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 8654324503E; Tue, 20 May 2025 14:19:52 +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=1747750792; cv=none; b=KOiMAuYcZoZYgb2wvDLJhQATndK8q4cwuKaSqDxvoVUX8IrDDYVK8grRkCHMz1jKQVGy5mEyApp5G/7Akj3/ldj5f/JWlTOZaKcQ3QGVPepXHerHQRfuWx5+/x9fwH/R90DUWSZS8a3a1QUn5HcfTRpF19EcSff8e0R169smKLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747750792; c=relaxed/simple; bh=hlkfmYdrxQGUd3wkaCTHo8t+dX8SDnGle89seSvbddU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kfu9u8F7GrujRvS9W8OJ05tqRI1qyzMGP9Oco4AG+jLbtbUydhH66T7CwrT79tbg7i9GVJwlDq04SX13V+SL/PtAeOYeu3Wd8wD78W4fgzifw9ftPOHIS7dOaWLTK8tg/5BiOhR6oM8Ge9D9DkJElkp4sYp1CPQ/JQ9AoTVvyVE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=H+W7NPkY; 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="H+W7NPkY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DAC9C4CEE9; Tue, 20 May 2025 14:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1747750792; bh=hlkfmYdrxQGUd3wkaCTHo8t+dX8SDnGle89seSvbddU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H+W7NPkYxv0wYQnPJtVAZgvNFLJb++zDHNOJg7PgYaH+esZMjvgAron6PXZ9T3l3w fv0NbZylTuZxuPM41eBucgN4Msn3sZMi5Gh7W1keG/RjOyRuWyBpIWVfMn82coBC5G 8UURKFsyGymMLTiG/t0bfQZSrKQWa7+6w/mjeI7g= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wupeng Ma , Joshua Hahn , Oscar Salvador , David Hildenbrand , Muchun Song , Andrew Morton Subject: [PATCH 6.14 123/145] mm: hugetlb: fix incorrect fallback for subpool Date: Tue, 20 May 2025 15:51:33 +0200 Message-ID: <20250520125815.366321869@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250520125810.535475500@linuxfoundation.org> References: <20250520125810.535475500@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wupeng Ma commit a833a693a490ecff8ba377654c6d4d333718b6b1 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2987,7 +2987,7 @@ struct folio *alloc_hugetlb_folio(struct 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; @@ -3140,8 +3140,16 @@ out_uncharge_cgroup_reservation: 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); @@ -6949,7 +6957,7 @@ bool hugetlb_reserve_pages(struct 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; @@ -7084,8 +7092,16 @@ bool hugetlb_reserve_pages(struct 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);