On Mon, 2007-12-10 at 19:57 +0100, Andi Kleen wrote:
> > Hi Andi,
> >
> > Does the attached patch fix the Oops?
>
> Nope, got that a few hours after boot again:
>
> -Andi
Hi Andi,
I appear to have misread d_find_alias(). It would seem that the only way
to ensure that a mountpoint won't be found is to remove it altogether
from the inode->i_dentry list. AFAICS that should be largely harmless
since the nfs sb->s_root is never visible to users, and is never part of
a dentry tree.
Cheers
Trond
--- Begin Message ---
- Subject: NFS: Fix an Oops in NFS unmount
- From: Trond Myklebust <[email protected]>
- Date:
Ensure that the dummy 'root dentry' is invisible to d_find_alias(). If not,
then it may be spliced into the tree if a parent directory from the same
filesystem gets mounted at a later time.
Signed-off-by: Trond Myklebust <[email protected]>
---
fs/nfs/getroot.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index 0ee4384..e6242cd 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -57,6 +57,17 @@ static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *i
}
/* Circumvent igrab(): we know the inode is not being freed */
atomic_inc(&inode->i_count);
+ /*
+ * Ensure that this dentry is invisible to d_find_alias().
+ * Otherwise, it may be spliced into the tree by
+ * d_materialise_unique if a parent directory from the same
+ * filesystem gets mounted at a later time.
+ * This again causes shrink_dcache_for_umount_subtree() to
+ * Oops, since the test for IS_ROOT() will fail.
+ */
+ spin_lock(&dcache_lock);
+ list_del_init(&sb->s_root->d_alias);
+ spin_unlock(&dcache_lock);
}
return 0;
}
--- End Message ---
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