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From: Eric Blake <ebb9 AT byu DOT net>
Subject:  unlink()/rmdir() on busy file on MVFS
Date: Fri, 28 Aug 2009 14:59:52 +0000 (UTC)
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I noticed this inconsistency:

shell 1:
$ df -T /cygdrive/[mu]
Filesystem    Type   1K-blocks      Used Available Use% Mounted on
M:            mvfs     1024000    512000    512000  50% /cygdrive/m
U:           smbfs    83886080  76761088   7124992  92% /cygdrive/u
$ cd /cygdrive/u
$ mkdir dir
$ touch dir/f

shell 2:
$ cd /cygdrive/u/dir
$ exec 3<f

shell 1:
$ rm dir/f
rm: cannot remove `dir/f': Device or resource busy
$ rmdir dir
rmdir: failed to remove `dir': Directory not empty

shell 2:
$ exec 3<&-
$ cd ..

shell 1:
$ rm dir/f
$ rmdir dir
$

So far, so good - since we can't delete in-use objects on remote systems, this 
is nice behavior.  But repeat the test on MVFS, and:

$ cd /cygdrive/m
$ mkdir dir
$ touch dir/f

shell 2:
$ cd /cygdrive/m/dir
$ exec 3<f

shell 1:
$ rm dir/f
$ ls dir
f

shell 2:
$ exec 3<&-

shell 1:
$ ls dir
$ rmdir dir
$ ls -d dir
dir

shell 2:
$ ls
ls: cannot open directory .: Permission denied
$ cd ..

shell 1:
$ ls -d dir
ls: cannot access dir: No such file or directory

Yes, the file and directory are being closed when the last client closes its 
handles, but it leads to confusing non-posix semantics in the meantime.

Any advice on what to try to make MVFS behave like other remote fs to reject 
deletion of in-use objects?  Or do we just leave it alone, since we've already 
faced more than our fair share of working around MVFS anomalies?

-- 
Eric Blake




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