> -----Original Message-----
> From: Jason Pyeron
> Sent: Thursday, December 04, 2014 16:34
> To: [email protected]
> Cc: 'brian m. carlson'
> Subject: RE: FW: [cygwin] Cygwin's git says "error:
> failed to read delta-pack base object"
>
> > -----Original Message-----
> > From: brian m. carlson
> > Sent: Wednesday, December 03, 2014 19:55
> >
> > On Wed, Dec 03, 2014 at 06:31:18PM -0500, Jason Pyeron wrote:
> > > I remember hitting this a while ago, but just gave up.
> > >
> > > It seems to be a problem for others too.
> > >
> > > Any ideas on how to debug this so it can be patched?
> > >
> > > -----Original Message-----
> > > From: Dave Lindbergh
> > > Sent: Wednesday, December 03, 2014 18:07
> > > To: cygwin
> > >
> > > Aha - you're right.
> > >
> > > It works fine on a local NTFS volume.
> > >
> > > I get the error when I do it on Z:, which is mapped to a
> > network drive
> > > (on another Windows box).
> > >
> > > Is there a workaround? Why does this happen?
> >
> > I don't think anyone is sure. My wild guess is that
> there's something
> > about the way that Cygwin wraps Windows calls that makes it
> > fail in this
> > case. It might be interesting to run the Windows and
> Cygwin versions
> > under an strace equivalent and see where things differ.
>
> [this was posted to the cygwin list]
>
> http://nerdfever.com/files/strace.txt
>
> >
> > It's an interesting problem, but I don't have any Windows
> > systems, so I
> > can't look into it.
>
> If it becomes a little less magic, I will chomp on the
> problem, but I cannot make a predictable test case.
Corrina at Cygwin devined the strace (see below) and I am working on a test
cases and hacks.
Pseudo code and observations
./sha1_file.c:write_loose_object(sha1)
{
filename=sha1_file_name(sha1)
(fd,tmp_file)=create_tmpfile(filename)
write_buffer(fd)
close_sha1_file(fd)
return move_temp_to_file(tmp_file, filename)
}
move_temp_to_file(tmpfile, filename)
{
// I am thinking about forcing renames to see if the problem exists then as
well
// if that "works" then a per repo config option allowing for forced renames
if (OBJECT_CREATION_USES_RENAMES) goto try_rename
else if link(tmpfile,filename)
if (failed except exist failures)
{
try_rename:
rename(tmpfile, filename)
if (ok) goto out
}
unlink_or_warn(tmpfile)
if (failed except exist failures) return error
out:
}
write_sha1_file(sha1)
{
return write_loose_object(sha1)
}
> -----Original Message-----
> From: Corinna Vinschen
> Sent: Friday, December 05, 2014 6:35
> To: [email protected]
<snip/>
> What I found in the strace is this:
>
> - Create file Z:\pic32mx-bmf\.git\objects\30\tmp_obj_YljwNZ
>
> - open file, write something, close file.
>
> - link (Z:\pic32mx-bmf\.git\objects\30\tmp_obj_YljwNZ,
>
> Z:\pic32mx-bmf\.git\objects\30\0bdeb2fd209d24afb865584da10b78aa8fefc4)
> succeeds.
>
> - unlink (Z:\pic32mx-bmf\.git\objects\30\tmp_obj_YljwNZ) succeeds
>
> - Trying to open
>
> Z:\pic32mx-bmf\.git\objects\30\0bdeb2fd209d24afb865584da10b78aa8fefc4
> but the file doesn't exist and NtCreateFile fails with status
> 0xC0000034, STATUS_OBJECT_NAME_NOT_FOUND --> ENOENT.
>
> - Subsequent unlink (Z:\pic32mx-bmf\.git\objects\30) fails with a
> STATUS_DIRECTORY_NOT_EMPTY --> ENOTEMPTY.
>
> - git seems to be prepared for such a case, the parent process calls
> opendir/readdir on the directory. Enumerating the files in
> Z:\pic32mx-bmf\.git\objects\30 shows the entries ".", ".." and
> "0bdeb2fd209d24afb865584da10b78aa8fefc4".
>
> - Then git calls lstat on the file, which results in NtOpenFile
> returning status STATUS_OBJECT_NAME_NOT_FOUND again.
>
> - From a POSIX POV this means "somebody else" deleted the file,
> so the dir is empty now. Git tries to delete the directory again,
> which again results in STATUS_DIRECTORY_NOT_EMPTY --> ENOTEMPTY
> and, internally, a sharing violation which disallows to move the
> directory out of the way.
>
> This looks suspiciously like a bug in the remote filesystem. Link
> succeeded, so there are two links to the same file in the directory.
> Unlinking link 1 succeeds, so there's still one link to the
> file in the
> directory, but link 2 is inaccessible as if the file has been deleted
> completely. Thus, a full POSIX git on this drive is broken.
>
> Can you please run
>
> /usr/lib/csih/getVolInfo /cygdrive/z
>
> and paste the output here? Maybe I can workaround this in the next
> Cygwin version.
>
>
> Corinna
>
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