From: rupert thurner Date: Thu, 23 Apr 2015 06:52:24 GMT Subject: Re: Issue: repack semi-frequently fails on Windows (msysgit) - suspecting file descriptor issues Message-ID: In-Reply-To: <20150416152849.GA30137@peff.net> hi, i made a screenshot a couple of weeks ago (attached), and it seems to match your description. rupert. On Thursday, April 16, 2015 at 5:28:54 PM UTC+2, Jeff King wrote: > > On Thu, Apr 16, 2015 at 01:35:05PM +0200, Andreas Mohr wrote: > > > I strongly suspect that git's repacking implementation > > (probably unrelated to msysgit-specific deviations, > > IOW, git *core* handling) > > simply is buggy > > in that it may keep certain file descriptors open > > at least a certain time (depending on scope of implementation/objects!?) > > beyond having finished its operation (rename?). > > Hrm. I do not see anything in builtin/fetch.c that closes the packfile > descriptors before running "gc --auto". So basically the sequence: > > 1. Fetch performs actual fetch. It needs to open packfiles to do > commit negotiation with other side (the hard work is done > by an index-pack subprocess, but it is likely we have to access > _some_ objects). > > 2. The packfiles remain open and mmap'd (at least on Linux) in the > sha1_file.c:packed_git list. > > 3. We spawn "gc --auto" and wait for it to finish. While we are > waiting, the descriptors are still open, but "gc --auto" will not be > able to delete any packs. > > But this seems too simple to be the problem, as it would mean that just > about any "gc --auto" that triggers a full repack would be a problem (so > anytime you have about 50 packs). But maybe the gc "autodetach" behavior > means it works racily. > > I was able to set up the situation deterministically by running the > script below: > > -- >8 -- > #!/bin/sh > > # XXX tweak this setting as appropriate > PATH_TO_GIT_BUILD=$HOME/compile/git > PATH=$PATH_TO_GIT_BUILD/bin-wrappers:$PATH > rm -rf parent child > > # make a parent/child where the child will have to access > # a packfile to fulfill another fetch > git init parent && > git -C parent commit --allow-empty -m base && > git clone parent child && > git -C parent commit --allow-empty -m extra && > > # we want to make our base pack really big, because otherwise > # git will open/mmap/close it. So we must exceed core.packedgitlimit > cd child && > $PATH_TO_GIT_BUILD/test-genrandom foo 5000000 >file && > git add file && > git commit -m large file && > git repack -ad && > git config core.packedGitLimit 1M && > > # now make some spare packs to bust the gc.autopacklimit > for i in 1 2 3 4 5; do > git commit --allow-empty -m $i && > git repack -d > done && > git config gc.autoPackLimit 3 && > git config gc.autoDetach false && > GIT_TRACE=1 git fetch > ``` > > I also instrumented my (v1.9.5) git build like this: > > diff --git a/builtin/fetch.c b/builtin/fetch.c > index 025bc3e..fc99e5e 100644 > --- a/builtin/fetch.c > +++ b/builtin/fetch.c > @@ -1174,6 +1174,12 @@ int cmd_fetch(int argc, const char **argv, const > char *prefix) > list.strdup_strings = 1; > string_list_clear(&list, 0); > > + { > + struct packed_git *p; > + for (p = packed_git; p; p = p->next) > + trace_printf("pack %s has descriptor %d\n", > + p->pack_name, p->pack_fd); > + } > run_command_v_opt(argv_gc_auto, RUN_GIT_CMD); > > return result; > diff --git a/builtin/repack.c b/builtin/repack.c > index bb2314c..e8b29cf 100644 > --- a/builtin/repack.c > +++ b/builtin/repack.c > @@ -105,6 +105,7 @@ static void remove_redundant_pack(const char > *dir_name, const char *base_name) > for (i = 0; i < ARRAY_SIZE(exts); i++) { > strbuf_setlen(&buf, plen); > strbuf_addstr(&buf, exts[i]); > + trace_printf("unlinking %s\n", buf.buf); > unlink(buf.buf); > } > strbuf_release(&buf); > > to confirm what was happening (because of course on Linux it is > perfectly fine to delete the open file). If this does trigger the bug > for you, though, it should be obvious even without the trace calls. :) > > -Peff > -- -- *** Please reply-to-all at all times *** *** (do not pretend to know who is subscribed and who is not) *** *** Please avoid top-posting. *** The msysGit Wiki is here: https://github.com/msysgit/msysgit/wiki - Github accounts are free. You received this message because you are subscribed to the Google Groups "msysGit" group. To post to this group, send email to msysgit@googlegroups.com To unsubscribe from this group, send email to msysgit+unsubscribe@googlegroups.com For more options, and view previous threads, visit this group at http://groups.google.com/group/msysgit?hl=en_US?hl=en --- You received this message because you are subscribed to the Google Groups "Git for Windows" group. To unsubscribe from this group and stop receiving emails from it, send an email to msysgit+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.