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[PATCH RFC] mm: Rework virtual memory accounting

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  [PATCH RFC] mm: Rework virtual memory accounting Cyrill Gorcunov <gorcunov@gmail.com> - 2015-12-28 22:20 +0100
    Re: [PATCH RFC] mm: Rework virtual memory accounting Linus Torvalds <torvalds@linux-foundation.org> - 2015-12-28 23:30 +0100
      Re: [PATCH RFC] mm: Rework virtual memory accounting Cyrill Gorcunov <gorcunov@gmail.com> - 2015-12-29 10:50 +0100
    Re: [PATCH RFC] mm: Rework virtual memory accounting Andrew Morton <akpm@linux-foundation.org> - 2015-12-29 00:20 +0100
      Re: [PATCH RFC] mm: Rework virtual memory accounting Cyrill Gorcunov <gorcunov@gmail.com> - 2015-12-29 10:50 +0100

#1298755 — [PATCH RFC] mm: Rework virtual memory accounting

Really sorry for delays. Konstantin, I slightly updated the
changelog (to point where problem came from). Linus are you
fine with accounting not only anonymous memory in VmData?

Guys, take a look please, comments are highly appreciated.
---

From: Konstantin Khlebnikov <koct9i@gmail.com>

When inspecting a vague code inside prctl(PR_SET_MM_MEM)
call (which testing the RLIMIT_DATA value to figure out
if we're allowed to assign new @start_brk, @brk, @start_data,
@end_data from mm_struct) it's been commited that RLIMIT_DATA
in a form it's implemented now doesn't do anything useful
because most of user-space libraries use mmap() syscall
for dynamic memory allocations.

Linus suggested to convert RLIMIT_DATA rlimit into something
suitable for anonymous memory accounting. But in this patch
we go further, and the changes are bundled together as:

 * keep vma counting if CONFIG_PROC_FS=n, will be used for limits
 * replace mm->shared_vm with better defined mm->data_vm
 * account anonymous executable areas as executable
 * account file-backed growsdown/up areas as stack
 * drop struct file* argument from vm_stat_account
 * enforce RLIMIT_DATA for size of data areas

This way code looks cleaner: now code/stack/data
classification depends only on vm_flags state:

 VM_EXEC & ~VM_WRITE            -> code  (VmExe + VmLib in proc)
 VM_GROWSUP | VM_GROWSDOWN      -> stack (VmStk)
 VM_WRITE & ~VM_SHARED & !stack -> data  (VmData)

The rest (VmSize - VmData - VmStk - VmExe - VmLib) could be
called "shared", but that might be strange beast like
readonly-private or VM_IO area.

 - RLIMIT_AS            limits whole address space "VmSize"
 - RLIMIT_STACK         limits stack "VmStk" (but each vma individually)
 - RLIMIT_DATA          now limits "VmData"

CC: Quentin Casasnovas <quentin.casasnovas@oracle.com>
CC: Vegard Nossum <vegard.nossum@oracle.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linuxfoundation.org>
CC: Willy Tarreau <w@1wt.eu>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Kees Cook <keescook@google.com>
CC: Vladimir Davydov <vdavydov@virtuozzo.com>
CC: Pavel Emelyanov <xemul@virtuozzo.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
 arch/ia64/kernel/perfmon.c |    3 --
 fs/proc/task_mmu.c         |    7 ++---
 include/linux/mm.h         |   13 ++-------
 include/linux/mm_types.h   |    2 -
 kernel/fork.c              |    5 +--
 mm/debug.c                 |    4 +-
 mm/mmap.c                  |   63 ++++++++++++++++++++++-----------------------
 mm/mprotect.c              |    8 ++++-
 mm/mremap.c                |    7 ++---
 9 files changed, 53 insertions(+), 59 deletions(-)

