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From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: Christoph Hellwig <hch@lst.de>, linux-xfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 31/33] iomap: add support for sub-pagesize buffered I/O without buffer heads
Date: Mon, 14 May 2018 11:00:08 -0500
Message-ID: <eebcc4bf-f646-edc6-264b-124b3880f3cb@suse.de> (raw)
In-Reply-To: <20180509074830.16196-32-hch@lst.de>



On 05/09/2018 02:48 AM, Christoph Hellwig wrote:
> After already supporting a simple implementation of buffered writes for
> the blocksize == PAGE_SIZE case in the last commit this adds full support
> even for smaller block sizes.   There are three bits of per-block
> information in the buffer_head structure that really matter for the iomap
> read and write path:
> 
>  - uptodate status (BH_uptodate)
>  - marked as currently under read I/O (BH_Async_Read)
>  - marked as currently under write I/O (BH_Async_Write)
> 
> Instead of having new per-block structures this now adds a per-page
> structure called struct iomap_page to track this information in a slightly
> different form:
> 
>  - a bitmap for the per-block uptodate status.  For worst case of a 64k
>    page size system this bitmap needs to contain 128 bits.  For the
>    typical 4k page size case it only needs 8 bits, although we still
>    need a full unsigned long due to the way the atomic bitmap API works.
>  - two atomic_t counters are used to track the outstanding read and write
>    counts
> 
> There is quite a bit of boilerplate code as the buffered I/O path uses
> various helper methods, but the actual code is very straight forward.
> 
> In this commit the code can't actually be used yet, as we need to
> switch from the old implementation to the new one together with the
> XFS writeback code.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/iomap.c            | 262 +++++++++++++++++++++++++++++++++++++-----
>  include/linux/iomap.h |  32 ++++++
>  2 files changed, 264 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/iomap.c b/fs/iomap.c
> index a3861945504f..4e7ac6aa88ef 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -17,6 +17,7 @@
>  #include <linux/iomap.h>
>  #include <linux/uaccess.h>
>  #include <linux/gfp.h>
> +#include <linux/migrate.h>
>  #include <linux/mm.h>
>  #include <linux/mm_inline.h>
>  #include <linux/swap.h>
> @@ -109,6 +110,107 @@ iomap_block_needs_zeroing(struct inode *inode, loff_t pos, struct iomap *iomap)
>         return iomap->type != IOMAP_MAPPED || pos > i_size_read(inode);
>  }
>  
> +static struct iomap_page *
> +iomap_page_create(struct inode *inode, struct page *page)
> +{
> +	struct iomap_page *iop = to_iomap_page(page);
> +
> +	if (iop || i_blocksize(inode) == PAGE_SIZE)
> +		return iop;

Why is this an equal comparison operator? Shouldn't this be >= to
include filesystem blocksize greater than PAGE_SIZE?

