/* * 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_ops_register to contain the pointers * to the cleancache "backend" implementation functions. */ static struct cleancache_ops *cleancache_ops __read_mostly; /* * Counters available via /sys/kernel/debug/frontswap (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; /* * When no backend is registered all calls to init_fs and init_shared_fs * are registered and fake poolids (FAKE_FS_POOLID_OFFSET or * FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array * [shared_|]fs_poolid_map) are given to the respective super block * (sb->cleancache_poolid) and no tmem_pools are created. When a backend * registers with cleancache the previous calls to init_fs and init_shared_fs * are executed to create tmem_pools and set the respective poolids. While no * backend is registered all "puts", "gets" and "flushes" are ignored or failed. */ #define MAX_INITIALIZABLE_FS 32 #define FAKE_FS_POOLID_OFFSET 1000 #define FAKE_SHARED_FS_POOLID_OFFSET 2000 #define FS_NO_BACKEND (-1) #define FS_UNKNOWN (-2) static int fs_poolid_map[MAX_INITIALIZABLE_FS]; static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS]; static char *uuids[MAX_INITIALIZABLE_FS]; /* * Mutex for the [shared_|]fs_poolid_map to guard against multiple threads * invoking umount (and ending in __cleancache_invalidate_fs) and also multiple * threads calling mount (and ending up in __cleancache_init_[shared|]fs). */ static DEFINE_MUTEX(poolid_mutex); /* * When set to false (default) all calls to the cleancache functions, except * the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded * by the if (!cleancache_ops) return. This means multiple threads (from * different filesystems) will be checking cleancache_ops. The usage of a * bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are * OK if the time between the backend's have been initialized (and * cleancache_ops has been set to not NULL) and when the filesystems start * actually calling the backends. The inverse (when unloading) is obviously * not good - but this shim does not do that (yet). */ /* * The backends and filesystems work all asynchronously. This is b/c the * backends can be built as modules. * The usual sequence of events is: * a) mount / -> __cleancache_init_fs is called. We set the * [shared_|]fs_poolid_map and uuids for. * * b). user does I/Os -> we call the rest of __cleancache_* functions * which return immediately as cleancache_ops is false. * * c). modprobe zcache -> cleancache_register_ops. We init the backend * and set cleancache_ops to true, and for any fs_poolid_map * (which is set by __cleancache_init_fs) we initialize the poolid. * * d). user does I/Os -> now that cleancache_ops is true all the * __cleancache_* functions can call the backend. They all check * that fs_poolid_map is valid and if so invoke the backend. * * e). umount / -> __cleancache_invalidate_fs, the fs_poolid_map is * reset (which is the second check in the __cleancache_* ops * to call the backend). * * The sequence of event could also be c), followed by a), and d). and e). The * c) would not happen anymore. There is also the chance of c), and one thread * doing a) + d), and another doing e). For that case we depend on the * filesystem calling __cleancache_invalidate_fs in the proper sequence (so * that it handles all I/Os before it invalidates the fs (which is last part * of unmounting process). * * Note: The acute reader will notice that there is no "rmmod zcache" case. * This is b/c the functionality for that is not yet implemented and when * done, will require some extra locking not yet devised. */ /* * Register operations for cleancache, returning previous thus allowing * detection of multiple backends and possible nesting. */ struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops) { struct cleancache_ops *old = cleancache_ops; int i; mutex_lock(&poolid_mutex); for (i = 0; i < MAX_INITIALIZABLE_FS; i++) { if (fs_poolid_map[i] == FS_NO_BACKEND) fs_poolid_map[i] = ops->init_fs(PAGE_SIZE); if (shared_fs_poolid_map[i] == FS_NO_BACKEND) shared_fs_poolid_map[i] = ops->init_shared_fs (uuids[i], PAGE_SIZE); } /* * We MUST set cleancache_ops _after_ we have called the backends * init_fs or init_shared_fs functions. Otherwise the compiler might * re-order where cleancache_ops is set in this function. */ barrier(); cleancache_ops = ops; mutex_unlock(&poolid_mutex); return old; } EXPORT_SYMBOL(cleancache_register_ops); /* Called by a cleancache-enabled filesystem at time of mount */ void __cleancache_init_fs(struct super_block *sb) { int i; mutex_lock(&poolid_mutex); for (i = 0; i < MAX_INITIALIZABLE_FS; i++) { if (fs_poolid_map[i] == FS_UNKNOWN) { sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET; if (cleancache_ops) fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE); else fs_poolid_map[i] = FS_NO_BACKEND; break; } } mutex_unlock(&poolid_mutex); } EXPORT_SYMBOL(__cleancache_init_fs); /* Called by a cleancache-enabled clustered filesystem at time of mount */ void __cleancache_init_shared_fs(char *uuid, struct super_block *sb) { int i; mutex_lock(&poolid_mutex); for (i = 0; i < MAX_INITIALIZABLE_FS; i++) { if (shared_fs_poolid_map[i] == FS_UNKNOWN) { sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET; uuids[i] = uuid; if (cleancache_ops) shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs (uuid, PAGE_SIZE); else shared_fs_poolid_map[i] = FS_NO_BACKEND; break; } } mutex_unlock(&poolid_mutex); } 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; } /* * Returns a pool_id that is associated with a given fake poolid. */ static int get_poolid_from_fake(int fake_pool_id) { if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) return shared_fs_poolid_map[fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET]; else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET]; return FS_NO_BACKEND; } /* * "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; int fake_pool_id; struct cleancache_filekey key = { .u.key = { 0 } }; if (!cleancache_ops) { cleancache_failed_gets++; goto out; } VM_BUG_ON_PAGE(!PageLocked(page), page); fake_pool_id = page->mapping->host->i_sb->cleancache_poolid; if (fake_pool_id < 0) goto out; pool_id = get_poolid_from_fake(fake_pool_id); if (cleancache_get_key(page->mapping->host, &key) < 0) goto out; if (pool_id >= 0) 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; int fake_pool_id; struct cleancache_filekey key = { .u.key = { 0 } }; if (!cleancache_ops) { cleancache_puts++; return; } VM_BUG_ON_PAGE(!PageLocked(page), page); fake_pool_id = page->mapping->host->i_sb->cleancache_poolid; if (fake_pool_id < 0) return; pool_id = get_poolid_from_fake(fake_pool_id); 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; int fake_pool_id = mapping->host->i_sb->cleancache_poolid; struct cleancache_filekey key = { .u.key = { 0 } }; if (!cleancache_ops) return; if (fake_pool_id >= 0) { pool_id = get_poolid_from_fake(fake_pool_id); if (pool_id < 0) return; 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; int fake_pool_id = mapping->host->i_sb->cleancache_poolid; struct cleancache_filekey key = { .u.key = { 0 } }; if (!cleancache_ops) return; if (fake_pool_id < 0) return; pool_id = get_poolid_from_fake(fake_pool_id); 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 index; int fake_pool_id = sb->cleancache_poolid; int old_poolid = fake_pool_id; mutex_lock(&poolid_mutex); if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) { index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET; old_poolid = shared_fs_poolid_map[index]; shared_fs_poolid_map[index] = FS_UNKNOWN; uuids[index] = NULL; } else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) { index = fake_pool_id - FAKE_FS_POOLID_OFFSET; old_poolid = fs_poolid_map[index]; fs_poolid_map[index] = FS_UNKNOWN; } sb->cleancache_poolid = -1; if (cleancache_ops) cleancache_ops->invalidate_fs(old_poolid); mutex_unlock(&poolid_mutex); } EXPORT_SYMBOL(__cleancache_invalidate_fs); static int __init init_cleancache(void) { int i; #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 for (i = 0; i < MAX_INITIALIZABLE_FS; i++) { fs_poolid_map[i] = FS_UNKNOWN; shared_fs_poolid_map[i] = FS_UNKNOWN; } return 0; } module_init(init_cleancache)