Index: linux-ml.git/arch/ia64/kernel/perfmon.c
===================================================================
--- linux-ml.git.orig/arch/ia64/kernel/perfmon.c
+++ linux-ml.git/arch/ia64/kernel/perfmon.c
@@ -2332,8 +2332,7 @@ pfm_smpl_buffer_alloc(struct task_struct
 	 */
 	insert_vm_struct(mm, vma);
 
-	vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file,
-							vma_pages(vma));
+	vm_stat_account(vma->vm_mm, vma->vm_flags, vma_pages(vma));
 	up_write(&task->mm->mmap_sem);
 
 	/*
Index: linux-ml.git/fs/proc/task_mmu.c
===================================================================
--- linux-ml.git.orig/fs/proc/task_mmu.c
+++ linux-ml.git/fs/proc/task_mmu.c
@@ -22,7 +22,7 @@
 
 void task_mem(struct seq_file *m, struct mm_struct *mm)
 {
-	unsigned long data, text, lib, swap, ptes, pmds;
+	unsigned long text, lib, swap, ptes, pmds;
 	unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss;
 
 	/*
@@ -39,7 +39,6 @@ void task_mem(struct seq_file *m, struct
 	if (hiwater_rss < mm->hiwater_rss)
 		hiwater_rss = mm->hiwater_rss;
 
-	data = mm->total_vm - mm->shared_vm - mm->stack_vm;
 	text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
 	lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
 	swap = get_mm_counter(mm, MM_SWAPENTS);
@@ -65,7 +64,7 @@ void task_mem(struct seq_file *m, struct
 		mm->pinned_vm << (PAGE_SHIFT-10),
 		hiwater_rss << (PAGE_SHIFT-10),
 		total_rss << (PAGE_SHIFT-10),
-		data << (PAGE_SHIFT-10),
+		mm->data_vm << (PAGE_SHIFT-10),
 		mm->stack_vm << (PAGE_SHIFT-10), text, lib,
 		ptes >> 10,
 		pmds >> 10,
@@ -85,7 +84,7 @@ unsigned long task_statm(struct mm_struc
 	*shared = get_mm_counter(mm, MM_FILEPAGES);
 	*text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
 								>> PAGE_SHIFT;
-	*data = mm->total_vm - mm->shared_vm;
+	*data = mm->data_vm + mm->stack_vm;
 	*resident = *shared + get_mm_counter(mm, MM_ANONPAGES);
 	return mm->total_vm;
 }
Index: linux-ml.git/include/linux/mm.h
===================================================================
--- linux-ml.git.orig/include/linux/mm.h
+++ linux-ml.git/include/linux/mm.h
@@ -1898,7 +1898,9 @@ extern void mm_drop_all_locks(struct mm_
 extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
 extern struct file *get_mm_exe_file(struct mm_struct *mm);
 
-extern int may_expand_vm(struct mm_struct *mm, unsigned long npages);
+extern bool may_expand_vm(struct mm_struct *, vm_flags_t, unsigned long npages);
+extern void vm_stat_account(struct mm_struct *, vm_flags_t, long npages);
+
 extern struct vm_area_struct *_install_special_mapping(struct mm_struct *mm,
 				   unsigned long addr, unsigned long len,
 				   unsigned long flags,
@@ -2116,15 +2118,6 @@ typedef int (*pte_fn_t)(pte_t *pte, pgta
 extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
 			       unsigned long size, pte_fn_t fn, void *data);
 
-#ifdef CONFIG_PROC_FS
-void vm_stat_account(struct mm_struct *, unsigned long, struct file *, long);
-#else
-static inline void vm_stat_account(struct mm_struct *mm,
-			unsigned long flags, struct file *file, long pages)
-{
-	mm->total_vm += pages;
-}
-#endif /* CONFIG_PROC_FS */
 
