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From: William Baker <williamtbakeremail@gmail.com>
To: Kevin Willford <Kevin.Willford@microsoft.com>,
	Junio C Hamano <gitster@pobox.com>,
	Utsav Shah via GitGitGadget <gitgitgadget@gmail.com>,
	William Baker <William.Baker@microsoft.com>
Cc: "git@vger.kernel.org" <git@vger.kernel.org>,
	Utsav Shah <ukshah2@illinois.edu>
Subject: Re: [PATCH 0/1] fsmonitor: skip sanity check if the index is split
Date: Mon, 11 Nov 2019 09:30:56 -0800	[thread overview]
Message-ID: <ba3736b8-9f44-5438-36c3-213d8a3d621e@gmail.com> (raw)
In-Reply-To: <BN6PR21MB07869E8D1DCAF189C4E472A891740@BN6PR21MB0786.namprd21.prod.outlook.com>


On 11/11/19 8:55 AM, Kevin Willford wrote:
>>
>> The istate->cache[] is a dynamic array whose size is managed via the usual
>> ALLOC_GROW() using istate->cache_nr and istate->cache_alloc, whether the
>> split-index feature is in use.  When your patch makes a difference, then,
>> doesn't the access to istate->cache[] pick up a random garbage and then flip
>> the bit?
>>
>> Puzzled...  In any case, "check is worse than over-eager, it simply is wrong" I
>> wrote in the message I am responding to is totally incorrect, it seems.  It
>> smells like lifting the check would just hide the underlying problem under the
>> rug?
> 
> I agree.  The only 2 places that excluding the split-index make sense are in
> read_fsmonitor_extension and write_fsmonitor_extension because the
> index_state that is being passing into those methods could be the delta index
> in which case the number of entries for the fsmonitor bitmap would almost
> always be more and cause the BUG to be hit which it should not be.
> 
> The reason it is not needed and should not be in the other 2 places is they
> are ran from tweak_fsmonitor which is ran at post_read_index_from which
> is after the base and delta indexes have been loaded into the indes_state and
> the index_state will have all the entries and if the fsmonitor bitmap is bigger
> than the number of entries then the BUG should be hit. 
> 

I agree.  While working on the 3444ec2e patch I missed that read_fsmonitor_extension
and write_fsmonitor_extension could be called with the delta index rather than the
full index.

I think it makes sense to leave the check in the other two places.

Thanks,
William



  parent reply	other threads:[~2019-11-11 17:31 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  7:09 Utsav Shah via GitGitGadget
2019-11-08  7:09 ` [PATCH 1/1] " Utsav Shah via GitGitGadget
2019-11-12 11:18   ` SZEDER Gábor
2019-11-12 21:08     ` Utsav Shah
2019-11-11  1:43 ` [PATCH 0/1] " Junio C Hamano
2019-11-11  2:01   ` Junio C Hamano
2019-11-11 16:55     ` Kevin Willford
2019-11-11 17:25       ` Utsav Shah
2019-11-11 18:21         ` Kevin Willford
2019-11-11 17:30       ` William Baker [this message]
2019-11-13  1:30       ` Junio C Hamano
2019-11-14  2:55         ` Utsav Shah
2019-11-14 16:41         ` William Baker
2019-11-15  5:04           ` Junio C Hamano

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