Don't mlock guardpage if the stack is growing up
Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack and
locking the guard page should be excluded in this case too.
This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates the number of used pages when locking
and when unlocking and reports an internal error if the numbers mismatch.
On PA-RISC, the kernel would incorrectly attempt to mlock the stack guard
page, this causes allocation of one more page and internal error in lvm2.
Signed-off-by: Mikulas Patocka <mikulas@xxxxxxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 6 ++++++
mm/memory.c | 21 ++++++++++++---------
2 files changed, 18 insertions(+), 9 deletions(-)
Index: linux-2.6.39-rc6-fast/include/linux/mm.h
===================================================================
--- linux-2.6.39-rc6-fast.orig/include/linux/mm.h 2011-05-07 05:59:51.000000000 +0200
+++ linux-2.6.39-rc6-fast/include/linux/mm.h 2011-05-07 05:59:52.000000000 +0200
@@ -1016,6 +1016,12 @@ static inline int vma_stack_continue(str
return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
}
+/* Is the vma a continuation of the stack vma below it? */
+static inline int vma_stack_growsup_continue(struct vm_area_struct *vma, unsigned long addr)
+{
+ return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP);
+}
+
extern unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len);
Index: linux-2.6.39-rc6-fast/mm/memory.c
===================================================================
--- linux-2.6.39-rc6-fast.orig/mm/memory.c 2011-05-07 05:59:51.000000000 +0200
+++ linux-2.6.39-rc6-fast/mm/memory.c 2011-05-07 05:59:52.000000000 +0200
@@ -1412,9 +1412,12 @@ no_page_table:
static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
{
- return (vma->vm_flags & VM_GROWSDOWN) &&
+ return ((vma->vm_flags & VM_GROWSDOWN) &&
(vma->vm_start == addr) &&
- !vma_stack_continue(vma->vm_prev, addr);
+ !vma_stack_continue(vma->vm_prev, addr)) ||
+ ((vma->vm_flags & VM_GROWSUP) &&
+ (vma->vm_end == addr + PAGE_SIZE) &&
+ !vma_stack_growsup_continue(vma->vm_next, addr + PAGE_SIZE));
}
/**
@@ -1551,18 +1554,18 @@ int __get_user_pages(struct task_struct
continue;
}
- /*
- * If we don't actually want the page itself,
- * and it's the stack guard page, just skip it.
- */
- if (!pages && stack_guard_page(vma, start))
- goto next_page;
-
do {
struct page *page;
unsigned int foll_flags = gup_flags;
/*
+ * If we don't actually want the page itself,
+ * and it's the stack guard page, just skip it.
+ */
+ if (!pages && stack_guard_page(vma, start))
+ goto next_page;
+
+ /*
* If we have a pending SIGKILL, don't keep faulting
* pages and potentially allocating memory.
*/
--
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