Re: 2.6.24-rc3-git4 NFS crossmnt regression

Eric W. Biederman
2007-12-07T23:37:29Z

Andrew Morton <akpm@linux-foundation.org> writes:

> On Fri, 07 Dec 2007 17:51:58 -0500
> Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
>
>>
>> On Fri, 2007-12-07 at 14:39 -0500, Shane wrote:
>> > On Dec 7, 2007 2:16 PM, Shane <gnome42@gmail.com> wrote:
>> > ...
>> > > Confirmed working in rc4-git5. I'll deploy this kernel in a few more
>> > > spots and check for other regressions.
>> >
>> > Hmm, I installed a new kernel built from the same sources on the NFS
>> > server. And now I don't see anything at all in the crossmnt dirs.
>> >
>> > ls /dirA/dirB/dirC --> zero output (empty dir)
>> >
>> > Are there any other pending fixes?
>> >
>> > Shane
>>
>> You've probably fallen afoul of
>>
>> http://bugzilla.kernel.org/show_bug.cgi?id=9504
>>
>
> Yeah.
>
> I have a tentative fix below but I can't seem to get Eric and Denis to get
> a suitable fix nailed down. It's urgent!

Andrew, if it is truly urgent please grab either fix, as they will sort
out the worst of the symptoms.

Mine is a little more thorough, and possibly a little less performant.
However since mounts don't appear to be residing under /proc/net it
isn't a significant issue.

> From: "Denis V. Lunev" <den@openvz.org>
>
> /proc/sys/fs/binfmt_misc dentry disappeared during d_revalidate.
> d_revalidate only dentries from shadowed one and below.
> http://bugzilla.kernel.org/show_bug.cgi?id=9504
>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Marcus Better <marcus@better.se>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> Cc: Marcus Better <marcus@better.se>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> fs/proc/generic.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff -puN fs/proc/generic.c~lost-content-of-proc-sys-fs-binfmt_misc
> fs/proc/generic.c
> --- a/fs/proc/generic.c~lost-content-of-proc-sys-fs-binfmt_misc
> +++ a/fs/proc/generic.c
> @@ -380,12 +380,17 @@ static int proc_revalidate_dentry(struct
> return 0;
> }
>
> -static struct dentry_operations proc_dentry_operations =
> +static struct dentry_operations proc_dentry_shadow_operations =
> {
> .d_delete = proc_delete_dentry,
> .d_revalidate = proc_revalidate_dentry,
> };
>
> +static struct dentry_operations proc_dentry_operations =
> +{
> + .d_delete = proc_delete_dentry,
> +};
> +
> /*
> * Don't create negative dentries here, return -ENOENT by hand
> * instead.
> @@ -394,6 +399,7 @@ struct dentry *proc_lookup(struct inode
> {
> struct inode *inode = NULL;
> struct proc_dir_entry * de;
> + int use_shadow = 0;
> int error = -ENOENT;
>
> lock_kernel();
> @@ -406,8 +412,10 @@ struct dentry *proc_lookup(struct inode
> if (!memcmp(dentry->d_name.name, de->name, de->namelen))
> {
> unsigned int ino;
>
> - if (de->shadow_proc)
> + if (de->shadow_proc) {
> de = de->shadow_proc(current, de);
> + use_shadow = 1;
> + }
> ino = de->low_ino;
> de_get(de);
> spin_unlock(&proc_subdir_lock);
> @@ -423,6 +431,8 @@ struct dentry *proc_lookup(struct inode
>
> if (inode) {
> dentry->d_op = &proc_dentry_operations;
> + dentry->d_op = use_shadow ?
> + &proc_dentry_shadow_operations : dentry->d_parent->d_op;
> d_add(dentry, inode);
> return NULL;
> }
> _