fs/cachefiles/interface.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* FS-Cache interface to CacheFiles
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/slab.h>
   9 #include <linux/mount.h>
  10 #include <linux/xattr.h>
  11 #include <linux/file.h>
  12 #include <linux/falloc.h>
  13 #include <trace/events/fscache.h>
  14 #include "internal.h"
  15
  16 static atomic_t cachefiles_object_debug_id;
  17
  18 /*
  19  * Allocate a cache object record.
  20  */
  21 static
  22 struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
  23 {
  24         struct fscache_volume *vcookie = cookie->volume;
  25         struct cachefiles_volume *volume = vcookie->cache_priv;
  26         struct cachefiles_object *object;
  27
  28         _enter("{%s},%x,", vcookie->key, cookie->debug_id);
  29
  30         object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
  31         if (!object)
  32                 return NULL;
  33
  34         refcount_set(&object->ref, 1);
  35
  36         spin_lock_init(&object->lock);
  37         INIT_LIST_HEAD(&object->cache_link);
  38         object->volume = volume;
  39         object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
  40         object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
  41
  42         fscache_count_object(vcookie->cache);
  43         trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
  44                              cachefiles_obj_new);
  45         return object;
  46 }
  47
  48 /*
  49  * Note that an object has been seen.
  50  */
  51 void cachefiles_see_object(struct cachefiles_object *object,
  52                            enum cachefiles_obj_ref_trace why)
  53 {
  54         trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
  55                              refcount_read(&object->ref), why);
  56 }
  57
  58 /*
  59  * Increment the usage count on an object;
  60  */
  61 struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
  62                                                  enum cachefiles_obj_ref_trace why)
  63 {
  64         int r;
  65
  66         __refcount_inc(&object->ref, &r);
  67         trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
  68         return object;
  69 }
  70
  71 /*
  72  * dispose of a reference to an object
  73  */
  74 void cachefiles_put_object(struct cachefiles_object *object,
  75                            enum cachefiles_obj_ref_trace why)
  76 {
  77         unsigned int object_debug_id = object->debug_id;
  78         unsigned int cookie_debug_id = object->cookie->debug_id;
  79         struct fscache_cache *cache;
  80         bool done;
  81         int r;
  82
  83         done = __refcount_dec_and_test(&object->ref, &r);
  84         trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
  85         if (done) {
  86                 _debug("- kill object OBJ%x", object_debug_id);
  87
  88                 ASSERTCMP(object->file, ==, NULL);
  89
  90                 kfree(object->d_name);
  91
  92                 cache = object->volume->cache->cache;
  93                 fscache_put_cookie(object->cookie, fscache_cookie_put_object);
  94                 object->cookie = NULL;
  95                 kmem_cache_free(cachefiles_object_jar, object);
  96                 fscache_uncount_object(cache);
  97         }
  98
  99         _leave("");
 100 }
 101
 102 /*
 103  * Adjust the size of a cache file if necessary to match the DIO size.  We keep
 104  * the EOF marker a multiple of DIO blocks so that we don't fall back to doing
 105  * non-DIO for a partial block straddling the EOF, but we also have to be
 106  * careful of someone expanding the file and accidentally accreting the
 107  * padding.
 108  */
 109 static int cachefiles_adjust_size(struct cachefiles_object *object)
 110 {
 111         struct iattr newattrs;
 112         struct file *file = object->file;
 113         uint64_t ni_size;
 114         loff_t oi_size;
 115         int ret;
 116
 117         ni_size = object->cookie->object_size;
 118         ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
 119
 120         _enter("{OBJ%x},[%llu]",
 121                object->debug_id, (unsigned long long) ni_size);
 122
 123         if (!file)
 124                 return -ENOBUFS;
 125
 126         oi_size = i_size_read(file_inode(file));
 127         if (oi_size == ni_size)
 128                 return 0;
 129
 130         inode_lock(file_inode(file));
 131
 132         /* if there's an extension to a partial page at the end of the backing
 133          * file, we need to discard the partial page so that we pick up new
 134          * data after it */
 135         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 136                 _debug("discard tail %llx", oi_size);
 137                 newattrs.ia_valid = ATTR_SIZE;
 138                 newattrs.ia_size = oi_size & PAGE_MASK;
 139                 ret = cachefiles_inject_remove_error();
 140                 if (ret == 0)
 141                         ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
 142                                             &newattrs, NULL);
 143                 if (ret < 0)
 144                         goto truncate_failed;
 145         }
 146
 147         newattrs.ia_valid = ATTR_SIZE;
 148         newattrs.ia_size = ni_size;
 149         ret = cachefiles_inject_write_error();
 150         if (ret == 0)
 151                 ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
 152                                     &newattrs, NULL);
 153
 154 truncate_failed:
 155         inode_unlock(file_inode(file));
 156
