>> fs/fuse/dir.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
>> index a1d9047..83c217e 100644
>> --- a/fs/fuse/dir.c
>> +++ b/fs/fuse/dir.c
>> @@ -226,6 +226,10 @@ static int fuse_dentry_revalidate(struct dentry
>> *entry, unsigned int flags)
>> if (!err) {
>> struct fuse_inode *fi = get_fuse_inode(inode);
>> if (outarg.nodeid != get_node_id(inode)) {
>> + if (!have_submounts(entry)) {
>> + shrink_dcache_parent(entry);
>> + d_drop(entry);
>> + }
Doing d_drop() on a subtree really has problems. Take this example:
cd /mnt/foo/bar
mkdir my-mount-point
[->d_revalidate() drops "/mnt/foo"]
mount whatever on ./my-mount-point
cd /
At this point that mount is not accessible in any way. The only way
to umount it is to lazy umount the parent mount. If the parent mount
was root, then that's not a practical thing to do.
AFAICS nothing prevents this from happening on NFS and root privs are
not required (e.g. mounting a fuse fs on an NFS home dir).
The other problem is that, unlike NFS, fuse doesn't currently
reconnect these subtrees when it finds them at a different point in
the tree. d_drop on it just makes things worse because at that point
that subtree will not be accessible anymore (while the fuse fs is
mounted, that is). This could be fixed pretty easily by using the
d_materialise_*() helpers.
But issues with mounting over an unhashed subtree *should* be addressed.
Recursively d_drop()-ing might still be the simplest way. Need to
make sure the subtree doesn't change in the meantime. Holding
rename_lock might do the trick. But then there's still an unlikely
race with mount()...
Thanks,
Miklos
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