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Subject[PATCH 16/45] FS-Cache: Add netfs registration [ver #41]
Date
Add functions to register and unregister a network filesystem or other client
of the FS-Cache service. This allocates and releases the cookie representing
the top-level index for a netfs, and makes it available to the netfs.

If the FS-Cache facility is disabled, then the calls are optimised away at
compile time.

Note that whilst this patch may appear to work with FS-Cache enabled and a
netfs attempting to use it, it will leak the cookie it allocates for the netfs
as fscache_relinquish_cookie() is implemented in a later patch. This will
cause the slab code to emit a warning when the module is removed.

Signed-off-by: David Howells <dhowells@redhat.com>
---
fs/fscache/Makefile | 1
fs/fscache/fsc-netfs.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fscache.h | 9 ++++
3 files changed, 112 insertions(+), 1 deletions(-)
create mode 100644 fs/fscache/fsc-netfs.c

diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index 51c91e4..a1b23b9 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -7,6 +7,7 @@ fscache-y := \
fsc-cookie.o \
fsc-fsdef.o \
fsc-main.o \
+ fsc-netfs.o \
fsc-proc.o \
fsc-stats.o

diff --git a/fs/fscache/fsc-netfs.c b/fs/fscache/fsc-netfs.c
new file mode 100644
index 0000000..7f871f1
--- /dev/null
+++ b/fs/fscache/fsc-netfs.c
@@ -0,0 +1,103 @@
+/* FS-Cache netfs (client) registration
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define FSCACHE_DEBUG_LEVEL COOKIE
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "fsc-internal.h"
+
+static LIST_HEAD(fscache_netfs_list);
+
+/*
+ * register a network filesystem for caching
+ */
+int __fscache_register_netfs(struct fscache_netfs *netfs)
+{
+ struct fscache_netfs *ptr;
+ int ret;
+
+ _enter("{%s}", netfs->name);
+
+ INIT_LIST_HEAD(&netfs->link);
+
+ /* allocate a cookie for the primary index */
+ netfs->primary_index =
+ kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
+
+ if (!netfs->primary_index) {
+ _leave(" = -ENOMEM");
+ return -ENOMEM;
+ }
+
+ /* initialise the primary index cookie */
+ atomic_set(&netfs->primary_index->usage, 1);
+ atomic_set(&netfs->primary_index->n_children, 0);
+
+ netfs->primary_index->def = &fscache_fsdef_netfs_def;
+ netfs->primary_index->parent = &fscache_fsdef_index;
+ netfs->primary_index->netfs_data = netfs;
+
+ atomic_inc(&netfs->primary_index->parent->usage);
+ atomic_inc(&netfs->primary_index->parent->n_children);
+
+ spin_lock_init(&netfs->primary_index->lock);
+ INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);
+
+ /* check the netfs type is not already present */
+ down_write(&fscache_addremove_sem);
+
+ ret = -EEXIST;
+ list_for_each_entry(ptr, &fscache_netfs_list, link) {
+ if (strcmp(ptr->name, netfs->name) == 0)
+ goto already_registered;
+ }
+
+ list_add(&netfs->link, &fscache_netfs_list);
+ ret = 0;
+
+ printk(KERN_NOTICE "FS-Cache: Netfs '%s' registered for caching\n",
+ netfs->name);
+
+already_registered:
+ up_write(&fscache_addremove_sem);
+
+ if (ret < 0) {
+ netfs->primary_index->parent = NULL;
+ __fscache_cookie_put(netfs->primary_index);
+ netfs->primary_index = NULL;
+ }
+
+ _leave(" = %d", ret);
+ return ret;
+}
+EXPORT_SYMBOL(__fscache_register_netfs);
+
+/*
+ * unregister a network filesystem from the cache
+ * - all cookies must have been released first
+ */
+void __fscache_unregister_netfs(struct fscache_netfs *netfs)
+{
+ _enter("{%s.%u}", netfs->name, netfs->version);
+
+ down_write(&fscache_addremove_sem);
+
+ list_del(&netfs->link);
+ fscache_relinquish_cookie(netfs->primary_index, 0);
+
+ up_write(&fscache_addremove_sem);
+
+ printk(KERN_NOTICE "FS-Cache: Netfs '%s' unregistered from caching\n",
+ netfs->name);
+
+ _leave("");
+}
+EXPORT_SYMBOL(__fscache_unregister_netfs);
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 0b66726..e4278b3 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -187,6 +187,8 @@ struct fscache_netfs {
* - these are undefined symbols when FS-Cache is not configured and the
* optimiser takes care of not using them
*/
+extern int __fscache_register_netfs(struct fscache_netfs *);
+extern void __fscache_unregister_netfs(struct fscache_netfs *);
extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *);
extern void __fscache_release_cache_tag(struct fscache_cache_tag *);

@@ -202,7 +204,10 @@ extern void __fscache_release_cache_tag(struct fscache_cache_tag *);
static inline
int fscache_register_netfs(struct fscache_netfs *netfs)
{
- return 0;
+ if (fscache_available())
+ return __fscache_register_netfs(netfs);
+ else
+ return 0;
}

/**
@@ -219,6 +224,8 @@ int fscache_register_netfs(struct fscache_netfs *netfs)
static inline
void fscache_unregister_netfs(struct fscache_netfs *netfs)
{
+ if (fscache_available())
+ __fscache_unregister_netfs(netfs);
}

/**


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