linux-kernel - Re: [PATCH] bcachefs: fix alignment of VMA for memory mapped files on THP

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Date: Thu, 20 Jun 2024 08:51:30 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Youling Tang <youling.tang@...ux.dev>
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Youling Tang <tangyouling@...inos.cn>
Subject: Re: [PATCH] bcachefs: fix alignment of VMA for memory mapped files
 on THP

On Thu, Jun 20, 2024 at 09:22:42AM +0800, Youling Tang wrote:
> From: Youling Tang <tangyouling@...inos.cn>
> 
> With CONFIG_READ_ONLY_THP_FOR_FS, the Linux kernel supports using THPs
> for read-only mmapped files, such as shared libraries. However, the
> kernel makes no attempt to actually align those mappings on 2MB
> boundaries, which makes it impossible to use those THPs most of the
> time. This issue applies to general file mapping THP as well as
> existing setups using CONFIG_READ_ONLY_THP_FOR_FS. This is easily
> fixed by using thp_get_unmapped_area for the unmapped_area function
> in bcachefs, which is what ext2, ext4, fuse, xfs and btrfs all use.
> 
> Similar to commit b0c582233a85 ("btrfs: fix alignment of VMA for
> memory mapped files on THP").
> 
> Signed-off-by: Youling Tang <tangyouling@...inos.cn>

Thanks - applied