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         if (cachefiles_ondemand_init_obj_info(object, volume)) {
  35                 kmem_cache_free(cachefiles_object_jar, object);
  36                 return NULL;
  37         }
  38
  39         refcount_set(&object->ref, 1);
  40
  41         spin_lock_init(&object->lock);
  42         INIT_LIST_HEAD(&object->cache_link);
  43         object->volume = volume;
  44         object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
  45         object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
  46
  47         fscache_count_object(vcookie->cache);
  48         trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
  49                              cachefiles_obj_new);
  50         return object;
  51 }
  52
  53 /*
  54  * Note that an object has been seen.
  55  */
  56 void cachefiles_see_object(struct cachefiles_object *object,
  57                            enum cachefiles_obj_ref_trace why)
  58 {
  59         trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
  60                              refcount_read(&object->ref), why);
  61 }
  62
  63 /*
  64  * Increment the usage count on an object;
  65  */
  66 struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
  67                                                  enum cachefiles_obj_ref_trace why)
  68 {
  69         int r;
  70
  71         __refcount_inc(&object->ref, &r);
  72         trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
  73         return object;
  74 }
  75
  76 /*
  77  * dispose of a reference to an object
  78  */
  79 void cachefiles_put_object(struct cachefiles_object *object,
  80                            enum cachefiles_obj_ref_trace why)
  81 {
  82         unsigned int object_debug_id = object->debug_id;
  83         unsigned int cookie_debug_id = object->cookie->debug_id;
  84         struct fscache_cache *cache;
  85         bool done;
  86         int r;
  87
  88         done = __refcount_dec_and_test(&object->ref, &r);
  89         trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
  90         if (done) {
  91                 _debug("- kill object OBJ%x", object_debug_id);
  92
  93                 ASSERTCMP(object->file, ==, NULL);
  94
  95                 kfree(object->d_name);
  96                 cachefiles_ondemand_deinit_obj_info(object);
  97                 cache = object->volume->cache->cache;
  98                 fscache_put_cookie(object->cookie, fscache_cookie_put_object);
  99                 object->cookie = NULL;
 100                 kmem_cache_free(cachefiles_object_jar, object);
 101                 fscache_uncount_object(cache);
 102         }
 103
 104         _leave("");
 105 }
 106
 107 /*
 108  * Adjust the size of a cache file if necessary to match the DIO size.  We keep
 109  * the EOF marker a multiple of DIO blocks so that we don't fall back to doing
 110  * non-DIO for a partial block straddling the EOF, but we also have to be
 111  * careful of someone expanding the file and accidentally accreting the
 112  * padding.
 113  */
 114 static int cachefiles_adjust_size(struct cachefiles_object *object)
 115 {
 116         struct iattr newattrs;
 117         struct file *file = object->file;
 118         uint64_t ni_size;
 119         loff_t oi_size;
 120         int ret;
 121
 122         ni_size = object->cookie->object_size;
 123         ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
 124
 125         _enter("{OBJ%x},[%llu]",
 126                object->debug_id, (unsigned long long) ni_size);
 127
 128         if (!file)
 129                 return -ENOBUFS;
 130
 131         oi_size = i_size_read(file_inode(file));
 132         if (oi_size == ni_size)
 133                 return 0;
 134
 135         inode_lock(file_inode(file));
 136
 137         /* if there's an extension to a partial page at the end of the backing
 138          * file, we need to discard the partial page so that we pick up new
 139          * data after it */
 140         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 141                 _debug("discard tail %llx", oi_size);
 142                 newattrs.ia_valid = ATTR_SIZE;
 143                 newattrs.ia_size = oi_size & PAGE_MASK;
 144                 ret = cachefiles_inject_remove_error();
 145                 if (ret == 0)
 146                         ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
 147                                             &newattrs, NULL);
 148                 if (ret < 0)
 149                         goto truncate_failed;
 150         }
 151
 152         newattrs.ia_valid = ATTR_SIZE;
 153         newattrs.ia_size = ni_size;
 154         ret = cachefiles_inject_write_error();
 155         if (ret == 0)
 156                 ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
 157                                     &newattrs, NULL);
 158
 159 truncate_failed:
 160         inode_unlock(file_inode(file));
 161
 162         if (ret < 0)
 163                 trace_cachefiles_io_error(NULL, file_inode(file), ret,
 164                                           cachefiles_trace_notify_change_error);
 165         if (ret == -EIO) {
 166                 cachefiles_io_error_obj(object, "Size set failed");
 167                 ret = -ENOBUFS;
 168         }
 169
 170         _leave(" = %d", ret);
 171         return ret;
