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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/cleancache.h>
 19 
 20 /*
 21  * This global enablement flag may be read thousands of times per second
 22  * by cleancache_get/put/flush even on systems where cleancache_ops
 23  * is not claimed (e.g. cleancache is config'ed on but remains
 24  * disabled), so is preferred to the slower alternative: a function
 25  * call that checks a non-global.
 26  */
 27 int cleancache_enabled;
 28 EXPORT_SYMBOL(cleancache_enabled);
 29 
 30 /*
 31  * cleancache_ops is set by cleancache_ops_register to contain the pointers
 32  * to the cleancache "backend" implementation functions.
 33  */
 34 static struct cleancache_ops cleancache_ops;
 35 
 36 /* useful stats available in /sys/kernel/mm/cleancache */
 37 static unsigned long cleancache_succ_gets;
 38 static unsigned long cleancache_failed_gets;
 39 static unsigned long cleancache_puts;
 40 static unsigned long cleancache_flushes;
 41 
 42 /*
 43  * register operations for cleancache, returning previous thus allowing
 44  * detection of multiple backends and possible nesting
 45  */
 46 struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
 47 {
 48         struct cleancache_ops old = cleancache_ops;
 49 
 50         cleancache_ops = *ops;
 51         cleancache_enabled = 1;
 52         return old;
 53 }
 54 EXPORT_SYMBOL(cleancache_register_ops);
 55 
 56 /* Called by a cleancache-enabled filesystem at time of mount */
 57 void __cleancache_init_fs(struct super_block *sb)
 58 {
 59         sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
 60 }
 61 EXPORT_SYMBOL(__cleancache_init_fs);
 62 
 63 /* Called by a cleancache-enabled clustered filesystem at time of mount */
 64 void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
 65 {
 66         sb->cleancache_poolid =
 67                 (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
 68 }
 69 EXPORT_SYMBOL(__cleancache_init_shared_fs);
 70 
 71 /*
 72  * If the filesystem uses exportable filehandles, use the filehandle as
 73  * the key, else use the inode number.
 74  */
 75 static int cleancache_get_key(struct inode *inode,
 76                               struct cleancache_filekey *key)
 77 {
 78         int (*fhfn)(struct dentry *, __u32 *fh, int *, int);
 79         int len = 0, maxlen = CLEANCACHE_KEY_MAX;
 80         struct super_block *sb = inode->i_sb;
 81 
 82         key->u.ino = inode->i_ino;
 83         if (sb->s_export_op != NULL) {
 84                 fhfn = sb->s_export_op->encode_fh;
 85                 if  (fhfn) {
 86                         struct dentry d;
 87                         d.d_inode = inode;
 88                         len = (*fhfn)(&d, &key->u.fh[0], &maxlen, 0);
 89                         if (len <= 0 || len == 255)
 90                                 return -1;
 91                         if (maxlen > CLEANCACHE_KEY_MAX)
 92                                 return -1;
 93                 }
 94         }
 95         return 0;
 96 }
 97 
 98 /*
 99  * "Get" data from cleancache associated with the poolid/inode/index
100  * that were specified when the data was put to cleanache and, if
101  * successful, use it to fill the specified page with data and return 0.
102  * The pageframe is unchanged and returns -1 if the get fails.
103  * Page must be locked by caller.
104  */
105 int __cleancache_get_page(struct page *page)
106 {
107         int ret = -1;
108         int pool_id;
109         struct cleancache_filekey key = { .u.key = { 0 } };
110 
111         VM_BUG_ON(!PageLocked(page));
112         pool_id = page->mapping->host->i_sb->cleancache_poolid;
113         if (pool_id < 0)
114                 goto out;
115 
116         if (cleancache_get_key(page->mapping->host, &key) < 0)
117                 goto out;
118 
119         ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
120         if (ret == 0)
121                 cleancache_succ_gets++;
122         else
123                 cleancache_failed_gets++;
124 out:
125         return ret;
126 }
127 EXPORT_SYMBOL(__cleancache_get_page);
128 
129 /*
130  * "Put" data from a page to cleancache and associate it with the
131  * (previously-obtained per-filesystem) poolid and the page's,
132  * inode and page index.  Page must be locked.  Note that a put_page
133  * always "succeeds", though a subsequent get_page may succeed or fail.
