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From: Dave Chinner <david@fromorbit.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	hch@lst.de, darrick.wong@oracle.com, ruansy.fnst@cn.fujitsu.com,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 01/13] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O
Date: Mon, 5 Aug 2019 10:06:46 +1000	[thread overview]
Message-ID: <20190805000646.GE7689@dread.disaster.area> (raw)
In-Reply-To: <20190802220048.16142-2-rgoldwyn@suse.de>

On Fri, Aug 02, 2019 at 05:00:36PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> Introduces a new type IOMAP_COW, which means the data at offset
> must be read from a srcmap and copied before performing the
> write on the offset.
> 
> The srcmap is used to identify where the read is to be performed
> from. This is passed to iomap->begin() of the respective
> filesystem, which is supposed to put in the details for
> reading before performing the copy for CoW.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/dax.c               |  8 +++++---
>  fs/ext2/inode.c        |  2 +-
>  fs/ext4/inode.c        |  2 +-
>  fs/gfs2/bmap.c         |  3 ++-
>  fs/iomap/apply.c       |  5 +++--
>  fs/iomap/buffered-io.c | 14 +++++++-------
>  fs/iomap/direct-io.c   |  2 +-
>  fs/iomap/fiemap.c      |  4 ++--
>  fs/iomap/seek.c        |  4 ++--
>  fs/iomap/swapfile.c    |  3 ++-
>  fs/xfs/xfs_iomap.c     |  9 ++++++---
>  include/linux/iomap.h  |  6 ++++--
>  12 files changed, 36 insertions(+), 26 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index a237141d8787..b21d9a9cde2b 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1090,7 +1090,7 @@ EXPORT_SYMBOL_GPL(__dax_zero_page_range);
>  
>  static loff_t
>  dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> -		struct iomap *iomap)
> +		struct iomap *iomap, struct iomap *srcmap)
>  {
>  	struct block_device *bdev = iomap->bdev;
>  	struct dax_device *dax_dev = iomap->dax_dev;
> @@ -1248,6 +1248,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
>  	unsigned long vaddr = vmf->address;
>  	loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
>  	struct iomap iomap = { 0 };
> +	struct iomap srcmap = { 0 };

I'm not found of defining multiple iomaps everywhere and passing
them explicitly to every function that might need them.  Perhaps
something like:

	DEFINE_IOMAP(iomap);

#define IOMAP_BASE_MAP		0
#define IOMAP_SOURCE_MAP	1
#define IOMAP_MAX_MAPS		2

#define DEFINE_IOMAP(name)	\
	(struct iomap #name[IOMAP_MAX_MAPS] = {{0}})

#define IOMAP_B(name)		((name)[IOMAP_BASE_MAP])
#define IOMAP_S(name)		((name)[IOMAP_SOURCE_MAP])

And now we only have to pass a single iomap parameter to each
function as "struct iomap **iomap". This makes the code somewhat
simpler, and we only ever need to use IOMAP_S(iomap) when
IOMAP_B(iomap)->type == IOMAP_COW.

The other advantage of this is that if we even need new
functionality that requires 2 (or more) iomaps, we don't have to
change APIs again....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2019-08-05  0:23 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 22:00 [PATCH v2 0/13] Btrfs iomap Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 01/13] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-08-03  0:39   ` Darrick J. Wong
2019-08-05  0:06   ` Dave Chinner [this message]
2019-08-02 22:00 ` [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW Goldwyn Rodrigues
2019-08-03  0:23   ` Darrick J. Wong
2019-08-04 23:52   ` Dave Chinner
2019-08-02 22:00 ` [PATCH 03/13] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 04/13] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-08-05  0:11   ` Dave Chinner
2019-08-22 15:05     ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 05/13] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-08-05  0:13   ` Dave Chinner
2019-08-22 15:01     ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 06/13] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 07/13] btrfs: basic direct read operation Goldwyn Rodrigues
2019-08-12 12:32   ` RITESH HARJANI
2019-08-22 15:00     ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 08/13] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 09/13] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 10/13] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-08-03  0:21   ` Darrick J. Wong
2019-08-05 16:08     ` Goldwyn Rodrigues
2019-08-04 23:43   ` Dave Chinner
2019-08-05 16:08     ` Goldwyn Rodrigues
2019-08-05 21:54       ` Dave Chinner
2019-08-08  4:26         ` Gao Xiang
2019-08-08  4:52           ` Gao Xiang
2019-08-08  5:49           ` Eric Biggers
2019-08-08  6:28             ` Gao Xiang
2019-08-08  8:16             ` Dave Chinner
2019-08-08  8:57               ` Gao Xiang
2019-08-08  9:29               ` Gao Xiang
2019-08-08 11:21                 ` Gao Xiang
2019-08-08 13:11                   ` Gao Xiang
2019-08-09 20:45             ` Matthew Wilcox
2019-08-09 23:45               ` Gao Xiang
2019-08-10  0:31                 ` Eric Biggers
2019-08-10  0:50                   ` Eric Biggers
2019-08-10  1:34                     ` Gao Xiang
2019-08-10  1:13                   ` Gao Xiang
2019-08-10  0:17               ` Eric Biggers
2019-08-02 22:00 ` [PATCH 11/13] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 12/13] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 13/13] btrfs: update inode size during bio completion Goldwyn Rodrigues

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