From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx160.postini.com [74.125.245.160]) by kanga.kvack.org (Postfix) with SMTP id 1DF506B0044 for ; Wed, 5 Dec 2012 17:01:37 -0500 (EST) Received: by mail-pb0-f41.google.com with SMTP id xa7so4162108pbc.14 for ; Wed, 05 Dec 2012 14:01:36 -0800 (PST) Date: Wed, 5 Dec 2012 14:01:41 -0800 (PST) From: Hugh Dickins Subject: [PATCH] tmpfs: fix shared mempolicy leak In-Reply-To: Message-ID: References: <1349801921-16598-1-git-send-email-mgorman@suse.de> <1349801921-16598-6-git-send-email-mgorman@suse.de> <20121204141501.GA2797@suse.de> <20121205095221.GB2489@suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Tommi Rantala , Mel Gorman , Andi Kleen , Andrew Morton , KOSAKI Motohiro , Dave Jones , Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org From: Mel Gorman This fixes a regression in 3.7-rc, which has since gone into stable. Commit 00442ad04a5e ("mempolicy: fix a memory corruption by refcount imbalance in alloc_pages_vma()") changed get_vma_policy() to raise the refcount on a shmem shared mempolicy; whereas shmem_alloc_page() went on expecting alloc_page_vma() to drop the refcount it had acquired. This deserves a rework: but for now fix the leak in shmem_alloc_page(). Hugh: shmem_swapin() did not need a fix, but surely it's clearer to use the same refcounting there as in shmem_alloc_page(), delete its onstack mempolicy, and the strange mpol_cond_copy() and __mpol_cond_copy() - those were invented to let swapin_readahead() make an unknown number of calls to alloc_pages_vma() with one mempolicy; but since 00442ad04a5e, alloc_pages_vma() has kept refcount in balance, so now no problem. Reported-and-tested-by: Tommi Rantala Signed-off-by: Mel Gorman Signed-off-by: Hugh Dickins Cc: stable@vger.kernel.org --- include/linux/mempolicy.h | 16 ---------------- mm/mempolicy.c | 22 ---------------------- mm/shmem.c | 26 ++++++++++++++++---------- 3 files changed, 16 insertions(+), 48 deletions(-) --- 3.7-rc8/include/linux/mempolicy.h 2012-10-14 16:16:57.637308925 -0700 +++ linux/include/linux/mempolicy.h 2012-12-04 22:38:21.812178829 -0800 @@ -82,16 +82,6 @@ static inline void mpol_cond_put(struct __mpol_put(pol); } -extern struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol, - struct mempolicy *frompol); -static inline struct mempolicy *mpol_cond_copy(struct mempolicy *tompol, - struct mempolicy *frompol) -{ - if (!frompol) - return frompol; - return __mpol_cond_copy(tompol, frompol); -} - extern struct mempolicy *__mpol_dup(struct mempolicy *pol); static inline struct mempolicy *mpol_dup(struct mempolicy *pol) { @@ -215,12 +205,6 @@ static inline void mpol_cond_put(struct { } -static inline struct mempolicy *mpol_cond_copy(struct mempolicy *to, - struct mempolicy *from) -{ - return from; -} - static inline void mpol_get(struct mempolicy *pol) { } --- 3078/mm/mempolicy.c 2012-10-20 20:56:24.675917367 -0700 +++ 3078X/mm/mempolicy.c 2012-12-04 22:33:31.516171929 -0800 @@ -2037,28 +2037,6 @@ struct mempolicy *__mpol_dup(struct memp return new; } -/* - * If *frompol needs [has] an extra ref, copy *frompol to *tompol , - * eliminate the * MPOL_F_* flags that require conditional ref and - * [NOTE!!!] drop the extra ref. Not safe to reference *frompol directly - * after return. Use the returned value. - * - * Allows use of a mempolicy for, e.g., multiple allocations with a single - * policy lookup, even if the policy needs/has extra ref on lookup. - * shmem_readahead needs this. - */ -struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol, - struct mempolicy *frompol) -{ - if (!mpol_needs_cond_ref(frompol)) - return frompol; - - *tompol = *frompol; - tompol->flags &= ~MPOL_F_SHARED; /* copy doesn't need unref */ - __mpol_put(frompol); - return tompol; -} - /* Slow path of a mempolicy comparison */ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b) { --- 3078/mm/shmem.c 2012-11-16 19:26:56.388459961 -0800 +++ 3078X/mm/shmem.c 2012-12-04 22:32:35.328170594 -0800 @@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpo static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, struct shmem_inode_info *info, pgoff_t index) { - struct mempolicy mpol, *spol; struct vm_area_struct pvma; - - spol = mpol_cond_copy(&mpol, - mpol_shared_policy_lookup(&info->policy, index)); + struct page *page; /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; /* Bias interleave by inode number to distribute better across nodes */ pvma.vm_pgoff = index + info->vfs_inode.i_ino; pvma.vm_ops = NULL; - pvma.vm_policy = spol; - return swapin_readahead(swap, gfp, &pvma, 0); + pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); + + page = swapin_readahead(swap, gfp, &pvma, 0); + + /* Drop reference taken by mpol_shared_policy_lookup() */ + mpol_cond_put(pvma.vm_policy); + + return page; } static struct page *shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info, pgoff_t index) { struct vm_area_struct pvma; + struct page *page; /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; @@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp pvma.vm_ops = NULL; pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); - /* - * alloc_page_vma() will drop the shared policy reference - */ - return alloc_page_vma(gfp, &pvma, 0); + page = alloc_page_vma(gfp, &pvma, 0); + + /* Drop reference taken by mpol_shared_policy_lookup() */ + mpol_cond_put(pvma.vm_policy); + + return page; } #else /* !CONFIG_NUMA */ #ifdef CONFIG_TMPFS -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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