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>

1 files changed, 109 insertions, 0 deletions

diff --git a/fs/cifs/cache.c b/fs/cifs/cache.c
index f46468fb6a9..15532abdac1 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,
+};
+