Linux-Fsdevel Archive on lore.kernel.org
 help / color / Atom feed
From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: "hch@lst.de" <hch@lst.de>
Cc: Goldwyn Rodrigues <RGoldwyn@suse.com>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 07/19] iomap: use a srcmap for a read-modify-write I/O
Date: Mon, 16 Sep 2019 10:57:54 -0700
Message-ID: <20190916175754.GE2229799@magnolia> (raw)
In-Reply-To: <20190910143959.GB6794@lst.de>

On Tue, Sep 10, 2019 at 04:39:59PM +0200, hch@lst.de wrote:
> On Tue, Sep 10, 2019 at 12:48:14PM +0000, Goldwyn Rodrigues wrote:
> > > +	if (srcmap.type)
> > > +		end = min(end, srcmap.offset + srcmap.length);
> > > +	if (pos + length > end)
> > > +		length = end - pos;
> > >  
> > 
> > 
> > Yes, that looks more correct. However, can we be smart and not bother
> > setting the minimum of end and srcmap.offset + srcmap.length if it is
> > not required? ie in situations where end coincides with block boundary.
> >  Or if srcmap.length falls short, until the last block boundary of
> > iomap? 
> > 
> > I did think about this scenario. This case is specific to CoW and
> > thought this is best handled by filesystem's iomap_begin(). If this
> > goes in, the filesystems would have to "falsify" srcmap length
> > information to maximize the amount of I/O that goes in one iteration.
> 
> The problem is really that we can easily run over the srcmap (that's
> what happened to me with XFS..)  One thing you've done in btrfs that
> I haven't done yet in XFS is to simply not bother with filling out
> the srcmap if we don't need to (that is if the iteration is fully
> page aligned in your patch set - the unshare op in this series will
> complicate things a little).  With that optimization the only case
> where the shortening of the iteration that matters is if the start
> is unaligned and needs a read-modify-write cycle, but the end is
> aligned and beyond the end of the srcmap.  Is that such an important
> case?

<shrug> You might as well, since it's still going to be a few weeks
until I carve off a iomap work branch for 5.5... :)

(He says stumbling in from vacation with half a brain)

--D

> > 
> > -- 
> > Goldwyn---end quoted text---

  reply index

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 18:27 iomap and xfs COW cleanups Christoph Hellwig
2019-09-09 18:27 ` [PATCH 01/19] iomap: better document the IOMAP_F_* flags Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-16 18:08   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 02/19] iomap: remove the unused iomap argument to __iomap_write_end Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-16 18:10   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 03/19] iomap: always use AOP_FLAG_NOFS in iomap_write_begin Christoph Hellwig
2019-09-16 18:11   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 04/19] iomap: ignore non-shared or non-data blocks in xfs_file_dirty Christoph Hellwig
2019-09-16 18:12   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 05/19] iomap: move the zeroing case out of iomap_read_page_sync Christoph Hellwig
2019-09-16 18:17   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 06/19] iomap: use write_begin to read pages to unshare Christoph Hellwig
2019-09-16 18:34   ` Darrick J. Wong
2019-09-30 11:07     ` Christoph Hellwig
2019-10-08 15:12       ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 07/19] iomap: use a srcmap for a read-modify-write I/O Christoph Hellwig
2019-09-10 12:48   ` Goldwyn Rodrigues
2019-09-10 14:39     ` hch
2019-09-16 17:57       ` Darrick J. Wong [this message]
2019-09-16 18:42   ` Darrick J. Wong
2019-09-18 18:15     ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 08/19] xfs: also call xfs_file_iomap_end_delalloc for zeroing operations Christoph Hellwig
2019-09-18 17:09   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 09/19] xfs: remove xfs_reflink_dirty_extents Christoph Hellwig
2019-09-18 17:17   ` Darrick J. Wong
2019-09-18 17:25     ` Christoph Hellwig
2019-09-18 17:31       ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 10/19] xfs: pass two imaps to xfs_reflink_allocate_cow Christoph Hellwig
2019-09-18 17:26   ` Darrick J. Wong
2019-09-30 11:10     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 11/19] xfs: refactor xfs_file_iomap_begin_delay Christoph Hellwig
2019-09-18 17:30   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 12/19] xfs: fill out the srcmap in iomap_begin Christoph Hellwig
2019-09-18 17:52   ` Darrick J. Wong
2019-10-01  6:26     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 13/19] xfs: factor out a helper to calculate the end_fsb Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-18 17:55   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 14/19] xfs: split out a new set of read-only iomap ops Christoph Hellwig
2019-09-18 17:56   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 15/19] xfs: move xfs_file_iomap_begin_delay around Christoph Hellwig
2019-09-18 17:59   ` Darrick J. Wong
2019-09-30 11:14     ` Christoph Hellwig
2019-09-09 18:27 ` [PATCH 16/19] xfs: split the iomap ops for buffered vs direct writes Christoph Hellwig
2019-09-18 18:00   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 17/19] xfs: rename the whichfork variable in xfs_buffered_write_iomap_begin Christoph Hellwig
2019-09-14  0:42   ` Allison Collins
2019-09-18 18:00   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 18/19] xfs: cleanup xfs_iomap_write_unwritten Christoph Hellwig
2019-09-18 18:06   ` Darrick J. Wong
2019-09-09 18:27 ` [PATCH 19/19] xfs: improve the IOMAP_NOWAIT check for COW inodes Christoph Hellwig
2019-09-18 18:09   ` Darrick J. Wong

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190916175754.GE2229799@magnolia \
    --to=darrick.wong@oracle.com \
    --cc=RGoldwyn@suse.com \
    --cc=hch@lst.de \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-xfs@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org linux-fsdevel@archiver.kernel.org
	public-inbox-index linux-fsdevel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox