NFS: Define and create superblock-level objects

Define and create superblock-level cache index objects (as managed by
nfs_server structs).

Each superblock object is created in a server level index object and is itself
an index into which inode-level objects are inserted.

Ideally there would be one superblock-level object per server, and the former
would be folded into the latter; however, since the "nosharecache" option
exists this isn't possible.

The superblock object key is a sequence consisting of:

 (1) Certain superblock s_flags.

 (2) Various connection parameters that serve to distinguish superblocks for
     sget().

 (3) The volume FSID.

 (4) The security flavour.

 (5) The uniquifier length.

 (6) The uniquifier text.  This is normally an empty string, unless the fsc=xyz
     mount option was used to explicitly specify a uniquifier.

The key blob is of variable length, depending on the length of (6).

The superblock object is given no coherency data to carry in the auxiliary data
permitted by the cache.  It is assumed that the superblock is always coherent.

This patch also adds uniquification handling such that two otherwise identical
superblocks, at least one of which is marked "nosharecache", won't end up
trying to share the on-disk cache.  It will be possible to manually provide a
uniquifier through a mount option with a later patch to avoid the error
otherwise produced.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index c3f056f89477..ab2de2c92b21 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -23,6 +23,9 @@
 
 #define NFSDBG_FACILITY         NFSDBG_FSCACHE
 
+static struct rb_root nfs_fscache_keys = RB_ROOT;
+static DEFINE_SPINLOCK(nfs_fscache_keys_lock);
+
 /*
  * Get the per-client index cookie for an NFS client if the appropriate mount
  * flag was set
@@ -50,3 +53,116 @@ void nfs_fscache_release_client_cookie(struct nfs_client *clp)
         fscache_relinquish_cookie(clp->fscache, 0);
         clp->fscache = NULL;
 }
+
+/*
+ * Get the cache cookie for an NFS superblock.  We have to handle
+ * uniquification here because the cache doesn't do it for us.
+ */
+void nfs_fscache_get_super_cookie(struct super_block *sb,
+                                  struct nfs_parsed_mount_data *data)
+{
+        struct nfs_fscache_key *key, *xkey;
+        struct nfs_server *nfss = NFS_SB(sb);
+        struct rb_node **p, *parent;
+        const char *uniq = data->fscache_uniq ?: "";
+        int diff, ulen;
+
+        ulen = strlen(uniq);
+        key = kzalloc(sizeof(*key) + ulen, GFP_KERNEL);
+        if (!key)
+                return;
+
+        key->nfs_client = nfss->nfs_client;
+        key->key.super.s_flags = sb->s_flags & NFS_MS_MASK;
+        key->key.nfs_server.flags = nfss->flags;
+        key->key.nfs_server.rsize = nfss->rsize;
+        key->key.nfs_server.wsize = nfss->wsize;
+        key->key.nfs_server.acregmin = nfss->acregmin;
+        key->key.nfs_server.acregmax = nfss->acregmax;
+        key->key.nfs_server.acdirmin = nfss->acdirmin;
+        key->key.nfs_server.acdirmax = nfss->acdirmax;
+        key->key.nfs_server.fsid = nfss->fsid;
+        key->key.rpc_auth.au_flavor = nfss->client->cl_auth->au_flavor;
+
+        key->key.uniq_len = ulen;
+        memcpy(key->key.uniquifier, uniq, ulen);
+
+        spin_lock(&nfs_fscache_keys_lock);
+        p = &nfs_fscache_keys.rb_node;
+        parent = NULL;
+        while (*p) {
+                parent = *p;
+                xkey = rb_entry(parent, struct nfs_fscache_key, node);
+
+                if (key->nfs_client < xkey->nfs_client)
+                        goto go_left;
+                if (key->nfs_client > xkey->nfs_client)
+                        goto go_right;
+
+                diff = memcmp(&key->key, &xkey->key, sizeof(key->key));
+                if (diff < 0)
+                        goto go_left;
+                if (diff > 0)
+                        goto go_right;
+
+                if (key->key.uniq_len == 0)
+                        goto non_unique;
+                diff = memcmp(key->key.uniquifier,
+                              xkey->key.uniquifier,
+                              key->key.uniq_len);
+                if (diff < 0)
+                        goto go_left;
+                if (diff > 0)
+                        goto go_right;
+                goto non_unique;
+
+        go_left:
+                p = &(*p)->rb_left;
+                continue;
+        go_right:
+                p = &(*p)->rb_right;
+        }
+
+        rb_link_node(&key->node, parent, p);
+        rb_insert_color(&key->node, &nfs_fscache_keys);
+        spin_unlock(&nfs_fscache_keys_lock);
+        nfss->fscache_key = key;
+
+        /* create a cache index for looking up filehandles */
+        nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache,
+                                               &nfs_fscache_super_index_def,
+                                               nfss);
+        dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",
+                 nfss, nfss->fscache);
+        return;
+
+non_unique:
+        spin_unlock(&nfs_fscache_keys_lock);
+        kfree(key);
+        nfss->fscache_key = NULL;
+        nfss->fscache = NULL;
+        printk(KERN_WARNING "NFS:"
+               " Cache request denied due to non-unique superblock keys\n");
+}
+
+/*
+ * release a per-superblock cookie
+ */
+void nfs_fscache_release_super_cookie(struct super_block *sb)
+{
+        struct nfs_server *nfss = NFS_SB(sb);
+
+        dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)\n",
+                 nfss, nfss->fscache);
+
+        fscache_relinquish_cookie(nfss->fscache, 0);
+        nfss->fscache = NULL;
+
+        if (nfss->fscache_key) {
+                spin_lock(&nfs_fscache_keys_lock);
+                rb_erase(&nfss->fscache_key->node, &nfs_fscache_keys);
+                spin_unlock(&nfs_fscache_keys_lock);
+                kfree(nfss->fscache_key);
+                nfss->fscache_key = NULL;
+        }
+}