On Tue, Feb 24, 2015 at 4:49 PM, NeilBrown <neilb@xxxxxxx> wrote:
> On Mon, 23 Feb 2015 22:09:09 -0500 Trond Myklebust
> <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>
>> On Mon, Feb 23, 2015 at 7:14 PM, Trond Myklebust
>> <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>> > If we're traversing a directory which contains a submounted filesystem,
>> > or one that has a referral, the NFS server that is processing the READDIR
>> > request will often return information for the underlying (mounted-on)
>> > directory. It may, or may not, also return filehandle information.
>> >
>> > If this happens, and the lookup in nfs_prime_dcache() returns the
>> > dentry for the submounted directory, the filehandle comparison will
>> > fail, and we call d_invalidate(). Post-commit 8ed936b5671bf
>> > ("vfs: Lazily remove mounts on unlinked files and directories."), this
>> > means the entire subtree is unmounted.
>> >
>> > The following minimal patch addresses this problem by punting on
>> > the invalidation if there is a submount.
>> >
>> > Kudos to Neil Brown <neilb@xxxxxxx> for having tracked down this
>> > issue (see link).
>> >
>> > Reported-by: Nix <nix@xxxxxxxxxxxxx>
>> > Link: http://lkml.kernel.org/r/87iofju9ht.fsf@xxxxxxxxxxxxxxxx
>> > Cc: stable@xxxxxxxxxxxxxxx # 3.18+
>> > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>> > ---
>> > fs/nfs/dir.c | 4 ++++
>> > 1 file changed, 4 insertions(+)
>> >
>> > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
>> > index 9b0c55cb2a2e..0da617a61c0b 100644
>> > --- a/fs/nfs/dir.c
>> > +++ b/fs/nfs/dir.c
>> > @@ -479,6 +479,10 @@ void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
>> >
>> > dentry = d_lookup(parent, &filename);
>> > if (dentry != NULL) {
>> > + /* Is there a mountpoint here? If so, just exit */
>> > + if (!nfs_fsid_equal(&NFS_SB(dentry->d_sb)->fsid,
>> > + &entry->fattr->fsid))
>> > + goto out;
>> > if (nfs_same_file(dentry, entry)) {
>> > nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
>> > status = nfs_refresh_inode(dentry->d_inode, entry->fattr);
>> > --
>>
>> ...and this of course needs the test for NFS_ATTR_FATTR_FSID from
>> 3/3.... I've updated.
>>
>>
>>
>
> Sorry ... I didn't see this before my earlier reply...
>
> What exactly do you do if NFS_ATTR_FATTR_FSID isn't set?
> Hopefully you "goto out".
>
Yes. The test is made immediately upon entering the function, and so a
simple 'return' is sufficient.
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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