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Date: Mon, 28 Sep 2009 14:37:48 +1000
From: Nigel Cunningham <ncunningham@...a.org.au>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC: Wu Fengguang <fengguang.wu@...el.com>,
LKML <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: No more bits in vm_area_struct's vm_flags.
Hi.
KAMEZAWA Hiroyuki wrote:
> Then, Nigel, you have 2 choices I think.
>
> (1) don't merge if vm_hints is set or (2) pass vm_hints to all
> __merge() functions.
>
> One of above will be accesptable for stakeholders... I personally
> like (1) but just trying (2) may be accepted.
>
> What I dislike is making vm_flags to be long long ;)
Okay. I've gone for option 1 for now. Here's what I
currently have (compile testing as I write)...
vm_flags in struct vm_area_struct is full. Move some of the less commonly
used flags to a new variable so that other flags that need to be in vm_flags
(because, for example, they need to be in variables that are passed around)
can be added.
Signed-off-by: Nigel Cunningham <nigel@...onice.net>
---
include/linux/mm.h | 16 ++++++++--------
include/linux/mm_types.h | 1 +
mm/madvise.c | 28 ++++++++++++++++++----------
mm/mmap.c | 2 ++
4 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 24c3956..040d0ce 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -85,10 +85,6 @@ extern unsigned int kobjsize(const void *objp);
#define VM_LOCKED 0x00002000
#define VM_IO 0x00004000 /* Memory mapped I/O or similar */
- /* Used by sys_madvise() */
-#define VM_SEQ_READ 0x00008000 /* App will access data sequentially */
-#define VM_RAND_READ 0x00010000 /* App will not benefit from clustered reads */
-
#define VM_DONTCOPY 0x00020000 /* Do not copy this vma on fork */
#define VM_DONTEXPAND 0x00040000 /* Cannot expand with mremap() */
#define VM_RESERVED 0x00080000 /* Count as reserved_vm like IO */
@@ -116,11 +112,15 @@ extern unsigned int kobjsize(const void *objp);
#define VM_STACK_FLAGS (VM_GROWSDOWN | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
#endif
+ /* Used by sys_madvise() */
+#define VM_SEQ_READ 0x00000001 /* App will access data sequentially */
+#define VM_RAND_READ 0x00000002 /* App will not benefit from clustered reads */
+
#define VM_READHINTMASK (VM_SEQ_READ | VM_RAND_READ)
-#define VM_ClearReadHint(v) (v)->vm_flags &= ~VM_READHINTMASK
-#define VM_NormalReadHint(v) (!((v)->vm_flags & VM_READHINTMASK))
-#define VM_SequentialReadHint(v) ((v)->vm_flags & VM_SEQ_READ)
-#define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ)
+#define VM_ClearReadHint(v) (v)->vm_hints &= ~VM_READHINTMASK
+#define VM_NormalReadHint(v) (!((v)->vm_hints & VM_READHINTMASK))
+#define VM_SequentialReadHint(v) ((v)->vm_hints & VM_SEQ_READ)
+#define VM_RandomReadHint(v) ((v)->vm_hints & VM_RAND_READ)
/*
* special vmas that are non-mergable, non-mlock()able
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 84a524a..5c66e3a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -178,6 +178,7 @@ struct vm_area_struct {
units, *not* PAGE_CACHE_SIZE */
struct file * vm_file; /* File we map to (can be NULL). */
void * vm_private_data; /* was vm_pte (shared mem) */
+ unsigned long vm_hints; /* Hints, see mm.h. */
unsigned long vm_truncate_count;/* truncate_count or restart_addr */
#ifndef CONFIG_MMU
diff --git a/mm/madvise.c b/mm/madvise.c
index 35b1479..59a93d3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -40,19 +40,22 @@ static long madvise_behavior(struct vm_area_struct * vma,
unsigned long start, unsigned long end, int behavior)
{
struct mm_struct * mm = vma->vm_mm;
- int error = 0;
+ int error = 0, skip_merge = 0;
pgoff_t pgoff;
- unsigned long new_flags = vma->vm_flags;
+ unsigned long new_flags = vma->vm_flags, new_hints = vma->vm_hints;
switch (behavior) {
case MADV_NORMAL:
- new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
+ new_hints = new_hints & ~VM_RAND_READ & ~VM_SEQ_READ;
+ skip_merge = 1;
break;
case MADV_SEQUENTIAL:
- new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
+ new_hints = (new_hints & ~VM_RAND_READ) | VM_SEQ_READ;
+ skip_merge = 1;
break;
case MADV_RANDOM:
- new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
+ new_hints = (new_hints & ~VM_SEQ_READ) | VM_RAND_READ;
+ skip_merge = 1;
break;
case MADV_DONTFORK:
new_flags |= VM_DONTCOPY;
@@ -78,11 +81,15 @@ static long madvise_behavior(struct vm_area_struct * vma,
}
pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
- *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
- vma->vm_file, pgoff, vma_policy(vma));
- if (*prev) {
- vma = *prev;
- goto success;
+
+ if (!skip_merge) {
+ *prev = vma_merge(mm, *prev, start, end, new_flags,
+ vma->anon_vma, vma->vm_file, pgoff,
+ vma_policy(vma));
+ if (*prev) {
+ vma = *prev;
+ goto success;
+ }
}
*prev = vma;
@@ -104,6 +111,7 @@ success:
* vm_flags is protected by the mmap_sem held in write mode.
*/
vma->vm_flags = new_flags;
+ vma->vm_hints = new_hints;
out:
if (error == -ENOMEM)
diff --git a/mm/mmap.c b/mm/mmap.c
index 73f5e4b..fb4bf98 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -670,6 +670,8 @@ static inline int is_mergeable_vma(struct vm_area_struct *vma,
return 0;
if (vma->vm_ops && vma->vm_ops->close)
return 0;
+ if (vma->vm_hints)
+ return 0;
return 1;
}
--
1.6.3.3
--
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