Re: [bug #17877] Invalid "No such file or directory" error on filesystem without stable inode numbers

[Miklos Szeredi]

> > Follow-up Comment #1, bug #17877 (project findutils):
> >
> > > There are several Linux filesystems (including smbfs, fat, and
> > > some FUSE based ones) which cannot provide stable inode numbers
> > > for unreferenced files or directories.
> 
> OP, can you provide a test case which demonstrates the problem?
> I will investigate when I have web and SSH access again next week.

The test case is to do "find . > /dev/null" on a large enough tree on
a machine with low enough memory, so that some of the inodes which fts
rememebers are evicted from the icache between the two stats.

Also attached a patch for fuse-2.5.3, which forces the kernel to drop
inodes from the cache immediately if there are no references to it.
This makes it easy to reliably reproduce the problem.

> > That's the problem.  If an OS can't provide stable inode numbers, it is not
> > POSIX compliant.  find shouldn't have to bend over backwards to work around
> > broken file systems.
> 
> I don't agree.   POSIX-compliant systems are allowed to support
> non-POSIX-compliant filesystems, and GNU findutils should be able to
> search them.
> 
> > You should be reporting this bug to the file system
> > people.
> 
> But you're right about this.

For some of the cases this is an intrinsic property of the filesystem,
not an implementation issue.  You cannot map a larger unique ID space
(e.g. path name) to a smaller unique ID space (st_ino) with bounded
memory requirements.

Miklos

Index: kernel/dir.c
===================================================================
RCS file: /cvsroot/fuse/fuse/kernel/dir.c,v
retrieving revision 1.101.2.1
diff -u -r1.101.2.1 dir.c
--- kernel/dir.c        10 Apr 2006 08:56:41 -0000      1.101.2.1
+++ kernel/dir.c        2 Oct 2006 10:12:29 -0000
@@ -185,12 +185,18 @@
 }
 #endif
 
+static int fuse_dentry_delete(struct dentry *entry)
+{
+       return 1;
+}
+
 static struct dentry_operations fuse_dentry_operations = {
 #ifdef KERNEL_2_6
        .d_revalidate   = fuse_dentry_revalidate,
 #else
        .d_revalidate   = fuse_dentry_revalidate_2_4,
 #endif
+       .d_delete = fuse_dentry_delete,
 };
 
 static inline int valid_mode(int m)
Index: kernel/inode.c
===================================================================
RCS file: /cvsroot/fuse/fuse/kernel/inode.c,v
retrieving revision 1.89
diff -u -r1.89 inode.c
--- kernel/inode.c      6 Jan 2006 18:29:39 -0000       1.89
+++ kernel/inode.c      2 Oct 2006 10:12:30 -0000
@@ -599,6 +599,7 @@
        .destroy_inode  = fuse_destroy_inode,
        .read_inode     = fuse_read_inode,
        .clear_inode    = fuse_clear_inode,
+       .drop_inode     = generic_delete_inode,
        .put_super      = fuse_put_super,
        .statfs         = fuse_statfs,
        .show_options   = fuse_show_options,