linux-ext4 - Re: [PATCH] e2freefrag: fix free blocks count during live scan

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Message-ID: <20181126025735.GB7904@thunk.org>
Date:   Sun, 25 Nov 2018 21:57:35 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-ext4 <linux-ext4@...r.kernel.org>, Elana.Hashman@...sigma.com
Subject: Re: [PATCH] e2freefrag: fix free blocks count during live scan

On Thu, Nov 08, 2018 at 10:44:31AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@...cle.com>
> 
> In e2freefrag live scan mode, we take the free block count from the
> ondisk superblock.  This leads to screwy histogram percentages:
> 
> Extent Size Range :  Free extents   Free Blocks  Percent
>     4M...    8M-  :             5          8234    1.05%
>    64M...  128M-  :             2         52279    6.64%
>   512M... 1024M-  :             1        202752   25.74%
> 
> ...because there could be superblock updates in the journal that haven't
> yet been checkpointed.  The online scan is perfectly capable of tallying
> the free blocks on its own, so teach it do that and make a more accurate
> report.
> 
> Reported-by: Elana Hashman <Elana.Hashman@...sigma.com>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>

Thanks, applied.

					- Ted