Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757146Ab3DXPcl (ORCPT ); Wed, 24 Apr 2013 11:32:41 -0400 Received: from mail-pd0-f196.google.com ([209.85.192.196]:64537 "EHLO mail-pd0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756355Ab3DXPck (ORCPT ); Wed, 24 Apr 2013 11:32:40 -0400 From: "Zhang Yi" To: Cc: "'Peter Zijlstra'" , "'Darren Hart'" , "'Thomas Gleixner'" , "'Ingo Molnar'" , "'Dave Hansen'" , Subject: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage Date: Wed, 24 Apr 2013 22:27:32 +0800 Message-ID: <000a01ce40f7$e9f4d700$bdde8500$@com> X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Ac5A99vA6WtbTvkoRKihXEqksCc9tg== Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4536 Lines: 137 Hi all, I reworked the patch base on your advices. For the line-wrapped bug before, I use this mailbox to send the mail . Signed-off-by: Zhang Yi Tested-by: Ma Chenggong Reviewed-by: Liu Dong Reviewed-by: Cui Yunfeng Reviewed-by: Lu Zhongjun Reviewed-by: Jiang Biao diff -uprN orig/linux3.9-rc7/include/linux/futex.h new/linux3.9-rc7/include/linux/futex.h --- orig/linux3.9-rc7/include/linux/futex.h 2013-04-15 00:45:16.000000000 +0000 +++ new/linux3.9-rc7/include/linux/futex.h 2013-04-19 16:33:58.725880000 +0000 @@ -19,7 +19,7 @@ handle_futex_death(u32 __user *uaddr, st * The key type depends on whether it's a shared or private mapping. * Don't rearrange members without looking at hash_futex(). * - * offset is aligned to a multiple of sizeof(u32) (== 4) by definition. + * There are three cmponents in offset: * We use the two low order bits of offset to tell what is the kind of key : * 00 : Private process futex (PTHREAD_PROCESS_PRIVATE) * (no reference on an inode or mm) @@ -27,6 +27,9 @@ handle_futex_death(u32 __user *uaddr, st * mapped on a file (reference on the underlying inode) * 10 : Shared futex (PTHREAD_PROCESS_SHARED) * (but private mapping on an mm, and reference taken on it) + * Bits 2 to (PAGE_SHIFT-1) indicates the offset of futex in its page. + * The rest hign order bits indicates the index if the page is a + * subpage of a compound page. */ #define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */ @@ -36,17 +39,17 @@ union futex_key { struct { unsigned long pgoff; struct inode *inode; - int offset; + long offset; } shared; struct { unsigned long address; struct mm_struct *mm; - int offset; + long offset; } private; struct { unsigned long word; void *ptr; - int offset; + long offset; } both; }; diff -uprN orig/linux3.9-rc7/kernel/futex.c new/linux3.9-rc7/kernel/futex.c --- orig/linux3.9-rc7/kernel/futex.c 2013-04-15 00:45:16.000000000 +0000 +++ new/linux3.9-rc7/kernel/futex.c 2013-04-19 16:24:05.629143000 +0000 @@ -215,6 +215,22 @@ static void drop_futex_key_refs(union fu } } +/* +* Get subpage index in compound page, for futex_key. +*/ +static inline int get_page_compound_index(struct page *page) +{ + struct page *head_page; + if (PageHead(page)) + return 0; + + head_page = compound_head(page); + if (compound_order(head_page) >= MAX_ORDER) + return page_to_pfn(page) - page_to_pfn(head_page); + else + return page - compound_head(page); +} + /** * get_futex_key() - Get parameters which are the keys for a futex * @uaddr: virtual address of the futex @@ -228,7 +244,8 @@ static void drop_futex_key_refs(union fu * The key words are stored in *key on success. * * For shared mappings, it's (page->index, file_inode(vma->vm_file), - * offset_within_page). For private mappings, it's (uaddr, current->mm). + * page_compound_index and offset_within_page). + * For private mappings, it's (uaddr, current->mm). * We can usually work out the index without swapping in the page. * * lock_page() might sleep, the caller should not hold a spinlock. @@ -239,7 +256,7 @@ get_futex_key(u32 __user *uaddr, int fsh unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; struct page *page, *page_head; - int err, ro = 0; + int err, ro = 0, comp_idx = 0; /* * The futex address must be "naturally" aligned. @@ -299,6 +316,7 @@ again: * freed from under us. */ if (page != page_head) { + comp_idx = get_page_compound_index(page); get_page(page_head); put_page(page); } @@ -311,6 +329,7 @@ again: #else page_head = compound_head(page); if (page != page_head) { + comp_idx = get_page_compound_index(page); get_page(page_head); put_page(page); } @@ -363,7 +382,9 @@ again: key->private.mm = mm; key->private.address = address; } else { - key->both.offset |= FUT_OFF_INODE; /* inode-based key */ + /* inode-based key */ + key->both.offset |= ((long)comp_idx << PAGE_SHIFT) + | FUT_OFF_INODE; key->shared.inode = page_head->mapping->host; key->shared.pgoff = page_head->index; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/