// SPDX-License-Identifier: GPL-2.0-only /* * Cleancache frontend * * This code provides the generic "frontend" layer to call a matching * "backend" driver implementation of cleancache. See * Documentation/vm/cleancache.rst for more information. * * Copyright (C) 2009-2010 Oracle Corp. All rights reserved. * Author: Dan Magenheimer */ #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 const 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(const 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); debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets); debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets); debugfs_create_u64("puts", 0444, root, &cleancache_puts); debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates); #endif return 0; } module_init(init_cleancache)