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From: "Darrick J. Wong" <djwong@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Shiyang Ruan <ruansy.fnst@fujitsu.com>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-btrfs@vger.kernel.org, nvdimm@lists.linux.dev,
	cluster-devel@redhat.com
Subject: Re: [PATCH 17/27] iomap: switch iomap_seek_hole to use iomap_iter
Date: Mon, 19 Jul 2021 10:22:47 -0700	[thread overview]
Message-ID: <20210719172247.GG22402@magnolia> (raw)
In-Reply-To: <20210719103520.495450-18-hch@lst.de>

On Mon, Jul 19, 2021 at 12:35:10PM +0200, Christoph Hellwig wrote:
> Rewrite iomap_seek_hole to use iomap_iter.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/iomap/seek.c | 46 +++++++++++++++++++++++-----------------------
>  1 file changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
> index ce6fb810854fec..7d6ed9af925e96 100644
> --- a/fs/iomap/seek.c
> +++ b/fs/iomap/seek.c
> @@ -1,7 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * Copyright (C) 2017 Red Hat, Inc.
> - * Copyright (c) 2018 Christoph Hellwig.
> + * Copyright (c) 2018-2021 Christoph Hellwig.
>   */
>  #include <linux/module.h>
>  #include <linux/compiler.h>
> @@ -10,21 +10,19 @@
>  #include <linux/pagemap.h>
>  #include <linux/pagevec.h>
>  
> -static loff_t
> -iomap_seek_hole_actor(struct inode *inode, loff_t start, loff_t length,
> -		      void *data, struct iomap *iomap, struct iomap *srcmap)
> +static loff_t iomap_seek_hole_iter(const struct iomap_iter *iter, loff_t *pos)

/me wonders if @pos should be named hole_pos (here and in the caller) to
make it a little easier to read...

>  {
> -	loff_t offset = start;
> +	loff_t length = iomap_length(iter);
>  
> -	switch (iomap->type) {
> +	switch (iter->iomap.type) {
>  	case IOMAP_UNWRITTEN:
> -		offset = mapping_seek_hole_data(inode->i_mapping, start,
> -				start + length, SEEK_HOLE);
> -		if (offset == start + length)
> +		*pos = mapping_seek_hole_data(iter->inode->i_mapping,
> +				iter->pos, iter->pos + length, SEEK_HOLE);
> +		if (*pos == iter->pos + length)
>  			return length;
> -		fallthrough;
> +		return 0;
>  	case IOMAP_HOLE:
> -		*(loff_t *)data = offset;
> +		*pos = iter->pos;
>  		return 0;
>  	default:
>  		return length;
> @@ -35,23 +33,25 @@ loff_t
>  iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
>  {
>  	loff_t size = i_size_read(inode);
> -	loff_t ret;
> +	struct iomap_iter iter = {
> +		.inode	= inode,
> +		.pos	= offset,
> +		.flags	= IOMAP_REPORT,
> +	};
> +	int ret;
>  
>  	/* Nothing to be found before or beyond the end of the file. */
>  	if (offset < 0 || offset >= size)
>  		return -ENXIO;
>  
> -	while (offset < size) {
> -		ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
> -				  ops, &offset, iomap_seek_hole_actor);
> -		if (ret < 0)
> -			return ret;
> -		if (ret == 0)
> -			break;
> -		offset += ret;
> -	}
> -
> -	return offset;
> +	iter.len = size - offset;
> +	while ((ret = iomap_iter(&iter, ops)) > 0)
> +		iter.processed = iomap_seek_hole_iter(&iter, &offset);
> +	if (ret < 0)
> +		return ret;
> +	if (iter.len)
> +		return offset;

...because what we're really saying here is that if seek_hole_iter found
a hole (and returned zero, thereby terminating the loop before iter.len
could reach zero), we want to return the position of the hole.

> +	return size;

Not sure why we return size here...?  Oh, because there's an implicit
hole at EOF, so we return i_size.  Uh, does this do the right thing if
->iomap_begin returns posteof mappings?  I don't see anything in
iomap_iter_advance that would stop iteration at EOF.

