[fuse-devel] "pwd", inodes, and readdir

[David S. <ds...@ja...>]

Here's a fairly subtle problem, and a possible fix.

The problem is that if you export a Fuse filesystem via NFS, and mount
it on some clients (OSX, Irix, HPUX, *BSD), getcwd() from within the
Fuse filesystem doesn't work (failing with ENOENT).  Since pwd calls
getcwd() this is a very annoying problem as pwd is used frequently in
scripts, etc.

The reason for the problem is in how getcwd() is implemented: it stats
the current directory ("."), notes the inode number, then opens the
directory ".."  and reads each entry looking for that inode.  Repeat
until we reach the root.

Unless use_ino is set, fuse does not fill in the d_ino field of a
struct dirent (it fills in (ino_t)-1 instead).  Since -1 never matches
the inode that getcwd() is looking for, getcwd() fails.

Here's a patch to fill in d_ino in directory listings.  If use_ino is
set, the passed-in inode is used of course.  This only changes the
behavior when use_ino isn't set.  Also, this isn't perfect - if the
cache no longer has the node in question, then -1 is returned for the
inode like it is now.  However, this is unlikely and if it does
happen, we're no worse off than we are now.

David