cifs: define superblock-level cache index objects and register them

Define superblock-level cache index objects (managed by cifsTconInfo structs).
Each superblock object is created in a server-level index object and in itself
an index into which inode-level objects are inserted.

The superblock object is keyed by sharename. The UniqueId/IndexNumber is used to
validate that the exported share is the same since we accessed it last time.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>

6 files changed, 142 insertions, 0 deletions

diff --git a/fs/cifs/cache.c b/fs/cifs/cache.c
index f46468fb6a90..15532abdac14 100644
--- a/fs/cifs/cache.c
+++ b/fs/cifs/cache.c
@@ -106,3 +106,112 @@ const struct fscache_cookie_def cifs_fscache_server_index_def = {
         .type = FSCACHE_COOKIE_TYPE_INDEX,
         .get_key = cifs_server_get_key,
 };
+
+/*
+ * Auxiliary data attached to CIFS superblock within the cache
+ */
+struct cifs_fscache_super_auxdata {
+        u64     resource_id;            /* unique server resource id */
+};
+
+static char *extract_sharename(const char *treename)
+{
+        const char *src;
+        char *delim, *dst;
+        int len;
+
+        /* skip double chars at the beginning */
+        src = treename + 2;
+
+        /* share name is always preceded by '\\' now */
+        delim = strchr(src, '\\');
+        if (!delim)
+                return ERR_PTR(-EINVAL);
+        delim++;
+        len = strlen(delim);
+
+        /* caller has to free the memory */
+        dst = kstrndup(delim, len, GFP_KERNEL);
+        if (!dst)
+                return ERR_PTR(-ENOMEM);
+
+        return dst;
+}
+
+/*
+ * Superblock object currently keyed by share name
+ */
+static uint16_t cifs_super_get_key(const void *cookie_netfs_data, void *buffer,
+                                   uint16_t maxbuf)
+{
+        const struct cifsTconInfo *tcon = cookie_netfs_data;
+        char *sharename;
+        uint16_t len;
+
+        sharename = extract_sharename(tcon->treeName);
+        if (IS_ERR(sharename)) {
+                cFYI(1, "CIFS: couldn't extract sharename\n");
+                sharename = NULL;
+                return 0;
+        }
+
+        len = strlen(sharename);
+        if (len > maxbuf)
+                return 0;
+
+        memcpy(buffer, sharename, len);
+
+        kfree(sharename);
+
+        return len;
+}
+
+static uint16_t
+cifs_fscache_super_get_aux(const void *cookie_netfs_data, void *buffer,
+                           uint16_t maxbuf)
+{
+        struct cifs_fscache_super_auxdata auxdata;
+        const struct cifsTconInfo *tcon = cookie_netfs_data;
+
+        memset(&auxdata, 0, sizeof(auxdata));
+        auxdata.resource_id = tcon->resource_id;
+
+        if (maxbuf > sizeof(auxdata))
+                maxbuf = sizeof(auxdata);
+
+        memcpy(buffer, &auxdata, maxbuf);
+
+        return maxbuf;
+}
+
+static enum
+fscache_checkaux cifs_fscache_super_check_aux(void *cookie_netfs_data,
+                                              const void *data,
+                                              uint16_t datalen)
+{
+        struct cifs_fscache_super_auxdata auxdata;
+        const struct cifsTconInfo *tcon = cookie_netfs_data;
+
+        if (datalen != sizeof(auxdata))
+                return FSCACHE_CHECKAUX_OBSOLETE;
+
+        memset(&auxdata, 0, sizeof(auxdata));
+        auxdata.resource_id = tcon->resource_id;
+
+        if (memcmp(data, &auxdata, datalen) != 0)
+                return FSCACHE_CHECKAUX_OBSOLETE;
+
+        return FSCACHE_CHECKAUX_OKAY;
+}
+
+/*
+ * Superblock object for FS-Cache
+ */
+const struct fscache_cookie_def cifs_fscache_super_index_def = {
+        .name = "CIFS.super",
+        .type = FSCACHE_COOKIE_TYPE_INDEX,
+        .get_key = cifs_super_get_key,
+        .get_aux = cifs_fscache_super_get_aux,
+        .check_aux = cifs_fscache_super_check_aux,
+};
+
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 793c8e3a0e53..a3e403e7e163 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -299,6 +299,10 @@ struct cifsTconInfo {
         bool local_lease:1; /* check leases (only) on local system not remote */
         bool broken_posix_open; /* e.g. Samba server versions < 3.3.2, 3.2.9 */
         bool need_reconnect:1; /* connection reset, tid now invalid */
+#ifdef CONFIG_CIFS_FSCACHE
+        u64 resource_id;                /* server resource id */
+        struct fscache_cookie *fscache; /* cookie for share */
+#endif
         /* BB add field for back pointer to sb struct(s)? */
 };
 
