Re: [PATCH] index-pack: never prune base_cache.
- From
Björn Steinbrink <b.steinbrink@gmx.de>
- Date
- Jul 23, 2008, 12:52 UTC
- Message-ID
- <20080723125226.GA11679@atjola.homenet>
- In-Reply-To
- <20080723121118.GA20614@artemis.madism.org>
On 2008.07.23 14:11:18 +0200, Pierre Habouzit wrote:
> It may belong to something (stdin) that is consumed.
Probably thanks to me, babbling about stdin without having a clue what I'm talking about, that rationale is wrong.
We may not prune base_cache since that object might come from a different pack than the one that we are processing. In such a case, we would try to restore the data for that object from the pack we're processing and fail miserably.
The patch itself should be fine.
Show 52 quoted lines
>
> Signed-off-by: Pierre Habouzit <madcoder@debian.org>
> ---
>
> On Wed, Jul 23, 2008 at 12:00:45PM +0000, Björn Steinbrink wrote:
> > On 2008.07.23 12:37:00 +0100, Johannes Schindelin wrote:
> > > Hi,
> > >
> > > Well, I cannot. However, I get some pread issue on i686. To be nice to
> > > kernel.org, I downloaded the pack in question:
> > >
> > > http://pacific.mpi-cbg.de/git/thin-pack.pack
> > >
> > > You should be able to reproduce the behavior by piping this into
> > >
> > > git-index-pack --stdin -v --fix-thin --keep=fetch-pack --pack_header=2,263
> >
> > OK, that gave me a seemingly sane backtrace. What seems to happen (AFA
> > my limited knowledge tells me):
> >
> > In fix_unresolved_deltas, we read base_obj from an existing pack, other
> > than the one we're reading. We then link that object to the base cache.
> >
> > Then in resolve_delta, we create the "result" base_data object and link
> > that one, too. Now this triggers the pruning, and because the cache is
> > so small, we prune the object that we read from the existing pack! Fast
> > forward a few function calls, we end up in get_base_data trying to
> > re-read the data for that object, but this time from the pack that we
> > got on stdin. And boom it goes.
> >
> > Does that make any sense to you?
>
> Yes, that's obvious, the pack that we read from stdin is consumed, we
> should *NEVER* prune base_cache. And indeed that little patch works for
> me.
>
> index-pack.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/index-pack.c b/index-pack.c
> index ac20a46..eb81ed4 100644
> --- a/index-pack.c
> +++ b/index-pack.c
> @@ -227,7 +227,7 @@ static void prune_base_data(struct base_data *retain)
> for (b = base_cache;
> base_cache_used > delta_base_cache_limit && b;
> b = b->child) {
> - if (b->data && b != retain) {
> + if (b != base_cache && b->data && b != retain) {
> free(b->data);
> b->data = NULL;
> base_cache_used -= b->size;