fs/nfs/read.c

   1 /*
   2  * linux/fs/nfs/read.c
   3  *
   4  * Block I/O for NFS
   5  *
   6  * Partial copy of Linus' read cache modifications to fs/nfs/file.c
   7  * modified for async RPC by okir@monad.swb.de
   8  */
   9
  10 #include <linux/time.h>
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/fcntl.h>
  14 #include <linux/stat.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/sunrpc/clnt.h>
  19 #include <linux/nfs_fs.h>
  20 #include <linux/nfs_page.h>
  21 #include <linux/module.h>
  22
  23 #include "nfs4_fs.h"
  24 #include "internal.h"
  25 #include "iostat.h"
  26 #include "fscache.h"
  27 #include "pnfs.h"
  28
  29 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  30
  31 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  32 static const struct nfs_rw_ops nfs_rw_read_ops;
  33
  34 static struct kmem_cache *nfs_rdata_cachep;
  35
  36 static struct nfs_pgio_header *nfs_readhdr_alloc(void)
  37 {
  38         return kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  39 }
  40
  41 static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
  42 {
  43         kmem_cache_free(nfs_rdata_cachep, rhdr);
  44 }
  45
  46 static
  47 int nfs_return_empty_page(struct page *page)
  48 {
  49         zero_user(page, 0, PAGE_CACHE_SIZE);
  50         SetPageUptodate(page);
  51         unlock_page(page);
  52         return 0;
  53 }
  54
  55 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
  56                               struct inode *inode, bool force_mds,
  57                               const struct nfs_pgio_completion_ops *compl_ops)
  58 {
  59         struct nfs_server *server = NFS_SERVER(inode);
  60         const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
  61
  62 #ifdef CONFIG_NFS_V4_1
  63         if (server->pnfs_curr_ld && !force_mds)
  64                 pg_ops = server->pnfs_curr_ld->pg_read_ops;
  65 #endif
  66         nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
  67                         server->rsize, 0);
  68 }
  69 EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
  70
  71 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
  72 {
  73         struct nfs_pgio_mirror *mirror;
  74
  75         pgio->pg_ops = &nfs_pgio_rw_ops;
  76
  77         /* read path should never have more than one mirror */
  78         WARN_ON_ONCE(pgio->pg_mirror_count != 1);
  79
  80         mirror = &pgio->pg_mirrors[0];
  81         mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
  82 }
  83 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
  84
  85 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
  86                        struct page *page)
  87 {
  88         struct nfs_page *new;
  89         unsigned int len;
  90         struct nfs_pageio_descriptor pgio;
  91         struct nfs_pgio_mirror *pgm;
  92
  93         len = nfs_page_length(page);
  94         if (len == 0)
  95                 return nfs_return_empty_page(page);
  96         new = nfs_create_request(ctx, page, NULL, 0, len);
  97         if (IS_ERR(new)) {
  98                 unlock_page(page);
  99                 return PTR_ERR(new);
 100         }
 101         if (len < PAGE_CACHE_SIZE)
 102                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 103
 104         nfs_pageio_init_read(&pgio, inode, false,
 105                              &nfs_async_read_completion_ops);
 106         nfs_pageio_add_request(&pgio, new);
 107         nfs_pageio_complete(&pgio);
 108
 109         /* It doesn't make sense to do mirrored reads! */
 110         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 111
 112         pgm = &pgio.pg_mirrors[0];
 113         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 114
 115         return 0;
 116 }
 117
 118 static void nfs_readpage_release(struct nfs_page *req)
 119 {
 120         struct inode *inode = d_inode(req->wb_context->dentry);
 121
 122         dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
 123                 (unsigned long long)NFS_FILEID(inode), req->wb_bytes,
 124                 (long long)req_offset(req));
 125
 126         if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
 127                 if (PageUptodate(req->wb_page))
 128                         nfs_readpage_to_fscache(inode, req->wb_page, 0);
 129
 130                 unlock_page(req->wb_page);
 131         }
 132         nfs_release_request(req);
 133 }
 134
 135 static void nfs_page_group_set_uptodate(struct nfs_page *req)
 136 {
 137         if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
 138                 SetPageUptodate(req->wb_page);
 139 }
 140
 141 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 142 {
 143         unsigned long bytes = 0;
 144
 145         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 146                 goto out;
 147         while (!list_empty(&hdr->pages)) {
 148                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 149                 struct page *page = req->wb_page;
 150                 unsigned long start = req->wb_pgbase;
 151                 unsigned long end = req->wb_pgbase + req->wb_bytes;
 152
 153                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 154                         /* note: regions of the page not covered by a
 155                          * request are zeroed in nfs_readpage_async /
 156                          * readpage_async_filler */
 157                         if (bytes > hdr->good_bytes) {
 158                                 /* nothing in this request was good, so zero
