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From: Joe Perches <joe@perches.com>
To: Shiyang Ruan <ruansy.fnst@fujitsu.com>,
	linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org
Cc: jack@suse.cz, darrick.wong@oracle.com, david@fromorbit.com,
	ocfs2-devel@oss.oracle.com, viro@zeniv.linux.org.uk,
	Goldwyn Rodrigues <rgoldwyn@suse.com>,
	dan.j.williams@intel.com, linux-btrfs@vger.kernel.org
Subject: Re: [Ocfs2-devel] [PATCH v2 08/10] fsdax: Dedup file range to use a compare function
Date: Wed, 03 Mar 2021 00:20:14 -0800	[thread overview]
Message-ID: <aed5d2b78c4ac121ca0cf46107334673a3c9a586.camel@perches.com> (raw)
In-Reply-To: <20210226002030.653855-9-ruansy.fnst@fujitsu.com>

On Fri, 2021-02-26 at 08:20 +0800, Shiyang Ruan wrote:
> With dax we cannot deal with readpage() etc. So, we create a dax
> comparison funciton which is similar with
> vfs_dedupe_file_range_compare().
> And introduce dax_remap_file_range_prep() for filesystem use.
[]
> diff --git a/fs/dax.c b/fs/dax.c
[]
> @@ -1856,3 +1856,54 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,l
>  	return dax_insert_pfn_mkwrite(vmf, pfn, order);
>  }
>  EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
> +
> +static loff_t dax_range_compare_actor(struct inode *ino1, loff_t pos1,
> +		struct inode *ino2, loff_t pos2, loff_t len, void *data,
> +		struct iomap *smap, struct iomap *dmap)
> +{
> +	void *saddr, *daddr;
> +	bool *same = data;
> +	int ret;
> +
> +	while (len) {
> +		if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE)
> +			goto next;
> +
> +		if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
> +			*same = false;
> +			break;
> +		}
> +
> +		ret = dax_iomap_direct_access(smap, pos1,
> +			ALIGN(pos1 + len, PAGE_SIZE), &saddr, NULL);
> +		if (ret < 0)
> +			return -EIO;
> +
> +		ret = dax_iomap_direct_access(dmap, pos2,
> +			ALIGN(pos2 + len, PAGE_SIZE), &daddr, NULL);
> +		if (ret < 0)
> +			return -EIO;
> +
> +		*same = !memcmp(saddr, daddr, len);
> +		if (!*same)
> +			break;
> +next:
> +		len -= len;
> +	}
> +
> +	return 0;
> +}

This code looks needlessly complex.

len is never decremented inside the while loop so the while loop
itself looks unnecessary.  Is there some missing decrement of len
or some other reason to use a while loop?

Is dax_iomap_direct_access some ugly macro that modifies a hidden len?

Why not remove the while loop and use straightforward code without
unnecessary indentatation?

{
	void *saddr;
	void *daddr;
	bool *same = data;
	int ret;

	if (!len ||
	    (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE))
		return 0;

	if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
		*same = false;
		return 0;
	}

	ret = dax_iomap_direct_access(smap, pos1, ALIGN(pos1 + len, PAGE_SIZE),
				      &saddr, NULL);
	if (ret < 0)
		return -EIO;

	ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE),
				      &daddr, NULL);
	if (ret < 0)
		return -EIO;

	*same = !memcmp(saddr, daddr, len);

	return 0;
}	

I didn't look at the rest.


