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mm: don't add a guard page if a prev vma grows-down too

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The kernel logic is described in v2.6.36-rc1-161-g7798330:
"If we've split the stack vma, only the lowest one has the guard page."

https://bugzilla.openvz.org/show_bug.cgi?id=2715
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrey Vagin
2013-08-26 17:14:59 +04:00
committed by Pavel Emelyanov
parent cec93fa155
commit 8f18db5f6a
1 changed files with 8 additions and 3 deletions
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11
proc_parse.c
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@@ -97,10 +97,9 @@ static int parse_vmflags(char *buf, struct vma_area *vma_area)
do {
/* mmap() block */
if (_vmflag_match(tok, "gd")) {
if (_vmflag_match(tok, "gd"))
vma_area->vma.flags |= MAP_GROWSDOWN;
vma_area->vma.start -= PAGE_SIZE; /* Guard page */
} else if (_vmflag_match(tok, "lo"))
else if (_vmflag_match(tok, "lo"))
vma_area->vma.flags |= MAP_LOCKED;
else if (_vmflag_match(tok, "nr"))
vma_area->vma.flags |= MAP_NORESERVE;
@@ -145,6 +144,7 @@ int parse_smaps(pid_t pid, struct vm_area_list *vma_area_list, bool use_map_file
{
struct vma_area *vma_area = NULL;
unsigned long start, end, pgoff;
bool prev_growsdown = false;
unsigned long ino;
char r, w, x, s;
int dev_maj, dev_min;
@@ -196,6 +196,11 @@ int parse_smaps(pid_t pid, struct vm_area_list *vma_area_list, bool use_map_file
}
if (vma_area) {
/* If we've split the stack vma, only the lowest one has the guard page. */
if ((vma_area->vma.flags & MAP_GROWSDOWN) && !prev_growsdown)
vma_area->vma.start -= PAGE_SIZE; /* Guard page */
prev_growsdown = (bool)(vma_area->vma.flags & MAP_GROWSDOWN);
list_add_tail(&vma_area->list, &vma_area_list->h);
vma_area_list->nr++;
if (privately_dump_vma(vma_area)) {