 159                                  * the full extent of the request */
 160                                 zero_user_segment(page, start, end);
 161
 162                         } else if (hdr->good_bytes - bytes < req->wb_bytes) {
 163                                 /* part of this request has good bytes, but
 164                                  * not all. zero the bad bytes */
 165                                 start += hdr->good_bytes - bytes;
 166                                 WARN_ON(start < req->wb_pgbase);
 167                                 zero_user_segment(page, start, end);
 168                         }
 169                 }
 170                 bytes += req->wb_bytes;
 171                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 172                         if (bytes <= hdr->good_bytes)
 173                                 nfs_page_group_set_uptodate(req);
 174                 } else
 175                         nfs_page_group_set_uptodate(req);
 176                 nfs_list_remove_request(req);
 177                 nfs_readpage_release(req);
 178         }
 179 out:
 180         hdr->release(hdr);
 181 }
 182
 183 static void nfs_initiate_read(struct nfs_pgio_header *hdr,
 184                               struct rpc_message *msg,
 185                               const struct nfs_rpc_ops *rpc_ops,
 186                               struct rpc_task_setup *task_setup_data, int how)
 187 {
 188         struct inode *inode = hdr->inode;
 189         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 190
 191         task_setup_data->flags |= swap_flags;
 192         rpc_ops->read_setup(hdr, msg);
 193 }
 194
 195 static void
 196 nfs_async_read_error(struct list_head *head)
 197 {
 198         struct nfs_page *req;
 199
 200         while (!list_empty(head)) {
 201                 req = nfs_list_entry(head->next);
 202                 nfs_list_remove_request(req);
 203                 nfs_readpage_release(req);
 204         }
 205 }
 206
 207 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 208         .error_cleanup = nfs_async_read_error,
 209         .completion = nfs_read_completion,
 210 };
 211
 212 /*
 213  * This is the callback from RPC telling us whether a reply was
 214  * received or some error occurred (timeout or socket shutdown).
 215  */
 216 static int nfs_readpage_done(struct rpc_task *task,
 217                              struct nfs_pgio_header *hdr,
 218                              struct inode *inode)
 219 {
 220         int status = NFS_PROTO(inode)->read_done(task, hdr);
 221         if (status != 0)
 222                 return status;
 223
 224         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
 225
 226         if (task->tk_status == -ESTALE) {
 227                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 228                 nfs_mark_for_revalidate(inode);
 229         }
 230         return 0;
 231 }
 232
 233 static void nfs_readpage_retry(struct rpc_task *task,
 234                                struct nfs_pgio_header *hdr)
 235 {
 236         struct nfs_pgio_args *argp = &hdr->args;
 237         struct nfs_pgio_res  *resp = &hdr->res;
 238
 239         /* This is a short read! */
 240         nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
 241         /* Has the server at least made some progress? */
 242         if (resp->count == 0) {
 243                 nfs_set_pgio_error(hdr, -EIO, argp->offset);
 244                 return;
 245         }
 246         /* Yes, so retry the read at the end of the hdr */
 247         hdr->mds_offset += resp->count;
 248         argp->offset += resp->count;
 249         argp->pgbase += resp->count;
 250         argp->count -= resp->count;
 251         rpc_restart_call_prepare(task);
 252 }
 253
 254 static void nfs_readpage_result(struct rpc_task *task,
 255                                 struct nfs_pgio_header *hdr)
 256 {
 257         if (hdr->res.eof) {
 258                 loff_t bound;
 259
 260                 bound = hdr->args.offset + hdr->res.count;
 261                 spin_lock(&hdr->lock);
 262                 if (bound < hdr->io_start + hdr->good_bytes) {
 263                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 264                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 265                         hdr->good_bytes = bound - hdr->io_start;
 266                 }
 267                 spin_unlock(&hdr->lock);
 268         } else if (hdr->res.count != hdr->args.count)
 269                 nfs_readpage_retry(task, hdr);
 270 }
 271
 272 /*
 273  * Read a page over NFS.
 274  * We read the page synchronously in the following case:
 275  *  -   The error flag is set for this page. This happens only when a
 276  *      previous async read operation failed.
 277  */
 278 int nfs_readpage(struct file *file, struct page *page)
 279 {
 280         struct nfs_open_context *ctx;
 281         struct inode *inode = page_file_mapping(page)->host;
 282         int             error;
 283
 284         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 285                 page, PAGE_CACHE_SIZE, page_file_index(page));
 286         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 287         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 288
 289         /*
 290          * Try to flush any pending writes to the file..
 291          *
 292          * NOTE! Because we own the page lock, there cannot
 293          * be any new pending writes generated at this point
 294          * for this page (other pages can be written to).
