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=1794273249; b=CIuAniO3dfVc8B8An7AkU6YVpAlY6Zvwy0VNXRTiNvH4oVtp4VCVNbN2//PTQsU1/h0n XWtqdu/1hrxddKRb+bFtCI1Y6X63/8sHTkQKjLCRaKhyfDB3B1lJaIhRoiMjZPyXn+FL4 K4E7/CwmqtSfASQ9BlB6BbE0ozYOMb+Ik1eLC+4IDXf/oFlovNgxmActCYwkYjZjwwvRA VBlOSnGxIHPABXrxek4E4/6GiiphQv4Rza+A85BRlQmqblp6Mpc0jl1ZaIurf+g+0ICsm d2ejhNIBFHHZMxfRRIjbi7+uYKB3HXdd/C4FdTXV05EizzTOtabZ9E8h2D0FHQKEEXw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794273249; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=/iwhHVefkbGqCF4CKIY/g81nZTJ9ta0H1pQCbsdzk+E=; b=MiI1pnP0cn18cvM9FwiWZ8qyLvYeR2cio3s83J3312VFfv18QzwgTpjkJVLqgbcnuNfr PsWWejf00oPeMusbWQXyMCSS7XcacYXEXqP1QFA8KzhAIsIN6KnlkZuwmFXSi4tkT6d9D FGVORPvX4MZx+FSZpCQ+12bkIMz9PxpWH7lc9mezoJF6cBJq2+ZN1StpRXQCaV+29p3IZ ELyRtKIx6vPnrseA0yVu9a5bPUG22xriqxhPphEKgGKCcbByIm9Fi+xm3rx6F4+loyFlj Hz/obt7bpKriJ7aBLhtt+7ldtRVhM6+Olk+QFeGhj+DQWwQDmqi1a9guACAtd8kYrtg== 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=N+TCvaI6; 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 4ECFC606A31C for ; Tue, 10 Nov 2026 01:14:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=N+TCvaI6 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73C9E1F008A1; Tue, 10 Nov 2026 01:14:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794273249; bh=/iwhHVefkbGqCF4CKIY/g81nZTJ9ta0H1pQCbsdzk+E=; h=From:To:Cc:Subject:Date; b=N+TCvaI6d7NZ+Rq0ptYiQKKPxp4j5xzDHmSYV7A5QI5nvydNX5I5gvq3JZI9N5VTB BTJffaR0+wQ3aZg0D5ADPAij2+0/rWE6fiot16bTboLizxeObs51VkyfqIhcOKI5pB IKf2j5QGzbY4tvoXHIuuzHgOEFuUvYSGcknilMyvlaHVR3ogrt2fXhlOaN2NZ6FIcW 1IOSHgiG5++CgqkwsTKW8W5F89QR+tsoRYu1hJ7jqB5UsEXrzDcMQCl6Luyk4B3mxf tMbzzrz4N9RSg3xr82WUgvGWTF+TMMAUrzkvkS0JT4vxa2VyIZM5pREME5T/gxXM9b GPj0LK6gI1Alg== From: Sasha Levin To: lance.yang@linux.dev, pfalcato@suse.de, david@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] khugepaged: fix readahead lock inversion in collapse_file()" failed to apply to 6.6-stable tree Date: Mon, 9 Nov 2026 20:14:07 -0500 Message-ID: <20261109201407-failed-6.6-eadce52a9ef6@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@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: 8bit The patch below does not apply to the 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x eadce52a9ef657d561b3e76c9b5f178bd99735f5 # git commit -s git send-email --to '' --in-reply-to '20261109201407-failed-6.6-eadce52a9ef6@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From eadce52a9ef657d561b3e76c9b5f178bd99735f5 Mon Sep 17 00:00:00 2001 From: Lance Yang Date: Mon, 26 Oct 2026 23:20:13 +0800 Subject: [PATCH] khugepaged: fix readahead lock inversion in collapse_file() collapse_file() can call page_cache_sync_readahead() while still holding source folios locked. If truncate holds mapping->invalidate_lock exclusively and waits for one of those folios, readahead waits for invalidate_lock and neither side can make progress. We need to release those folio locks before starting readahead. On a page cache miss, roll back first, populate the collapse range, and retry once. Doing readahead after rollback avoids an extra pass when all folios are already present. If another miss occurs on retry, give up rather than keep retrying while truncate or reclaim removes folios. Keep page_cache_sync_readahead() and wait for read I/O with filemap_lock_folio(), releasing each folio before moving to the next. The existing uptodate check during collapse still handles read errors. Shmem uses shmem_get_folio() for swapin and fallocated folios without taking mapping->invalidate_lock, so it is unaffected. Reported-by: syzbot+16bf7cd0ebeb1de93aa5@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=16bf7cd0ebeb1de93aa5 Fixes: 730633f0b7f9 ("mm: Protect operations adding pages to page cache with invalidate_lock") Cc: stable@vger.kernel.org Signed-off-by: Lance Yang Reviewed-by: Pedro Falcato Acked-by: David Hildenbrand (Arm) Acked-by: Zi Yan Reviewed-by: Baolin Wang Link: https://patch.msgid.link/20261026152013.10511-1-lance.yang@linux.dev Signed-off-by: David Hildenbrand (Arm) --- mm/khugepaged.c | 44 +++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index ce794d9760a87..6d5a44cf3a00b 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2240,6 +2240,8 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); enum scan_result result = SCAN_SUCCEED; int nr_none = 0; + bool do_readahead = false; + bool readahead_done = false; /* * MADV_COLLAPSE ignores shmem huge config, so do not check shmem @@ -2257,6 +2259,10 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, mapping_set_update(&xas, mapping); +retry: + result = SCAN_SUCCEED; + do_readahead = false; + xas_set_order(&xas, start, HPAGE_PMD_ORDER); __folio_set_locked(new_folio); if (is_shmem) __folio_set_swapbacked(new_folio); @@ -2321,17 +2327,9 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, } } else { /* !is_shmem */ if (!folio || xa_is_value(folio)) { - xas_unlock_irq(&xas); - page_cache_sync_readahead(mapping, &file->f_ra, - file, index, - end - index); - /* drain lru cache to help folio_isolate_lru() */ - lru_add_drain(); - folio = filemap_lock_folio(mapping, index); - if (IS_ERR(folio)) { - result = SCAN_FAIL; - goto xa_unlocked; - } + do_readahead = !readahead_done; + result = SCAN_FAIL; + goto xa_locked; } else if (folio_test_dirty(folio)) { /* * This page is dirty because it hasn't @@ -2654,6 +2652,30 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, new_folio->mapping = NULL; folio_unlock(new_folio); + + /* Readahead may take invalidate_lock; source folios are unlocked. */ + if (do_readahead) { + for (index = start; index < end;) { + folio = filemap_lock_folio(mapping, index); + if (IS_ERR(folio)) { + page_cache_sync_readahead(mapping, &file->f_ra, + file, index, end - index); + folio = filemap_lock_folio(mapping, index); + if (IS_ERR(folio)) { + result = SCAN_FAIL; + goto out_put; + } + } + index = folio_next_index(folio); + folio_unlock(folio); + folio_put(folio); + } + /* Drain the local LRU batch before retrying isolation. */ + lru_add_drain(); + readahead_done = true; + goto retry; + } +out_put: folio_put(new_folio); out: VM_BUG_ON(!list_empty(&pagelist)); -- 2.53.0