From patchwork Tue Aug 16 17:45:28 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Barry X-Patchwork-Id: 1072072 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p7GHk7cO030090 for ; Tue, 16 Aug 2011 17:46:07 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751543Ab1HPRpr (ORCPT ); Tue, 16 Aug 2011 13:45:47 -0400 Received: from exprod6og115.obsmtp.com ([64.18.1.35]:52424 "EHLO exprod6og115.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751233Ab1HPRpq (ORCPT ); Tue, 16 Aug 2011 13:45:46 -0400 Received: from cfexcas02.americas.cray.com ([136.162.34.11]) (using TLSv1) by exprod6ob115.postini.com ([64.18.5.12]) with SMTP ID DSNKTkqsuYfDn7xxerx0m+5B0LYgwAZjIEe+@postini.com; Tue, 16 Aug 2011 10:45:46 PDT Received: from lnx-abarry.us.cray.com (172.31.17.80) by cfexcas02.americas.cray.com (172.30.74.226) with Microsoft SMTP Server (TLS) id 8.3.192.1; Tue, 16 Aug 2011 12:45:28 -0500 Message-ID: <4E4AACB8.3090007@cray.com> Date: Tue, 16 Aug 2011 12:45:28 -0500 From: Andrew Barry User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100317 SUSE/3.0.4-2.3 Lightning/1.0b1 Thunderbird/3.0.4 MIME-Version: 1.0 To: "linux-kernel@vger.kernel.org" CC: Hugh Dickins , Avi Kivity , Marcelo Tosatti , Jan Kiszka , "qemu-devel@nongnu.org" , "agraf@suse.de" , kvm , Paul Mackerras , KOSAKI Motohiro , Andrew Morton , KAMEZAWA Hiroyuki , Mel Gorman , Andrew Hastings , Adam Litke , Minchan Kim Subject: [RFC PATCH] mm/hugepages: Fix race between hugetlbfs umount and quota update. References: <20110811064059.GU6342@yookeroo.fritz.box> <20110813010839.GC30552@yookeroo.fritz.box> <4E4980BF.7090801@cray.com> <20110816034748.GG18203@yookeroo.fritz.box> In-Reply-To: <20110816034748.GG18203@yookeroo.fritz.box> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Tue, 16 Aug 2011 17:46:07 +0000 (UTC) Discussion was titled: Fix refcounting in hugetlbfs quota handling This patch fixes a race between the umount of a hugetlbfs filesystem, and quota updates in that filesystem, which can result in the update of the filesystem quota record, after the record structure has been freed. Rather than an address-space struct pointer, it puts a hugetlbfs_sb_info struct pointer into page_private of the page struct. A reference count and an active bit are added to the hugetlbfs_sb_info struct; the reference count is increased by hugetlb_get_quota and decreased by hugetlb_put_quota. When hugetlbfs is unmounted, it frees the hugetlbfs_sb_info struct, but only if the reference count is zero, otherwise it clears the active bit. The last hugetlb_put_quota then frees the hugetlbfs_sb_info struct. Signed-off-by: Andrew Barry --- fs/hugetlbfs/inode.c | 40 ++++++++++++++++++++++++++-------------- include/linux/hugetlb.h | 9 +++++++-- mm/hugetlb.c | 22 +++++++++++----------- 3 files changed, 44 insertions(+), 27 deletions(-) @@ -551,8 +551,8 @@ static void free_huge_page(struct page * enqueue_huge_page(h, page); } spin_unlock(&hugetlb_lock); - if (mapping) - hugetlb_put_quota(mapping, 1); + if (sbinfo) + hugetlb_put_quota(sbinfo, 1); } static void prep_new_huge_page(struct hstate *h, struct page *page, int nid) @@ -1035,7 +1035,7 @@ static struct page *alloc_huge_page(stru if (chg < 0) return ERR_PTR(-VM_FAULT_OOM); if (chg) - if (hugetlb_get_quota(inode->i_mapping, chg)) + if (hugetlb_get_quota(HUGETLBFS_SB(inode->i_mapping->host->i_sb), chg)) return ERR_PTR(-VM_FAULT_SIGBUS); spin_lock(&hugetlb_lock); @@ -1045,12 +1045,12 @@ static struct page *alloc_huge_page(stru if (!page) { page = alloc_buddy_huge_page(h, NUMA_NO_NODE); if (!page) { - hugetlb_put_quota(inode->i_mapping, chg); + hugetlb_put_quota(HUGETLBFS_SB(inode->i_mapping->host->i_sb), chg); return ERR_PTR(-VM_FAULT_SIGBUS); } } - set_page_private(page, (unsigned long) mapping); + set_page_private(page, (unsigned long) HUGETLBFS_SB(inode->i_mapping->host->i_sb)); vma_commit_reservation(h, vma, addr); @@ -2086,7 +2086,7 @@ static void hugetlb_vm_op_close(struct v if (reserve) { hugetlb_acct_memory(h, -reserve); - hugetlb_put_quota(vma->vm_file->f_mapping, reserve); + hugetlb_put_quota(HUGETLBFS_SB(vma->vm_file->f_mapping->host->i_sb), reserve); } } } @@ -2884,7 +2884,7 @@ int hugetlb_reserve_pages(struct inode * return chg; /* There must be enough filesystem quota for the mapping */ - if (hugetlb_get_quota(inode->i_mapping, chg)) + if (hugetlb_get_quota(HUGETLBFS_SB(inode->i_mapping->host->i_sb), chg)) return -ENOSPC; /* @@ -2893,7 +2893,7 @@ int hugetlb_reserve_pages(struct inode * */ ret = hugetlb_acct_memory(h, chg); if (ret < 0) { - hugetlb_put_quota(inode->i_mapping, chg); + hugetlb_put_quota(HUGETLBFS_SB(inode->i_mapping->host->i_sb), chg); return ret; } @@ -2922,7 +2922,7 @@ void hugetlb_unreserve_pages(struct inod inode->i_blocks -= (blocks_per_huge_page(h) * freed); spin_unlock(&inode->i_lock); - hugetlb_put_quota(inode->i_mapping, (chg - freed)); + hugetlb_put_quota(HUGETLBFS_SB(inode->i_mapping->host->i_sb), (chg - freed)); hugetlb_acct_memory(h, -(chg - freed)); } On 08/15/2011 10:47 PM, David Gibson wrote: > On Mon, Aug 15, 2011 at 03:25:35PM -0500, Andrew Barry wrote: >> I've been doing something similar to this last proposal. I put a >> hugetlbfs_sb_info pointer into page_private, and dropped a reference counter and >> an active/inactive bit into the hugetlbfs_sb_info struct. At Umount time, the >> sbinfo is freed, only if the reference count is zero. Otherwise, the last >> put_quota frees the sbinfo structure. This fixed the race we were seeing between >> umount and a put_quota from an rdma transaction. I just gave it a cursory test >> on a 3.0 kernel; it has seen quite a lot more testing on a 2.6.32-derived >> kernel, with no more hits of the umount race. >> >> Does this address the problems you were thinking about? > > Ah, this looks much better than my patch. And the fact that you've > seen your race demonstrates clearly that this isn't just a kvm > problem. I hope we can push this upstream very soon - what can I do > to help? > >> -Andrew Barry >> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 87b6e04..2ed1cca 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -615,8 +615,12 @@ static void hugetlbfs_put_super(struct s struct hugetlbfs_sb_info *sbi = HUGETLBFS_SB(sb); if (sbi) { + sbi->active = HPAGE_INACTIVE; sb->s_fs_info = NULL; - kfree(sbi); + + /*Free only if used quota is zero. */ + if (sbi->used_blocks == 0) + kfree(sbi); } } @@ -851,6 +855,8 @@ hugetlbfs_fill_super(struct super_block sbinfo->free_blocks = config.nr_blocks; sbinfo->max_inodes = config.nr_inodes; sbinfo->free_inodes = config.nr_inodes; + sbinfo->used_blocks = 0; + sbinfo->active = HPAGE_ACTIVE; sb->s_maxbytes = MAX_LFS_FILESIZE; sb->s_blocksize = huge_page_size(config.hstate); sb->s_blocksize_bits = huge_page_shift(config.hstate); @@ -874,30 +880,36 @@ out_free: return -ENOMEM; } -int hugetlb_get_quota(struct address_space *mapping, long delta) +int hugetlb_get_quota(struct hugetlbfs_sb_info *sbinfo, long delta) { int ret = 0; - struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb); - if (sbinfo->free_blocks > -1) { - spin_lock(&sbinfo->stat_lock); - if (sbinfo->free_blocks - delta >= 0) + spin_lock(&sbinfo->stat_lock); + if ((sbinfo->free_blocks == -1) || (sbinfo->free_blocks - delta >= 0)) { + if (sbinfo->free_blocks != -1) sbinfo->free_blocks -= delta; - else - ret = -ENOMEM; - spin_unlock(&sbinfo->stat_lock); + sbinfo->used_blocks += delta; + sbinfo->active = HPAGE_ACTIVE; + } else { + ret = -ENOMEM; } + spin_unlock(&sbinfo->stat_lock); return ret; } -void hugetlb_put_quota(struct address_space *mapping, long delta) +void hugetlb_put_quota(struct hugetlbfs_sb_info *sbinfo, long delta) { - struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb); - - if (sbinfo->free_blocks > -1) { - spin_lock(&sbinfo->stat_lock); + spin_lock(&sbinfo->stat_lock); + if (sbinfo->free_blocks > -1) sbinfo->free_blocks += delta; + sbinfo->used_blocks -= delta; + /* If hugetlbfs_put_super couldn't free sbinfo due to + * an outstanding quota reference, free it now. */ + if ((sbinfo->used_blocks == 0) && (sbinfo->active == HPAGE_INACTIVE)) { + spin_unlock(&sbinfo->stat_lock); + kfree(sbinfo); + } else { spin_unlock(&sbinfo->stat_lock); } } diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 19644e0..8780a91 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -142,11 +142,16 @@ struct hugetlbfs_config { struct hstate *hstate; }; +#define HPAGE_INACTIVE 0 +#define HPAGE_ACTIVE 1 + struct hugetlbfs_sb_info { long max_blocks; /* blocks allowed */ long free_blocks; /* blocks free */ long max_inodes; /* inodes allowed */ long free_inodes; /* inodes free */ + long used_blocks; /* blocks used */ + long active; /* active bit */ spinlock_t stat_lock; struct hstate *hstate; }; @@ -171,8 +176,8 @@ extern const struct file_operations huge extern const struct vm_operations_struct hugetlb_vm_ops; struct file *hugetlb_file_setup(const char *name, size_t size, vm_flags_t acct, struct user_struct **user, int creat_flags); -int hugetlb_get_quota(struct address_space *mapping, long delta); -void hugetlb_put_quota(struct address_space *mapping, long delta); +int hugetlb_get_quota(struct hugetlbfs_sb_info *sbinfo, long delta); +void hugetlb_put_quota(struct hugetlbfs_sb_info *sbinfo, long delta); static inline int is_file_hugepages(struct file *file) { diff --git a/mm/hugetlb.c b/mm/hugetlb.c index dae27ba..cf26ae9 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -533,9 +533,9 @@ static void free_huge_page(struct page * */ struct hstate *h = page_hstate(page); int nid = page_to_nid(page); - struct address_space *mapping; + struct hugetlbfs_sb_info *sbinfo; - mapping = (struct address_space *) page_private(page); + sbinfo = ( struct hugetlbfs_sb_info *) page_private(page); set_page_private(page, 0); page->mapping = NULL; BUG_ON(page_count(page));