 295          */
 296         error = nfs_wb_page(inode, page);
 297         if (error)
 298                 goto out_unlock;
 299         if (PageUptodate(page))
 300                 goto out_unlock;
 301
 302         error = -ESTALE;
 303         if (NFS_STALE(inode))
 304                 goto out_unlock;
 305
 306         if (file == NULL) {
 307                 error = -EBADF;
 308                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 309                 if (ctx == NULL)
 310                         goto out_unlock;
 311         } else
 312                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 313
 314         if (!IS_SYNC(inode)) {
 315                 error = nfs_readpage_from_fscache(ctx, inode, page);
 316                 if (error == 0)
 317                         goto out;
 318         }
 319
 320         error = nfs_readpage_async(ctx, inode, page);
 321
 322 out:
 323         put_nfs_open_context(ctx);
 324         return error;
 325 out_unlock:
 326         unlock_page(page);
 327         return error;
 328 }
 329
 330 struct nfs_readdesc {
 331         struct nfs_pageio_descriptor *pgio;
 332         struct nfs_open_context *ctx;
 333 };
 334
 335 static int
 336 readpage_async_filler(void *data, struct page *page)
 337 {
 338         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 339         struct nfs_page *new;
 340         unsigned int len;
 341         int error;
 342
 343         len = nfs_page_length(page);
 344         if (len == 0)
 345                 return nfs_return_empty_page(page);
 346
 347         new = nfs_create_request(desc->ctx, page, NULL, 0, len);
 348         if (IS_ERR(new))
 349                 goto out_error;
 350
 351         if (len < PAGE_CACHE_SIZE)
 352                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 353         if (!nfs_pageio_add_request(desc->pgio, new)) {
 354                 error = desc->pgio->pg_error;
 355                 goto out_unlock;
 356         }
 357         return 0;
 358 out_error:
 359         error = PTR_ERR(new);
 360 out_unlock:
 361         unlock_page(page);
 362         return error;
 363 }
 364
 365 int nfs_readpages(struct file *filp, struct address_space *mapping,
 366                 struct list_head *pages, unsigned nr_pages)
 367 {
 368         struct nfs_pageio_descriptor pgio;
 369         struct nfs_pgio_mirror *pgm;
 370         struct nfs_readdesc desc = {
 371                 .pgio = &pgio,
 372         };
 373         struct inode *inode = mapping->host;
 374         unsigned long npages;
 375         int ret = -ESTALE;
 376
 377         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 378                         inode->i_sb->s_id,
 379                         (unsigned long long)NFS_FILEID(inode),
 380                         nr_pages);
 381         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 382
 383         if (NFS_STALE(inode))
 384                 goto out;
 385
 386         if (filp == NULL) {
 387                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 388                 if (desc.ctx == NULL)
 389                         return -EBADF;
 390         } else
 391                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 392
 393         /* attempt to read as many of the pages as possible from the cache
 394          * - this returns -ENOBUFS immediately if the cookie is negative
 395          */
 396         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 397                                          pages, &nr_pages);
 398         if (ret == 0)
 399                 goto read_complete; /* all pages were read */
 400
 401         nfs_pageio_init_read(&pgio, inode, false,
 402                              &nfs_async_read_completion_ops);
 403
 404         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 405         nfs_pageio_complete(&pgio);
 406
 407         /* It doesn't make sense to do mirrored reads! */
 408         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 409
 410         pgm = &pgio.pg_mirrors[0];
 411         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 412         npages = (pgm->pg_bytes_written + PAGE_CACHE_SIZE - 1) >>
 413                  PAGE_CACHE_SHIFT;
 414         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 415 read_complete:
 416         put_nfs_open_context(desc.ctx);
 417 out:
 418         return ret;
 419 }
 420
 421 int __init nfs_init_readpagecache(void)
 422 {
 423         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 424                                              sizeof(struct nfs_pgio_header),
 425                                              0, SLAB_HWCACHE_ALIGN,
 426                                              NULL);
 427         if (nfs_rdata_cachep == NULL)
 428                 return -ENOMEM;
 429
 430         return 0;
 431 }
 432
 433 void nfs_destroy_readpagecache(void)
 434 {
 435         kmem_cache_destroy(nfs_rdata_cachep);
 436 }
 437
 438 static const struct nfs_rw_ops nfs_rw_read_ops = {
 439         .rw_mode                = FMODE_READ,
 440         .rw_alloc_header        = nfs_readhdr_alloc,
 441         .rw_free_header         = nfs_readhdr_free,
 442         .rw_done                = nfs_readpage_done,
 443         .rw_result              = nfs_readpage_result,
 444         .rw_initiate            = nfs_initiate_read,
 445 };