 #ifdef CONFIG_DEBUG_PAGEALLOC
 extern bool _debug_pagealloc_enabled;
Index: linux-ml.git/include/linux/mm_types.h
===================================================================
--- linux-ml.git.orig/include/linux/mm_types.h
+++ linux-ml.git/include/linux/mm_types.h
@@ -426,7 +426,7 @@ struct mm_struct {
 	unsigned long total_vm;		/* Total pages mapped */
 	unsigned long locked_vm;	/* Pages that have PG_mlocked set */
 	unsigned long pinned_vm;	/* Refcount permanently increased */
-	unsigned long shared_vm;	/* Shared pages (files) */
+	unsigned long data_vm;		/* VM_WRITE & ~VM_SHARED/GROWSDOWN */
 	unsigned long exec_vm;		/* VM_EXEC & ~VM_WRITE */
 	unsigned long stack_vm;		/* VM_GROWSUP/DOWN */
 	unsigned long def_flags;
Index: linux-ml.git/kernel/fork.c
===================================================================
--- linux-ml.git.orig/kernel/fork.c
+++ linux-ml.git/kernel/fork.c
@@ -413,7 +413,7 @@ static int dup_mmap(struct mm_struct *mm
 	RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
 
 	mm->total_vm = oldmm->total_vm;
-	mm->shared_vm = oldmm->shared_vm;
+	mm->data_vm = oldmm->data_vm;
 	mm->exec_vm = oldmm->exec_vm;
 	mm->stack_vm = oldmm->stack_vm;
 
@@ -432,8 +432,7 @@ static int dup_mmap(struct mm_struct *mm
 		struct file *file;
 
 		if (mpnt->vm_flags & VM_DONTCOPY) {
-			vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
-							-vma_pages(mpnt));
+			vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
 			continue;
 		}
 		charge = 0;
Index: linux-ml.git/mm/debug.c
===================================================================
--- linux-ml.git.orig/mm/debug.c
+++ linux-ml.git/mm/debug.c
@@ -175,7 +175,7 @@ void dump_mm(const struct mm_struct *mm)
 		"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
 		"pgd %p mm_users %d mm_count %d nr_ptes %lu nr_pmds %lu map_count %d\n"
 		"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
-		"pinned_vm %lx shared_vm %lx exec_vm %lx stack_vm %lx\n"
+		"pinned_vm %lx data_vm %lx exec_vm %lx stack_vm %lx\n"
 		"start_code %lx end_code %lx start_data %lx end_data %lx\n"
 		"start_brk %lx brk %lx start_stack %lx\n"
 		"arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
@@ -209,7 +209,7 @@ void dump_mm(const struct mm_struct *mm)
 		mm_nr_pmds((struct mm_struct *)mm),
 		mm->map_count,
 		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
-		mm->pinned_vm, mm->shared_vm, mm->exec_vm, mm->stack_vm,
+		mm->pinned_vm, mm->data_vm, mm->exec_vm, mm->stack_vm,
 		mm->start_code, mm->end_code, mm->start_data, mm->end_data,
 		mm->start_brk, mm->brk, mm->start_stack,
 		mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
Index: linux-ml.git/mm/mmap.c
===================================================================
--- linux-ml.git.orig/mm/mmap.c
+++ linux-ml.git/mm/mmap.c
@@ -1208,24 +1208,6 @@ none:
 	return NULL;
 }
 
-#ifdef CONFIG_PROC_FS
-void vm_stat_account(struct mm_struct *mm, unsigned long flags,
-						struct file *file, long pages)
-{
-	const unsigned long stack_flags
-		= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
-
-	mm->total_vm += pages;
-
-	if (file) {
-		mm->shared_vm += pages;
-		if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
-			mm->exec_vm += pages;
-	} else if (flags & stack_flags)
-		mm->stack_vm += pages;
-}
-#endif /* CONFIG_PROC_FS */
-
 /*
  * If a hint addr is less than mmap_min_addr change hint to be as
  * low as possible but still greater than mmap_min_addr
@@ -1544,7 +1526,7 @@ unsigned long mmap_region(struct file *f
 	unsigned long charged = 0;
 
 	/* Check against address space limit. */
-	if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
+	if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
 		unsigned long nr_pages;
 