 172 }
 173
 174 /*
 175  * Attempt to look up the nominated node in this cache
 176  */
 177 static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
 178 {
 179         struct cachefiles_object *object;
 180         struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
 181         const struct cred *saved_cred;
 182         bool success;
 183
 184         object = cachefiles_alloc_object(cookie);
 185         if (!object)
 186                 goto fail;
 187
 188         _enter("{OBJ%x}", object->debug_id);
 189
 190         if (!cachefiles_cook_key(object))
 191                 goto fail_put;
 192
 193         cookie->cache_priv = object;
 194
 195         cachefiles_begin_secure(cache, &saved_cred);
 196
 197         success = cachefiles_look_up_object(object);
 198         if (!success)
 199                 goto fail_withdraw;
 200
 201         cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);
 202
 203         spin_lock(&cache->object_list_lock);
 204         list_add(&object->cache_link, &cache->object_list);
 205         spin_unlock(&cache->object_list_lock);
 206         cachefiles_adjust_size(object);
 207
 208         cachefiles_end_secure(cache, saved_cred);
 209         _leave(" = t");
 210         return true;
 211
 212 fail_withdraw:
 213         cachefiles_end_secure(cache, saved_cred);
 214         cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
 215         fscache_caching_failed(cookie);
 216         _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
 217         /* The caller holds an access count on the cookie, so we need them to
 218          * drop it before we can withdraw the object.
 219          */
 220         return false;
 221
 222 fail_put:
 223         cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
 224 fail:
 225         return false;
 226 }
 227
 228 /*
 229  * Shorten the backing object to discard any dirty data and free up
 230  * any unused granules.
 231  */
 232 static bool cachefiles_shorten_object(struct cachefiles_object *object,
 233                                       struct file *file, loff_t new_size)
 234 {
 235         struct cachefiles_cache *cache = object->volume->cache;
 236         struct inode *inode = file_inode(file);
 237         loff_t i_size, dio_size;
 238         int ret;
 239
 240         dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
 241         i_size = i_size_read(inode);
 242
 243         trace_cachefiles_trunc(object, inode, i_size, dio_size,
 244                                cachefiles_trunc_shrink);
 245         ret = cachefiles_inject_remove_error();
 246         if (ret == 0)
 247                 ret = vfs_truncate(&file->f_path, dio_size);
 248         if (ret < 0) {
 249                 trace_cachefiles_io_error(object, file_inode(file), ret,
 250                                           cachefiles_trace_trunc_error);
 251                 cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
 252                 cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
 253                 return false;
 254         }
 255
 256         if (new_size < dio_size) {
 257                 trace_cachefiles_trunc(object, inode, dio_size, new_size,
 258                                        cachefiles_trunc_dio_adjust);
 259                 ret = cachefiles_inject_write_error();
 260                 if (ret == 0)
 261                         ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
 262                                             new_size, dio_size - new_size);
 263                 if (ret < 0) {
 264                         trace_cachefiles_io_error(object, file_inode(file), ret,
 265                                                   cachefiles_trace_fallocate_error);
 266                         cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
 267                         cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
 268                         return false;
 269                 }
 270         }
 271
 272         return true;
 273 }
 274
 275 /*
 276  * Resize the backing object.
 277  */
 278 static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
 279                                      loff_t new_size)
 280 {
 281         struct cachefiles_object *object = cachefiles_cres_object(cres);
 282         struct cachefiles_cache *cache = object->volume->cache;
 283         struct fscache_cookie *cookie = object->cookie;
 284         const struct cred *saved_cred;
 285         struct file *file = cachefiles_cres_file(cres);
 286         loff_t old_size = cookie->object_size;
 287
 288         _enter("%llu->%llu", old_size, new_size);
 289
 290         if (new_size < old_size) {
 291                 cachefiles_begin_secure(cache, &saved_cred);
 292                 cachefiles_shorten_object(object, file, new_size);
 293                 cachefiles_end_secure(cache, saved_cred);
 294                 object->cookie->object_size = new_size;
 295                 return;
 296         }
 297
 298         /* The file is being expanded.  We don't need to do anything
 299          * particularly.  cookie->initial_size doesn't change and so the point
 300          * at which we have to download before doesn't change.
 301          */
 302         cookie->object_size = new_size;
 303 }
 304
 305 /*
 306  * Commit changes to the object as we drop it.
