linux-kernel - Re: [PATCH 1/1]ext4: Fix WARN_ON

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Message-ID: <CA+aCy1Gkf+cdmbVwEoHhdMdbwuL2pcDvN_ZED24aJdL_YhU=BA@mail.gmail.com>
Date:	Tue, 5 Jul 2016 08:57:51 +0530
From:	Pranay Srivastava <pranjas@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>,
	"Pranay Kr. Srivastava" <pranjas@...il.com>,
	adilger.kernel@...ger.ca, linux-ext4 <linux-ext4@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1]ext4: Fix WARN_ON_ONCE when marking buffer dirty

On Mon, Jul 4, 2016 at 7:59 PM, Theodore Ts'o <tytso@....edu> wrote:
> On Thu, Jun 30, 2016 at 02:12:30PM +0300, Pranay Kr. Srivastava wrote:
>> Signed-off-by: Pranay Kr. Srivastava <pranjas@...il.com>
>
> The description for why the change is being made should go in the
> commit.  (No need to put the description in a separate cover letter.)
> I ended up rewriting the commit description as follows, to make it
> much more understandable:
>
>     ext4: Fix WARN_ON_ONCE in ext4_commit_super()
>
>     If there are racing calls to ext4_commit_super() it's possible for
>     another writeback of the superblock to result in the buffer being
>     marked with an error after we check if the buffer is marked as
>     having a write error and the buffer up-to-date flag is set again.
>     If that happens mark_buffer_dirty() can end up throwing a
>     WARN_ON_ONCE.
>
>     Fix this by moving this check to write before we call
>     write_buffer_dirty(), and keeping the buffer locked during this
>     whole sequence.
>
>     Signed-off-by: Pranay Kr. Srivastava <pranjas@...il.com>
>     Signed-off-by: Theodore Ts'o <tytso@....edu>
>
> Note that the one-line summary needs to carry as much information as
> possible so someone who is scanning the commits using git log
> --oneline has a chance of understanding it.  This means the high-level
> *why* of the commit, not a summary of what the changes in the C code.
> Also note the increased context of when the misbehaviour could occur
> in the commit description, which was missing in the cover letter.
>
> When I'm processing patches, if I'm in a hurry, patches that require
> extra work or which aren't Obviously Right, sometimes get deferred by
> a few days.  This patch fell in that category.
>
> Adding to the commit descrtipion additional context and/or
> instructions for how to reproduce the problem you are trying to
> remediate will often make life much easier for me, and accelerate how
> quickly I'll get to your patch.
>
> Cheers,
>
>                                                         - Ted

Thank you Theodore Sir. Points duly noted, I'll take care from now on
while sending
patches.


-- 
        ---P.K.S