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Linux/fs/9p/cache.c

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  1 /*
  2  * V9FS cache definitions.
  3  *
  4  *  Copyright (C) 2009 by Abhishek Kulkarni <adkulkar@umail.iu.edu>
  5  *
  6  *  This program is free software; you can redistribute it and/or modify
  7  *  it under the terms of the GNU General Public License version 2
  8  *  as published by the Free Software Foundation.
  9  *
 10  *  This program is distributed in the hope that it will be useful,
 11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13  *  GNU General Public License for more details.
 14  *
 15  *  You should have received a copy of the GNU General Public License
 16  *  along with this program; if not, write to:
 17  *  Free Software Foundation
 18  *  51 Franklin Street, Fifth Floor
 19  *  Boston, MA  02111-1301  USA
 20  *
 21  */
 22 
 23 #include <linux/jiffies.h>
 24 #include <linux/file.h>
 25 #include <linux/slab.h>
 26 #include <linux/stat.h>
 27 #include <linux/sched.h>
 28 #include <linux/fs.h>
 29 #include <net/9p/9p.h>
 30 
 31 #include "v9fs.h"
 32 #include "cache.h"
 33 
 34 #define CACHETAG_LEN  11
 35 
 36 struct fscache_netfs v9fs_cache_netfs = {
 37         .name           = "9p",
 38         .version        = 0,
 39 };
 40 
 41 /**
 42  * v9fs_random_cachetag - Generate a random tag to be associated
 43  *                        with a new cache session.
 44  *
 45  * The value of jiffies is used for a fairly randomly cache tag.
 46  */
 47 
 48 static
 49 int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
 50 {
 51         v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
 52         if (!v9ses->cachetag)
 53                 return -ENOMEM;
 54 
 55         return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
 56 }
 57 
 58 static uint16_t v9fs_cache_session_get_key(const void *cookie_netfs_data,
 59                                            void *buffer, uint16_t bufmax)
 60 {
 61         struct v9fs_session_info *v9ses;
 62         uint16_t klen = 0;
 63 
 64         v9ses = (struct v9fs_session_info *)cookie_netfs_data;
 65         p9_debug(P9_DEBUG_FSC, "session %p buf %p size %u\n",
 66                  v9ses, buffer, bufmax);
 67 
 68         if (v9ses->cachetag)
 69                 klen = strlen(v9ses->cachetag);
 70 
 71         if (klen > bufmax)
 72                 return 0;
 73 
 74         memcpy(buffer, v9ses->cachetag, klen);
 75         p9_debug(P9_DEBUG_FSC, "cache session tag %s\n", v9ses->cachetag);
 76         return klen;
 77 }
 78 
 79 const struct fscache_cookie_def v9fs_cache_session_index_def = {
 80         .name           = "9P.session",
 81         .type           = FSCACHE_COOKIE_TYPE_INDEX,
 82         .get_key        = v9fs_cache_session_get_key,
 83 };
 84 
 85 void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
 86 {
 87         /* If no cache session tag was specified, we generate a random one. */
 88         if (!v9ses->cachetag)
 89                 v9fs_random_cachetag(v9ses);
 90 
 91         v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
 92                                                 &v9fs_cache_session_index_def,
 93                                                 v9ses, true);
 94         p9_debug(P9_DEBUG_FSC, "session %p get cookie %p\n",
 95                  v9ses, v9ses->fscache);
 96 }
 97 
 98 void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
 99 {
100         p9_debug(P9_DEBUG_FSC, "session %p put cookie %p\n",
101                  v9ses, v9ses->fscache);
102         fscache_relinquish_cookie(v9ses->fscache, 0);
103         v9ses->fscache = NULL;
104 }
105 
106 
107 static uint16_t v9fs_cache_inode_get_key(const void *cookie_netfs_data,
108                                          void *buffer, uint16_t bufmax)
109 {
110         const struct v9fs_inode *v9inode = cookie_netfs_data;
111         memcpy(buffer, &v9inode->qid.path, sizeof(v9inode->qid.path));
112         p9_debug(P9_DEBUG_FSC, "inode %p get key %llu\n",
113                  &v9inode->vfs_inode, v9inode->qid.path);
114         return sizeof(v9inode->qid.path);
115 }
116 
117 static void v9fs_cache_inode_get_attr(const void *cookie_netfs_data,
118                                       uint64_t *size)
119 {
120         const struct v9fs_inode *v9inode = cookie_netfs_data;
121         *size = i_size_read(&v9inode->vfs_inode);
122 
123         p9_debug(P9_DEBUG_FSC, "inode %p get attr %llu\n",
124                  &v9inode->vfs_inode, *size);
125 }
126 
127 static uint16_t v9fs_cache_inode_get_aux(const void *cookie_netfs_data,
128                                          void *buffer, uint16_t buflen)
129 {
130         const struct v9fs_inode *v9inode = cookie_netfs_data;
131         memcpy(buffer, &v9inode->qid.version, sizeof(v9inode->qid.version));
132         p9_debug(P9_DEBUG_FSC, "inode %p get aux %u\n",
133                  &v9inode->vfs_inode, v9inode->qid.version);
