From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: lsf-pc@lists.linux-foundation.org
Cc: linux-fsdevel@vger.kernel.org, Jan Kara <jack@suse.cz>,
Theodore Ts'o <tytso@mit.edu>,
Matthew Wilcox <willy@infradead.org>,
linux-ext4@vger.kernel.org
Subject: Re: [LSF/MM/BPF TOPIC]: Challenges and Ideas in Transitioning EXT* and other FS to iomap
Date: Sat, 24 Feb 2024 15:49:23 +0530 [thread overview]
Message-ID: <87y1ba17x0.fsf@doe.com> (raw)
In-Reply-To: <871q922v9u.fsf@doe.com>
"Ritesh Harjani (IBM)" <ritesh.list@gmail.com> writes:
++ linux-ext4
> In continuation from last year's efforts on conversion of ext* filesystems to iomap,
> I would like to propose an LSFMM session on the said topic. Last year's session
> was mainly centered around documentation discussion around iomap (so that it can help others
> converting their filesystems to iomap), and I think we now have a kernelnewbies page [1]
> which can provide good details on how one can start transitioning their filesystem to iomap
> interface.
>
> Note, ext2/ext4 filesystems direct-io path now utilizes iomap where ext2
> DIO conversion happened last year during LSFMM [2] [3]. I have also submitted patches
> for ext2 buffered-io path for regular files to move to iomap and thereby enabling
> large folio support to it. Along similar lines there are also patches around EXT4
> buffered-io conversion to iomap.
>
> Some of the challenges
> =======================
> 1. For EXT2 directory handling which uses page cache and buffer heads, moving that path to
> iomap has challenges with writeback path since iomap also uses folio->private to keep some
> of its internal state (iomap_folio_state).
> 2. One other thing which was pointed out by Matthew is the BH_Boundary handling currently missing
> in iomap. This can lead to non-optimized data I/O patterns causing performance penalty.
> 3. Filesystems need a mechanism to validate cached logical->physical block translations
> in iomap writeback code (can this be lifted to common code?)
> 4. Another missing piece from iomap is the metadata handling for filesystems. There is no
> interface which iomap provides that the FS can utilize to move away from buffer heads
> for its metadata operations. It can be argued that it is not the responsibility of iomap, however
> filesystems do need a mechanism for their metadata handling operations.
>
> Proposal
> =========
> In this talk I would like to discuss about the efforts, challenges & the lessons learnt in doing the conversion of
> ext2's DIO and buffered-io paths to iomap, which might help others in conversion of their filesystem.
> I would also like to have a discussion on the current open challenges we have in converting ext2 (buffered-io path)
> and discuss on what ideas people have, which we can consider for transitioning ext* and other filesystems to iomap.
>
> PS: As we speak, I am in the process of rebasing ext2 bufferred-io path to latest upstream kernel.
> It's mostly done and I am also looking into some of the open problems listed by community.
>
>
> References
> ============
> [1]: https://kernelnewbies.org/KernelProjects/iomap
> [2]: https://lore.kernel.org/linux-ext4/cover.1682069716.git.ritesh.list@gmail.com/
> [3]: https://lwn.net/Articles/935934/
> [4]: https://lore.kernel.org/linux-ext4/cover.1700505907.git.ritesh.list@gmail.com/
next parent reply other threads:[~2024-02-24 10:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <871q922v9u.fsf@doe.com>
2024-02-24 10:19 ` Ritesh Harjani [this message]
2024-03-06 11:09 ` [LSF/MM/BPF TOPIC]: Challenges and Ideas in Transitioning EXT* and other FS to iomap Ritesh Harjani
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=87y1ba17x0.fsf@doe.com \
--to=ritesh.list@gmail.com \
--cc=jack@suse.cz \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=lsf-pc@lists.linux-foundation.org \
--cc=tytso@mit.edu \
--cc=willy@infradead.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 read-only IMAP folder(s) and NNTP newsgroup(s).