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Message-ID: <CA+55aFzXJo78Ah_Qiy6cSHdXHv165nXJ2nTD186NNdCXBABZjA@mail.gmail.com>
Date: Thu, 11 Aug 2011 17:48:56 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
Jan Kiszka <jan.kiszka@....de>, qemu-devel@...gnu.org,
agraf@...e.de, kvm <kvm@...r.kernel.org>,
Paul Mackerras <paulus@...ba.org>,
linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
Minchan Kim <minchan.kim@...il.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: Fix refcounting in hugetlbfs quota handling
On Wed, Aug 10, 2011 at 11:40 PM, David Gibson
<david@...son.dropbear.id.au> wrote:
>
> This patch, therefore, stores a pointer to the inode instead of the
> address_space in the page private data for hugepages. More
> importantly it correctly adjusts the reference count on the inodes
> when they're added to the page private data. This ensures that the
> inode (and therefore the super block) will not be freed before we use
> it from free_huge_page.
Looks sane, but I *really* want some acks from people who use/know
hugetlbfs. Who would that be? I'm adding random people who have
acked/signed-off patches to hugetlbfs recently..
Linus
--- patch left quoted for new people ---
> Signed-off-by: David Gibson <david@...son.dropbear.id.au>
>
> Index: working-2.6/fs/hugetlbfs/inode.c
> ===================================================================
> --- working-2.6.orig/fs/hugetlbfs/inode.c 2011-08-10 16:45:47.864758406 +1000
> +++ working-2.6/fs/hugetlbfs/inode.c 2011-08-10 17:22:21.899638039 +1000
> @@ -874,10 +874,10 @@ out_free:
> return -ENOMEM;
> }
>
> -int hugetlb_get_quota(struct address_space *mapping, long delta)
> +int hugetlb_get_quota(struct inode *inode, long delta)
> {
> int ret = 0;
> - struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb);
> + struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(inode->i_sb);
>
> if (sbinfo->free_blocks > -1) {
> spin_lock(&sbinfo->stat_lock);
> @@ -891,9 +891,9 @@ int hugetlb_get_quota(struct address_spa
> return ret;
> }
>
> -void hugetlb_put_quota(struct address_space *mapping, long delta)
> +void hugetlb_put_quota(struct inode *inode, long delta)
> {
> - struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(mapping->host->i_sb);
> + struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(inode->i_sb);
>
> if (sbinfo->free_blocks > -1) {
> spin_lock(&sbinfo->stat_lock);
> Index: working-2.6/include/linux/hugetlb.h
> ===================================================================
> --- working-2.6.orig/include/linux/hugetlb.h 2011-08-10 16:58:27.952527484 +1000
> +++ working-2.6/include/linux/hugetlb.h 2011-08-10 17:22:08.723572707 +1000
> @@ -171,8 +171,8 @@ 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 inode *inode, long delta);
> +void hugetlb_put_quota(struct inode *inode, long delta);
>
> static inline int is_file_hugepages(struct file *file)
> {
> Index: working-2.6/mm/hugetlb.c
> ===================================================================
> --- working-2.6.orig/mm/hugetlb.c 2011-08-10 16:44:12.212284092 +1000
> +++ working-2.6/mm/hugetlb.c 2011-08-10 17:21:49.603477888 +1000
> @@ -533,10 +533,12 @@ static void free_huge_page(struct page *
> */
> struct hstate *h = page_hstate(page);
> int nid = page_to_nid(page);
> - struct address_space *mapping;
> + struct inode *inode;
>
> - mapping = (struct address_space *) page_private(page);
> + inode = (struct inode *) page_private(page);
> set_page_private(page, 0);
> + iput(inode);
> +
> page->mapping = NULL;
> BUG_ON(page_count(page));
> BUG_ON(page_mapcount(page));
> @@ -551,8 +553,8 @@ static void free_huge_page(struct page *
> enqueue_huge_page(h, page);
> }
> spin_unlock(&hugetlb_lock);
> - if (mapping)
> - hugetlb_put_quota(mapping, 1);
> + if (inode)
> + hugetlb_put_quota(inode, 1);
> }
>
> static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
> @@ -1035,7 +1037,7 @@ 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(inode, chg))
> return ERR_PTR(-VM_FAULT_SIGBUS);
>
> spin_lock(&hugetlb_lock);
> @@ -1045,12 +1047,12 @@ 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(inode, chg);
> return ERR_PTR(-VM_FAULT_SIGBUS);
> }
> }
>
> - set_page_private(page, (unsigned long) mapping);
> + set_page_private(page, (unsigned long) igrab(inode));
>
> vma_commit_reservation(h, vma, addr);
>
> @@ -2086,7 +2088,8 @@ 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(vma->vm_file->f_mapping->host,
> + reserve);
> }
> }
> }
> @@ -2884,7 +2887,7 @@ 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(inode, chg))
> return -ENOSPC;
>
> /*
> @@ -2893,7 +2896,7 @@ 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(inode, chg);
> return ret;
> }
>
> @@ -2922,7 +2925,7 @@ 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(inode, (chg - freed));
> hugetlb_acct_memory(h, -(chg - freed));
> }
>
>
> --
> David Gibson | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
> | _way_ _around_!
> http://www.ozlabs.org/~dgibson
> --
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