linux-kernel - Re: [PATCH] erofs: apply proper VMA alignment for memory mapped files on THP

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Message-ID: <3db6b039-a071-4736-aaa8-fe1a7934f981@linux.alibaba.com>
Date: Wed, 6 Mar 2024 15:55:06 +0800
From: Jingbo Xu <jefflexu@...ux.alibaba.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>, linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] erofs: apply proper VMA alignment for memory mapped files
 on THP



On 3/6/24 2:51 PM, Gao Xiang wrote:
> 
> 
> On 2024/3/6 13:31, Gao Xiang wrote:
>> There are mainly two reasons that thp_get_unmapped_area() should be
>> used for EROFS as other filesystems:
>>
>>   - It's needed to enable PMD mappings as a FSDAX filesystem, see
>>     commit 74d2fad1334d ("thp, dax: add thp_get_unmapped_area for pmd
>>     mappings");
>>
>>   - It's useful together with CONFIG_READ_ONLY_THP_FOR_FS which enables
>>     THPs for read-only mmapped files (e.g. shared libraries) even without
>>     FSDAX.  See commit 1854bc6e2420 ("mm/readahead: Align file mappings
>>     for non-DAX").
> 
> Refine this part as
> 
>  - It's useful together with large folios and CONFIG_READ_ONLY_THP_FOR_FS
>    which enable THPs for mmapped files (e.g. shared libraries) even without
>    ...
> 
>>
>> Fixes: 06252e9ce05b ("erofs: dax support for non-tailpacking regular
>> file")
> 
> Fixes: ce529cc25b18 ("erofs: enable large folios for iomap mode")
> Fixes: be62c5198861 ("erofs: enable large folios for fscache mode")
> 
>> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
>> ---
>>   fs/erofs/data.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
>> index c98aeda8abb2..3d9721b3faa8 100644
>> --- a/fs/erofs/data.c
>> +++ b/fs/erofs/data.c
>> @@ -447,5 +447,6 @@ const struct file_operations erofs_file_fops = {
>>       .llseek        = generic_file_llseek,
>>       .read_iter    = erofs_file_read_iter,
>>       .mmap        = erofs_file_mmap,
>> +    .get_unmapped_area = thp_get_unmapped_area,
>>       .splice_read    = filemap_splice_read,
>>   };


LGTM.

Reviewed-by: Jingbo Xu \<jefflexu@...ux.alibaba.com>

-- 
Thanks,
Jingbo