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From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Dave Chinner <david@fromorbit.com>, Matthew Wilcox <willy@infradead.org>, Christoph Hellwig <hch@infradead.org>, Christian Brauner <brauner@kernel.org>, Ojaswin Mujoo <ojaswin@linux.ibm.com>, Jan Kara <jack@suse.cz>, Luis Chamberlain <mcgrof@kernel.org>
Subject: Re: [PATCH] Documentation: document the design of iomap and how to port
In-Reply-To: <20240611215049.GC52987@frogsfrogsfrogs>
Date: Wed, 12 Jun 2024 12:25:47 +0530
Message-ID: <871q52abv0.fsf@gmail.com>
References: <20240608001707.GD52973@frogsfrogsfrogs> <874ja118g7.fsf@gmail.com> <20240610231111.GW52987@frogsfrogsfrogs> <875xug9dyt.fsf@gmail.com> <20240611215049.GC52987@frogsfrogsfrogs>
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"Darrick J. Wong" <djwong@kernel.org> writes:

> On Tue, Jun 11, 2024 at 12:13:22PM +0530, Ritesh Harjani wrote:
>> "Darrick J. Wong" <djwong@kernel.org> writes:
>> 

<snip>
>> >> > + * ``addr`` describes the device address, in bytes.
>> >> > +
>> >> > + * ``bdev`` describes the block device for this mapping.
>> >> > +   This only needs to be set for mapped or unwritten operations.
>> >> > +
>> >> > + * ``dax_dev`` describes the DAX device for this mapping.
>> >> > +   This only needs to be set for mapped or unwritten operations, and
>> >> > +   only for a fsdax operation.
>> >> 
>> >> Looks like we can make this union (bdev and dax_dev). Since depending
>> >> upon IOMAP_DAX or not we only set either dax_dev or bdev.
>> >
>> > Separate patch. ;)
>> >
>> 
>> Yes, in a way I was trying to get an opinion from you and others on
>> whether it make sense to make bdev and dax_dev as union :)
>> 
>> Looks like this series [1] could be the reason for that. 
>> 
>> [1]: https://lore.kernel.org/all/20211129102203.2243509-1-hch@lst.de/#t
>> 
>> I also don't see any reference to dax code from fs/iomap/buffered-io.c
>> So maybe we don't need this dax.h header in this file.
>> 
>> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
>> index c5802a459334..e1a6cca3cec2 100644
>> --- a/fs/iomap/buffered-io.c
>> +++ b/fs/iomap/buffered-io.c
>> @@ -10,7 +10,6 @@
>>  #include <linux/pagemap.h>
>>  #include <linux/uio.h>
>>  #include <linux/buffer_head.h>
>> -#include <linux/dax.h>
>>  #include <linux/writeback.h>
>>  #include <linux/list_sort.h>
>>  #include <linux/swap.h>
>
> Yes, given that both you and hch have mentioned it, could one of you
> send a cleanup series for that?
>

Sure, Thanks Darrick and Christoph.
I can queue this with my other work where I am improving iomap for
indirect-block mapping, so that it will be easier to get testing done on
all of this together.

-ritesh