Re: [PATCH] mm: update the description for madvise_remove

Re: [PATCH] mm: update the description for madvise_remove

[David Rientjes]

On Tue, 24 Jun 2014, Wang Sheng-Hui wrote:

> 
> Currently, we have more filesystems supporting fallocate, e.g
> ext4/btrfs. Remove the outdated comment for madvise_remove.
> 
> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
> ---
>  mm/madvise.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index a402f8f..0938b30 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -292,9 +292,6 @@ static long madvise_dontneed(struct vm_area_struct *vma,
>  /*
>   * Application wants to free up the pages and associated backing store.
>   * This is effectively punching a hole into the middle of a file.
> - *
> - * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
> - * Other filesystems return -ENOSYS.
>   */
>  static long madvise_remove(struct vm_area_struct *vma,
>                                 struct vm_area_struct **prev,

[For those without context: this patch has been merged into the -mm tree.]

This reference also exists in the man-page for madvise(2), are you 
planning on removing it as well?

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Re: [PATCH] mm: update the description for madvise_remove

[Wang Sheng-Hui]

Patch to man-page.

[PATCH] madvise.2: update the description for MADV_REMOVE

Currently we have more filesystems supporting fallcate, e.g ext4/btrfs,
which can response to MADV_REMOVE gracefully.

And if filesystems don't support fallocate, the return error would be
EOPNOTSUPP, instead of ENOSYS.

Signed-off-by: Wang Sheng-Hui <shhuiw-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 man2/madvise.2 | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/man2/madvise.2 b/man2/madvise.2
index 032ead7..4ce869c 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -99,13 +99,9 @@ or zero-fill-on-demand pages for mappings
 without an underlying file.
 .TP
 .BR MADV_REMOVE " (since Linux 2.6.16)"
-Free up a given range of pages
-and its associated backing store.
-Currently,
-.\" 2.6.18-rc5
-only shmfs/tmpfs supports this; other filesystems return with the
-error
-.BR ENOSYS .
+Free up a given range of pages and its associated backing store.
+Filesystems that don't support fallocate will return error
+.BR EOPNOTSUPP.
 .\" Databases want to use this feature to drop a section of their
 .\" bufferpool (shared memory segments) - without writing back to
 .\" disk/swap space.  This feature is also useful for supporting
-- 
1.8.3.2



On 2014年06月25日 06:44, David Rientjes wrote:
> On Tue, 24 Jun 2014, Wang Sheng-Hui wrote:
> 
>>
>> Currently, we have more filesystems supporting fallocate, e.g
>> ext4/btrfs. Remove the outdated comment for madvise_remove.
>>
>> Signed-off-by: Wang Sheng-Hui <shhuiw-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> ---
>>  mm/madvise.c | 3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index a402f8f..0938b30 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -292,9 +292,6 @@ static long madvise_dontneed(struct vm_area_struct *vma,
>>  /*
>>   * Application wants to free up the pages and associated backing store.
>>   * This is effectively punching a hole into the middle of a file.
>> - *
>> - * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
>> - * Other filesystems return -ENOSYS.
>>   */
>>  static long madvise_remove(struct vm_area_struct *vma,
>>                                 struct vm_area_struct **prev,
> 
> [For those without context: this patch has been merged into the -mm tree.]
> 
> This reference also exists in the man-page for madvise(2), are you 
> planning on removing it as well?
> 

Re: [PATCH] mm: update the description for madvise_remove

[David Rientjes]

On Wed, 25 Jun 2014, Wang Sheng-Hui wrote:

> Patch to man-page.
> 
> [PATCH] madvise.2: update the description for MADV_REMOVE
> 
> Currently we have more filesystems supporting fallcate, e.g ext4/btrfs,
> which can response to MADV_REMOVE gracefully.
> 
> And if filesystems don't support fallocate, the return error would be
> EOPNOTSUPP, instead of ENOSYS.
> 
> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>

Great, thanks!  This looks like it can be applied immediately and doesn't 
require us to wait for any kernel change.

Good catch with the return value.

> ---
>  man2/madvise.2 | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/man2/madvise.2 b/man2/madvise.2
> index 032ead7..4ce869c 100644
> --- a/man2/madvise.2
> +++ b/man2/madvise.2
> @@ -99,13 +99,9 @@ or zero-fill-on-demand pages for mappings
>  without an underlying file.
>  .TP
>  .BR MADV_REMOVE " (since Linux 2.6.16)"
> -Free up a given range of pages
> -and its associated backing store.
> -Currently,
> -.\" 2.6.18-rc5
> -only shmfs/tmpfs supports this; other filesystems return with the
> -error
> -.BR ENOSYS .
> +Free up a given range of pages and its associated backing store.
> +Filesystems that don't support fallocate will return error
> +.BR EOPNOTSUPP.
>  .\" Databases want to use this feature to drop a section of their
>  .\" bufferpool (shared memory segments) - without writing back to
>  .\" disk/swap space.  This feature is also useful for supporting

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