 		/*
@@ -1556,7 +1538,8 @@ unsigned long mmap_region(struct file *f
 
 		nr_pages = count_vma_pages_range(mm, addr, addr + len);
 
-		if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
+		if (!may_expand_vm(mm, vm_flags,
+					(len >> PAGE_SHIFT) - nr_pages))
 			return -ENOMEM;
 	}
 
@@ -1655,7 +1638,7 @@ unsigned long mmap_region(struct file *f
 out:
 	perf_event_mmap(vma);
 
-	vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
+	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
 		if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
 					vma == get_gate_vma(current->mm)))
@@ -2102,7 +2085,7 @@ static int acct_stack_growth(struct vm_a
 	unsigned long new_start, actual_size;
 
 	/* address space limit tests */
-	if (!may_expand_vm(mm, grow))
+	if (!may_expand_vm(mm, vma->vm_flags, grow))
 		return -ENOMEM;
 
 	/* Stack limit test */
@@ -2199,8 +2182,7 @@ int expand_upwards(struct vm_area_struct
 				spin_lock(&mm->page_table_lock);
 				if (vma->vm_flags & VM_LOCKED)
 					mm->locked_vm += grow;
-				vm_stat_account(mm, vma->vm_flags,
-						vma->vm_file, grow);
+				vm_stat_account(mm, vma->vm_flags, grow);
 				anon_vma_interval_tree_pre_update_vma(vma);
 				vma->vm_end = address;
 				anon_vma_interval_tree_post_update_vma(vma);
@@ -2275,8 +2257,7 @@ int expand_downwards(struct vm_area_stru
 				spin_lock(&mm->page_table_lock);
 				if (vma->vm_flags & VM_LOCKED)
 					mm->locked_vm += grow;
-				vm_stat_account(mm, vma->vm_flags,
-						vma->vm_file, grow);
+				vm_stat_account(mm, vma->vm_flags, grow);
 				anon_vma_interval_tree_pre_update_vma(vma);
 				vma->vm_start = address;
 				vma->vm_pgoff -= grow;
@@ -2390,7 +2371,7 @@ static void remove_vma_list(struct mm_st
 
 		if (vma->vm_flags & VM_ACCOUNT)
 			nr_accounted += nrpages;
-		vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
+		vm_stat_account(mm, vma->vm_flags, -nrpages);
 		vma = remove_vma(vma);
 	} while (vma);
 	vm_unacct_memory(nr_accounted);
@@ -2760,7 +2741,7 @@ static unsigned long do_brk(unsigned lon
 	}
 
 	/* Check against address space limits *after* clearing old maps... */
-	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
+	if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
 		return -ENOMEM;
 
 	if (mm->map_count > sysctl_max_map_count)
@@ -2795,6 +2776,7 @@ static unsigned long do_brk(unsigned lon
 out:
 	perf_event_mmap(vma);
 	mm->total_vm += len >> PAGE_SHIFT;
+	mm->data_vm += len >> PAGE_SHIFT;
 	if (flags & VM_LOCKED)
 		mm->locked_vm += (len >> PAGE_SHIFT);
 	vma->vm_flags |= VM_SOFTDIRTY;
@@ -2986,7 +2968,7 @@ out:
  * Return true if the calling process may expand its vm space by the passed
  * number of pages
  */
-int may_expand_vm(struct mm_struct *mm, unsigned long npages)
+bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
 {
 	unsigned long cur = mm->total_vm;	/* pages */
 	unsigned long lim;
@@ -2994,8 +2976,25 @@ int may_expand_vm(struct mm_struct *mm,
 	lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
 
 	if (cur + npages > lim)
-		return 0;
-	return 1;
+		return false;
+
+	if ((flags & (VM_WRITE | VM_SHARED | (VM_STACK_FLAGS &
+				(VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE)
+		return mm->data_vm + npages <= rlimit(RLIMIT_DATA);
+
+	return true;
+}
+
+void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
+{
+	mm->total_vm += npages;
+
+	if ((flags & (VM_EXEC | VM_WRITE)) == VM_EXEC)
+		mm->exec_vm += npages;
+	else if (flags & (VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)))
+		mm->stack_vm += npages;
+	else if ((flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
+		mm->data_vm += npages;
 }
 
 static int special_mapping_fault(struct vm_area_struct *vma,
@@ -3077,7 +3076,7 @@ static struct vm_area_struct *__install_
 	if (ret)
 		goto out;
 
