FreeBSD/Linux Kernel Cross Reference
sys/mm/cleancache.c

     /*
      * 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>
    
    /*
     * This global enablement flag may be read thousands of times per second
     * by cleancache_get/put/invalidate even on systems where cleancache_ops
     * is not claimed (e.g. cleancache is config'ed on but remains
     * disabled), so is preferred to the slower alternative: a function
     * call that checks a non-global.
     */
    int cleancache_enabled __read_mostly;
    EXPORT_SYMBOL(cleancache_enabled);
    
    /*
     * 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;
    
    /*
     * 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;
    
            cleancache_ops = *ops;
            cleancache_enabled = 1;
            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)
    {
            sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
    }
    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)
    {
            sb->cleancache_poolid =
                    (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
    }
    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 <= 0 || len == 255)
                                    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.
    */
   int __cleancache_get_page(struct page *page)
   {
           int ret = -1;
           int pool_id;
           struct cleancache_filekey key = { .u.key = { 0 } };
   
           VM_BUG_ON(!PageLocked(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.
    */
   void __cleancache_put_page(struct page *page)
   {
           int pool_id;
           struct cleancache_filekey key = { .u.key = { 0 } };
   
           VM_BUG_ON(!PageLocked(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.
    */
   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 (pool_id >= 0) {
                   VM_BUG_ON(!PageLocked(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.
    */
   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 (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 reutrned by a subsequent
    * cleancache_init_fs or cleancache_init_shared_fs
    */
   void __cleancache_invalidate_fs(struct super_block *sb)
   {
           if (sb->cleancache_poolid >= 0) {
                   int old_poolid = sb->cleancache_poolid;
                   sb->cleancache_poolid = -1;
                   (*cleancache_ops.invalidate_fs)(old_poolid);
           }
   }
   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)

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