[PATCH] mm/madvise: fix WILLNEED on SHM/ANON to actually do something

[PATCH] mm/madvise: fix WILLNEED on SHM/ANON to actually do something

[David Herrmann]

Currently, madvise(MADV_WILLNEED) on shmem with swap enabled is a no-op.
Problem is, we use find_get_page() to lookup shmem pages in the given
range. However, what we're actually interested in is swapped-out pages.
Therefore, our current code is a no-op:
    page = find_get_page(mapping, index);
    if (!radix_tree_exceptional_entry(page))
        bail-out;

find_get_page() never returns exceptional entries. Fix this by using
find_get_entry(). This was probably meant to be used right from the
beginning.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
---
 mm/madvise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 539eeb9..a402f8f 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -195,7 +195,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 	for (; start < end; start += PAGE_SIZE) {
 		index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 
-		page = find_get_page(mapping, index);
+		page = find_get_entry(mapping, index);
 		if (!radix_tree_exceptional_entry(page)) {
 			if (page)
 				page_cache_release(page);
-- 
1.9.3

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm/madvise: fix WILLNEED on SHM/ANON to actually do something

[David Rientjes]

On Fri, 23 May 2014, David Herrmann wrote:

> diff --git a/mm/madvise.c b/mm/madvise.c
> index 539eeb9..a402f8f 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -195,7 +195,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
>  	for (; start < end; start += PAGE_SIZE) {
>  		index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
>  
> -		page = find_get_page(mapping, index);
> +		page = find_get_entry(mapping, index);
>  		if (!radix_tree_exceptional_entry(page)) {
>  			if (page)
>  				page_cache_release(page);

This is already in -mm from Johannes, see 
http://marc.info/?l=linux-kernel&m=139998616712729.  Check out 
http://www.ozlabs.org/~akpm/mmotm/ for this kernel.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm/madvise: fix WILLNEED on SHM/ANON to actually do something

[David Herrmann]

Hi

On Fri, May 23, 2014 at 10:55 PM, David Rientjes <rientjes@google.com> wrote:
> On Fri, 23 May 2014, David Herrmann wrote:
>
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index 539eeb9..a402f8f 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -195,7 +195,7 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
>>       for (; start < end; start += PAGE_SIZE) {
>>               index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
>>
>> -             page = find_get_page(mapping, index);
>> +             page = find_get_entry(mapping, index);
>>               if (!radix_tree_exceptional_entry(page)) {
>>                       if (page)
>>                               page_cache_release(page);
>
> This is already in -mm from Johannes, see
> http://marc.info/?l=linux-kernel&m=139998616712729.  Check out
> http://www.ozlabs.org/~akpm/mmotm/ for this kernel.

Didn't check -mm, sorry. Thanks for the links!
David

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>