From: Thomas Rast Date: Sat, 09 Nov 2013 14:24:30 GMT Subject: Re: [PATCH] checkout: most of the time we have good leading directories Message-ID: <87iow1ps9t.fsf@linux-k42r.v.cablecom.net> In-Reply-To: Junio C Hamano writes: > When "git checkout" wants to create a path, e.g. a/b/c/d/e, after > seeing if the entire thing already exists (in which case we check if > that is up-to-date and do not bother to check it out, or we unlink > and recreate it), we validate that the leading directory path is > without funny symlinks by seeing a/, a/b/, a/b/c/ and then a/b/c/d/ > are all without funny symlinks, by calling has_dirs_only_path() in > this order. > > When we are checking out many files (imagine: initial checkout), > however, it is likely that an earlier checkout would have already > made sure that the leading directory a/b/c/d/ is in good order; by > first checking the whole path a/b/c/d/ first, we can often bypass > calls to has_dirs_only_path() for leading part. Naively one would think that this is just as much work -- to correctly verify that the path consist only of actual directories (not symlinks) we have to lstat() every component regardless. It seems the reason this is an optimization is that has_dirs_only_path() caches its results, so that we can get 'a/b/c/d/ is okay in every component' from the cache. Is this analysis correct? If so, can you spell that out in the commit message? -- Thomas Rast tr@thomasrast.ch