 307  */
 308 static void cachefiles_commit_object(struct cachefiles_object *object,
 309                                      struct cachefiles_cache *cache)
 310 {
 311         bool update = false;
 312
 313         if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
 314                 update = true;
 315         if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
 316                 update = true;
 317         if (update)
 318                 cachefiles_set_object_xattr(object);
 319
 320         if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
 321                 cachefiles_commit_tmpfile(cache, object);
 322 }
 323
 324 /*
 325  * Finalise and object and close the VFS structs that we have.
 326  */
 327 static void cachefiles_clean_up_object(struct cachefiles_object *object,
 328                                        struct cachefiles_cache *cache)
 329 {
 330         if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
 331                 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 332                         cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
 333                         _debug("- inval object OBJ%x", object->debug_id);
 334                         cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
 335                 } else {
 336                         cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
 337                         _debug("- inval object OBJ%x tmpfile", object->debug_id);
 338                 }
 339         } else {
 340                 cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
 341                 cachefiles_commit_object(object, cache);
 342         }
 343
 344         cachefiles_unmark_inode_in_use(object, object->file);
 345         if (object->file) {
 346                 fput(object->file);
 347                 object->file = NULL;
 348         }
 349 }
 350
 351 /*
 352  * Withdraw caching for a cookie.
 353  */
 354 static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
 355 {
 356         struct cachefiles_object *object = cookie->cache_priv;
 357         struct cachefiles_cache *cache = object->volume->cache;
 358         const struct cred *saved_cred;
 359
 360         _enter("o=%x", object->debug_id);
 361         cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
 362
 363         if (!list_empty(&object->cache_link)) {
 364                 spin_lock(&cache->object_list_lock);
 365                 cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
 366                 list_del_init(&object->cache_link);
 367                 spin_unlock(&cache->object_list_lock);
 368         }
 369
 370         cachefiles_ondemand_clean_object(object);
 371
 372         if (object->file) {
 373                 cachefiles_begin_secure(cache, &saved_cred);
 374                 cachefiles_clean_up_object(object, cache);
 375                 cachefiles_end_secure(cache, saved_cred);
 376         }
 377
 378         cookie->cache_priv = NULL;
 379         cachefiles_put_object(object, cachefiles_obj_put_detach);
 380 }
 381
 382 /*
 383  * Invalidate the storage associated with a cookie.
 384  */
 385 static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
 386 {
 387         struct cachefiles_object *object = cookie->cache_priv;
 388         struct file *new_file, *old_file;
 389         bool old_tmpfile;
 390
 391         _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
 392
 393         old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 394
 395         if (!object->file) {
 396                 fscache_resume_after_invalidation(cookie);
 397                 _leave(" = t [light]");
 398                 return true;
 399         }
 400
 401         new_file = cachefiles_create_tmpfile(object);
 402         if (IS_ERR(new_file))
 403                 goto failed;
 404
 405         /* Substitute the VFS target */
 406         _debug("sub");
 407         spin_lock(&object->lock);
 408
 409         old_file = object->file;
 410         object->file = new_file;
 411         object->content_info = CACHEFILES_CONTENT_NO_DATA;
 412         set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 413         set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
 414
 415         spin_unlock(&object->lock);
 416         _debug("subbed");
 417
 418         /* Allow I/O to take place again */
 419         fscache_resume_after_invalidation(cookie);
 420
 421         if (old_file) {
 422                 if (!old_tmpfile) {
 423                         struct cachefiles_volume *volume = object->volume;
 424                         struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
 425
 426                         inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 427                         cachefiles_bury_object(volume->cache, object, fan,
 428                                                old_file->f_path.dentry,
 429                                                FSCACHE_OBJECT_INVALIDATED);
 430                 }
 431                 fput(old_file);
 432         }
 433
 434         _leave(" = t");
 435         return true;
 436
 437 failed:
 438         _leave(" = f");
 439         return false;
 440 }
 441
 442 const struct fscache_cache_ops cachefiles_cache_ops = {
 443         .name                   = "cachefiles",
 444         .acquire_volume         = cachefiles_acquire_volume,
 445         .free_volume            = cachefiles_free_volume,
 446         .lookup_cookie          = cachefiles_lookup_cookie,
 447         .withdraw_cookie        = cachefiles_withdraw_cookie,
 448         .invalidate_cookie      = cachefiles_invalidate_cookie,
 449         .begin_operation        = cachefiles_begin_operation,
 450         .resize_cookie          = cachefiles_resize_cookie,
 451         .prepare_to_write       = cachefiles_prepare_to_write,
 452 };