Hi Matheus, On Fri, 5 Jul 2019, Matheus Tavares Bernardino wrote: > On Thu, Jul 4, 2019 at 6:30 PM Johannes Schindelin > <Johannes.Schindelin@xxxxxx> wrote: > > > > Hi Matheus, > > > > On Thu, 4 Jul 2019, Matheus Tavares Bernardino wrote: > > > > > > I wanted to take a look at the failures to see if I could help, [...] > > > Could you point me to the right place, please? > [...] > > > > I usually click on the "Tests" tab in that page: > > https://dev.azure.com/gitgitgadget/git/_build/results?buildId=11495&view=ms.vss-test-web.build-test-results-tab > > > > You can click on any of the 1,384 (!) failing test cases, it will pop up a > > pane on the right-hand side that shows the trace of that failing test > > case. For the full trace of that test script, go to "Attachments" and > > download the `Standard_Error_Output.log` (via the horizontal bread-crumbs > > menu you can see when hovering over the file name). > > Thanks for the explanation! I inspected some of the > `Standard_Error_Output.log`'s and it seems the problem is always with > local clone (which started to use dir-iterator in this series). It > seems all .git/objects/ dirs are being ignored. That makes sense, > since st_ino will always be 0 on Windows. But your fixup patch should > solve this. Is there any azure build for it? There is no direct Azure Pipeline run for it, as I have not created a branch with the fixup on top of your branch. But the shears/pu branch in https://github.com/git-for-windows/git/branches does have the fixup, and passes all tests. > [...] > > > > > > Hm, I think `stat()` itself uses this strategy of an arbitrary cut-off > > > when resolving a path. So we may also "ignore" circular symlinks and > > > let the iteration continue until the point where `stat()` will return > > > an ELOOP. (But it may be expensive...) > > > > This would not be equivalent, though, as your code also tried to address > > circular references when two or more symlinks are involved, e.g. when > > one symlink points to a directory that has another symlink that points to > > the directory containing the first symlink. > > Hm, `stat()` also addresses this case doesn't it? For example: > > $ mkdir a b > $ ln -s ../a b/s2a > $ ln -s ../b a/s2b > $ stat b/s2a/s2b/s2a/.../s2b > > Gives me: > "too many levels of symbolic links" Okay, then. Even better. (With the caveat that I don't know how ubiquitous this behavior is, I assume you only tested on Linux.) > > > > Do we _have_ to, though? At some stage the path we come up with is beyond > > > > `PATH_MAX` and we can stop right then and there. > > > > > > > > Besides, the way `find_recursive_symlinks()` is implemented adds quadratic > > > > behavior. > > > > > > Yes, indeed. But it only happens when we have a path like this: > > > `symlink_to_dir1/symlink_to_dir2/symlink_to_dir3/symlink_to_dir4/...`, > > > right? I think this case won't be very usual on actual filesystems, > > > thought. > > > > No, the check is performed in a loop, and that loop is executed whether > > you have symlinks or not. That loop is executed for every item in the > > iteration, and as we cannot assume a flat directory in general (in fact, > > we should assume a directory depth proportional to the total number of > > files), that adds that quadratic behavior. > > Oh, you're right. Sorry for the noise, I forgot this function was not > only called for symlinks but for every directory entry :( > > An alternative solution would be to use `lstat()` together with > `stat()` to only feed symlinked dirs to this function. This should > reduce a lot the number of calls. Although it'd still be quadratic in > the worst case, would that be any good? Why not just skip this logic? At least for now? It really blocks the development of this patch series, causing `pu` to be broken until the test failures are resolved. > [...] > > > > But I also think there are enough > > > > reasons to do away with this function in the first place. > > > > > > We can delegate the circular symlinks problem to `stat()'s ELOOP` > > > > Not really. I mean, we _already_ delegate to the `ELOOP` condition, we > > cannot even avoid it as long as we keep using `stat()` instead of > > `lstat()` > > Yes, indeed. What I meant is that we may chose to _fully_ delegate to > ELOOP. The way it is now, we should detect circular symlinks way > before stat() fails. For example, with the case I showed above, we > would stop at "b/s2a/s2b" whereas stat() would only fail at a much > longer "b/s2a/s2b/s2a/s2b/...", far beyond in the iteration. Sounds like the solution to me that I wanted: drop the special code to detect circular symlinks. In other words: I like that idea. > > > The only downside is the overhead of iterating through directories which > > > will be latter discarded for being in circular symlinks' chains. I mean, > > > the overhead at dir-iterator shouldn't be much, but the one on the code > > > using this API to do something for each of these directories (and its > > > contents), may be. Also we would need to "undo" the work done for each > > > of these directories if we want to ignore circular symlinks and continue > > > the iteration, whereas if we try to detect it a priori, we can skip it > > > from the beginning. > > > > Given that the intent of this patch series is a mere refactoring, I wonder > > why the new, contentious circular symlink detection is slipped into it > > anyway. It complicates the task, makes reviewing a lot harder, and it > > holds up the refactoring. > > Yes, I apologize for that. I should have split this into 2 or maybe 3 > patchsets... This series started really simple just trying to apply > the dir-iterator API into local clone. But then, other things became > necessary and it got more complex. > > So, should I send a fixup patch removing find_recursive_symlinks() or > reroll the series? There's also the option to use stat()+lstat() to > reduce calls to this function, but it doesn't solve the problem on > Windows, anyway. I would suggest to send another iteration that removes `find_recursive_symlinks()`. Junio most likely interpreted my objections as a veto against advancing the current iteration to `next`, meaning that you're good to even rewrite completely in the next iteration, should you feel the need to. No need for "Oops, fix that" follow-up commits at this stage. Ciao, Dscho