134  */
135 void __cleancache_put_page(struct page *page)
136 {
137         int pool_id;
138         struct cleancache_filekey key = { .u.key = { 0 } };
139 
140         VM_BUG_ON(!PageLocked(page));
141         pool_id = page->mapping->host->i_sb->cleancache_poolid;
142         if (pool_id >= 0 &&
143               cleancache_get_key(page->mapping->host, &key) >= 0) {
144                 (*cleancache_ops.put_page)(pool_id, key, page->index, page);
145                 cleancache_puts++;
146         }
147 }
148 EXPORT_SYMBOL(__cleancache_put_page);
149 
150 /*
151  * Flush any data from cleancache associated with the poolid and the
152  * page's inode and page index so that a subsequent "get" will fail.
153  */
154 void __cleancache_flush_page(struct address_space *mapping, struct page *page)
155 {
156         /* careful... page->mapping is NULL sometimes when this is called */
157         int pool_id = mapping->host->i_sb->cleancache_poolid;
158         struct cleancache_filekey key = { .u.key = { 0 } };
159 
160         if (pool_id >= 0) {
161                 VM_BUG_ON(!PageLocked(page));
162                 if (cleancache_get_key(mapping->host, &key) >= 0) {
163                         (*cleancache_ops.flush_page)(pool_id, key, page->index);
164                         cleancache_flushes++;
165                 }
166         }
167 }
168 EXPORT_SYMBOL(__cleancache_flush_page);
169 
170 /*
171  * Flush all data from cleancache associated with the poolid and the
172  * mappings's inode so that all subsequent gets to this poolid/inode
173  * will fail.
174  */
175 void __cleancache_flush_inode(struct address_space *mapping)
176 {
177         int pool_id = mapping->host->i_sb->cleancache_poolid;
178         struct cleancache_filekey key = { .u.key = { 0 } };
179 
180         if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
181                 (*cleancache_ops.flush_inode)(pool_id, key);
182 }
183 EXPORT_SYMBOL(__cleancache_flush_inode);
184 
185 /*
186  * Called by any cleancache-enabled filesystem at time of unmount;
187  * note that pool_id is surrendered and may be reutrned by a subsequent
188  * cleancache_init_fs or cleancache_init_shared_fs
189  */
190 void __cleancache_flush_fs(struct super_block *sb)
191 {
192         if (sb->cleancache_poolid >= 0) {
193                 int old_poolid = sb->cleancache_poolid;
194                 sb->cleancache_poolid = -1;
195                 (*cleancache_ops.flush_fs)(old_poolid);
196         }
197 }
198 EXPORT_SYMBOL(__cleancache_flush_fs);
199 
200 #ifdef CONFIG_SYSFS
201 
202 /* see Documentation/ABI/xxx/sysfs-kernel-mm-cleancache */
203 
204 #define CLEANCACHE_SYSFS_RO(_name) \
205         static ssize_t cleancache_##_name##_show(struct kobject *kobj, \
206                                 struct kobj_attribute *attr, char *buf) \
207         { \
208                 return sprintf(buf, "%lu\n", cleancache_##_name); \
209         } \
210         static struct kobj_attribute cleancache_##_name##_attr = { \
211                 .attr = { .name = __stringify(_name), .mode = 0444 }, \
212                 .show = cleancache_##_name##_show, \
213         }
214 
215 CLEANCACHE_SYSFS_RO(succ_gets);
216 CLEANCACHE_SYSFS_RO(failed_gets);
217 CLEANCACHE_SYSFS_RO(puts);
218 CLEANCACHE_SYSFS_RO(flushes);
219 
220 static struct attribute *cleancache_attrs[] = {
221         &cleancache_succ_gets_attr.attr,
222         &cleancache_failed_gets_attr.attr,
223         &cleancache_puts_attr.attr,
224         &cleancache_flushes_attr.attr,
225         NULL,
226 };
227 
228 static struct attribute_group cleancache_attr_group = {
229         .attrs = cleancache_attrs,
230         .name = "cleancache",
231 };
232 
233 #endif /* CONFIG_SYSFS */
234 
235 static int __init init_cleancache(void)
236 {
237 #ifdef CONFIG_SYSFS
238         int err;
239 
240         err = sysfs_create_group(mm_kobj, &cleancache_attr_group);
241 #endif /* CONFIG_SYSFS */
242         return 0;
243 }
244 module_init(init_cleancache)
245 

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