-	mm->total_vm += len >> PAGE_SHIFT;
+	vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
 
 	perf_event_mmap(vma);
 
Index: linux-ml.git/mm/mprotect.c
===================================================================
--- linux-ml.git.orig/mm/mprotect.c
+++ linux-ml.git/mm/mprotect.c
@@ -278,6 +278,10 @@ mprotect_fixup(struct vm_area_struct *vm
 	 * even if read-only so there is no need to account for them here
 	 */
 	if (newflags & VM_WRITE) {
+		/* Check space limits when area turns into data. */
+		if (!may_expand_vm(mm, newflags, nrpages) &&
+				may_expand_vm(mm, oldflags, nrpages))
+			return -ENOMEM;
 		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 						VM_SHARED|VM_NORESERVE))) {
 			charged = nrpages;
@@ -334,8 +338,8 @@ success:
 		populate_vma_page_range(vma, start, end, NULL);
 	}
 
-	vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
-	vm_stat_account(mm, newflags, vma->vm_file, nrpages);
+	vm_stat_account(mm, oldflags, -nrpages);
+	vm_stat_account(mm, newflags, nrpages);
 	perf_event_mmap(vma);
 	return 0;
 
Index: linux-ml.git/mm/mremap.c
===================================================================
--- linux-ml.git.orig/mm/mremap.c
+++ linux-ml.git/mm/mremap.c
@@ -317,7 +317,7 @@ static unsigned long move_vma(struct vm_
 	 * If this were a serious issue, we'd add a flag to do_munmap().
 	 */
 	hiwater_vm = mm->hiwater_vm;
-	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
+	vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
 
 	if (do_munmap(mm, old_addr, old_len) < 0) {
 		/* OOM: unable to split vma, just get accounts right */
@@ -379,7 +379,8 @@ static struct vm_area_struct *vma_to_res
 			return ERR_PTR(-EAGAIN);
 	}
 
-	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
+	if (!may_expand_vm(mm, vma->vm_flags,
+				(new_len - old_len) >> PAGE_SHIFT))
 		return ERR_PTR(-ENOMEM);
 
 	if (vma->vm_flags & VM_ACCOUNT) {
@@ -541,7 +542,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
 				goto out;
 			}
 
-			vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
+			vm_stat_account(mm, vma->vm_flags, pages);
 			if (vma->vm_flags & VM_LOCKED) {
 				mm->locked_vm += pages;
 				locked = true;
--
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#1298774

On Mon, Dec 28, 2015 at 1:10 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> Really sorry for delays. Konstantin, I slightly updated the
> changelog (to point where problem came from). Linus are you
> fine with accounting not only anonymous memory in VmData?

The patch looks ok to me. I guess if somebody relies on old behavior
we may have to tweak it a bit, but on the whole this looks sane and
I'd be happy to merge it in the 4.5 merge window (and maybe even have
it marked for stable if it works out)

               Linus
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#1298927

On Mon, Dec 28, 2015 at 02:22:23PM -0800, Linus Torvalds wrote:
> On Mon, Dec 28, 2015 at 1:10 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> > Really sorry for delays. Konstantin, I slightly updated the
> > changelog (to point where problem came from). Linus are you
> > fine with accounting not only anonymous memory in VmData?
> 
> The patch looks ok to me. I guess if somebody relies on old behavior
> we may have to tweak it a bit, but on the whole this looks sane and
> I'd be happy to merge it in the 4.5 merge window (and maybe even have
> it marked for stable if it works out)

