linux-ext4 - Re: [PATCHv5 3/6] ext4: Move ext4 bmap to use iomap infrastructure.

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Message-Id: <20200302085840.A41E3A4053@d06av23.portsmouth.uk.ibm.com>
Date:   Mon, 2 Mar 2020 14:28:39 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>, jack@...e.cz
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, linux-fsdevel@...r.kernel.org,
        hch@...radead.org, cmaiolino@...hat.com, david@...morbit.com
Subject: Re: [PATCHv5 3/6] ext4: Move ext4 bmap to use iomap infrastructure.



On 2/28/20 8:55 PM, Darrick J. Wong wrote:
> On Fri, Feb 28, 2020 at 02:56:56PM +0530, Ritesh Harjani wrote:
>> ext4_iomap_begin is already implemented which provides ext4_map_blocks,
>> so just move the API from generic_block_bmap to iomap_bmap for iomap
>> conversion.
>>
>> Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
>> Reviewed-by: Jan Kara <jack@...e.cz>
>> ---
>>   fs/ext4/inode.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index 6cf3b969dc86..81fccbae0aea 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -3214,7 +3214,7 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
>>   			return 0;
>>   	}
>>   
>> -	return generic_block_bmap(mapping, block, ext4_get_block);
>> +	return iomap_bmap(mapping, block, &ext4_iomap_ops);
> 
> /me notes that iomap_bmap will filemap_write_and_wait for you, so one
> could optimize ext4_bmap to avoid the double-flush by moving the
> filemap_write_and_wait at the top of the function into the JDATA state
> clearing block.

IIUC, delalloc and data=journal mode are both mutually exclusive.
So we could get rid of calling filemap_write_and_wait() all together
from ext4_bmap().
And as you pointed filemap_write_and_wait() is called by default in
iomap_bmap which should cover for delalloc case.


@Jan/Darrick,
Could you check if the attached patch looks good. If yes then
will add your Reviewed-by and send a v6.

Thanks for the review!!

-ritesh



View attachment "0001-ext4-Move-ext4-bmap-to-use-iomap-infrastructure.patch" of type "text/x-patch" (1691 bytes)