--D

>  }
>  EXPORT_SYMBOL_GPL(iomap_seek_hole);
>  
> -- 
> 2.30.2
> 

  reply	other threads:[~2021-07-19 17:22 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 10:34 RFC: switch iomap to an iterator model Christoph Hellwig
2021-07-19 10:34 ` [PATCH 01/27] iomap: fix a trivial comment typo in trace.h Christoph Hellwig
2021-07-19 16:00   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 02/27] iomap: remove the iomap arguments to ->page_{prepare,done} Christoph Hellwig
2021-07-19 16:04   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 03/27] iomap: mark the iomap argument to iomap_sector const Christoph Hellwig
2021-07-19 16:08   ` Darrick J. Wong
2021-07-20  9:52     ` Nikolay Borisov
2021-07-26  8:12     ` Christoph Hellwig
2021-07-19 10:34 ` [PATCH 04/27] fs: mark the iomap argument to __block_write_begin_int const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 05/27] fsdax: mark the iomap argument to dax_iomap_sector as const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 06/27] iomap: mark the iomap argument to iomap_read_inline_data const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 07/27] iomap: mark the iomap argument to iomap_read_page_sync const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 08/27] iomap: add the new iomap_iter model Christoph Hellwig
2021-07-19 16:56   ` Darrick J. Wong
2021-07-26  8:15     ` Christoph Hellwig
2021-07-19 21:48   ` Dave Chinner
2021-07-26  8:17     ` Christoph Hellwig
2021-07-19 10:35 ` [PATCH 09/27] iomap: switch readahead and readpage to use iomap_iter Christoph Hellwig
2021-07-19 10:35 ` [PATCH 10/27] iomap: switch iomap_file_buffered_write " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 11/27] iomap: switch iomap_file_unshare " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 12/27] iomap: switch iomap_zero_range " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 13/27] iomap: switch iomap_page_mkwrite " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 14/27] iomap: switch __iomap_dio_rw " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 15/27] iomap: switch iomap_fiemap " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 16/27] iomap: switch iomap_bmap " Christoph Hellwig
2021-07-19 17:05   ` Darrick J. Wong
2021-07-26  8:19     ` Christoph Hellwig
2021-07-26 16:39       ` Darrick J. Wong
2021-07-27  6:31         ` Christoph Hellwig
2021-07-27 14:32           ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 17/27] iomap: switch iomap_seek_hole " Christoph Hellwig
2021-07-19 17:22   ` Darrick J. Wong [this message]
2021-07-26  8:22     ` Christoph Hellwig
2021-07-26 16:41       ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 18/27] iomap: switch iomap_seek_data " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 19/27] iomap: switch iomap_swapfile_activate " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 20/27] fsdax: switch dax_iomap_rw " Christoph Hellwig
2021-07-19 22:10   ` Dave Chinner
2021-07-26  8:25     ` Christoph Hellwig
2021-07-19 10:35 ` [PATCH 21/27] iomap: remove iomap_apply Christoph Hellwig
2021-07-19 17:48   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 22/27] iomap: pass an iomap_iter to various buffered I/O helpers Christoph Hellwig
2021-07-19 17:48   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 23/27] iomap: rework unshare flag Christoph Hellwig
2021-07-19 17:44   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 24/27] fsdax: factor out helpers to simplify the dax fault code Christoph Hellwig
2021-07-19 10:35 ` [PATCH 25/27] fsdax: factor out a dax_fault_actor() helper Christoph Hellwig
2021-07-19 10:35 ` [PATCH 26/27] fsdax: switch the fault handlers to use iomap_iter Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 27/27] iomap: constify iomap_iter_srcmap Christoph Hellwig
2021-07-19 17:44   ` Darrick J. Wong
2021-07-19 17:57 ` RFC: switch iomap to an iterator model Darrick J. Wong
2021-07-27  8:07   ` DAX setup pains, was " Christoph Hellwig
2021-07-29 20:33 ` Darrick J. Wong

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