From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> To: LKML <linux-kernel@vger.kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Christoph Lameter <cl@linux.com>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Andi Kleen <andi@firstfloor.org>, linux-mm <linux-mm@kvack.org> Subject: [PATCH 3/4] hugetlb, rmap: fix confusing page locking in hugetlb_cow() Date: Fri, 10 Sep 2010 13:23:05 +0900 [thread overview] Message-ID: <1284092586-1179-4-git-send-email-n-horiguchi@ah.jp.nec.com> (raw) In-Reply-To: <1284092586-1179-1-git-send-email-n-horiguchi@ah.jp.nec.com> if(!trylock_page) block in avoidcopy path of hugetlb_cow() looks confusing and is buggy. Originally this trylock_page() is intended to make sure that old_page is locked even when old_page != pagecache_page, because then only pagecache_page is locked. This patch fixes it by moving page locking into hugetlb_fault(). Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> --- mm/hugetlb.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git v2.6.36-rc3/mm/hugetlb.c v2.6.36-rc3/mm/hugetlb.c index 9519f3f..2e17e0e 100644 --- v2.6.36-rc3/mm/hugetlb.c +++ v2.6.36-rc3/mm/hugetlb.c @@ -2324,11 +2324,8 @@ retry_avoidcopy: * and just make the page writable */ avoidcopy = (page_mapcount(old_page) == 1); if (avoidcopy) { - if (!trylock_page(old_page)) { - if (PageAnon(old_page)) - page_move_anon_rmap(old_page, vma, address); - } else - unlock_page(old_page); + if (PageAnon(old_page)) + page_move_anon_rmap(old_page, vma, address); set_huge_ptep_writable(vma, address, ptep); return 0; } @@ -2631,10 +2628,14 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, vma, address); } - if (!pagecache_page) { - page = pte_page(entry); + /* + * hugetlb_cow() requires page locks of pte_page(entry) and + * pagecache_page, so here we need take the former one + * when page != pagecache_page or !pagecache_page. + */ + page = pte_page(entry); + if (page != pagecache_page) lock_page(page); - } spin_lock(&mm->page_table_lock); /* Check for a racing update before calling hugetlb_cow */ @@ -2661,9 +2662,8 @@ out_page_table_lock: if (pagecache_page) { unlock_page(pagecache_page); put_page(pagecache_page); - } else { - unlock_page(page); } + unlock_page(page); out_mutex: mutex_unlock(&hugetlb_instantiation_mutex); -- 1.7.2.2
WARNING: multiple messages have this Message-ID (diff)
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> To: LKML <linux-kernel@vger.kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Christoph Lameter <cl@linux.com>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Andi Kleen <andi@firstfloor.org>, linux-mm <linux-mm@kvack.org> Subject: [PATCH 3/4] hugetlb, rmap: fix confusing page locking in hugetlb_cow() Date: Fri, 10 Sep 2010 13:23:05 +0900 [thread overview] Message-ID: <1284092586-1179-4-git-send-email-n-horiguchi@ah.jp.nec.com> (raw) In-Reply-To: <1284092586-1179-1-git-send-email-n-horiguchi@ah.jp.nec.com> if(!trylock_page) block in avoidcopy path of hugetlb_cow() looks confusing and is buggy. Originally this trylock_page() is intended to make sure that old_page is locked even when old_page != pagecache_page, because then only pagecache_page is locked. This patch fixes it by moving page locking into hugetlb_fault(). Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> --- mm/hugetlb.