[PATCH] futex: bugfix for futex-key conflict when futex usehugepage

[Zhang Yi]

Hi all,

I reworked the patch base on yourÂadvicesã
For the line-wrapped bug before, I use this mailbox to send the mail .


Signed-off-by: Zhang Yi <zhang.yi20@xxxxxxxxxx>Tested-by: Ma Chenggong <ma.chenggong@xxxxxxxxxx>Reviewed-by: Liu Dong <liu.dong3@xxxxxxxxxx>Reviewed-by: Cui Yunfeng <cui.yunfeng@xxxxxxxxxx>Reviewed-by: Lu Zhongjun <lu.zhongjun@xxxxxxxxxx>Reviewed-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>

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 : * Â00 : 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) * Â10 : 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.Â*/ÂÂ#define FUT_OFF_INODE  Â1 /* We set bit 0 if key has a reference on inode */@@ -36,17 +39,17 @@ union futex_key {Â	struct {Â		unsigned long pgoff;Â		struct inode *inode;-		int offset;+		long offset;Â	} shared;Â	struct {Â		unsigned long address;Â		struct mm_struct *mm;-		int offset;+		long offset;Â	} private;Â	struct {Â		unsigned long word;Â		void *ptr;-		int offset;+		long offset;Â	} both;Â};Âdiff -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 fuÂ	}Â}Â+/*+* 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);+}+Â/** * 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). ÂFor 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 fshÂ	unsigned long address = (unsigned long)uaddr;Â	struct mm_struct *mm = current->mm;Â	struct page *page, *page_head;-	int err, ro = 0;+	int err, ro = 0, comp_idx = 0;ÂÂ	/*Â	 * The futex address must be "naturally" aligned.@@ -299,6 +316,7 @@ again:Â			 * freed from under us.Â			 */Â			if (page != page_head) {+				comp_idx = get_page_compound_index(page);Â				get_page(page_head);Â				put_page(page);Â			}@@ -311,6 +329,7 @@ again:Â#elseÂ	page_head = compound_head(page);Â	if (page != page_head) {+		comp_idx = get_page_compound_index(page);Â		get_page(page_head);Â		put_page(page);Â	}@@ -363,7 +382,9 @@ again:Â		key->private.mm = mm;Â		key->private.address = address;Â	} else {-		key->both.offset |= FUT_OFF_INODE; /* inode-based key */+		/* inode-based key */+		key->both.offset |= ((long)comp_idx << PAGE_SHIFT)+				  | FUT_OFF_INODE;Â		key->shared.inode = page_head->mapping->host;Â		key->shared.pgoff = page_head->index;Â	}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/