linux-ext4 - Re: [PATCH v4 7/8] ext4: reorder map.m_flags checks in ext4_set

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Message-Id: <20191009063548.90C434203F@d06av24.portsmouth.uk.ibm.com>
Date:   Wed, 9 Oct 2019 12:05:47 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Matthew Bobrowski <mbobrowski@...browski.org>, tytso@....edu,
        jack@...e.cz, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hch@...radead.org, david@...morbit.com, darrick.wong@...cle.com
Subject: Re: [PATCH v4 7/8] ext4: reorder map.m_flags checks in
 ext4_set_iomap()



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@...browski.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@...ux.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;
>