134         return sizeof(v9inode->qid.version);
135 }
136 
137 static enum
138 fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
139                                             const void *buffer,
140                                             uint16_t buflen)
141 {
142         const struct v9fs_inode *v9inode = cookie_netfs_data;
143 
144         if (buflen != sizeof(v9inode->qid.version))
145                 return FSCACHE_CHECKAUX_OBSOLETE;
146 
147         if (memcmp(buffer, &v9inode->qid.version,
148                    sizeof(v9inode->qid.version)))
149                 return FSCACHE_CHECKAUX_OBSOLETE;
150 
151         return FSCACHE_CHECKAUX_OKAY;
152 }
153 
154 static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
155 {
156         struct v9fs_inode *v9inode = cookie_netfs_data;
157         struct pagevec pvec;
158         pgoff_t first;
159         int loop, nr_pages;
160 
161         pagevec_init(&pvec, 0);
162         first = 0;
163 
164         for (;;) {
165                 nr_pages = pagevec_lookup(&pvec, v9inode->vfs_inode.i_mapping,
166                                           first,
167                                           PAGEVEC_SIZE - pagevec_count(&pvec));
168                 if (!nr_pages)
169                         break;
170 
171                 for (loop = 0; loop < nr_pages; loop++)
172                         ClearPageFsCache(pvec.pages[loop]);
173 
174                 first = pvec.pages[nr_pages - 1]->index + 1;
175 
176                 pvec.nr = nr_pages;
177                 pagevec_release(&pvec);
178                 cond_resched();
179         }
180 }
181 
182 const struct fscache_cookie_def v9fs_cache_inode_index_def = {
183         .name           = "9p.inode",
184         .type           = FSCACHE_COOKIE_TYPE_DATAFILE,
185         .get_key        = v9fs_cache_inode_get_key,
186         .get_attr       = v9fs_cache_inode_get_attr,
187         .get_aux        = v9fs_cache_inode_get_aux,
188         .check_aux      = v9fs_cache_inode_check_aux,
189         .now_uncached   = v9fs_cache_inode_now_uncached,
190 };
191 
192 void v9fs_cache_inode_get_cookie(struct inode *inode)
193 {
194         struct v9fs_inode *v9inode;
195         struct v9fs_session_info *v9ses;
196 
197         if (!S_ISREG(inode->i_mode))
198                 return;
199 
200         v9inode = V9FS_I(inode);
201         if (v9inode->fscache)
202                 return;
203 
204         v9ses = v9fs_inode2v9ses(inode);
205         v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
206                                                   &v9fs_cache_inode_index_def,
207                                                   v9inode, true);
208 
209         p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
210                  inode, v9inode->fscache);
211 }
212 
213 void v9fs_cache_inode_put_cookie(struct inode *inode)
214 {
215         struct v9fs_inode *v9inode = V9FS_I(inode);
216 
217         if (!v9inode->fscache)
218                 return;
219         p9_debug(P9_DEBUG_FSC, "inode %p put cookie %p\n",
220                  inode, v9inode->fscache);
221 
222         fscache_relinquish_cookie(v9inode->fscache, 0);
223         v9inode->fscache = NULL;
224 }
225 
226 void v9fs_cache_inode_flush_cookie(struct inode *inode)
227 {
228         struct v9fs_inode *v9inode = V9FS_I(inode);
229 
230         if (!v9inode->fscache)
231                 return;
232         p9_debug(P9_DEBUG_FSC, "inode %p flush cookie %p\n",
233                  inode, v9inode->fscache);
234 
235         fscache_relinquish_cookie(v9inode->fscache, 1);
236         v9inode->fscache = NULL;
237 }
238 
239 void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
240 {
241         struct v9fs_inode *v9inode = V9FS_I(inode);
242 
243         if (!v9inode->fscache)
244                 return;
245 
246         mutex_lock(&v9inode->fscache_lock);
247 
248         if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
249                 v9fs_cache_inode_flush_cookie(inode);
250         else
251                 v9fs_cache_inode_get_cookie(inode);
252 
253         mutex_unlock(&v9inode->fscache_lock);
254 }
255 
256 void v9fs_cache_inode_reset_cookie(struct inode *inode)
257 {
258         struct v9fs_inode *v9inode = V9FS_I(inode);
259         struct v9fs_session_info *v9ses;
260         struct fscache_cookie *old;
261 
262         if (!v9inode->fscache)
263                 return;
264 
265         old = v9inode->fscache;
266 
267         mutex_lock(&v9inode->fscache_lock);
268         fscache_relinquish_cookie(v9inode->fscache, 1);
269 
270         v9ses = v9fs_inode2v9ses(inode);
271         v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
272                                                   &v9fs_cache_inode_index_def,
273                                                   v9inode, true);
274         p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
275                  inode, old, v9inode->fscache);