-- 
Goldwyn

  reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-09  7:47 stop using buffer heads in xfs and iomap Christoph Hellwig
2018-05-09  7:47 ` [PATCH 01/33] block: add a lower-level bio_add_page interface Christoph Hellwig
2018-05-09 15:12   ` Matthew Wilcox
2018-05-10  6:40     ` Christoph Hellwig
2018-05-10 21:49       ` Andreas Dilger
2018-05-11  6:29         ` Christoph Hellwig
2018-05-15 16:47           ` Jens Axboe
2018-05-10  8:52   ` Ming Lei
2018-05-11  6:24     ` Christoph Hellwig
2018-05-16  5:06   ` Ritesh Harjani
2018-05-16 18:05     ` Christoph Hellwig
2018-05-17  4:18       ` Ritesh Harjani
2018-05-09  7:47 ` [PATCH 02/33] fs: factor out a __generic_write_end helper Christoph Hellwig
2018-05-09 15:15   ` Matthew Wilcox
2018-05-10  6:40     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 03/33] fs: move page_cache_seek_hole_data to iomap.c Christoph Hellwig
2018-05-09  7:48 ` [PATCH 04/33] fs: remove the buffer_unwritten check in page_seek_hole_data Christoph Hellwig
2018-05-17 11:33   ` Andreas Grünbacher
2018-05-09  7:48 ` [PATCH 05/33] fs: use ->is_partially_uptodate in page_cache_seek_hole_data Christoph Hellwig
2018-05-09  7:48 ` [PATCH 06/33] mm: give the 'ret' variable a better name __do_page_cache_readahead Christoph Hellwig
2018-05-09 15:45   ` Matthew Wilcox
2018-05-10  6:41     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 07/33] mm: split ->readpages calls to avoid non-contiguous pages lists Christoph Hellwig
2018-05-09 15:46   ` Matthew Wilcox
2018-05-09  7:48 ` [PATCH 08/33] iomap: use __bio_add_page in iomap_dio_zero Christoph Hellwig
2018-05-09  7:48 ` [PATCH 09/33] iomap: add a iomap_sector helper Christoph Hellwig
2018-05-09  7:48 ` [PATCH 10/33] iomap: add an iomap-based bmap implementation Christoph Hellwig
2018-05-09 16:46   ` Darrick J. Wong
2018-05-10  6:42     ` Christoph Hellwig
2018-05-10 15:08       ` Darrick J. Wong
2018-05-11  6:25         ` Christoph Hellwig
2018-05-12  1:56           ` Darrick J. Wong
2018-05-09  7:48 ` [PATCH 11/33] iomap: add an iomap-based readpage and readpages implementation Christoph Hellwig
2018-05-10  1:17   ` Dave Chinner
2018-05-10  6:44     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 12/33] xfs: use iomap_bmap Christoph Hellwig
2018-05-09  7:48 ` [PATCH 13/33] xfs: use iomap for blocksize == PAGE_SIZE readpage and readpages Christoph Hellwig
2018-05-09  7:48 ` [PATCH 14/33] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09  7:48 ` [PATCH 15/33] xfs: simplify xfs_aops_discard_page Christoph Hellwig
2018-05-09  7:48 ` [PATCH 16/33] xfs: move locking into xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09  7:48 ` [PATCH 17/33] xfs: make xfs_writepage_map extent map centric Christoph Hellwig
2018-05-09  7:48 ` [PATCH 18/33] xfs: remove the now unused XFS_BMAPI_IGSTATE flag Christoph Hellwig
2018-05-09  7:48 ` [PATCH 19/33] xfs: remove xfs_reflink_find_cow_mapping Christoph Hellwig
2018-05-09  7:48 ` [PATCH 20/33] xfs: remove xfs_reflink_trim_irec_to_next_cow Christoph Hellwig
2018-05-09  7:48 ` [PATCH 21/33] xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly Christoph Hellwig
2018-05-09  7:48 ` [PATCH 22/33] xfs: don't clear imap_valid for a non-uptodate buffers Christoph Hellwig
2018-05-09  7:48 ` [PATCH 23/33] xfs: remove the imap_valid flag Christoph Hellwig
2018-05-09  7:48 ` [PATCH 24/33] xfs: don't look at buffer heads in xfs_add_to_ioend Christoph Hellwig
2018-05-09  7:48 ` [PATCH 25/33] xfs: move all writeback buffer_head manipulation into xfs_map_at_offset Christoph Hellwig
2018-05-09  7:48 ` [PATCH 26/33] xfs: allow writeback on pages without buffer heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 27/33] xfs: remove xfs_start_page_writeback Christoph Hellwig
2018-05-09  7:48 ` [PATCH 28/33] xfs: refactor the tail of xfs_writepage_map Christoph Hellwig
2018-05-09  7:48 ` [PATCH 29/33] xfs: do not set the page uptodate in xfs_writepage_map Christoph Hellwig
2018-05-09  7:48 ` [PATCH 30/33] iomap: add initial support for writes without buffer heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 31/33] iomap: add support for sub-pagesize buffered I/O " Christoph Hellwig
2018-05-14 16:00   ` Goldwyn Rodrigues [this message]
2018-05-15  7:26     ` Christoph Hellwig
2018-05-15 13:47       ` Goldwyn Rodrigues
2018-05-16  5:46         ` Dave Chinner
2018-05-09  7:48 ` [PATCH 32/33] xfs: add support for sub-pagesize writeback without buffer_heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 33/33] fs: remove __block_write_begin and iomap_to_bh Christoph Hellwig
2018-05-10 15:13 ` stop using buffer heads in xfs and iomap Darrick J. Wong
2018-05-11  6:22   ` Christoph Hellwig
2018-05-11  6:39     ` Darrick J. Wong

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