linux-kernel - Re: [PATCH 3/3] ext4: Find desired extent in ext4_ext_shift

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Message-ID: <CAJrWOzDDy+GETUTAiRT7Sunj_LK8A8Uq9Nodwd+UBFpvY2WsXg@mail.gmail.com>
Date:   Fri, 6 Jan 2017 21:21:19 +0100
From:   Roman Penyaev <roman.penyaev@...fitbricks.com>
To:     "Theodore Ts'o" <tytso@....edu>,
        Roman Penyaev <roman.penyaev@...fitbricks.com>,
        Namjae Jeon <namjae.jeon@...sung.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] ext4: Find desired extent in ext4_ext_shift_extents()
 using binsearch

On Thu, Jan 5, 2017 at 12:58 AM, Theodore Ts'o <tytso@....edu> wrote:
> It looks like the original (before your patch) 1k failures due to a
> bug introduced via the block.git tree, which has since been fixed in
> Linus's mainline tree as of today.  It wouldn't surprise me if the bug
> interacted poorly your changes, so things will probably better with
> your patches applied directly on top of the tip of Linus's tree.
>
> That being said, it looks like there were still regressions introduced
> on the 4k configuration, so I'm in the middle of rerunning my baseline
> and trying out your patches as well.

I found a bug in my third patch, where I try to optimize linear search.
I missed the fact, that ext4_ext_binsearch() searches for the closest
extent from the left, but this linear search code does search for closest
extent from the right.

I ran the 'kvm-xfstests.sh -c 4k -g auto' against b25ead75e7b6 4.10-rc2
with and without my changes.  No failures.

1k configuration was run against latest Linus's mainline.  Also no
regressions were found: these two "generic/270, generic/273" fail
regardless my changes.

I will resend the patchset without latest patch shortly.

--
Roman