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index b2063ce113ec..6e1fe3a7f27d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1837,6 +1837,7 @@ cifs_put_tcon(struct cifsTconInfo *tcon)
         _FreeXid(xid);
 
         tconInfoFree(tcon);
+        cifs_fscache_release_super_cookie(tcon);
         cifs_put_smb_ses(ses);
 }
 
@@ -1906,6 +1907,8 @@ cifs_get_tcon(struct cifsSesInfo *ses, struct smb_vol *volume_info)
         list_add(&tcon->tcon_list, &ses->tcon_list);
         write_unlock(&cifs_tcp_ses_lock);
 
+        cifs_fscache_get_super_cookie(tcon);
+
         return tcon;
 
 out_fail:
diff --git a/fs/cifs/fscache.c b/fs/cifs/fscache.c
index ea97b76f8aa6..eba9beb94a4c 100644
--- a/fs/cifs/fscache.c
+++ b/fs/cifs/fscache.c
@@ -39,3 +39,20 @@ void cifs_fscache_release_client_cookie(struct TCP_Server_Info *server)
         server->fscache = NULL;
 }
 
+void cifs_fscache_get_super_cookie(struct cifsTconInfo *tcon)
+{
+        struct TCP_Server_Info *server = tcon->ses->server;
+
+        tcon->fscache =
+                fscache_acquire_cookie(server->fscache,
+                                &cifs_fscache_super_index_def, tcon);
+        cFYI(1, "CIFS: get superblock cookie (0x%p/0x%p)",
+                                server->fscache, tcon->fscache);
+}
+
+void cifs_fscache_release_super_cookie(struct cifsTconInfo *tcon)
+{
+        cFYI(1, "CIFS: releasing superblock cookie (0x%p)", tcon->fscache);
+        fscache_relinquish_cookie(tcon->fscache, 0);
+        tcon->fscache = NULL;
+}
diff --git a/fs/cifs/fscache.h b/fs/cifs/fscache.h
index 8972306c58a5..d2ba628b72cd 100644
--- a/fs/cifs/fscache.h
+++ b/fs/cifs/fscache.h
@@ -29,6 +29,7 @@
 
 extern struct fscache_netfs cifs_fscache_netfs;
 extern const struct fscache_cookie_def cifs_fscache_server_index_def;
+extern const struct fscache_cookie_def cifs_fscache_super_index_def;
 
 extern int cifs_fscache_register(void);
 extern void cifs_fscache_unregister(void);
@@ -38,6 +39,8 @@ extern void cifs_fscache_unregister(void);
  */
 extern void cifs_fscache_get_client_cookie(struct TCP_Server_Info *);
 extern void cifs_fscache_release_client_cookie(struct TCP_Server_Info *);
+extern void cifs_fscache_get_super_cookie(struct cifsTconInfo *);
+extern void cifs_fscache_release_super_cookie(struct cifsTconInfo *);
 
 #else /* CONFIG_CIFS_FSCACHE */
 static inline int cifs_fscache_register(void) { return 0; }
@@ -47,6 +50,9 @@ static inline void
 cifs_fscache_get_client_cookie(struct TCP_Server_Info *server) {}
 static inline void
 cifs_fscache_get_client_cookie(struct TCP_Server_Info *server); {}
+static inline void cifs_fscache_get_super_cookie(struct cifsTconInfo *tcon) {}
+static inline void
+cifs_fscache_release_super_cookie(struct cifsTconInfo *tcon) {}
 
 #endif /* CONFIG_CIFS_FSCACHE */
 
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index fe9b2f5fb492..f884cb51622a 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -807,6 +807,9 @@ struct inode *cifs_root_iget(struct super_block *sb, unsigned long ino)
         if (!inode)
                 return ERR_PTR(-ENOMEM);
 
+        /* populate tcon->resource_id */
+        cifs_sb->tcon->resource_id = CIFS_I(inode)->uniqueid;
+
         if (rc && cifs_sb->tcon->ipc) {
                 cFYI(1, "ipc connection - fake read inode");
                 inode->i_mode |= S_IFDIR;