- how to install and setup the Linux NFS/RDMA client and server software
nfsroot.txt
- short guide on setting up a diskless box with NFS root filesystem.
+pnfs.txt
+ - short explanation of some of the internals of the pnfs client code
rpc-cache.txt
- introduction to the caching mechanisms in the sunrpc layer.
idmapper.txt
--- /dev/null
+Reference counting in pnfs:
+==========================
+
+The are several inter-related caches. We have layouts which can
+reference multiple devices, each of which can reference multiple data servers.
+Each data server can be referenced by multiple devices. Each device
+can be referenced by multiple layouts. To keep all of this straight,
+we need to reference count.
+
+
+struct pnfs_layout_hdr
+----------------------
+The on-the-wire command LAYOUTGET corresponds to struct
+pnfs_layout_segment, usually referred to by the variable name lseg.
+Each nfs_inode may hold a pointer to a cache of of these layout
+segments in nfsi->layout, of type struct pnfs_layout_hdr.
+
+We reference the header for the inode pointing to it, across each
+outstanding RPC call that references it (LAYOUTGET, LAYOUTRETURN,
+LAYOUTCOMMIT), and for each lseg held within.
+
+Each header is also (when non-empty) put on a list associated with
+struct nfs_client (cl_layouts). Being put on this list does not bump
+the reference count, as the layout is kept around by the lseg that
+keeps it in the list.
+
+deviceid_cache
+--------------
+lsegs reference device ids, which are resolved per nfs_client and
+layout driver type. The device ids are held in a RCU cache (struct
+nfs4_deviceid_cache). The cache itself is referenced across each
+mount. The entries (struct nfs4_deviceid) themselves are held across
+the lifetime of each lseg referencing them.
+
+RCU is used because the deviceid is basically a write once, read many
+data structure. The hlist size of 32 buckets needs better
+justification, but seems reasonable given that we can have multiple
+deviceid's per filesystem, and multiple filesystems per nfs_client.
+
+The hash code is copied from the nfsd code base. A discussion of
+hashing and variations of this algorithm can be found at:
+http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809
+
+data server cache
+-----------------
+file driver devices refer to data servers, which are kept in a module
+level cache. Its reference is held over the lifetime of the deviceid
+pointing to it.
config NFS_V4_1
bool "NFS client support for NFSv4.1 (EXPERIMENTAL)"
- depends on NFS_V4 && EXPERIMENTAL
+ depends on NFS_FS && NFS_V4 && EXPERIMENTAL
+ select PNFS_FILE_LAYOUT
help
This option enables support for minor version 1 of the NFSv4 protocol
- (draft-ietf-nfsv4-minorversion1) in the kernel's NFS client.
+ (RFC 5661) in the kernel's NFS client.
If unsure, say N.
+config PNFS_FILE_LAYOUT
+ tristate
+
config ROOT_NFS
bool "Root file system on NFS"
depends on NFS_FS=y && IP_PNP
#define NFSDBG_FACILITY NFSDBG_PNFS
-/* STUB that returns the equivalent of "no module found" */
+/* Locking:
+ *
+ * pnfs_spinlock:
+ * protects pnfs_modules_tbl.
+ */
+static DEFINE_SPINLOCK(pnfs_spinlock);
+
+/*
+ * pnfs_modules_tbl holds all pnfs modules
+ */
+static LIST_HEAD(pnfs_modules_tbl);
+
+/* Return the registered pnfs layout driver module matching given id */
+static struct pnfs_layoutdriver_type *
+find_pnfs_driver_locked(u32 id)
+{
+ struct pnfs_layoutdriver_type *local;
+
+ list_for_each_entry(local, &pnfs_modules_tbl, pnfs_tblid)
+ if (local->id == id)
+ goto out;
+ local = NULL;
+out:
+ dprintk("%s: Searching for id %u, found %p\n", __func__, id, local);
+ return local;
+}
+
static struct pnfs_layoutdriver_type *
find_pnfs_driver(u32 id)
{
- return NULL;
+ struct pnfs_layoutdriver_type *local;
+
+ spin_lock(&pnfs_spinlock);
+ local = find_pnfs_driver_locked(id);
+ spin_unlock(&pnfs_spinlock);
+ return local;
}
void
unset_pnfs_layoutdriver(struct nfs_server *nfss)
{
+ if (nfss->pnfs_curr_ld) {
+ nfss->pnfs_curr_ld->uninitialize_mountpoint(nfss);
+ module_put(nfss->pnfs_curr_ld->owner);
+ }
nfss->pnfs_curr_ld = NULL;
}
goto out_no_driver;
}
}
+ if (!try_module_get(ld_type->owner)) {
+ dprintk("%s: Could not grab reference on module\n", __func__);
+ goto out_no_driver;
+ }
server->pnfs_curr_ld = ld_type;
+ if (ld_type->initialize_mountpoint(server)) {
+ printk(KERN_ERR
+ "%s: Error initializing mount point for layout driver %u.\n",
+ __func__, id);
+ module_put(ld_type->owner);
+ goto out_no_driver;
+ }
dprintk("%s: pNFS module for %u set\n", __func__, id);
return;
dprintk("%s: Using NFSv4 I/O\n", __func__);
server->pnfs_curr_ld = NULL;
}
+
+int
+pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
+{
+ int status = -EINVAL;
+ struct pnfs_layoutdriver_type *tmp;
+
+ if (ld_type->id == 0) {
+ printk(KERN_ERR "%s id 0 is reserved\n", __func__);
+ return status;
+ }
+
+ spin_lock(&pnfs_spinlock);
+ tmp = find_pnfs_driver_locked(ld_type->id);
+ if (!tmp) {
+ list_add(&ld_type->pnfs_tblid, &pnfs_modules_tbl);
+ status = 0;
+ dprintk("%s Registering id:%u name:%s\n", __func__, ld_type->id,
+ ld_type->name);
+ } else {
+ printk(KERN_ERR "%s Module with id %d already loaded!\n",
+ __func__, ld_type->id);
+ }
+ spin_unlock(&pnfs_spinlock);
+
+ return status;
+}
+EXPORT_SYMBOL_GPL(pnfs_register_layoutdriver);
+
+void
+pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
+{
+ dprintk("%s Deregistering id:%u\n", __func__, ld_type->id);
+ spin_lock(&pnfs_spinlock);
+ list_del(&ld_type->pnfs_tblid);
+ spin_unlock(&pnfs_spinlock);
+}
+EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);
/* Per-layout driver specific registration structure */
struct pnfs_layoutdriver_type {
+ struct list_head pnfs_tblid;
+ const u32 id;
+ const char *name;
+ struct module *owner;
+ int (*initialize_mountpoint) (struct nfs_server *);
+ int (*uninitialize_mountpoint) (struct nfs_server *);
};
+extern int pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *);
+extern void pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *);
+
void set_pnfs_layoutdriver(struct nfs_server *, u32 id);
void unset_pnfs_layoutdriver(struct nfs_server *);
git://bbs.cooldavid.org / net-next-2.6.git / commitdiff