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TOMOYO Linux Cross Reference
Linux/mm/cleancache.c

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  1 /*
  2  * Cleancache frontend
  3  *
  4  * This code provides the generic "frontend" layer to call a matching
  5  * "backend" driver implementation of cleancache.  See
  6  * Documentation/vm/cleancache.txt for more information.
  7  *
  8  * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
  9  * Author: Dan Magenheimer
 10  *
 11  * This work is licensed under the terms of the GNU GPL, version 2.
 12  */
 13 
 14 #include <linux/module.h>
 15 #include <linux/fs.h>
 16 #include <linux/exportfs.h>
 17 #include <linux/mm.h>
 18 #include <linux/debugfs.h>
 19 #include <linux/cleancache.h>
 20 
 21 /*
 22  * This global enablement flag may be read thousands of times per second
 23  * by cleancache_get/put/invalidate even on systems where cleancache_ops
 24  * is not claimed (e.g. cleancache is config'ed on but remains
 25  * disabled), so is preferred to the slower alternative: a function
 26  * call that checks a non-global.
 27  */
 28 int cleancache_enabled __read_mostly;
 29 EXPORT_SYMBOL(cleancache_enabled);
 30 
 31 /*
 32  * cleancache_ops is set by cleancache_ops_register to contain the pointers
 33  * to the cleancache "backend" implementation functions.
 34  */
 35 static struct cleancache_ops cleancache_ops __read_mostly;
 36 
 37 /*
 38  * Counters available via /sys/kernel/debug/frontswap (if debugfs is
 39  * properly configured.  These are for information only so are not protected
 40  * against increment races.
 41  */
 42 static u64 cleancache_succ_gets;
 43 static u64 cleancache_failed_gets;
 44 static u64 cleancache_puts;
 45 static u64 cleancache_invalidates;
 46 
 47 /*
 48  * register operations for cleancache, returning previous thus allowing
 49  * detection of multiple backends and possible nesting
 50  */
 51 struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
 52 {
 53         struct cleancache_ops old = cleancache_ops;
 54 
 55         cleancache_ops = *ops;
 56         cleancache_enabled = 1;
 57         return old;
 58 }
 59 EXPORT_SYMBOL(cleancache_register_ops);
 60 
 61 /* Called by a cleancache-enabled filesystem at time of mount */
 62 void __cleancache_init_fs(struct super_block *sb)
 63 {
 64         sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
 65 }
 66 EXPORT_SYMBOL(__cleancache_init_fs);
 67 
 68 /* Called by a cleancache-enabled clustered filesystem at time of mount */
 69 void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
 70 {
 71         sb->cleancache_poolid =
 72                 (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
 73 }
 74 EXPORT_SYMBOL(__cleancache_init_shared_fs);
 75 
 76 /*
 77  * If the filesystem uses exportable filehandles, use the filehandle as
 78  * the key, else use the inode number.
 79  */
 80 static int cleancache_get_key(struct inode *inode,
 81                               struct cleancache_filekey *key)
 82 {
 83         int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
 84         int len = 0, maxlen = CLEANCACHE_KEY_MAX;
 85         struct super_block *sb = inode->i_sb;
 86 
 87         key->u.ino = inode->i_ino;
 88         if (sb->s_export_op != NULL) {
 89                 fhfn = sb->s_export_op->encode_fh;
 90                 if  (fhfn) {
 91                         len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
 92                         if (len <= 0 || len == 255)
 93                                 return -1;
 94                         if (maxlen > CLEANCACHE_KEY_MAX)
 95                                 return -1;
 96                 }
 97         }
 98         return 0;
 99 }
100 
101 /*
102  * "Get" data from cleancache associated with the poolid/inode/index
103  * that were specified when the data was put to cleanache and, if
104  * successful, use it to fill the specified page with data and return 0.
105  * The pageframe is unchanged and returns -1 if the get fails.
106  * Page must be locked by caller.
