From 15487eba1006de0db3c8d9f78ef16700a4d0a217 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Wed, 5 Dec 2012 14:01:41 -0800 Subject: tmpfs: fix shared mempolicy leak commit 18a2f371f5edf41810f6469cb9be39931ef9deb9 upstream. 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 Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mempolicy.c | 22 ---------------------- mm/shmem.c | 22 +++++++++++++--------- 2 files changed, 13 insertions(+), 31 deletions(-) (limited to 'mm') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 5dce7d4..04282ba 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1973,28 +1973,6 @@ struct mempolicy *__mpol_dup(struct mempolicy *old) 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 */ int __mpol_equal(struct mempolicy *a, struct mempolicy *b) { diff --git a/mm/shmem.c b/mm/shmem.c index 769941f..b952332 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1168,19 +1168,20 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp, struct shmem_inode_info *info, unsigned long idx) { - struct mempolicy mpol, *spol; struct vm_area_struct pvma; struct page *page; - spol = mpol_cond_copy(&mpol, - mpol_shared_policy_lookup(&info->policy, idx)); - /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; pvma.vm_pgoff = idx; pvma.vm_ops = NULL; - pvma.vm_policy = spol; + pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx); + page = swapin_readahead(entry, gfp, &pvma, 0); + + /* Drop reference taken by mpol_shared_policy_lookup() */ + mpol_cond_put(pvma.vm_policy); + return page; } @@ -1188,6 +1189,7 @@ static struct page *shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info, unsigned long idx) { struct vm_area_struct pvma; + struct page *page; /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; @@ -1195,10 +1197,12 @@ static struct page *shmem_alloc_page(gfp_t gfp, pvma.vm_ops = NULL; pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx); - /* - * 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 -- cgit v1.1