[PATCH] futex: bugfix for futex-key conflict when futex use hugepage

Zhang Yi
2013-04-24T14:21:20Z

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 <zhang.yi20@zte.com.cn>Tested-by: Ma Chenggong <ma.chenggong@zte.com.cn>Reviewed-by: Liu Dong <liu.dong3@zte.com.cn>Reviewed-by: Cui Yunfeng <cui.yunfeng@zte.com.cn>Reviewed-by: Lu Zhongjun <lu.zhongjun@zte.com.cn>Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>

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;  }