From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Wengang Wang <wen.gang.wang@oracle.com>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 0/9] xfs file non-exclusive online defragment
Date: Thu, 14 Dec 2023 20:06:41 -0800 [thread overview]
Message-ID: <ZXvQ0YDfHBuvLXbY@infradead.org> (raw)
In-Reply-To: <20231214213502.GI361584@frogsfrogsfrogs>
On Thu, Dec 14, 2023 at 01:35:02PM -0800, Darrick J. Wong wrote:
> I'm kinda surprised you don't just turn on alwayscow mode, use an
> iomap_funshare-like function to read in and dirty pagecache (which will
> hopefully create a new large cow fork mapping) and then flush it all
> back out with writeback. Then you don't need all this state tracking,
> kthreads management, and copying file data through the buffer cache.
> Wouldn't that be a lot simpler?
Yes, although with a caveat or two.
We did that for the zoned XFS project, where a 'defragmentation' like
this which we call garbage collection is an essential part of the
operation to free entire zones. I ended up initially implementing it
using iomap_file_unshare as that is page cache coherent and a nicely
available library function. But it turns out iomap_file_unshare sucks
badly as it will read the data sychronously one block at a time.
I ended up coming up with my own duplication of iomap_file_unshare
that doesn't do it which is a bit hack by solves this problem.
I'd love to eventually merge it back into iomap_file_unshare, for
which we really need to work on our writeback iterators.
The relevant commit or the new helper is here:
http://git.infradead.org/users/hch/xfs.git/commitdiff/cc4a639e3052fefb385f63a0db5dfe07db4e9d58
which also need a hacky readahead helper:
http://git.infradead.org/users/hch/xfs.git/commitdiff/f6d545fc00300ddfd3e297d17e4f229ad2f15c3e
The code using this for zoned GC is here:
http://git.infradead.org/users/hch/xfs.git/blob/refs/heads/xfs-zoned:/fs/xfs/xfs_zone_alloc.c#l764
It probably would make sense to be able to also use this for a regular
fs for the online defrag use case, although the wire up would be a bit
different.
next prev parent reply other threads:[~2023-12-15 4:06 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 17:05 [PATCH 0/9] xfs file non-exclusive online defragment Wengang Wang
2023-12-14 17:05 ` [PATCH 1/9] xfs: defrag: introduce strucutures and numbers Wengang Wang
2023-12-15 5:35 ` kernel test robot
2023-12-14 17:05 ` [PATCH 2/9] xfs: defrag: initialization and cleanup Wengang Wang
2023-12-15 14:09 ` kernel test robot
2023-12-14 17:05 ` [PATCH 3/9] xfs: defrag implement stop/suspend/resume/status Wengang Wang
2023-12-14 17:05 ` [PATCH 4/9] xfs: defrag: allocate/cleanup defragmentation Wengang Wang
2023-12-14 17:05 ` [PATCH 5/9] xfs: defrag: process some cases in xfs_defrag_process Wengang Wang
2023-12-14 17:05 ` [PATCH 6/9] xfs: defrag: piece picking up Wengang Wang
2023-12-14 17:05 ` [PATCH 7/9] xfs: defrag: guarantee contigurous blocks in cow fork Wengang Wang
2023-12-14 17:05 ` [PATCH 8/9] xfs: defrag: copy data from old blocks to new blocks Wengang Wang
2023-12-14 17:05 ` [PATCH 9/9] xfs: defrag: map " Wengang Wang
2023-12-14 21:35 ` [PATCH 0/9] xfs file non-exclusive online defragment Darrick J. Wong
2023-12-15 3:15 ` Dave Chinner
2023-12-15 17:07 ` Wengang Wang
2023-12-15 17:30 ` Darrick J. Wong
2023-12-15 20:03 ` Wengang Wang
2023-12-15 20:20 ` Dave Chinner
2023-12-18 16:27 ` Wengang Wang
2023-12-19 21:17 ` Wengang Wang
2023-12-19 21:29 ` Dave Chinner
2023-12-19 22:23 ` Wengang Wang
2023-12-15 4:06 ` Christoph Hellwig [this message]
2023-12-15 16:48 ` Wengang Wang
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=ZXvQ0YDfHBuvLXbY@infradead.org \
--to=hch@infradead.org \
--cc=djwong@kernel.org \
--cc=linux-xfs@vger.kernel.org \
--cc=wen.gang.wang@oracle.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.