276 
277         mutex_unlock(&v9inode->fscache_lock);
278 }
279 
280 int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
281 {
282         struct inode *inode = page->mapping->host;
283         struct v9fs_inode *v9inode = V9FS_I(inode);
284 
285         BUG_ON(!v9inode->fscache);
286 
287         return fscache_maybe_release_page(v9inode->fscache, page, gfp);
288 }
289 
290 void __v9fs_fscache_invalidate_page(struct page *page)
291 {
292         struct inode *inode = page->mapping->host;
293         struct v9fs_inode *v9inode = V9FS_I(inode);
294 
295         BUG_ON(!v9inode->fscache);
296 
297         if (PageFsCache(page)) {
298                 fscache_wait_on_page_write(v9inode->fscache, page);
299                 BUG_ON(!PageLocked(page));
300                 fscache_uncache_page(v9inode->fscache, page);
301         }
302 }
303 
304 static void v9fs_vfs_readpage_complete(struct page *page, void *data,
305                                        int error)
306 {
307         if (!error)
308                 SetPageUptodate(page);
309 
310         unlock_page(page);
311 }
312 
313 /**
314  * __v9fs_readpage_from_fscache - read a page from cache
315  *
316  * Returns 0 if the pages are in cache and a BIO is submitted,
317  * 1 if the pages are not in cache and -error otherwise.
318  */
319 
320 int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
321 {
322         int ret;
323         const struct v9fs_inode *v9inode = V9FS_I(inode);
324 
325         p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
326         if (!v9inode->fscache)
327                 return -ENOBUFS;
328 
329         ret = fscache_read_or_alloc_page(v9inode->fscache,
330                                          page,
331                                          v9fs_vfs_readpage_complete,
332                                          NULL,
333                                          GFP_KERNEL);
334         switch (ret) {
335         case -ENOBUFS:
336         case -ENODATA:
337                 p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
338                 return 1;
339         case 0:
340                 p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
341                 return ret;
342         default:
343                 p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
344                 return ret;
345         }
346 }
347 
348 /**
349  * __v9fs_readpages_from_fscache - read multiple pages from cache
350  *
351  * Returns 0 if the pages are in cache and a BIO is submitted,
352  * 1 if the pages are not in cache and -error otherwise.
353  */
354 
355 int __v9fs_readpages_from_fscache(struct inode *inode,
356                                   struct address_space *mapping,
357                                   struct list_head *pages,
358                                   unsigned *nr_pages)
359 {
360         int ret;
361         const struct v9fs_inode *v9inode = V9FS_I(inode);
362 
363         p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
364         if (!v9inode->fscache)
365                 return -ENOBUFS;
366 
367         ret = fscache_read_or_alloc_pages(v9inode->fscache,
368                                           mapping, pages, nr_pages,
369                                           v9fs_vfs_readpage_complete,
370                                           NULL,
371                                           mapping_gfp_mask(mapping));
372         switch (ret) {
373         case -ENOBUFS:
374         case -ENODATA:
375                 p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
376                 return 1;
377         case 0:
378                 BUG_ON(!list_empty(pages));
379                 BUG_ON(*nr_pages != 0);
380                 p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
381                 return ret;
382         default:
383                 p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
384                 return ret;
385         }
386 }
387 
388 /**
389  * __v9fs_readpage_to_fscache - write a page to the cache
390  *
391  */
392 
393 void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
394 {
395         int ret;
396         const struct v9fs_inode *v9inode = V9FS_I(inode);
397 
398         p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
399         ret = fscache_write_page(v9inode->fscache, page, GFP_KERNEL);
400         p9_debug(P9_DEBUG_FSC, "ret =  %d\n", ret);
401         if (ret != 0)
402                 v9fs_uncache_page(inode, page);
403 }
404 
405 /*
406  * wait for a page to complete writing to the cache
407  */
408 void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
409 {
410         const struct v9fs_inode *v9inode = V9FS_I(inode);
411         p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
412         if (PageFsCache(page))
413                 fscache_wait_on_page_write(v9inode->fscache, page);
414 }
415 

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