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Don't lock guardpage if the stack is growing up

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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 number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc/<pid>/maps for the
  grows-up case, and to move things around a bit to clean it all up and
  share the infrstructure with the /proc bits.

  Tested on ia64 that has both grow-up and grow-down segments  - Linus ]

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Tested-by: Tony Luck <tony.luck@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mikulas Patocka 2011-05-09 13:01:09 +02:00 committed by Linus Torvalds
parent 26822eebb2
commit a09a79f668
3 changed files with 37 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/proc/task_mmu.c
View File

@ -214,7 +214,7 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
int flags = vma->vm_flags;
unsigned long ino = 0;
unsigned long long pgoff = 0;
unsigned long start;
unsigned long start, end;
dev_t dev = 0;
int len;
@ -227,13 +227,15 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
/* We don't show the stack guard page in /proc/maps */
start = vma->vm_start;
if (vma->vm_flags & VM_GROWSDOWN)
if (!vma_stack_continue(vma->vm_prev, vma->vm_start))
if (stack_guard_page_start(vma, start))
start += PAGE_SIZE;
end = vma->vm_end;
if (stack_guard_page_end(vma, end))
end -= PAGE_SIZE;
seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
start,
vma->vm_end,
end,
flags & VM_READ ? 'r' : '-',
flags & VM_WRITE ? 'w' : '-',
flags & VM_EXEC ? 'x' : '-',

24
include/linux/mm.h
View File

@ -1011,11 +1011,33 @@ int set_page_dirty_lock(struct page *page);
int clear_page_dirty_for_io(struct page *page);
/* Is the vma a continuation of the stack vma above it? */
static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
{
return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
}
static inline int stack_guard_page_start(struct vm_area_struct *vma,
unsigned long addr)
{
return (vma->vm_flags & VM_GROWSDOWN) &&
(vma->vm_start == addr) &&
!vma_growsdown(vma->vm_prev, addr);
}
/* Is the vma a continuation of the stack vma below it? */
static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr)
{
return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP);
}
static inline int stack_guard_page_end(struct vm_area_struct *vma,
unsigned long addr)
{
return (vma->vm_flags & VM_GROWSUP) &&
(vma->vm_end == addr) &&
!vma_growsup(vma->vm_next, addr);
}
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);

16
mm/memory.c
View File

@ -1412,9 +1412,8 @@ no_page_table:
static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
{
return (vma->vm_flags & VM_GROWSDOWN) &&
(vma->vm_start == addr) &&
!vma_stack_continue(vma->vm_prev, addr);
return stack_guard_page_start(vma, addr) ||
stack_guard_page_end(vma, addr+PAGE_SIZE);
}
/**
@ -1551,12 +1550,6 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
continue;
}
/*
* For mlock, just skip the stack guard page.
*/
if ((gup_flags & FOLL_MLOCK) && stack_guard_page(vma, start))
goto next_page;
do {
struct page *page;
unsigned int foll_flags = gup_flags;
@ -1573,6 +1566,11 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
int ret;
unsigned int fault_flags = 0;
/* For mlock, just skip the stack guard page. */
if (foll_flags & FOLL_MLOCK) {
if (stack_guard_page(vma, start))
goto next_page;
}
if (foll_flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
if (nonblocking)