From: The pNFS Team <linux-nfs@xxxxxxxxxxxxxxx> Allow a module implementing a layout type to register, and have its mount/umount routines called for filesystems that the server declares support it. Signed-off-by: TBD - melding/reorganization of several patches --- Documentation/filesystems/nfs/00-INDEX | 2 + Documentation/filesystems/nfs/pnfs.txt | 48 ++++++++++++++++++ fs/nfs/Kconfig | 2 +- fs/nfs/pnfs.c | 82 +++++++++++++++++++++++++++++++- fs/nfs/pnfs.h | 9 ++++ 5 files changed, 140 insertions(+), 3 deletions(-) create mode 100644 Documentation/filesystems/nfs/pnfs.txt diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX index 2f68cd6..8d930b9 100644 --- a/Documentation/filesystems/nfs/00-INDEX +++ b/Documentation/filesystems/nfs/00-INDEX @@ -12,5 +12,7 @@ nfs-rdma.txt - 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 code rpc-cache.txt - introduction to the caching mechanisms in the sunrpc layer. diff --git a/Documentation/filesystems/nfs/pnfs.txt b/Documentation/filesystems/nfs/pnfs.txt new file mode 100644 index 0000000..bc0b9cf --- /dev/null +++ b/Documentation/filesystems/nfs/pnfs.txt @@ -0,0 +1,48 @@ +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. diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig index 6c2aad4..5f1b936 100644 --- a/fs/nfs/Kconfig +++ b/fs/nfs/Kconfig @@ -78,7 +78,7 @@ config NFS_V4_1 depends on NFS_V4 && EXPERIMENTAL 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. diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index 2e5dba1..5a8a676 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -32,16 +32,53 @@ #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; + + dprintk("PNFS: %s: Searching for %u\n", __func__, id); + list_for_each_entry(local, &pnfs_modules_tbl, pnfs_tblid) + if (local->id == id) { + if (!try_module_get(local->owner)) + local = NULL; + goto out; + } + local = NULL; +out: + 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; } /* Unitialize a mountpoint in a layout driver */ 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; } @@ -68,6 +105,13 @@ set_pnfs_layoutdriver(struct nfs_server *server, u32 id) goto out_no_driver; } } + 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; + } server->pnfs_curr_ld = ld_type; dprintk("%s: pNFS module for %u set\n", __func__, id); return; @@ -76,3 +120,37 @@ out_no_driver: 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; + + 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 { + module_put(tmp->owner); + 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); diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h index c628ef1..61531f3 100644 --- a/fs/nfs/pnfs.h +++ b/fs/nfs/pnfs.h @@ -36,8 +36,17 @@ /* 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 *); -- 1.7.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
