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Subject[PATCH 08/21] mm: ia64 use expand_upwards
ia64 has expand_backing_store function for growing its Register Backing
Store vma upwards. But more complete code for this purpose is found in
the CONFIG_STACK_GROWSUP part of mm/mmap.c. Uglify its #ifdefs further
to provide expand_upwards for ia64 as well as expand_stack for parisc.

The Register Backing Store vma should be marked VM_ACCOUNT. Implement
the intention of growing it only a page at a time, instead of passing an
address outside of the vma to handle_mm_fault, with unknown consequences.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
arch/ia64/mm/fault.c | 34 +++++++---------------------------
arch/ia64/mm/init.c | 2 +-
include/linux/mm.h | 3 ++-
mm/mmap.c | 17 ++++++++++++++---
4 files changed, 24 insertions(+), 32 deletions(-)
--- mm07/arch/ia64/mm/fault.c 2005-09-30 11:58:53.000000000 +0100
+++ mm08/arch/ia64/mm/fault.c 2005-10-11 23:55:38.000000000 +0100
@@ -20,32 +20,6 @@
extern void die (char *, struct pt_regs *, long);

/*
- * This routine is analogous to expand_stack() but instead grows the
- * register backing store (which grows towards higher addresses).
- * Since the register backing store is access sequentially, we
- * disallow growing the RBS by more than a page at a time. Note that
- * the VM_GROWSUP flag can be set on any VM area but that's fine
- * because the total process size is still limited by RLIMIT_STACK and
- * RLIMIT_AS.
- */
-static inline long
-expand_backing_store (struct vm_area_struct *vma, unsigned long address)
-{
- unsigned long grow;
-
- grow = PAGE_SIZE >> PAGE_SHIFT;
- if (address - vma->vm_start > current->signal->rlim[RLIMIT_STACK].rlim_cur
- || (((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->signal->rlim[RLIMIT_AS].rlim_cur))
- return -ENOMEM;
- vma->vm_end += PAGE_SIZE;
- vma->vm_mm->total_vm += grow;
- if (vma->vm_flags & VM_LOCKED)
- vma->vm_mm->locked_vm += grow;
- vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
- return 0;
-}
-
-/*
* Return TRUE if ADDRESS points at a page in the kernel's mapped segment
* (inside region 5, on ia64) and that page is present.
*/
@@ -185,7 +159,13 @@ ia64_do_page_fault (unsigned long addres
if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
|| REGION_OFFSET(address) >= RGN_MAP_LIMIT)
goto bad_area;
- if (expand_backing_store(vma, address))
+ /*
+ * Since the register backing store is accessed sequentially,
+ * we disallow growing it by more than a page at a time.
+ */
+ if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
+ goto bad_area;
+ if (expand_upwards(vma, address))
goto bad_area;
}
goto good_area;
--- mm07/arch/ia64/mm/init.c 2005-09-21 12:16:14.000000000 +0100
+++ mm08/arch/ia64/mm/init.c 2005-10-11 23:55:38.000000000 +0100
@@ -158,7 +158,7 @@ ia64_init_addr_space (void)
vma->vm_start = current->thread.rbs_bot & PAGE_MASK;
vma->vm_end = vma->vm_start + PAGE_SIZE;
vma->vm_page_prot = protection_map[VM_DATA_DEFAULT_FLAGS & 0x7];
- vma->vm_flags = VM_DATA_DEFAULT_FLAGS | VM_GROWSUP;
+ vma->vm_flags = VM_DATA_DEFAULT_FLAGS|VM_GROWSUP|VM_ACCOUNT;
down_write(&current->mm->mmap_sem);
if (insert_vm_struct(current->mm, vma)) {
up_write(&current->mm->mmap_sem);
--- mm07/include/linux/mm.h 2005-10-11 23:54:33.000000000 +0100
+++ mm08/include/linux/mm.h 2005-10-11 23:55:38.000000000 +0100
@@ -904,7 +904,8 @@ void handle_ra_miss(struct address_space
unsigned long max_sane_readahead(unsigned long nr);

/* Do stack extension */
-extern int expand_stack(struct vm_area_struct * vma, unsigned long address);
+extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
+extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);

/* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);
--- mm07/mm/mmap.c 2005-10-11 23:54:33.000000000 +0100
+++ mm08/mm/mmap.c 2005-10-11 23:55:38.000000000 +0100
@@ -1504,11 +1504,15 @@ static int acct_stack_growth(struct vm_a
return 0;
}

-#ifdef CONFIG_STACK_GROWSUP
+#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
/*
- * vma is the first one with address > vma->vm_end. Have to extend vma.
+ * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
+ * vma is the last one with address > vma->vm_end. Have to extend vma.
*/
-int expand_stack(struct vm_area_struct * vma, unsigned long address)
+#ifdef CONFIG_STACK_GROWSUP
+static inline
+#endif
+int expand_upwards(struct vm_area_struct *vma, unsigned long address)
{
int error;

@@ -1546,6 +1550,13 @@ int expand_stack(struct vm_area_struct *
anon_vma_unlock(vma);
return error;
}
+#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
+
+#ifdef CONFIG_STACK_GROWSUP
+int expand_stack(struct vm_area_struct *vma, unsigned long address)
+{
+ return expand_upwards(vma, address);
+}

struct vm_area_struct *
find_extend_vma(struct mm_struct *mm, unsigned long addr)
-
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