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 EAD9A1C700D for ; Mon, 19 May 2025 13:13:17 +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=1747660398; cv=none; b=POpCiWtJR+emHpy7aNX0Vbs/mitT+ZqCLzeYDw+1V7GfjHJOy4RAXPTKsAZ35GXXkzkv6wHQfzjsyOe27hHYEVA63aXYf6g3gNsyOFMlJB5nw92ZSt54Uztz2jKMGNf24frNhCmbSFQe4crlIwM8APPK1j6yFrRne9DlkRupvVA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747660398; c=relaxed/simple; bh=rloZA8+6SLz74izSzq5ihTsud/F9o3bN1Cr3+4Z0Ktw=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ZzwAmv8reiG86M5p8eXmdnU6KTa1ciuRbA1uF5QkDTHcPRD90Eghuv7xXO8qwKw58pg5khuaK26o3944nrzv0c6v1SER79jStzBxBEgGgZqxiHTcUu9J7T1YpbRSNEkbv2Guq5FQfXFXIpUp06isgslJdAD5+A9OoEr9koWKa8k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MWos5ugL; 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="MWos5ugL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 090F1C4CEE4; Mon, 19 May 2025 13:13:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1747660397; bh=rloZA8+6SLz74izSzq5ihTsud/F9o3bN1Cr3+4Z0Ktw=; h=Subject:To:Cc:From:Date:From; b=MWos5ugLzDwOnWNTmfuCH7XqxfKRlDree69/GfKPjEUw9mcdUCW8+8XOKryJaseVC lj0OxrUnOgOBvf5WexH73A6BCns1Je/RWKY+YOxzhiG8k2yStUbz/0qScHnpwPh9/x YYE0og+Ar2dq/CMlTcMTi0jTkFiMHCBqxHQiqJjI= Subject: FAILED: patch "[PATCH] mm: hugetlb: fix incorrect fallback for subpool" failed to apply to 5.15-stable tree To: mawupeng1@huawei.com,akpm@linux-foundation.org,david@redhat.com,joshua.hahnjy@gmail.com,muchun.song@linux.dev,osalvador@suse.de,stable@vger.kernel.org Cc: From: Date: Mon, 19 May 2025 15:13:08 +0200 Message-ID: <2025051908-repulsive-crazed-331a@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x a833a693a490ecff8ba377654c6d4d333718b6b1 # git commit -s git send-email --to '' --in-reply-to '2025051908-repulsive-crazed-331a@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a833a693a490ecff8ba377654c6d4d333718b6b1 Mon Sep 17 00:00:00 2001 From: Wupeng Ma Date: Thu, 10 Apr 2025 14:26:33 +0800 Subject: [PATCH] mm: hugetlb: fix incorrect fallback for subpool During our testing with hugetlb subpool enabled, we observe that hstate->resv_huge_pages may underflow into negative values. Root cause analysis reveals a race condition in subpool reservation fallback handling as follow: hugetlb_reserve_pages() /* Attempt subpool reservation */ gbl_reserve = hugepage_subpool_get_pages(spool, chg); /* Global reservation may fail after subpool allocation */ if (hugetlb_acct_memory(h, gbl_reserve) < 0) goto out_put_pages; out_put_pages: /* This incorrectly restores reservation to subpool */ hugepage_subpool_put_pages(spool, chg); When hugetlb_acct_memory() fails after subpool allocation, the current implementation over-commits subpool reservations by returning the full 'chg' value instead of the actual allocated 'gbl_reserve' amount. This discrepancy propagates to global reservations during subsequent releases, eventually causing resv_huge_pages underflow. This problem can be trigger easily with the following steps: 1. reverse hugepage for hugeltb allocation 2. mount hugetlbfs with min_size to enable hugetlb subpool 3. alloc hugepages with two task(make sure the second will fail due to insufficient amount of hugepages) 4. with for a few seconds and repeat step 3 which will make hstate->resv_huge_pages to go below zero. To fix this problem, return corrent amount of pages to subpool during the fallback after hugepage_subpool_get_pages is called. Link: https://lkml.kernel.org/r/20250410062633.3102457-1-mawupeng1@huawei.com Fixes: 1c5ecae3a93f ("hugetlbfs: add minimum size accounting to subpools") Signed-off-by: Wupeng Ma Tested-by: Joshua Hahn Reviewed-by: Oscar Salvador Cc: David Hildenbrand Cc: Ma Wupeng Cc: Muchun Song Cc: Signed-off-by: Andrew Morton diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6ea1be71aa42..7ae38bfb9096 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3010,7 +3010,7 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, struct hugepage_subpool *spool = subpool_vma(vma); struct hstate *h = hstate_vma(vma); struct folio *folio; - long retval, gbl_chg; + long retval, gbl_chg, gbl_reserve; map_chg_state map_chg; int ret, idx; struct hugetlb_cgroup *h_cg = NULL; @@ -3163,8 +3163,16 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h), h_cg); out_subpool_put: - if (map_chg) - hugepage_subpool_put_pages(spool, 1); + /* + * put page to subpool iff the quota of subpool's rsv_hpages is used + * during hugepage_subpool_get_pages. + */ + if (map_chg && !gbl_chg) { + gbl_reserve = hugepage_subpool_put_pages(spool, 1); + hugetlb_acct_memory(h, -gbl_reserve); + } + + out_end_reservation: if (map_chg != MAP_CHG_ENFORCED) vma_end_reservation(h, vma, addr); @@ -7239,7 +7247,7 @@ bool hugetlb_reserve_pages(struct inode *inode, struct vm_area_struct *vma, vm_flags_t vm_flags) { - long chg = -1, add = -1; + long chg = -1, add = -1, spool_resv, gbl_resv; struct hstate *h = hstate_inode(inode); struct hugepage_subpool *spool = subpool_inode(inode); struct resv_map *resv_map; @@ -7374,8 +7382,16 @@ bool hugetlb_reserve_pages(struct inode *inode, return true; out_put_pages: - /* put back original number of pages, chg */ - (void)hugepage_subpool_put_pages(spool, chg); + spool_resv = chg - gbl_reserve; + if (spool_resv) { + /* put sub pool's reservation back, chg - gbl_reserve */ + gbl_resv = hugepage_subpool_put_pages(spool, spool_resv); + /* + * subpool's reserved pages can not be put back due to race, + * return to hstate. + */ + hugetlb_acct_memory(h, -gbl_resv); + } out_uncharge_cgroup: hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h), chg * pages_per_huge_page(h), h_cg);