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  parent reply	other threads:[~2021-03-03  8:24 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-26  0:20 [Ocfs2-devel] [PATCH v2 00/10] fsdax, xfs: Add reflink&dedupe support for fsdax Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 01/10] fsdax: Factor helpers to simplify dax fault code Shiyang Ruan
2021-03-03  9:13   ` Christoph Hellwig
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 02/10] fsdax: Factor helper: dax_fault_actor() Shiyang Ruan
2021-03-03  9:28   ` Christoph Hellwig
2021-03-12  9:01     ` ruansy.fnst
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 03/10] fsdax: Output address in dax_iomap_pfn() and rename it Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 05/10] fsdax: Replace mmap entry in case of CoW Shiyang Ruan
2021-03-03  9:30   ` Christoph Hellwig
2021-03-03  9:41     ` ruansy.fnst
2021-03-03  9:44       ` Christoph Hellwig
2021-03-03  9:48   ` Christoph Hellwig
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 08/10] fsdax: Dedup file range to use a compare function Shiyang Ruan
2021-02-26  8:28   ` Shiyang Ruan
2021-03-03  8:20   ` Joe Perches [this message]
2021-03-03  8:45     ` ruansy.fnst
2021-03-03  9:04       ` Joe Perches
2021-03-03  9:39       ` hch
2021-03-03  9:46         ` ruansy.fnst
2021-03-04  5:42   ` [Ocfs2-devel] [RESEND PATCH v2.1 " Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 09/10] fs/xfs: Handle CoW for fsdax write() path Shiyang Ruan
2021-03-03  9:43   ` Christoph Hellwig
2021-03-03  9:57     ` ruansy.fnst
2021-03-03 10:43       ` Christoph Hellwig
2021-03-04  1:35         ` ruansy.fnst
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 10/10] fs/xfs: Add dedupe support for fsdax Shiyang Ruan
2021-02-26  9:45 ` [Ocfs2-devel] Question about the "EXPERIMENTAL" tag for dax in XFS ruansy.fnst
2021-02-26 19:04   ` Darrick J. Wong
2021-02-26 19:24     ` Dan Williams
2021-02-26 20:51       ` Dave Chinner
2021-02-26 20:59         ` Dan Williams
2021-02-26 21:27           ` Dave Chinner
2021-02-26 22:41             ` Dan Williams
2021-02-27 22:36               ` Dave Chinner
2021-02-27 23:40                 ` Dan Williams
2021-02-28 22:38                   ` Dave Chinner
2021-03-01 20:55                     ` Dan Williams
2021-03-01 22:46                       ` Dave Chinner
2021-03-02  0:32                         ` Dan Williams
2021-03-02  2:42                           ` Dave Chinner
2021-03-02  3:33                             ` Dan Williams
2021-03-02  5:38                               ` Dave Chinner
2021-03-02  5:50                                 ` Dan Williams
2021-03-02  3:28                       ` Darrick J. Wong
2021-03-02  5:41                         ` Dan Williams
2021-03-02  7:57                           ` Dave Chinner
2021-03-02 17:49                             ` Dan Williams
2021-03-04 23:40                               ` Darrick J. Wong
2021-03-01  7:26       ` Yasunori Goto
2021-03-01 21:34         ` Dan Williams
     [not found] ` <20210226002030.653855-5-ruansy.fnst@fujitsu.com>
2021-03-03  9:29   ` [Ocfs2-devel] [PATCH v2 04/10] fsdax: Introduce dax_iomap_cow_copy() Christoph Hellwig
     [not found] ` <20210226002030.653855-7-ruansy.fnst@fujitsu.com>
2021-03-03  9:31   ` [Ocfs2-devel] [PATCH v2 06/10] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero Christoph Hellwig
     [not found] ` <20210226002030.653855-8-ruansy.fnst@fujitsu.com>
2021-02-26  4:14   ` [Ocfs2-devel] [PATCH v2 07/10] iomap: Introduce iomap_apply2() for operations on two files Darrick J. Wong
2021-02-26  8:11     ` ruansy.fnst
2021-02-26  8:25   ` Shiyang Ruan
2021-03-04  5:41   ` [Ocfs2-devel] [RESEND PATCH v2.1 " Shiyang Ruan
2021-03-11 12:30     ` Christoph Hellwig
2021-03-09  6:36 ` [Ocfs2-devel] [PATCH v2 00/10] fsdax, xfs: Add reflink&dedupe support for fsdax Xiaoguang Wang
2021-03-10  1:32   ` ruansy.fnst
2021-03-09 16:19 ` Goldwyn Rodrigues
2021-03-10  1:26   ` ruansy.fnst
2021-03-10 12:30 ` Neal Gompa
2021-03-10 13:02   ` Matthew Wilcox
2021-03-10 13:36     ` Neal Gompa
2021-03-10 13:55       ` Matthew Wilcox
2021-03-10 14:21     ` Goldwyn Rodrigues
2021-03-10 14:26       ` Matthew Wilcox
2021-03-10 17:04         ` Goldwyn Rodrigues
2021-03-11  0:53         ` Dan Williams
2021-03-11  8:26           ` Neal Gompa
2021-03-13 13:07         ` Adam Borowski
2021-03-13 16:24           ` Neal Gompa
2021-03-13 22:00             ` Adam Borowski

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