Thank you!
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#1298789

On Tue, 29 Dec 2015 00:10:15 +0300 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> When inspecting a vague code inside prctl(PR_SET_MM_MEM)
> call (which testing the RLIMIT_DATA value to figure out
> if we're allowed to assign new @start_brk, @brk, @start_data,
> @end_data from mm_struct) it's been commited that RLIMIT_DATA
> in a form it's implemented now doesn't do anything useful
> because most of user-space libraries use mmap() syscall
> for dynamic memory allocations.
> 
> Linus suggested to convert RLIMIT_DATA rlimit into something
> suitable for anonymous memory accounting. But in this patch
> we go further, and the changes are bundled together as:
> 
>  * keep vma counting if CONFIG_PROC_FS=n, will be used for limits
>  * replace mm->shared_vm with better defined mm->data_vm
>  * account anonymous executable areas as executable
>  * account file-backed growsdown/up areas as stack
>  * drop struct file* argument from vm_stat_account
>  * enforce RLIMIT_DATA for size of data areas
> 
> This way code looks cleaner: now code/stack/data
> classification depends only on vm_flags state:
> 
>  VM_EXEC & ~VM_WRITE            -> code  (VmExe + VmLib in proc)
>  VM_GROWSUP | VM_GROWSDOWN      -> stack (VmStk)
>  VM_WRITE & ~VM_SHARED & !stack -> data  (VmData)
> 
> The rest (VmSize - VmData - VmStk - VmExe - VmLib) could be
> called "shared", but that might be strange beast like
> readonly-private or VM_IO area.
> 
>  - RLIMIT_AS            limits whole address space "VmSize"
>  - RLIMIT_STACK         limits stack "VmStk" (but each vma individually)
>  - RLIMIT_DATA          now limits "VmData"

This clashes with
mm-mmapc-remove-redundant-local-variables-for-may_expand_vm.patch,
below.  I resolved it thusly:

bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
{
	if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
		return false;

	if ((flags & (VM_WRITE | VM_SHARED | (VM_STACK_FLAGS &
				(VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE)
		return mm->data_vm + npages <= rlimit(RLIMIT_DATA);

	return true;
}



From: Chen Gang <gang.chen.5i5j@gmail.com>
Subject: mm/mmap.c: remove redundant local variables for may_expand_vm()

Simplify may_expand_vm()

[akpm@linux-foundation.org: further simplification, per Naoya Horiguchi]
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |    9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff -puN mm/mmap.c~mm-mmapc-remove-redundant-local-variables-for-may_expand_vm mm/mmap.c
--- a/mm/mmap.c~mm-mmapc-remove-redundant-local-variables-for-may_expand_vm
+++ a/mm/mmap.c
@@ -2988,14 +2988,7 @@ out:
  */
 int may_expand_vm(struct mm_struct *mm, unsigned long npages)
 {
-	unsigned long cur = mm->total_vm;	/* pages */
-	unsigned long lim;
-
-	lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
-
-	if (cur + npages > lim)
-		return 0;
-	return 1;
+	return mm->total_vm + npages <= rlimit(RLIMIT_AS) >> PAGE_SHIFT;
 }
 
 static int special_mapping_fault(struct vm_area_struct *vma,
_

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#1298925

On Mon, Dec 28, 2015 at 03:10:02PM -0800, Andrew Morton wrote:
> On Tue, 29 Dec 2015 00:10:15 +0300 Cyrill Gorcunov <gorcunov@gmail.com> wrote:
...
> 
> This clashes with
> mm-mmapc-remove-redundant-local-variables-for-may_expand_vm.patch,
> below.  I resolved it thusly:
> 
> bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
> {
> 	if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
> 		return false;
> 
> 	if ((flags & (VM_WRITE | VM_SHARED | (VM_STACK_FLAGS &
> 				(VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE)
> 		return mm->data_vm + npages <= rlimit(RLIMIT_DATA);
> 
> 	return true;
> }

Thanks, Andrew!
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