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From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	david@fromorbit.com, riteshh@linux.ibm.com,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 02/15] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O
Date: Tue, 3 Sep 2019 09:12:38 -0500	[thread overview]
Message-ID: <20190903141237.7qtppmbqg3eg22fl@fiona> (raw)
In-Reply-To: <20190903031843.GC5340@magnolia>

On 20:18 02/09, Darrick J. Wong wrote:
> On Mon, Sep 02, 2019 at 06:31:04PM +0200, Christoph Hellwig wrote:
> > On Sun, Sep 01, 2019 at 03:08:23PM -0500, Goldwyn Rodrigues wrote:
> > > --- a/include/linux/iomap.h
> > > +++ b/include/linux/iomap.h
> > > @@ -37,6 +37,7 @@ struct vm_fault;
> > >  #define IOMAP_MAPPED	0x03	/* blocks allocated at @addr */
> > >  #define IOMAP_UNWRITTEN	0x04	/* blocks allocated at @addr in unwritten state */
> > >  #define IOMAP_INLINE	0x05	/* data inline in the inode */
> > > +#define IOMAP_COW	0x06	/* copy data from srcmap before writing */
> > 
> > I don't think IOMAP_COW can be a type - it is a flag given that we
> > can do COW operations that allocate normal written extents (e.g. for
> > direct I/O or DAX) and for delayed allocations.
> 
> If iomap_apply always zeros out @srcmap before calling ->iomap_begin, do
> we even need a flag/type code?  Or does it suffice to check that
> srcmap.length > 0 and use it appropriately?
> 

While I understand your idea, it would be more robust to use the flag.
Makes it clean and scalable for other aspects of two iomaps (like extent
comparisons).

-- 
Goldwyn

  reply	other threads:[~2019-09-03 14:12 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-01 20:08 [PATCH v3 0/15] Btrfs iomap Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 01/15] iomap: Introduce CONFIG_FS_IOMAP_DEBUG Goldwyn Rodrigues
2019-09-01 20:50   ` Darrick J. Wong
2019-09-02 16:29   ` Christoph Hellwig
2019-09-02 17:09     ` Darrick J. Wong
2019-09-02 17:18       ` Christoph Hellwig
2019-09-03 15:06         ` Darrick J. Wong
2019-09-01 20:08 ` [PATCH 02/15] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-09-02 16:31   ` Christoph Hellwig
2019-09-03  3:18     ` Darrick J. Wong
2019-09-03 14:12       ` Goldwyn Rodrigues [this message]
2019-09-03 14:05     ` Goldwyn Rodrigues
2019-09-03 14:56       ` Darrick J. Wong
2019-09-01 20:08 ` [PATCH 03/15] iomap: Read page from srcmap for IOMAP_COW Goldwyn Rodrigues
2019-09-02 16:31   ` Christoph Hellwig
2019-09-02 17:01     ` Darrick J. Wong
2019-09-02 17:13       ` Christoph Hellwig
2019-09-01 20:08 ` [PATCH 04/15] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 05/15] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 06/15] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 07/15] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 08/15] fs: Export generic_file_buffered_read() Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 09/15] btrfs: basic direct read operation Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 10/15] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 11/15] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 12/15] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-09-02 16:41   ` Christoph Hellwig
2019-09-01 20:08 ` [PATCH 13/15] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 14/15] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-09-01 20:08 ` [PATCH 15/15] btrfs: update inode size during bio completion Goldwyn Rodrigues
2019-09-02 16:43 ` [PATCH v3 0/15] Btrfs iomap Christoph Hellwig
2019-09-03  3:51   ` Shiyang Ruan
2019-09-03  4:29     ` Darrick J. Wong
2019-09-03  5:00       ` Shiyang Ruan
2019-09-03  6:21     ` Christoph Hellwig
2019-09-03 13:44   ` Goldwyn Rodrigues

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