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Diffstat (limited to 'mm/cleancache.c')
| -rw-r--r-- | mm/cleancache.c | 319 |
1 files changed, 319 insertions, 0 deletions
diff --git a/mm/cleancache.c b/mm/cleancache.c new file mode 100644 index 000000000..8fc508111 --- /dev/null +++ b/mm/cleancache.c @@ -0,0 +1,319 @@ +/* + * 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) |