linux-ext4 - Re: [PATCH 04/22] ext4: Fix credit estimate for final inode freeing

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Message-ID: <20191024103038.GN31271@quack2.suse.cz>
Date:   Thu, 24 Oct 2019 12:30:38 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 04/22] ext4: Fix credit estimate for final inode freeing

On Sun 20-10-19 21:07:23, Theodore Y. Ts'o wrote:
> On Fri, Oct 04, 2019 at 12:05:50AM +0200, Jan Kara wrote:
> > Estimate for the number of credits needed for final freeing of inode in
> > ext4_evict_inode() was to small. We may modify 4 blocks (inode & sb for
> > orphan deletion, bitmap & group descriptor for inode freeing) and not
> > just 3.
> 
> The modification for the inode should already be included in the
> calculation for ext4_blocks_for_truncate(), no?  So we only need 3
> extra blocks (sb, inode bitmap, and bg descriptor for the inode).

Yes, but 'extra_credits' is also passed to ext4_xattr_delete_inode() and if
that needs to restart a transaction, it needs to reserve enough for inode
modification in that new transaction. This patch is actually a result of
assertion checks I was getting with more accurate transaction restart
handling implemented later in this series...

I agree we can actually subtract 3 from
ext4_blocks_for_truncate(inode)+extra_credits when starting the initial
transaction as inode changes get double-accounted there. I can do that
and I'll also update the changelog to explain this better.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR