr, PAGE_SIZE); + + if (!__dump_emit(cprm, zeroes, chunk)) return false; - nr -= PAGE_SIZE; + + nr -= chunk; } - return __dump_emit(cprm, zeroes, nr); + return true; } /* Flush the accumulated hole before writing data. */ -- 2.53.0