Re: [PATCH 09/12] mm/readahead: Align file mappings for non-DAX

From: Rongwei Wang <rongwei.wang@linux.alibaba.com>
To: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org
Cc: William Kucharski <william.kucharski@oracle.com>
Subject: Re: [PATCH 09/12] mm/readahead: Align file mappings for non-DAX
Date: Mon, 17 Jan 2022 11:17:55 +0800	[thread overview]
Message-ID: <d4ac99a0-6c45-e81b-c08a-56083c4cdd6e@linux.alibaba.com> (raw)
In-Reply-To: <20220116121822.1727633-10-willy@infradead.org>

On 1/16/22 8:18 PM, Matthew Wilcox (Oracle) wrote:
> From: William Kucharski <william.kucharski@oracle.com>
> 
> When we have the opportunity to use PMDs to map a file, we want to follow
> the same rules as DAX.
> 
> Signed-off-by: William Kucharski <william.kucharski@oracle.com>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   mm/huge_memory.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f58524394dc1..28c29a0d854b 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -582,13 +582,10 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
>   	unsigned long ret;
>   	loff_t off = (loff_t)pgoff << PAGE_SHIFT;
>   
> -	if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
> -		goto out;
> -
>   	ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
>   	if (ret)
>   		return ret;
> -out:
> +
>   	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
Hi, Matthew

It seems this patch will make all file mappings align with PMD_SIZE? And 
support realize all file THP, not only executable file THP?

Actually, what I want to say is we had merged a similar patch to only 
align DSO mapping in glibc:

"718fdd8 elf: Properly align PT_LOAD segments [BZ #28676]"

>   }
>   EXPORT_SYMBOL_GPL(thp_get_unmapped_area);