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Subject[PATCH] hugetlb: fix resv_map leak in error path
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When called for anonymous (non-shared) mappings,
hugetlb_reserve_pages() does a resv_map_alloc(). It depends on
code in hugetlbfs's vm_ops->close() to release that allocation.

However, in the mmap() failure path, we do a plain unmap_region()
without the remove_vma() which actually calls vm_ops->close().

This is a decent fix. This leak could get reintroduced if
new code (say, after hugetlb_reserve_pages() in
hugetlbfs_file_mmap()) decides to return an error. But, I think
it would have to unroll the reservation anyway.

This hasn't been extensively tested. Pretty much compile and
boot tested along with Christoph's test case:

http://marc.info/?l=linux-mm&m=133728900729735

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
ecked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reported/tested-by: Christoph Lameter <cl@linux.com>

---
linux-2.6.git-dave/mm/hugetlb.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
diff -puN mm/hugetlb.c~hugetlb-fix-leak mm/hugetlb.c
--- linux-2.6.git/mm/hugetlb.c~hugetlb-fix-leak 2012-05-21 13:24:38.369857759 -0700
+++ linux-2.6.git-dave/mm/hugetlb.c 2012-05-21 13:24:38.377857849 -0700
@@ -2157,6 +2157,15 @@ static void hugetlb_vm_op_open(struct vm
kref_get(&reservations->refs);
}

+static void resv_map_put(struct vm_area_struct *vma)
+{
+ struct resv_map *reservations = vma_resv_map(vma);
+
+ if (!reservations)
+ return;
+ kref_put(&reservations->refs, resv_map_release);
+}
+
static void hugetlb_vm_op_close(struct vm_area_struct *vma)
{
struct hstate *h = hstate_vma(vma);
@@ -2173,7 +2182,7 @@ static void hugetlb_vm_op_close(struct v
reserve = (end - start) -
region_count(&reservations->regions, start, end);

- kref_put(&reservations->refs, resv_map_release);
+ resv_map_put(vma);

if (reserve) {
hugetlb_acct_memory(h, -reserve);
@@ -2990,12 +2999,16 @@ int hugetlb_reserve_pages(struct inode *
set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
}

- if (chg < 0)
- return chg;
+ if (chg < 0) {
+ ret = chg;
+ goto out_err;
+ }

/* There must be enough pages in the subpool for the mapping */
- if (hugepage_subpool_get_pages(spool, chg))
- return -ENOSPC;
+ if (hugepage_subpool_get_pages(spool, chg)) {
+ ret = -ENOSPC;
+ goto out_err;
+ }

/*
* Check enough hugepages are available for the reservation.
@@ -3004,7 +3017,7 @@ int hugetlb_reserve_pages(struct inode *
ret = hugetlb_acct_memory(h, chg);
if (ret < 0) {
hugepage_subpool_put_pages(spool, chg);
- return ret;
+ goto out_err;
}

/*
@@ -3021,6 +3034,9 @@ int hugetlb_reserve_pages(struct inode *
if (!vma || vma->vm_flags & VM_MAYSHARE)
region_add(&inode->i_mapping->private_list, from, to);
return 0;
+out_err:
+ resv_map_put(vma);
+ return ret;
}

void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
diff -puN Documentation/stable_kernel_rules.txt~hugetlb-fix-leak Documentation/stable_kernel_rules.txt
_


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