 157         if (ret < 0)
 158                 trace_cachefiles_io_error(NULL, file_inode(file), ret,
 159                                           cachefiles_trace_notify_change_error);
 160         if (ret == -EIO) {
 161                 cachefiles_io_error_obj(object, "Size set failed");
 162                 ret = -ENOBUFS;
 163         }
 164
 165         _leave(" = %d", ret);
 166         return ret;
 167 }
 168
 169 /*
 170  * Attempt to look up the nominated node in this cache
 171  */
 172 static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
 173 {
 174         struct cachefiles_object *object;
 175         struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
 176         const struct cred *saved_cred;
 177         bool success;
 178
 179         object = cachefiles_alloc_object(cookie);
 180         if (!object)
 181                 goto fail;
 182
 183         _enter("{OBJ%x}", object->debug_id);
 184
 185         if (!cachefiles_cook_key(object))
 186                 goto fail_put;
 187
 188         cookie->cache_priv = object;
 189
 190         cachefiles_begin_secure(cache, &saved_cred);
 191
 192         success = cachefiles_look_up_object(object);
 193         if (!success)
 194                 goto fail_withdraw;
 195
 196         cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);
 197
 198         spin_lock(&cache->object_list_lock);
 199         list_add(&object->cache_link, &cache->object_list);
 200         spin_unlock(&cache->object_list_lock);
 201         cachefiles_adjust_size(object);
 202
 203         cachefiles_end_secure(cache, saved_cred);
 204         _leave(" = t");
 205         return true;
 206
 207 fail_withdraw:
 208         cachefiles_end_secure(cache, saved_cred);
 209         cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
 210         fscache_caching_failed(cookie);
 211         _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
 212         /* The caller holds an access count on the cookie, so we need them to
 213          * drop it before we can withdraw the object.
 214          */
 215         return false;
 216
 217 fail_put:
 218         cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
 219 fail:
 220         return false;
 221 }
 222
 223 /*
 224  * Shorten the backing object to discard any dirty data and free up
 225  * any unused granules.
 226  */
 227 static bool cachefiles_shorten_object(struct cachefiles_object *object,
 228                                       struct file *file, loff_t new_size)
 229 {
 230         struct cachefiles_cache *cache = object->volume->cache;
 231         struct inode *inode = file_inode(file);
 232         loff_t i_size, dio_size;
 233         int ret;
 234
 235         dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
 236         i_size = i_size_read(inode);
 237
 238         trace_cachefiles_trunc(object, inode, i_size, dio_size,
 239                                cachefiles_trunc_shrink);
 240         ret = cachefiles_inject_remove_error();
 241         if (ret == 0)
 242                 ret = vfs_truncate(&file->f_path, dio_size);
 243         if (ret < 0) {
 244                 trace_cachefiles_io_error(object, file_inode(file), ret,
 245                                           cachefiles_trace_trunc_error);
 246                 cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
 247                 cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
 248                 return false;
 249         }
 250
 251         if (new_size < dio_size) {
 252                 trace_cachefiles_trunc(object, inode, dio_size, new_size,
 253                                        cachefiles_trunc_dio_adjust);
 254                 ret = cachefiles_inject_write_error();
 255                 if (ret == 0)
 256                         ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
 257                                             new_size, dio_size - new_size);
 258                 if (ret < 0) {
 259                         trace_cachefiles_io_error(object, file_inode(file), ret,
 260                                                   cachefiles_trace_fallocate_error);
 261                         cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
 262                         cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
 263                         return false;
 264                 }
 265         }
 266
 267         return true;
 268 }
 269
 270 /*
 271  * Resize the backing object.
 272  */
 273 static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
 274                                      loff_t new_size)
 275 {
 276         struct cachefiles_object *object = cachefiles_cres_object(cres);
 277         struct cachefiles_cache *cache = object->volume->cache;
 278         struct fscache_cookie *cookie = object->cookie;
 279         const struct cred *saved_cred;
 280         struct file *file = cachefiles_cres_file(cres);
 281         loff_t old_size = cookie->object_size;
 282
 283         _enter("%llu->%llu", old_size, new_size);
 284
 285         if (new_size < old_size) {
 286                 cachefiles_begin_secure(cache, &saved_cred);
 287                 cachefiles_shorten_object(object, file, new_size);
 288                 cachefiles_end_secure(cache, saved_cred);
 289                 object->cookie->object_size = new_size;
 290                 return;
 291         }
 292
 293         /* The file is being expanded.  We don't need to do anything
 294          * particularly.  cookie->initial_size doesn't change and so the point
 295          * at which we have to download before doesn't change.
