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 [thread overview]
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---
next prev parent reply other threads:[~2019-09-16 17:58 UTC|newest]
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 publicly 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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).