From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D77082F1FE1 for ; Mon, 29 Dec 2025 11:35:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767008118; cv=none; b=OhU/n2XQdV0SZoP0aPtkfDlirE0W6hQoPUGzlbQAjjRJWnzHHp7DXTL0ihg9g8xTvza9NJOQvM2bbGnUkc+vZRcGvEv2w/j0r4SsqnPdDnczInoa+jS04bZ2bnuO8rIK0e3XI1p0OdWdm4xKhN4J6a1+6uH/lSs/1lKwKaUH+18= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767008118; c=relaxed/simple; bh=AfJAfm6CpeyOTYyjis35gTooCjrFazh6E8u5OEyEh1M=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ojs+vP5jZ+p1GSW2mXpt3A2IjC/s4LF8/MXxtjAyPdPtxyY36JFF70wXMqwJMYMnIDcBCzCM6xPjWfBIabvMykVPlHaWkT2/E9URnmeFxRukxTaJ/DBIKop6/f2Uob/oU4Eg44leyO3nv83IjG7xOWqXeBHX0IPdd3XHcxE4Eyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fc2M8VL5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="fc2M8VL5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66169C4CEF7; Mon, 29 Dec 2025 11:35:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767008117; bh=AfJAfm6CpeyOTYyjis35gTooCjrFazh6E8u5OEyEh1M=; h=Subject:To:Cc:From:Date:From; b=fc2M8VL5h8jUhPCgRSBKTqKcQhzdL9LVXqVq0o/MizhyIf+29Bp0t2bfwI8ZT3POX WufhQtoLFR7dpFvzl1whPTyTWqAiMUh3zooB3Clegz+hF/KJY9rlsCiq6WXcs0cRMX hZmvvZK80GDHLkvfnL9UvT+qolTdGWfihuHoZ4uk= Subject: FAILED: patch "[PATCH] erofs: fix unexpected EIO under memory pressure" failed to apply to 6.18-stable tree To: junbeom.yeom@samsung.com,hsiangkao@linux.alibaba.com,jw5454.kim@samsung.com,sj1557.seo@samsung.com Cc: From: Date: Mon, 29 Dec 2025 12:35:15 +0100 Message-ID: <2025122915-kitchen-june-49ec@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 4012d78562193ef5eb613bad4b0c0fa187637cfe # git commit -s git send-email --to '' --in-reply-to '2025122915-kitchen-june-49ec@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4012d78562193ef5eb613bad4b0c0fa187637cfe Mon Sep 17 00:00:00 2001 From: Junbeom Yeom Date: Fri, 19 Dec 2025 21:40:31 +0900 Subject: [PATCH] erofs: fix unexpected EIO under memory pressure erofs readahead could fail with ENOMEM under the memory pressure because it tries to alloc_page with GFP_NOWAIT | GFP_NORETRY, while GFP_KERNEL for a regular read. And if readahead fails (with non-uptodate folios), the original request will then fall back to synchronous read, and `.read_folio()` should return appropriate errnos. However, in scenarios where readahead and read operations compete, read operation could return an unintended EIO because of an incorrect error propagation. To resolve this, this patch modifies the behavior so that, when the PCL is for read(which means pcl.besteffort is true), it attempts actual decompression instead of propagating the privios error except initial EIO. - Page size: 4K - The original size of FileA: 16K - Compress-ratio per PCL: 50% (Uncompressed 8K -> Compressed 4K) [page0, page1] [page2, page3] [PCL0]---------[PCL1] - functions declaration: . pread(fd, buf, count, offset) . readahead(fd, offset, count) - Thread A tries to read the last 4K - Thread B tries to do readahead 8K from 4K - RA, besteffort == false - R, besteffort == true pread(FileA, buf, 4K, 12K) do readahead(page3) // failed with ENOMEM wait_lock(page3) if (!uptodate(page3)) goto do_read readahead(FileA, 4K, 8K) // Here create PCL-chain like below: // [null, page1] [page2, null] // [PCL0:RA]-----[PCL1:RA] ... do read(page3) // found [PCL1:RA] and add page3 into it, // and then, change PCL1 from RA to R ... // Now, PCL-chain is as below: // [null, page1] [page2, page3] // [PCL0:RA]-----[PCL1:R] // try to decompress PCL-chain... z_erofs_decompress_queue err = 0; // failed with ENOMEM, so page 1 // only for RA will not be uptodated. // it's okay. err = decompress([PCL0:RA], err) // However, ENOMEM propagated to next // PCL, even though PCL is not only // for RA but also for R. As a result, // it just failed with ENOMEM without // trying any decompression, so page2 // and page3 will not be uptodated. ** BUG HERE ** --> err = decompress([PCL1:R], err) return err as ENOMEM ... wait_lock(page3) if (!uptodate(page3)) return EIO <-- Return an unexpected EIO! ... Fixes: 2349d2fa02db ("erofs: sunset unneeded NOFAILs") Cc: stable@vger.kernel.org Reviewed-by: Jaewook Kim Reviewed-by: Sungjong Seo Signed-off-by: Junbeom Yeom Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 65da21504632..3d31f7840ca0 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -1262,7 +1262,7 @@ static int z_erofs_parse_in_bvecs(struct z_erofs_backend *be, bool *overlapped) return err; } -static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, int err) +static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, bool eio) { struct erofs_sb_info *const sbi = EROFS_SB(be->sb); struct z_erofs_pcluster *pcl = be->pcl; @@ -1270,7 +1270,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, int err) const struct z_erofs_decompressor *alg = z_erofs_decomp[pcl->algorithmformat]; bool try_free = true; - int i, j, jtop, err2; + int i, j, jtop, err2, err = eio ? -EIO : 0; struct page *page; bool overlapped; const char *reason; @@ -1413,12 +1413,12 @@ static int z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io, .pcl = io->head, }; struct z_erofs_pcluster *next; - int err = io->eio ? -EIO : 0; + int err = 0; for (; be.pcl != Z_EROFS_PCLUSTER_TAIL; be.pcl = next) { DBG_BUGON(!be.pcl); next = READ_ONCE(be.pcl->next); - err = z_erofs_decompress_pcluster(&be, err) ?: err; + err = z_erofs_decompress_pcluster(&be, io->eio) ?: err; } return err; }