The patch titled mempolicy: fix reference counting bugs has been removed from the -mm tree. Its filename was fix-mempolicy-reference-counting-bugs.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: mempolicy: fix reference counting bugs From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx> Address 3 known bugs in the current memory policy reference counting method. I have a series of patches to rework the reference counting to reduce overhead in the allocation path. However, that series will require testing in -mm once I repost it. 1) alloc_page_vma() does not release the extra reference taken for vma/shared mempolicy when the mode == MPOL_INTERLEAVE. This can result in leaking mempolicy structures. This is probably occurring, but not being noticed. Fix: add the conditional release of the reference. 2) hugezonelist unconditionally releases a reference on the mempolicy when mode == MPOL_INTERLEAVE. This can result in decrementing the reference count for system default policy [should have no ill effect] or premature freeing of task policy. If this occurred, the next allocation using task mempolicy would use the freed structure and probably BUG out. Fix: add the necessary check to the release. 3) The current reference counting method assumes that vma 'get_policy()' methods automatically add an extra reference a non-NULL returned mempolicy. This is true for shmem_get_policy() used by tmpfs mappings, including regular page shm segments. However, SHM_HUGETLB shm's, backed by hugetlbfs, just use the vma policy without the extra reference. This results in freeing of the vma policy on the first allocation, with reuse of the freed mempolicy structure on subsequent allocations. Fix: Rather than add another condition to the conditional reference release, which occur in the allocation path, just add a reference when returning the vma policy in shm_get_policy() to match the assumptions. Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx> Cc: Greg KH <greg@xxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxx> Cc: Christoph Lameter <clameter@xxxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: <eric.whitney@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- ipc/shm.c | 5 +++-- mm/mempolicy.c | 7 ++++++- 2 files changed, 9 insertions(+), 3 deletions(-) diff -puN ipc/shm.c~fix-mempolicy-reference-counting-bugs ipc/shm.c --- a/ipc/shm.c~fix-mempolicy-reference-counting-bugs +++ a/ipc/shm.c @@ -271,9 +271,10 @@ static struct mempolicy *shm_get_policy( if (sfd->vm_ops->get_policy) pol = sfd->vm_ops->get_policy(vma, addr); - else if (vma->vm_policy) + else if (vma->vm_policy) { pol = vma->vm_policy; - else + mpol_get(pol); /* get_vma_policy() expects this */ + } else pol = current->mempolicy; return pol; } diff -puN mm/mempolicy.c~fix-mempolicy-reference-counting-bugs mm/mempolicy.c --- a/mm/mempolicy.c~fix-mempolicy-reference-counting-bugs +++ a/mm/mempolicy.c @@ -1296,7 +1296,9 @@ struct zonelist *huge_zonelist(struct vm unsigned nid; nid = interleave_nid(pol, vma, addr, HPAGE_SHIFT); - __mpol_free(pol); /* finished with pol */ + if (unlikely(pol != &default_policy && + pol != current->mempolicy)) + __mpol_free(pol); /* finished with pol */ return NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_flags); } @@ -1360,6 +1362,9 @@ alloc_page_vma(gfp_t gfp, struct vm_area unsigned nid; nid = interleave_nid(pol, vma, addr, PAGE_SHIFT); + if (unlikely(pol != &default_policy && + pol != current->mempolicy)) + __mpol_free(pol); /* finished with pol */ return alloc_page_interleave(gfp, 0, nid); } zl = zonelist_policy(gfp, pol); _ Patches currently in -mm which might be from Lee.Schermerhorn@xxxxxx are origin.patch mm-filter-based-on-a-nodemask-as-well-as-a-gfp_mask-doc-fixes.patch mm-filter-based-on-a-nodemask-as-well-as-a-gfp_mask-make-dequeue_huge_page_vma-obey-mpol_bind-nodemask.patch mm-filter-based-on-a-nodemask-as-well-as-a-gfp_mask-make-dequeue_huge_page_vma-obey-mpol_bind-nodemask-rework.patch mempolicy-convert-mpol-constants-to-enum.patch mempolicy-support-optional-mode-flags.patch mempolicy-add-mpol_f_static_nodes-flag.patch mempolicy-add-mpol_f_relative_nodes-flag.patch mempolicy-update-numa-memory-policy-documentation.patch mempolicy-move-rebind-functions.patch mempolicy-create-mempolicy_operations-structure.patch mempolicy-create-mempolicy_operations-structure-fix.patch mempolicy-small-header-file-cleanup.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html