linux-kernel - Re: [PATCH v2 25/25] mm: Align THP mappings for non-DAX

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Message-ID: <20200212075006.GJ7068@infradead.org>
Date:   Tue, 11 Feb 2020 23:50:06 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        William Kucharski <william.kucharski@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 25/25] mm: Align THP mappings for non-DAX

> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index b52e007f0856..b8d9e0d76062 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -577,13 +577,10 @@ 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);
>  }
>  EXPORT_SYMBOL_GPL(thp_get_unmapped_area);

There is no point in splitting thp_get_unmapped_area and
__thp_get_unmapped_area with this applied (and arguably even before
that).  But we still have ext2 and ext4 that use thp_get_unmapped_area but
only support huge page mappings for DAX, do we need to handle those somehow?