--- /dev/null
+/*
+ * Cleancache frontend
+ *
+ * This code provides the generic "frontend" layer to call a matching
+ * "backend" driver implementation of cleancache. See
+ * Documentation/vm/cleancache.txt for more information.
+ *
+ * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
+ * Author: Dan Magenheimer
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/exportfs.h>
+#include <linux/mm.h>
+#include <linux/debugfs.h>
+#include <linux/cleancache.h>
+
+/*
+ * cleancache_ops is set by cleancache_register_ops to contain the pointers
+ * to the cleancache "backend" implementation functions.
+ */
+static struct cleancache_ops *cleancache_ops __read_mostly;
+
+/*
+ * Counters available via /sys/kernel/debug/cleancache (if debugfs is
+ * properly configured. These are for information only so are not protected
+ * against increment races.
+ */
+static u64 cleancache_succ_gets;
+static u64 cleancache_failed_gets;
+static u64 cleancache_puts;
+static u64 cleancache_invalidates;
+
+static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
+{
+ switch (sb->cleancache_poolid) {
+ case CLEANCACHE_NO_BACKEND:
+ __cleancache_init_fs(sb);
+ break;
+ case CLEANCACHE_NO_BACKEND_SHARED:
+ __cleancache_init_shared_fs(sb);
+ break;
+ }
+}
+
+/*
+ * Register operations for cleancache. Returns 0 on success.
+ */
+int cleancache_register_ops(struct cleancache_ops *ops)
+{
+ if (cmpxchg(&cleancache_ops, NULL, ops))
+ return -EBUSY;
+
+ /*
+ * A cleancache backend can be built as a module and hence loaded after
+ * a cleancache enabled filesystem has called cleancache_init_fs. To
+ * handle such a scenario, here we call ->init_fs or ->init_shared_fs
+ * for each active super block. To differentiate between local and
+ * shared filesystems, we temporarily initialize sb->cleancache_poolid
+ * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
+ * respectively in case there is no backend registered at the time
+ * cleancache_init_fs or cleancache_init_shared_fs is called.
+ *
+ * Since filesystems can be mounted concurrently with cleancache
+ * backend registration, we have to be careful to guarantee that all
+ * cleancache enabled filesystems that has been mounted by the time
+ * cleancache_register_ops is called has got and all mounted later will
+ * get cleancache_poolid. This is assured by the following statements
+ * tied together:
+ *
+ * a) iterate_supers skips only those super blocks that has started
+ * ->kill_sb
+ *
+ * b) if iterate_supers encounters a super block that has not finished
+ * ->mount yet, it waits until it is finished
+ *
+ * c) cleancache_init_fs is called from ->mount and
+ * cleancache_invalidate_fs is called from ->kill_sb
+ *
+ * d) we call iterate_supers after cleancache_ops has been set
+ *
+ * From a) it follows that if iterate_supers skips a super block, then
+ * either the super block is already dead, in which case we do not need
+ * to bother initializing cleancache for it, or it was mounted after we
+ * initiated iterate_supers. In the latter case, it must have seen
+ * cleancache_ops set according to d) and initialized cleancache from
+ * ->mount by itself according to c). This proves that we call
+ * ->init_fs at least once for each active super block.
+ *
+ * From b) and c) it follows that if iterate_supers encounters a super
+ * block that has already started ->init_fs, it will wait until ->mount
+ * and hence ->init_fs has finished, then check cleancache_poolid, see
+ * that it has already been set and therefore do nothing. This proves
+ * that we call ->init_fs no more than once for each super block.
+ *
+ * Combined together, the last two paragraphs prove the function
+ * correctness.
+ *
+ * Note that various cleancache callbacks may proceed before this
+ * function is called or even concurrently with it, but since
+ * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
+ * until the corresponding ->init_fs has been actually called and
+ * cleancache_ops has been set.
+ */
+ iterate_supers(cleancache_register_ops_sb, NULL);
+ return 0;
+}
+EXPORT_SYMBOL(cleancache_register_ops);
+
+/* Called by a cleancache-enabled filesystem at time of mount */
+void __cleancache_init_fs(struct super_block *sb)
+{
+ int pool_id = CLEANCACHE_NO_BACKEND;
+
+ if (cleancache_ops) {
+ pool_id = cleancache_ops->init_fs(PAGE_SIZE);
+ if (pool_id < 0)
+ pool_id = CLEANCACHE_NO_POOL;
+ }
+ sb->cleancache_poolid = pool_id;
+}
+EXPORT_SYMBOL(__cleancache_init_fs);
+
+/* Called by a cleancache-enabled clustered filesystem at time of mount */
+void __cleancache_init_shared_fs(struct super_block *sb)
+{
+ int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
+
+ if (cleancache_ops) {
+ pool_id = cleancache_ops->init_shared_fs(sb->s_uuid, PAGE_SIZE);
+ if (pool_id < 0)
+ pool_id = CLEANCACHE_NO_POOL;
+ }
+ sb->cleancache_poolid = pool_id;
+}
+EXPORT_SYMBOL(__cleancache_init_shared_fs);
+
+/*
+ * If the filesystem uses exportable filehandles, use the filehandle as
+ * the key, else use the inode number.
