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=1794047928; b=BnQOrk091D7/DjOA/Ug3bIhYASJD6qQ6stlQNJYYnEeFuHoW3BEiIf8LCeXjQDWMr8CK C+FPorvJswOxCNkszxWo8+MNJPb7Wj5+zcMoYA9+zj1zG6MN+GcZOo1NtirkvudNUGryP slKAfQpSshSEf6dQVS50yPaxylJ/EEdki9bMzL4QntVjssRe3W9oVAkv6OGfhqE9AIL5l 1OlRKhpJE5DASV7CHa1muqM38rg+HiALkptrURw0GgnAu4GEWm1kjnR7+Sa2rjQCmZHCF 7Ug84zCCxV+0zu2sqBvoHNvIRV7y14EDa9eRDIEbAzTM96vvJNG/0IqZXK/qd8/E7zw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047928; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=sYCDhy/ddNpDHnEN08LAQMRF7rTMlDQVSwDfoqQyqoU=; b=Yi/gfoUFW8Ld8JTcMZWX6Y5742SrQ6PHaRIs9N0cxnESEouPbdOCCrSMOrZQrsQJFnMh Iz54s98fiNvD6PkIp7GPzAMm3e39KWrX7+f1YPoUweYNQF8g3L0lHHnABdmjwdETsY5yx M+kcEtwwuI8dAUG0kZF4HS89N6z16BmFCjDgltKxI20ef6Bklk7gTirON21qecuzEtU+M IfG6j7+v4LS/dz75VLW8yaIr9aMWnwdOKNAipbEZctgDtX1kDaT6L2uCOkbsdwb/fL9JI /pEfNaeUzGsA+oTq6FcyyzIzU+IMHOfXnocBGLcqw7Vj57vkWxSLIdvXRz5LBAUionw== 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="JWcG/nNJ"; 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 7D1A6606A326 for ; Sat, 7 Nov 2026 10:38:48 +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=JWcG/nNJ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63AF21F0089F; Sat, 7 Nov 2026 10:38:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047928; bh=sYCDhy/ddNpDHnEN08LAQMRF7rTMlDQVSwDfoqQyqoU=; h=From:To:Cc:Subject:Date; b=JWcG/nNJXsNo+oy3jISIahWP3Qe4wOpKYvoI12BHvNpqMB8J7RGhM2uEnhYrYVMxH HBl0WUldU5MxcS2gc+Dnc3sx4fSa54K9uAM/2qHV1ARxPbfMWz9LMZ1VjskxVtGD/3 E0nHeHkObYojHa765i9uH4ZnOYnw/nNn0A7V2L1vZDat6sxpnR4ZxwdmLs7qxW7ACF saGkdup+LxWcGPoQhPMB55J7jx0TelIb1z1C00ZGO12ZmfjLix1aEvYmxlKLajSbKP 2UuzEcJ1iNyeOWZxXic8wrIDCPSCfRrmIibUkkNPVaxppbrzWZ5oATUkvdDQtjORtn u5UiAq1i5HlEw== From: Sasha Levin To: josef@toxicpanda.com, david@kernel.org, akpm@linux-foundation.org, mason@kernel.org, ljs@kernel.org, muchun.song@linux.dev, lance.yang@linux.dev, liam@infradead.org, vbabka@kernel.org, jannh@google.com, pfalcato@suse.de, osalvador@suse.de, linmiaohe@huawei.com, nao.horiguchi@gmail.com, agl@us.ibm.com, mgorman@techsingularity.net, riel@surriel.com, peterx@redhat.com, kas@kernel.org, rppt@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/hugetlb: don't clear the resv_map of a VMA whose lock is held" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:38:45 -0500 Message-ID: <20261107053845-failed-6.6-d42032c0fe3c@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 d42032c0fe3ca007986c1229128775af0340fbec # git commit -s git send-email --to '' --in-reply-to '20261107053845-failed-6.6-d42032c0fe3c@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From d42032c0fe3ca007986c1229128775af0340fbec Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 15 Oct 2026 18:07:11 +0200 Subject: [PATCH] mm/hugetlb: don't clear the resv_map of a VMA whose lock is held Since commit bf4916922c60 ("hugetlbfs: extend hugetlb_vma_lock to private VMAs") the lock of a private hugetlb VMA that owns a reservation is the rw_sema of its resv_map. The hugetlb_vma_*lock*() helpers find it through vma->vm_private_data, anew for every lock and every unlock. At the end of mremap() the old VMA has to let go of the resv_map, which now belongs to the new VMA: clear_vma_resv_huge_pages() stores NULL into vm_private_data. mremap() holds mmap_lock for writing and has write locked the VMA, which keeps away everybody who comes through the mm. It does not keep away those who find the VMA through the file. For hole punch and truncation hugetlb_vmdelete_list() does hugetlb_vma_trylock_write(vma); locks resv_map->rw_sema unmap_hugepage_range(vma, ...); vm_private_data = NULL hugetlb_vma_unlock_write(vma); no resv_map: does nothing and the rw_sema stays write locked for ever: WARNING: lock held when returning to user space! mremap_punch/116 is leaving the kernel with locks still held! locks held by mremap_punch/116: 1, last CPU#1: #0: (&resv_map->rw_sema){+.+.}-{4:4}, at: hugetlb_vmdelete_list+0x46/0x160 The next fault in the new VMA sleeps in hugetlb_vma_lock_read(), uninterruptibly, and it holds its entry of hugetlb_fault_mutex_table[]. That table is global, so a fault of any other process on a page that hashes to the same entry sleeps uninterruptibly as well. All those who take the lock of a private VMA without taking the mmap/vma lock are affected: rmap walks. So hold i_mmap_rwsem around the clearing of the resv_map. No change of behaviour, other than that mremap() of a hugetlb VMA takes i_mmap_rwsem once more. Original fix generated by an LLM and sent in private by Josef. [david: avoid local variable, move and refine comment, description cleanups+simplifications] Link: https://lore.kernel.org/20261015-urgent_fixes-v1-5-42796911043b@kernel.org Fixes: bf4916922c60 ("hugetlbfs: extend hugetlb_vma_lock to private VMAs") Signed-off-by: Josef Bacik Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Andrew Morton Reported-by: Chris Mason Reviewed-by: Lorenzo Stoakes (ARM) Acked-by: Muchun Song Reviewed-by: Lance Yang Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: Oscar Salvador Cc: Miaohe Lin Cc: Naoya Horiguchi Cc: Adam Litke Cc: Mel Gorman Cc: Rik van Riel Cc: Peter Xu Cc: Kiryl Shutsemau Cc: Mike Rapoport Cc: --- mm/hugetlb.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 4fca859bbd7ea..4a7c52802cde5 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7509,6 +7509,15 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) */ void fixup_hugetlb_reservations(struct vm_area_struct *vma) { - if (is_vm_hugetlb_page(vma)) - clear_vma_resv_huge_pages(vma); + if (!is_vm_hugetlb_page(vma)) + return; + + /* + * Rmap walks might still find this VMA and take the lock + * inside the reservation map for __vma_private_lock(). Don't clear + * the reservation map while that is possible. + */ + i_mmap_lock_write(vma->vm_file->f_mapping); + clear_vma_resv_huge_pages(vma); + i_mmap_unlock_write(vma->vm_file->f_mapping); } -- 2.53.0