Re: [PATCH] madvise.2: madvise(, , MADV_REMOVE) supports ext4, ocfs2 and xfs as well

[Jan Chaloupka <jchaloup-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Hi Michael,

On 02/04/2015 10:28 AM, Michael Kerrisk (man-pages) wrote:
> Hello Jan,
>
> On 18 October 2014 at 17:22, Jan Chaloupka <jchaloup-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>> As from upstream commit:
>>
>> commit 3f31d07571eeea18a7d34db9af21d2285b807a17
>> Author: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
>> Date:   Tue May 29 15:06:40 2012 -0700
>>
>>       mm/fs: route MADV_REMOVE to FALLOC_FL_PUNCH_HOLE
>>
>>       Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
>>       to use do_fallocate() instead of vmtruncate_range(): which extends
>>       madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.
>>
>> madvise(,,MADV_REMOVE) support was extended by ext4, ocfs2 and xfs.
>>
>> bug report: https://bugzilla.redhat.com/show_bug.cgi?id=1120294
>>
>> Justification from Rafael Aquini:
>> Well, that code is committed in kernel since v3.5 (2012) and it surely is
>> the expected behaviour since. It seems to me that madvise(2) man page text
>> for MADV_REMOVE just got out-of-date in that regard.
>>
>> This patch mentions this support in madvise.2 man page.
>>
>> Reworded and corrected by Michael Kerrisk and Hugh Dickins. Thank you.
> Sorry for the delay. I've applied this patch (and tweaked it a little, but
> not in essential details). Not yet pushed to kernel.,org yet.

Thanks :)

> Cheers,
>
> Michael
>
>
>> Signed-off-by: Jan Chaloupka <jchaloup-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>> ---
>>   man2/madvise.2 |   17 ++++++++++++-----
>>   1 file changed, 12 insertions(+), 5 deletions(-)
>>
>> diff --git a/man2/madvise.2 b/man2/madvise.2
>> index 032ead7..b955864 100644
>> --- a/man2/madvise.2
>> +++ b/man2/madvise.2
>> @@ -101,11 +101,18 @@ without an underlying file.
>>   .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 .
>> +Originally, only shmfs/tmpfs supported this; but since Linux 3.5,
>> +any filesystem which supports the
>> +.BR fallocate(2)
>> +mode
>> +.BR FALLOC_FL_PUNCH_HOLE
>> +also supports the
>> +.BR madvise(2)
>> +advice
>> +.BR MADV_REMOVE .
>> +Other filesystems return with the
>> +.BR EOPNOTSUPP
>> +error.
>>   .\" 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
>>
>
>

-- 
Jan Chaloupka
------------------------------
* Software Engineer          *
* ENG Base Operating Systems *
* Red Hat Czech, s. r. o.    *
* UTC+1 (CET), jchaloup      *

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