linux-kernel - Re: [PATCH] f2fs: fix to map blocks correctly for direct read

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Message-ID: <ZyQtcbtzpixFd6Zs@google.com>
Date: Fri, 1 Nov 2024 01:22:57 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	kernel test robot <oliver.sang@...el.com>,
	Cyril Hrubis <chrubis@...e.cz>
Subject: Re: [PATCH] f2fs: fix to map blocks correctly for direct read

On 10/31, Chao Yu wrote:
> f2fs_map_blocks() supports to map continuous holes or preallocated
> address, we should avoid setting F2FS_MAP_MAPPED for these cases
> only, otherwise, it may fail f2fs_iomap_begin(), and make direct
> write fallbacking to use buffered IO and flush, result in performance
> regression.

Is this fixing direct write or read?

> 
> Fixes: 9f0f6bf42714 ("f2fs: support to map continuous holes or preallocated address")
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202409122103.e45aa13b-oliver.sang@intel.com
> Cc: Cyril Hrubis <chrubis@...e.cz>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>  fs/f2fs/data.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 306b86b0595d..38b85160c6bd 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1676,7 +1676,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>  		/* reserved delalloc block should be mapped for fiemap. */
>  		if (blkaddr == NEW_ADDR)
>  			map->m_flags |= F2FS_MAP_DELALLOC;
> -		if (flag != F2FS_GET_BLOCK_DIO || !is_hole)
> +		/*
> +		 * f2fs_map_blocks() supports to map continuous holes or
> +		 * preallocated address, don't set F2FS_MAP_MAPPED for these
> +		 * cases only.
> +		 */
> +		if (flag != F2FS_GET_BLOCK_DIO || map->m_may_create || !is_hole)

So, this is adding map->m_may_create, which is for writes?

>  			map->m_flags |= F2FS_MAP_MAPPED;
>  
>  		map->m_pblk = blkaddr;
> -- 
> 2.40.1