107  */
108 int __cleancache_get_page(struct page *page)
109 {
110         int ret = -1;
111         int pool_id;
112         struct cleancache_filekey key = { .u.key = { 0 } };
113 
114         VM_BUG_ON(!PageLocked(page));
115         pool_id = page->mapping->host->i_sb->cleancache_poolid;
116         if (pool_id < 0)
117                 goto out;
118 
119         if (cleancache_get_key(page->mapping->host, &key) < 0)
120                 goto out;
121 
122         ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
123         if (ret == 0)
124                 cleancache_succ_gets++;
125         else
126                 cleancache_failed_gets++;
127 out:
128         return ret;
129 }
130 EXPORT_SYMBOL(__cleancache_get_page);
131 
132 /*
133  * "Put" data from a page to cleancache and associate it with the
134  * (previously-obtained per-filesystem) poolid and the page's,
135  * inode and page index.  Page must be locked.  Note that a put_page
136  * always "succeeds", though a subsequent get_page may succeed or fail.
137  */
138 void __cleancache_put_page(struct page *page)
139 {
140         int pool_id;
141         struct cleancache_filekey key = { .u.key = { 0 } };
142 
143         VM_BUG_ON(!PageLocked(page));
144         pool_id = page->mapping->host->i_sb->cleancache_poolid;
145         if (pool_id >= 0 &&
146               cleancache_get_key(page->mapping->host, &key) >= 0) {
147                 (*cleancache_ops.put_page)(pool_id, key, page->index, page);
148                 cleancache_puts++;
149         }
150 }
151 EXPORT_SYMBOL(__cleancache_put_page);
152 
153 /*
154  * Invalidate any data from cleancache associated with the poolid and the
155  * page's inode and page index so that a subsequent "get" will fail.
156  */
157 void __cleancache_invalidate_page(struct address_space *mapping,
158                                         struct page *page)
159 {
160         /* careful... page->mapping is NULL sometimes when this is called */
161         int pool_id = mapping->host->i_sb->cleancache_poolid;
162         struct cleancache_filekey key = { .u.key = { 0 } };
163 
164         if (pool_id >= 0) {
165                 VM_BUG_ON(!PageLocked(page));
166                 if (cleancache_get_key(mapping->host, &key) >= 0) {
167                         (*cleancache_ops.invalidate_page)(pool_id,
168                                                           key, page->index);
169                         cleancache_invalidates++;
170                 }
171         }
172 }
173 EXPORT_SYMBOL(__cleancache_invalidate_page);
174 
175 /*
176  * Invalidate all data from cleancache associated with the poolid and the
177  * mappings's inode so that all subsequent gets to this poolid/inode
178  * will fail.
179  */
180 void __cleancache_invalidate_inode(struct address_space *mapping)
181 {
182         int pool_id = mapping->host->i_sb->cleancache_poolid;
183         struct cleancache_filekey key = { .u.key = { 0 } };
184 
185         if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
186                 (*cleancache_ops.invalidate_inode)(pool_id, key);
187 }
188 EXPORT_SYMBOL(__cleancache_invalidate_inode);
189 
190 /*
191  * Called by any cleancache-enabled filesystem at time of unmount;
192  * note that pool_id is surrendered and may be reutrned by a subsequent
193  * cleancache_init_fs or cleancache_init_shared_fs
194  */
195 void __cleancache_invalidate_fs(struct super_block *sb)
196 {
197         if (sb->cleancache_poolid >= 0) {
198                 int old_poolid = sb->cleancache_poolid;
199                 sb->cleancache_poolid = -1;
200                 (*cleancache_ops.invalidate_fs)(old_poolid);
201         }
202 }
203 EXPORT_SYMBOL(__cleancache_invalidate_fs);
204 
205 static int __init init_cleancache(void)
206 {
207 #ifdef CONFIG_DEBUG_FS
208         struct dentry *root = debugfs_create_dir("cleancache", NULL);
209         if (root == NULL)
210                 return -ENXIO;
211         debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
212         debugfs_create_u64("failed_gets", S_IRUGO,
213                                 root, &cleancache_failed_gets);
214         debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
215         debugfs_create_u64("invalidates", S_IRUGO,
216                                 root, &cleancache_invalidates);
217 #endif
218         return 0;
219 }
220 module_init(init_cleancache)
221 

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