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Re: [PATCH V2] xfs_repair: fix record_allocation list manipulation

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH V2] xfs_repair: fix record_allocation list manipulation
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 22 Sep 2009 08:02:31 -0400
Cc: xfs-oss <xfs@xxxxxxxxxxx>
In-reply-to: <4AB4EDBC.9050609@xxxxxxxxxxx>
References: <4AB300CC.5020707@xxxxxxxxxxx> <4AB4EDBC.9050609@xxxxxxxxxxx>
User-agent: Mutt/1.5.19 (2009-01-05)
On Sat, Sep 19, 2009 at 09:42:04AM -0500, Eric Sandeen wrote:
> clang found this one too as a "Dead assignment"
>
> Unless my pointer-fu is totally messed up, this function
> was never actually updating the list head.
>
> This would mean that the later free_allocations() calls in
> incore_ext_teardown() and free_rt_dup_extent_tree() don't
> actually free any items, and therefore leak memory.
>
> V2: now with correct pointer-fu.

Barry already had this in his repair speedups patchkit, but I left it
out for now because I wasn't too sure how this could work at all.
After reviewing it again I noticed that it can actually work because the
addr pointer in the ba_rec_t is unused, and we make use of the fact that
the ba_rec_t is the first field in the structure to be tacked.  Entirely
to subtile for my taste.  Id' prefer to just put a list_head into the
extent_alloc_rec_t and rt_extent_alloc_rec_t and openconde the
tracking/freeing of the beast.  The list_head if just as large as the
ba_rec_t and make sure the list handlinjg is right, and the openconding
gets rid of the annoying assumption that the ba_rec_t is the first thing
in the structure to be tracked.  It should also be a net-removal of
code.

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