linux-ext4 - Re: [PATCH v2 0/4] Write-hint for FS journal

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Date:   Wed, 23 Jan 2019 19:35:39 +0100
From:   Javier González <javier@...igon.com>
To:     Kanchan Joshi <joshi.k@...sung.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-nvme@...ts.infradead.org,
        jack@...e.com, david@...morbit.com, tytso@....edu,
        prakash.v@...sung.com
Subject: Re: [PATCH v2 0/4] Write-hint for FS journal


> On 9 Jan 2019, at 16.30, Kanchan Joshi <joshi.k@...sung.com> wrote:
> 
> Towards supporing write-hints/streams for filesystem journal.
> 
> Here is the v1 patch for background -
> https://marc.info/?l=linux-fsdevel&m=154444637519020&w=2
> 
> Changes since v1:
> - introduce four more hints for in-kernel use, as recommended by Dave chinner
>  & Jens axboe. This isolates kernel-mode hints from user-mode ones.
> - remove mount-option to specify write-hint, as recommended by Jan kara &
>  Dave chinner. Rather, FS always sets write-hint for journal. This gets ignored
>  if device does not support stream.
> - Removed code-redundancy for write_dirty_buffer (Jan kara's review comment)
> 
> 
> Kanchan Joshi (4):
>  block: Increase count of supported write-hints
>  fs: introduce four macros for in-kernel hints
>  fs: introduce APIs to enable sending write-hint with buffer-head
>  fs/ext4,jbd2: add support for passing write-hint with journal.
> 
> fs/buffer.c                 | 18 ++++++++++++++++--
> fs/ext4/super.c             |  2 ++
> fs/jbd2/commit.c            | 11 +++++++----
> fs/jbd2/journal.c           |  3 ++-
> fs/jbd2/revoke.c            |  3 ++-
> include/linux/blkdev.h      |  5 ++++-
> include/linux/buffer_head.h |  3 +++
> include/linux/fs.h          |  5 +++++
> include/linux/jbd2.h        |  8 ++++++++
> 9 files changed, 49 insertions(+), 9 deletions(-)
> 
> --
> 2.7.4

Worth sharing the paper where you describe the design and the numbers
you collected [1]. Also, addressing Dave's comment on stream support, it
points to a Samsung drive supporting streams (PM963). In this context,
you should verify in V3 that we are at least passing xfstests and
blktests with these changes.

[1] https://www.usenix.org/system/files/conference/fast18/fast18-rho.pdf

Javier

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