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([2600:1700:e72:80a0:bcf4:c194:74a1:9906]) by smtp.gmail.com with ESMTPSA id b8sm3859240ots.6.2021.05.18.11.16.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 May 2021 11:16:49 -0700 (PDT) Subject: Re: [PATCH v3 02/12] sparse-index: include EXTENDED flag when expanding To: Elijah Newren Cc: Derrick Stolee via GitGitGadget , Git Mailing List , Junio C Hamano , Matheus Tavares Bernardino , Derrick Stolee , Derrick Stolee References: <8aa41e749471df3bd9d593b8f55db6506eafea12.1621017072.git.gitgitgadget@gmail.com> From: Derrick Stolee Message-ID: Date: Tue, 18 May 2021 14:16:46 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 5/18/2021 1:48 PM, Elijah Newren wrote: > On Tue, May 18, 2021 at 7:57 AM Derrick Stolee wrote: >> >> On 5/17/2021 9:33 PM, Elijah Newren wrote: >>> Is it possible that the setting of CE_EXTENDED is just a workaround >>> that happens to force the index to be written in cases where the logic >>> is otherwise thinking it can get away without one? Or is there >>> something I'm missing about why the CE_EXTENDED flag is actually >>> needed here? >> >> This is happening within the context of ensure_full_index(), so we >> are creating new cache entries and want to mimic what they would >> look like on-disk. Something within do_write_index() discovers that >> since CE_SKIP_WORKTREE is set, then also CE_EXTENDED should be set >> in order to ensure that the on-disk representation has enough room >> for the CE_SKIP_WORKTREE bit. > > Yeah, I think it's this part: > > /* reduce extended entries if possible */ > cache[i]->ce_flags &= ~CE_EXTENDED; > if (cache[i]->ce_flags & CE_EXTENDED_FLAGS) { > extended++; > cache[i]->ce_flags |= CE_EXTENDED; > } > >> >> I suppose this might not have a meaningful purpose other than when >> I compare a full index against an expanded sparse-index and check >> if their flags match. > > Ah, you're just setting this flag in advance of do_write_index() being > called so that you can compare in memory values and check they match > without doing a write-to-disk-and-read-back cycle. Makes sense, but > it'd be nice to see this in the commit message. Will do. Thanks, -Stolee