fs/cachefiles/io.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* kiocb-using read/write
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/mount.h>
   9 #include <linux/slab.h>
  10 #include <linux/file.h>
  11 #include <linux/uio.h>
  12 #include <linux/sched/mm.h>
  13 #include <linux/netfs.h>
  14 #include "internal.h"
  15
  16 struct cachefiles_kiocb {
  17         struct kiocb            iocb;
  18         refcount_t              ki_refcnt;
  19         loff_t                  start;
  20         union {
  21                 size_t          skipped;
  22                 size_t          len;
  23         };
  24         netfs_io_terminated_t   term_func;
  25         void                    *term_func_priv;
  26         bool                    was_async;
  27 };
  28
  29 static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
  30 {
  31         if (refcount_dec_and_test(&ki->ki_refcnt)) {
  32                 fput(ki->iocb.ki_filp);
  33                 kfree(ki);
  34         }
  35 }
  36
  37 /*
  38  * Handle completion of a read from the cache.
  39  */
  40 static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2)
  41 {
  42         struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
  43
  44         _enter("%ld,%ld", ret, ret2);
  45
  46         if (ki->term_func) {
  47                 if (ret >= 0)
  48                         ret += ki->skipped;
  49                 ki->term_func(ki->term_func_priv, ret, ki->was_async);
  50         }
  51
  52         cachefiles_put_kiocb(ki);
  53 }
  54
  55 /*
  56  * Initiate a read from the cache.
  57  */
  58 static int cachefiles_read(struct netfs_cache_resources *cres,
  59                            loff_t start_pos,
  60                            struct iov_iter *iter,
  61                            bool seek_data,
  62                            netfs_io_terminated_t term_func,
  63                            void *term_func_priv)
  64 {
  65         struct cachefiles_kiocb *ki;
  66         struct file *file = cres->cache_priv2;
  67         unsigned int old_nofs;
  68         ssize_t ret = -ENOBUFS;
  69         size_t len = iov_iter_count(iter), skipped = 0;
  70
  71         _enter("%pD,%li,%llx,%zx/%llx",
  72                file, file_inode(file)->i_ino, start_pos, len,
  73                i_size_read(file->f_inode));
  74
  75         /* If the caller asked us to seek for data before doing the read, then
  76          * we should do that now.  If we find a gap, we fill it with zeros.
  77          */
  78         if (seek_data) {
  79                 loff_t off = start_pos, off2;
  80
  81                 off2 = vfs_llseek(file, off, SEEK_DATA);
  82                 if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
  83                         skipped = 0;
  84                         ret = off2;
  85                         goto presubmission_error;
  86                 }
  87
  88                 if (off2 == -ENXIO || off2 >= start_pos + len) {
  89                         /* The region is beyond the EOF or there's no more data
  90                          * in the region, so clear the rest of the buffer and
  91                          * return success.
  92                          */
  93                         iov_iter_zero(len, iter);
  94                         skipped = len;
  95                         ret = 0;
  96                         goto presubmission_error;
  97                 }
  98
  99                 skipped = off2 - off;
 100                 iov_iter_zero(skipped, iter);
 101         }
 102
 103         ret = -ENOBUFS;
 104         ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
 105         if (!ki)
 106                 goto presubmission_error;
 107
 108         refcount_set(&ki->ki_refcnt, 2);
 109         ki->iocb.ki_filp        = file;
 110         ki->iocb.ki_pos         = start_pos + skipped;
 111         ki->iocb.ki_flags       = IOCB_DIRECT;
 112         ki->iocb.ki_hint        = ki_hint_validate(file_write_hint(file));
 113         ki->iocb.ki_ioprio      = get_current_ioprio();
 114         ki->skipped             = skipped;
 115         ki->term_func           = term_func;
 116         ki->term_func_priv      = term_func_priv;
 117         ki->was_async           = true;
 118
 119         if (ki->term_func)
 120                 ki->iocb.ki_complete = cachefiles_read_complete;
 121
 122         get_file(ki->iocb.ki_filp);
 123
 124         old_nofs = memalloc_nofs_save();
 125         ret = vfs_iocb_iter_read(file, &ki->iocb, iter);
 126         memalloc_nofs_restore(old_nofs);
 127         switch (ret) {
 128         case -EIOCBQUEUED:
 129                 goto in_progress;
 130
 131         case -ERESTARTSYS:
 132         case -ERESTARTNOINTR:
 133         case -ERESTARTNOHAND:
 134         case -ERESTART_RESTARTBLOCK:
 135                 /* There's no easy way to restart the syscall since other AIO's
 136                  * may be already running. Just fail this IO with EINTR.