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git v2.6.36-rc3/mm/hugetlb.c v2.6.36-rc3/mm/hugetlb.c index 9519f3f..2e17e0e 100644 --- v2.6.36-rc3/mm/hugetlb.c +++ v2.6.36-rc3/mm/hugetlb.c @@ -2324,11 +2324,8 @@ retry_avoidcopy: * and just make the page writable */ avoidcopy = (page_mapcount(old_page) == 1); if (avoidcopy) { - if (!trylock_page(old_page)) { - if (PageAnon(old_page)) - page_move_anon_rmap(old_page, vma, address); - } else - unlock_page(old_page); + if (PageAnon(old_page)) + page_move_anon_rmap(old_page, vma, address); set_huge_ptep_writable(vma, address, ptep); return 0; } @@ -2631,10 +2628,14 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, vma, address); } - if (!pagecache_page) { - page = pte_page(entry); + /* + * hugetlb_cow() requires page locks of pte_page(entry) and + * pagecache_page, so here we need take the former one + * when page != pagecache_page or !pagecache_page. + */ + page = pte_page(entry); + if (page != pagecache_page) lock_page(page); - } spin_lock(&mm->page_table_lock); /* Check for a racing update before calling hugetlb_cow */ @@ -2661,9 +2662,8 @@ out_page_table_lock: if (pagecache_page) { unlock_page(pagecache_page); put_page(pagecache_page); - } else { - unlock_page(page); } + unlock_page(page); out_mutex: mutex_unlock(&hugetlb_instantiation_mutex); -- 1.7.2.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2010-09-10 4:26 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-09-10 4:23 [PATCH 0/4] hugetlb, rmap: fixes and cleanups Naoya Horiguchi 2010-09-10 4:23 ` Naoya Horiguchi 2010-09-10 4:23 ` [PATCH 1/4] hugetlb, rmap: always use anon_vma root pointer Naoya Horiguchi 2010-09-10 4:23 ` Naoya Horiguchi 2010-09-10 14:37 ` Andrea Arcangeli 2010-09-10 14:37 ` Andrea Arcangeli 2010-09-10 14:40 ` Rik van Riel 2010-09-10 14:40 ` Rik van Riel 2010-09-10 17:19 ` Linus Torvalds 2010-09-10 17:19 ` Linus Torvalds 2010-09-10 21:50 ` Andi Kleen 2010-09-10 21:50 ` Andi Kleen 2010-09-10 22:07 ` Linus Torvalds 2010-09-10 22:07 ` Linus Torvalds 2010-09-11 2:09 ` Rik van Riel 2010-09-11 2:09 ` Rik van Riel 2010-09-10 4:23 ` [PATCH 2/4] hugetlb, rmap: use hugepage_add_new_anon_rmap() in hugetlb_cow() Naoya Horiguchi 2010-09-10 4:23 ` Naoya Horiguchi 2010-09-10 14:39 ` Andrea Arcangeli 2010-09-10 14:39 ` Andrea Arcangeli 2010-09-10 14:40 ` Rik van Riel 2010-09-10 14:40 ` Rik van Riel 2010-09-10 4:23 ` Naoya Horiguchi [this message] 2010-09-10 4:23 ` [PATCH 3/4] hugetlb, rmap: fix confusing page locking " Naoya Horiguchi 2010-09-10 14:41 ` Rik van Riel 2010-09-10 14:41 ` Rik van Riel 2010-09-10 17:15 ` Linus Torvalds 2010-09-10 17:15 ` Linus Torvalds 2010-09-23 23:50 ` Naoya Horiguchi 2010-09-23 23:50 ` Naoya Horiguchi 2010-09-10 4:23 ` [PATCH 4/4] hugetlb, rmap: add BUG_ON(!PageLocked) in hugetlb_add_anon_rmap() Naoya Horiguchi 2010-09-10 4:23 ` Naoya Horiguchi 2010-09-10 14:42 ` Rik van Riel 2010-09-10 14:42 ` Rik van Riel 2010-09-10 14:44 ` Andrea Arcangeli 2010-09-10 14:44 ` Andrea Arcangeli 2010-09-10 9:04 ` [PATCH 0/4] hugetlb, rmap: fixes and cleanups Andi Kleen 2010-09-10 9:04 ` Andi Kleen 2010-09-10 11:47 ` Naoya Horiguchi 2010-09-10 11:47 ` Naoya Horiguchi 2010-09-10 14:30 ` Andi Kleen 2010-09-10 14:30 ` Andi Kleen
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