>> --------------------------------- CUT HERE
>> -----------------------------
>> From: Trond Myklebust <Trond.Myklebust@netapp.com>
>> Date: Thu, 25 Oct 2007 13:56:10 -0400
>> NFS: Fix the ustat() regression
>>
>> Since 2.6.18, the superblock sb->s_root has been a dummy dentry
>> with a
>> dummy inode. This breaks ustat(), which actually uses sb->s_root in a
>> vfstat() call.
>>
>> Fix this by making the s_root a dummy alias to the directory inode
>> that was
>> used when creating the superblock.
>>
>> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
>> ---
>>
>> fs/nfs/getroot.c | 81 +++++++++++++++++
>> +------------------------------------
>> 1 files changed, 27 insertions(+), 54 deletions(-)
>>
>> diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
>> index 522e5ad..0ee4384 100644
>> --- a/fs/nfs/getroot.c
>> +++ b/fs/nfs/getroot.c
>> @@ -43,6 +43,25 @@
>> #define NFSDBG_FACILITY NFSDBG_CLIENT
>>
>> /*
>> + * Set the superblock root dentry.
>> + * Note that this function frees the inode in case of error.
>> + */
>> +static int nfs_superblock_set_dummy_root(struct super_block *sb,
>> struct inode *inode)
>> +{
>> + /* The mntroot acts as the dummy root dentry for this superblock */
>> + if (sb->s_root == NULL) {
>> + sb->s_root = d_alloc_root(inode);
>> + if (sb->s_root == NULL) {
>> + iput(inode);
>> + return -ENOMEM;
>> + }
>> + /* Circumvent igrab(): we know the inode is not being freed */
>> + atomic_inc(&inode->i_count);
>> + }
>> + return 0;
>> +}
>> +
>> +/*
>> * get an NFS2/NFS3 root dentry from the root filehandle
>> */
>> struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh
>> *mntfh)
>> @@ -54,33 +73,6 @@ struct dentry *nfs_get_root(struct super_block
>> *sb, struct nfs_fh *mntfh)
>> struct inode *inode;
>> int error;
>>
>> - /* create a dummy root dentry with dummy inode for this
>> superblock */
>> - if (!sb->s_root) {
>> - struct nfs_fh dummyfh;
>> - struct dentry *root;
>> - struct inode *iroot;
>> -
>> - memset(&dummyfh, 0, sizeof(dummyfh));
>> - memset(&fattr, 0, sizeof(fattr));
>> - nfs_fattr_init(&fattr);
>> - fattr.valid = NFS_ATTR_FATTR;
>> - fattr.type = NFDIR;
>> - fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
>> - fattr.nlink = 2;
>> -
>> - iroot = nfs_fhget(sb, &dummyfh, &fattr);
>> - if (IS_ERR(iroot))
>> - return ERR_PTR(PTR_ERR(iroot));
>> -
>> - root = d_alloc_root(iroot);
>> - if (!root) {
>> - iput(iroot);
>> - return ERR_PTR(-ENOMEM);
>> - }
>> -
>> - sb->s_root = root;
>> - }
>> -
>> /* get the actual root for this mount */
>> fsinfo.fattr = &fattr;
>>
>> @@ -96,6 +88,10 @@ struct dentry *nfs_get_root(struct super_block
>> *sb, struct nfs_fh *mntfh)
>> return ERR_PTR(PTR_ERR(inode));
>> }
>>
>> + error = nfs_superblock_set_dummy_root(sb, inode);
>> + if (error != 0)
>> + return ERR_PTR(error);
>> +
>> /* root dentries normally start off anonymous and get spliced in
>> later
>> * if the dentry tree reaches them; however if the dentry already
>> * exists, we'll pick it up at this point and use it as the root
>> @@ -241,33 +237,6 @@ struct dentry *nfs4_get_root(struct
>> super_block *sb, struct nfs_fh *mntfh)
>>
>> dprintk("--> nfs4_get_root()\n");
>>
>> - /* create a dummy root dentry with dummy inode for this
>> superblock */
>> - if (!sb->s_root) {
>> - struct nfs_fh dummyfh;
>> - struct dentry *root;
>> - struct inode *iroot;
>> -
>> - memset(&dummyfh, 0, sizeof(dummyfh));
>> - memset(&fattr, 0, sizeof(fattr));
>> - nfs_fattr_init(&fattr);
>> - fattr.valid = NFS_ATTR_FATTR;
>> - fattr.type = NFDIR;
>> - fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
>> - fattr.nlink = 2;
>> -
>> - iroot = nfs_fhget(sb, &dummyfh, &fattr);
>> - if (IS_ERR(iroot))
>> - return ERR_PTR(PTR_ERR(iroot));
>> -
>> - root = d_alloc_root(iroot);
>> - if (!root) {
>> - iput(iroot);
>> - return ERR_PTR(-ENOMEM);
>> - }
>> -
>> - sb->s_root = root;
>> - }
>> -
>> /* get the info about the server and filesystem */
>> error = nfs4_server_capabilities(server, mntfh);
>> if (error < 0) {
>> @@ -289,6 +258,10 @@ struct dentry *nfs4_get_root(struct
>> super_block *sb, struct nfs_fh *mntfh)
>> return ERR_PTR(PTR_ERR(inode));
>> }
>>
>> + error = nfs_superblock_set_dummy_root(sb, inode);
>> + if (error != 0)
>> + return ERR_PTR(error);
>> +
>> /* root dentries normally start off anonymous and get spliced in
>> later
>> * if the dentry tree reaches them; however if the dentry already
>> * exists, we'll pick it up at this point and use it as the root
>>
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