[patch 06/39] [PATCH] hugetlbfs mmap ENOMEM failure

From: Chris Wright
Date: Mon Feb 27 2006 - 17:41:01 EST


-stable review patch. If anyone has any objections, please let us know.
------------------

2.6.15's hugepage faulting introduced huge_pages_needed accounting into
hugetlbfs: to count how many pages are already in cache, for spot check
on how far a new mapping may be allowed to extend the file. But it's
muddled: each hugepage found covers HPAGE_SIZE, not PAGE_SIZE. Once
pages were already in cache, it would overshoot, wrap its hugepages
count backwards, and so fail a harmless repeat mapping with -ENOMEM.
Fixes the problem found by Don Dupuis.

Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Acked-By: Adam Litke <agl@xxxxxxxxxx>
Acked-by: William Irwin <wli@xxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---

fs/hugetlbfs/inode.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

--- linux-2.6.15.4.orig/fs/hugetlbfs/inode.c
+++ linux-2.6.15.4/fs/hugetlbfs/inode.c
@@ -71,8 +71,8 @@ huge_pages_needed(struct address_space *
unsigned long start = vma->vm_start;
unsigned long end = vma->vm_end;
unsigned long hugepages = (end - start) >> HPAGE_SHIFT;
- pgoff_t next = vma->vm_pgoff;
- pgoff_t endpg = next + ((end - start) >> PAGE_SHIFT);
+ pgoff_t next = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
+ pgoff_t endpg = next + hugepages;

pagevec_init(&pvec, 0);
while (next < endpg) {

--
-
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