 137                  */
 138                 ret = -EINTR;
 139                 fallthrough;
 140         default:
 141                 ki->was_async = false;
 142                 cachefiles_read_complete(&ki->iocb, ret, 0);
 143                 if (ret > 0)
 144                         ret = 0;
 145                 break;
 146         }
 147
 148 in_progress:
 149         cachefiles_put_kiocb(ki);
 150         _leave(" = %zd", ret);
 151         return ret;
 152
 153 presubmission_error:
 154         if (term_func)
 155                 term_func(term_func_priv, ret < 0 ? ret : skipped, false);
 156         return ret;
 157 }
 158
 159 /*
 160  * Handle completion of a write to the cache.
 161  */
 162 static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2)
 163 {
 164         struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
 165         struct inode *inode = file_inode(ki->iocb.ki_filp);
 166
 167         _enter("%ld,%ld", ret, ret2);
 168
 169         /* Tell lockdep we inherited freeze protection from submission thread */
 170         __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
 171         __sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
 172
 173         if (ki->term_func)
 174                 ki->term_func(ki->term_func_priv, ret, ki->was_async);
 175
 176         cachefiles_put_kiocb(ki);
 177 }
 178
 179 /*
 180  * Initiate a write to the cache.
 181  */
 182 static int cachefiles_write(struct netfs_cache_resources *cres,
 183                             loff_t start_pos,
 184                             struct iov_iter *iter,
 185                             netfs_io_terminated_t term_func,
 186                             void *term_func_priv)
 187 {
 188         struct cachefiles_kiocb *ki;
 189         struct inode *inode;
 190         struct file *file = cres->cache_priv2;
 191         unsigned int old_nofs;
 192         ssize_t ret = -ENOBUFS;
 193         size_t len = iov_iter_count(iter);
 194
 195         _enter("%pD,%li,%llx,%zx/%llx",
 196                file, file_inode(file)->i_ino, start_pos, len,
 197                i_size_read(file->f_inode));
 198
 199         ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
 200         if (!ki)
 201                 goto presubmission_error;
 202
 203         refcount_set(&ki->ki_refcnt, 2);
 204         ki->iocb.ki_filp        = file;
 205         ki->iocb.ki_pos         = start_pos;
 206         ki->iocb.ki_flags       = IOCB_DIRECT | IOCB_WRITE;
 207         ki->iocb.ki_hint        = ki_hint_validate(file_write_hint(file));
 208         ki->iocb.ki_ioprio      = get_current_ioprio();
 209         ki->start               = start_pos;
 210         ki->len                 = len;
 211         ki->term_func           = term_func;
 212         ki->term_func_priv      = term_func_priv;
 213         ki->was_async           = true;
 214
 215         if (ki->term_func)
 216                 ki->iocb.ki_complete = cachefiles_write_complete;
 217
 218         /* Open-code file_start_write here to grab freeze protection, which
 219          * will be released by another thread in aio_complete_rw().  Fool
 220          * lockdep by telling it the lock got released so that it doesn't
 221          * complain about the held lock when we return to userspace.
 222          */
 223         inode = file_inode(file);
 224         __sb_start_write(inode->i_sb, SB_FREEZE_WRITE);
 225         __sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
 226
 227         get_file(ki->iocb.ki_filp);
 228
 229         old_nofs = memalloc_nofs_save();
 230         ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
 231         memalloc_nofs_restore(old_nofs);
 232         switch (ret) {
 233         case -EIOCBQUEUED:
 234                 goto in_progress;
 235
 236         case -ERESTARTSYS:
 237         case -ERESTARTNOINTR:
 238         case -ERESTARTNOHAND:
 239         case -ERESTART_RESTARTBLOCK:
 240                 /* There's no easy way to restart the syscall since other AIO's
 241                  * may be already running. Just fail this IO with EINTR.
 242                  */
 243                 ret = -EINTR;
 244                 fallthrough;
 245         default:
 246                 ki->was_async = false;
 247                 cachefiles_write_complete(&ki->iocb, ret, 0);
 248                 if (ret > 0)
 249                         ret = 0;
 250                 break;
 251         }
 252
 253 in_progress:
 254         cachefiles_put_kiocb(ki);
 255         _leave(" = %zd", ret);
 256         return ret;
 257
 258 presubmission_error:
 259         if (term_func)
 260                 term_func(term_func_priv, -ENOMEM, false);
 261         return -ENOMEM;
 262 }
 263
 264 /*
 265  * Prepare a read operation, shortening it to a cached/uncached
 266  * boundary as appropriate.