+ */
+static int cleancache_get_key(struct inode *inode,
+ struct cleancache_filekey *key)
+{
+ int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
+ int len = 0, maxlen = CLEANCACHE_KEY_MAX;
+ struct super_block *sb = inode->i_sb;
+
+ key->u.ino = inode->i_ino;
+ if (sb->s_export_op != NULL) {
+ fhfn = sb->s_export_op->encode_fh;
+ if (fhfn) {
+ len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
+ if (len <= FILEID_ROOT || len == FILEID_INVALID)
+ return -1;
+ if (maxlen > CLEANCACHE_KEY_MAX)
+ return -1;
+ }
+ }
+ return 0;
+}
+
+/*
+ * "Get" data from cleancache associated with the poolid/inode/index
+ * that were specified when the data was put to cleanache and, if
+ * successful, use it to fill the specified page with data and return 0.
+ * The pageframe is unchanged and returns -1 if the get fails.
+ * Page must be locked by caller.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+int __cleancache_get_page(struct page *page)
+{
+ int ret = -1;
+ int pool_id;
+ struct cleancache_filekey key = { .u.key = { 0 } };
+
+ if (!cleancache_ops) {
+ cleancache_failed_gets++;
+ goto out;
+ }
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ pool_id = page->mapping->host->i_sb->cleancache_poolid;
+ if (pool_id < 0)
+ goto out;
+
+ if (cleancache_get_key(page->mapping->host, &key) < 0)
+ goto out;
+
+ ret = cleancache_ops->get_page(pool_id, key, page->index, page);
+ if (ret == 0)
+ cleancache_succ_gets++;
+ else
+ cleancache_failed_gets++;
+out:
+ return ret;
+}
+EXPORT_SYMBOL(__cleancache_get_page);
+
+/*
+ * "Put" data from a page to cleancache and associate it with the
+ * (previously-obtained per-filesystem) poolid and the page's,
+ * inode and page index. Page must be locked. Note that a put_page
+ * always "succeeds", though a subsequent get_page may succeed or fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_put_page(struct page *page)
+{
+ int pool_id;
+ struct cleancache_filekey key = { .u.key = { 0 } };
+
+ if (!cleancache_ops) {
+ cleancache_puts++;
+ return;
+ }
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ pool_id = page->mapping->host->i_sb->cleancache_poolid;
+ if (pool_id >= 0 &&
+ cleancache_get_key(page->mapping->host, &key) >= 0) {
+ cleancache_ops->put_page(pool_id, key, page->index, page);
+ cleancache_puts++;
+ }
+}
+EXPORT_SYMBOL(__cleancache_put_page);
+
+/*
+ * Invalidate any data from cleancache associated with the poolid and the
+ * page's inode and page index so that a subsequent "get" will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_invalidate_page(struct address_space *mapping,
+ struct page *page)
+{
+ /* careful... page->mapping is NULL sometimes when this is called */
+ int pool_id = mapping->host->i_sb->cleancache_poolid;
+ struct cleancache_filekey key = { .u.key = { 0 } };
+
+ if (!cleancache_ops)
+ return;
+
+ if (pool_id >= 0) {
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ if (cleancache_get_key(mapping->host, &key) >= 0) {
+ cleancache_ops->invalidate_page(pool_id,
+ key, page->index);
+ cleancache_invalidates++;
+ }
+ }
+}
+EXPORT_SYMBOL(__cleancache_invalidate_page);
+
+/*
+ * Invalidate all data from cleancache associated with the poolid and the
+ * mappings's inode so that all subsequent gets to this poolid/inode
+ * will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
+ */
+void __cleancache_invalidate_inode(struct address_space *mapping)
+{
+ int pool_id = mapping->host->i_sb->cleancache_poolid;
+ struct cleancache_filekey key = { .u.key = { 0 } };
+
+ if (!cleancache_ops)
+ return;
+
+ if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
+ cleancache_ops->invalidate_inode(pool_id, key);
+}
+EXPORT_SYMBOL(__cleancache_invalidate_inode);
+
+/*
+ * Called by any cleancache-enabled filesystem at time of unmount;
+ * note that pool_id is surrendered and may be returned by a subsequent
+ * cleancache_init_fs or cleancache_init_shared_fs.
+ */
+void __cleancache_invalidate_fs(struct super_block *sb)
+{
+ int pool_id;
+
+ pool_id = sb->cleancache_poolid;
+ sb->cleancache_poolid = CLEANCACHE_NO_POOL;
+
+ if (cleancache_ops && pool_id >= 0)
+ cleancache_ops->invalidate_fs(pool_id);
+}
+EXPORT_SYMBOL(__cleancache_invalidate_fs);
+
+static int __init init_cleancache(void)
+{
+#ifdef CONFIG_DEBUG_FS
+ struct dentry *root = debugfs_create_dir("cleancache", NULL);
+ if (root == NULL)
+ return -ENXIO;
+ debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
+ debugfs_create_u64("failed_gets", S_IRUGO,
+ root, &cleancache_failed_gets);
+ debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
+ debugfs_create_u64("invalidates", S_IRUGO,
+ root, &cleancache_invalidates);
+#endif
+ return 0;
+}
+module_init(init_cleancache)
Code Review / kvmfornfv.git / blobdiff