 296          */
 297         cookie->object_size = new_size;
 298 }
 299
 300 /*
 301  * Commit changes to the object as we drop it.
 302  */
 303 static void cachefiles_commit_object(struct cachefiles_object *object,
 304                                      struct cachefiles_cache *cache)
 305 {
 306         bool update = false;
 307
 308         if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
 309                 update = true;
 310         if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
 311                 update = true;
 312         if (update)
 313                 cachefiles_set_object_xattr(object);
 314
 315         if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
 316                 cachefiles_commit_tmpfile(cache, object);
 317 }
 318
 319 /*
 320  * Finalise and object and close the VFS structs that we have.
 321  */
 322 static void cachefiles_clean_up_object(struct cachefiles_object *object,
 323                                        struct cachefiles_cache *cache)
 324 {
 325         if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
 326                 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 327                         cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
 328                         _debug("- inval object OBJ%x", object->debug_id);
 329                         cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
 330                 } else {
 331                         cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
 332                         _debug("- inval object OBJ%x tmpfile", object->debug_id);
 333                 }
 334         } else {
 335                 cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
 336                 cachefiles_commit_object(object, cache);
 337         }
 338
 339         cachefiles_unmark_inode_in_use(object, object->file);
 340         if (object->file) {
 341                 fput(object->file);
 342                 object->file = NULL;
 343         }
 344 }
 345
 346 /*
 347  * Withdraw caching for a cookie.
 348  */
 349 static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
 350 {
 351         struct cachefiles_object *object = cookie->cache_priv;
 352         struct cachefiles_cache *cache = object->volume->cache;
 353         const struct cred *saved_cred;
 354
 355         _enter("o=%x", object->debug_id);
 356         cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
 357
 358         if (!list_empty(&object->cache_link)) {
 359                 spin_lock(&cache->object_list_lock);
 360                 cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
 361                 list_del_init(&object->cache_link);
 362                 spin_unlock(&cache->object_list_lock);
 363         }
 364
 365         cachefiles_ondemand_clean_object(object);
 366
 367         if (object->file) {
 368                 cachefiles_begin_secure(cache, &saved_cred);
 369                 cachefiles_clean_up_object(object, cache);
 370                 cachefiles_end_secure(cache, saved_cred);
 371         }
 372
 373         cookie->cache_priv = NULL;
 374         cachefiles_put_object(object, cachefiles_obj_put_detach);
 375 }
 376
 377 /*
 378  * Invalidate the storage associated with a cookie.
 379  */
 380 static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
 381 {
 382         struct cachefiles_object *object = cookie->cache_priv;
 383         struct file *new_file, *old_file;
 384         bool old_tmpfile;
 385
 386         _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
 387
 388         old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 389
 390         if (!object->file) {
 391                 fscache_resume_after_invalidation(cookie);
 392                 _leave(" = t [light]");
 393                 return true;
 394         }
 395
 396         new_file = cachefiles_create_tmpfile(object);
 397         if (IS_ERR(new_file))
 398                 goto failed;
 399
 400         /* Substitute the VFS target */
 401         _debug("sub");
 402         spin_lock(&object->lock);
 403
 404         old_file = object->file;
 405         object->file = new_file;
 406         object->content_info = CACHEFILES_CONTENT_NO_DATA;
 407         set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 408         set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
 409
 410         spin_unlock(&object->lock);
 411         _debug("subbed");
 412
 413         /* Allow I/O to take place again */
 414         fscache_resume_after_invalidation(cookie);
 415
 416         if (old_file) {
 417                 if (!old_tmpfile) {
 418                         struct cachefiles_volume *volume = object->volume;
 419                         struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
 420
 421                         inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 422                         cachefiles_bury_object(volume->cache, object, fan,
 423                                                old_file->f_path.dentry,
 424                                                FSCACHE_OBJECT_INVALIDATED);
 425                 }
 426                 fput(old_file);
 427         }
 428
 429         _leave(" = t");
 430         return true;
 431
 432 failed:
 433         _leave(" = f");
 434         return false;
 435 }
 436
 437 const struct fscache_cache_ops cachefiles_cache_ops = {
 438         .name                   = "cachefiles",
 439         .acquire_volume         = cachefiles_acquire_volume,
 440         .free_volume            = cachefiles_free_volume,
 441         .lookup_cookie          = cachefiles_lookup_cookie,
 442         .withdraw_cookie        = cachefiles_withdraw_cookie,
 443         .invalidate_cookie      = cachefiles_invalidate_cookie,
 444         .begin_operation        = cachefiles_begin_operation,
 445         .resize_cookie          = cachefiles_resize_cookie,
 446         .prepare_to_write       = cachefiles_prepare_to_write,
 447 };