 267  */
 268 static enum netfs_read_source cachefiles_prepare_read(struct netfs_read_subrequest *subreq,
 269                                                       loff_t i_size)
 270 {
 271         struct fscache_retrieval *op = subreq->rreq->cache_resources.cache_priv;
 272         struct cachefiles_object *object;
 273         struct cachefiles_cache *cache;
 274         const struct cred *saved_cred;
 275         struct file *file = subreq->rreq->cache_resources.cache_priv2;
 276         loff_t off, to;
 277
 278         _enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
 279
 280         object = container_of(op->op.object,
 281                               struct cachefiles_object, fscache);
 282         cache = container_of(object->fscache.cache,
 283                              struct cachefiles_cache, cache);
 284
 285         if (!file)
 286                 goto cache_fail_nosec;
 287
 288         if (subreq->start >= i_size)
 289                 return NETFS_FILL_WITH_ZEROES;
 290
 291         cachefiles_begin_secure(cache, &saved_cred);
 292
 293         off = vfs_llseek(file, subreq->start, SEEK_DATA);
 294         if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
 295                 if (off == (loff_t)-ENXIO)
 296                         goto download_and_store;
 297                 goto cache_fail;
 298         }
 299
 300         if (off >= subreq->start + subreq->len)
 301                 goto download_and_store;
 302
 303         if (off > subreq->start) {
 304                 off = round_up(off, cache->bsize);
 305                 subreq->len = off - subreq->start;
 306                 goto download_and_store;
 307         }
 308
 309         to = vfs_llseek(file, subreq->start, SEEK_HOLE);
 310         if (to < 0 && to >= (loff_t)-MAX_ERRNO)
 311                 goto cache_fail;
 312
 313         if (to < subreq->start + subreq->len) {
 314                 if (subreq->start + subreq->len >= i_size)
 315                         to = round_up(to, cache->bsize);
 316                 else
 317                         to = round_down(to, cache->bsize);
 318                 subreq->len = to - subreq->start;
 319         }
 320
 321         cachefiles_end_secure(cache, saved_cred);
 322         return NETFS_READ_FROM_CACHE;
 323
 324 download_and_store:
 325         if (cachefiles_has_space(cache, 0, (subreq->len + PAGE_SIZE - 1) / PAGE_SIZE) == 0)
 326                 __set_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
 327 cache_fail:
 328         cachefiles_end_secure(cache, saved_cred);
 329 cache_fail_nosec:
 330         return NETFS_DOWNLOAD_FROM_SERVER;
 331 }
 332
 333 /*
 334  * Prepare for a write to occur.
 335  */
 336 static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
 337                                     loff_t *_start, size_t *_len, loff_t i_size)
 338 {
 339         loff_t start = *_start;
 340         size_t len = *_len, down;
 341
 342         /* Round to DIO size */
 343         down = start - round_down(start, PAGE_SIZE);
 344         *_start = start - down;
 345         *_len = round_up(down + len, PAGE_SIZE);
 346         return 0;
 347 }
 348
 349 /*
 350  * Clean up an operation.
 351  */
 352 static void cachefiles_end_operation(struct netfs_cache_resources *cres)
 353 {
 354         struct fscache_retrieval *op = cres->cache_priv;
 355         struct file *file = cres->cache_priv2;
 356
 357         _enter("");
 358
 359         if (file)
 360                 fput(file);
 361         if (op) {
 362                 fscache_op_complete(&op->op, false);
 363                 fscache_put_retrieval(op);
 364         }
 365
 366         _leave("");
 367 }
 368
 369 static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
 370         .end_operation          = cachefiles_end_operation,
 371         .read                   = cachefiles_read,
 372         .write                  = cachefiles_write,
 373         .prepare_read           = cachefiles_prepare_read,
 374         .prepare_write          = cachefiles_prepare_write,
 375 };
 376
 377 /*
 378  * Open the cache file when beginning a cache operation.
 379  */
 380 int cachefiles_begin_read_operation(struct netfs_read_request *rreq,
 381                                     struct fscache_retrieval *op)
 382 {
 383         struct cachefiles_object *object;
 384         struct cachefiles_cache *cache;
 385         struct path path;
 386         struct file *file;
 387
 388         _enter("");
 389
 390         object = container_of(op->op.object,
 391                               struct cachefiles_object, fscache);
 392         cache = container_of(object->fscache.cache,
 393                              struct cachefiles_cache, cache);
 394
 395         path.mnt = cache->mnt;
 396         path.dentry = object->backer;
 397         file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
 398                                    d_inode(object->backer), cache->cache_cred);
 399         if (IS_ERR(file))
 400                 return PTR_ERR(file);
 401         if (!S_ISREG(file_inode(file)->i_mode))
 402                 goto error_file;
 403         if (unlikely(!file->f_op->read_iter) ||
 404             unlikely(!file->f_op->write_iter)) {
 405                 pr_notice("Cache does not support read_iter and write_iter\n");
 406                 goto error_file;
 407         }
 408
 409         fscache_get_retrieval(op);
 410         rreq->cache_resources.cache_priv = op;
 411         rreq->cache_resources.cache_priv2 = file;
 412         rreq->cache_resources.ops = &cachefiles_netfs_cache_ops;
 413         rreq->cookie_debug_id = object->fscache.debug_id;
 414         _leave("");
 415         return 0;
 416
 417 error_file:
 418         fput(file);
 419         return -EIO;
 420 }