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Subject: Re: [PATCH v4 7/8] ext4: reorder map.m_flags checks in
 ext4_set_iomap()
To:     Matthew Bobrowski <mbobrowski@mbobrowski.org>, tytso@mit.edu,
        jack@suse.cz, adilger.kernel@dilger.ca
Cc:     linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com
References: <cover.1570100361.git.mbobrowski@mbobrowski.org>
 <3551610e53aa1984210a4de04ad6e1a89f5bf0a3.1570100361.git.mbobrowski@mbobrowski.org>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Wed, 9 Oct 2019 12:05:47 +0530
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On 10/3/19 5:04 PM, Matthew Bobrowski wrote:
> For iomap direct IO write code path changes, we need to accommodate
> for the case where the block mapping flags passed to ext4_map_blocks()
> will result in m_flags having both EXT4_MAP_MAPPED and
> EXT4_MAP_UNWRITTEN bits set. In order for the allocated unwritten
> extents to be converted properly in the end_io handler, iomap->type
> must be set to IOMAP_UNWRITTEN, so we need to reshuffle the
> conditional statement in order to achieve this.
> 
> This change is a no-op for DAX code path as the block mapping flag
> passed to ext4_map_blocks() when IS_DAX(inode) never results in
> EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN being set at once.
> 
> Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>

You may be changing the function parameters & name here,
(in ext4_set_iomap)
But functionality wise the patch looks good to me.

You may add:
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>


> ---
>   fs/ext4/inode.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e133dda55063..63ad23ae05b8 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3420,10 +3420,20 @@ static int ext4_set_iomap(struct inode *inode, struct iomap *iomap, u16 type,
>   		iomap->type = type;
>   		iomap->addr = IOMAP_NULL_ADDR;
>   	} else {
> -		if (map->m_flags & EXT4_MAP_MAPPED) {
> -			iomap->type = IOMAP_MAPPED;
> -		} else if (map->m_flags & EXT4_MAP_UNWRITTEN) {
> +		/*
> +		 * Flags passed to ext4_map_blocks() for direct I/O
> +		 * writes can result in map->m_flags having both
> +		 * EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN bits set. In
> +		 * order for allocated extents to be converted to
> +		 * written extents in the ->end_io handler correctly,
> +		 * we need to ensure that the iomap->type is set
> +		 * approprately. Thus, we need to check whether
> +		 * EXT4_MAP_UNWRITTEN is set first.
> +		 */
> +		if (map->m_flags & EXT4_MAP_UNWRITTEN) {
>   			iomap->type = IOMAP_UNWRITTEN;
> +		} else if (map->m_flags & EXT4_MAP_MAPPED) {
> +			iomap->type = IOMAP_MAPPED;
>   		} else {
>   			WARN_ON_ONCE(1);
>   			return -EIO;
>