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         if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
  76                 pgio->pg_ops->pg_cleanup(pgio);
  77
  78         pgio->pg_ops = &nfs_pgio_rw_ops;
  79
  80         /* read path should never have more than one mirror */
  81         WARN_ON_ONCE(pgio->pg_mirror_count != 1);
  82
  83         mirror = &pgio->pg_mirrors[0];
  84         mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
  85 }
  86 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
  87
  88 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
  89                        struct page *page)
  90 {
  91         struct nfs_page *new;
  92         unsigned int len;
  93         struct nfs_pageio_descriptor pgio;
  94         struct nfs_pgio_mirror *pgm;
  95
  96         len = nfs_page_length(page);
  97         if (len == 0)
  98                 return nfs_return_empty_page(page);
  99         new = nfs_create_request(ctx, page, NULL, 0, len);
 100         if (IS_ERR(new)) {
 101                 unlock_page(page);
 102                 return PTR_ERR(new);
 103         }
 104         if (len < PAGE_CACHE_SIZE)
 105                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 106
 107         nfs_pageio_init_read(&pgio, inode, false,
 108                              &nfs_async_read_completion_ops);
 109         nfs_pageio_add_request(&pgio, new);
 110         nfs_pageio_complete(&pgio);
 111
 112         /* It doesn't make sense to do mirrored reads! */
 113         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 114
 115         pgm = &pgio.pg_mirrors[0];
 116         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 117
 118         return 0;
 119 }
 120
 121 static void nfs_readpage_release(struct nfs_page *req)
 122 {
 123         struct inode *inode = d_inode(req->wb_context->dentry);
 124
 125         dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
 126                 (unsigned long long)NFS_FILEID(inode), req->wb_bytes,
 127                 (long long)req_offset(req));
 128
 129         if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
 130                 if (PageUptodate(req->wb_page))
 131                         nfs_readpage_to_fscache(inode, req->wb_page, 0);
 132
 133                 unlock_page(req->wb_page);
 134         }
 135         nfs_release_request(req);
 136 }
 137
 138 static void nfs_page_group_set_uptodate(struct nfs_page *req)
 139 {
 140         if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
 141                 SetPageUptodate(req->wb_page);
 142 }
 143
 144 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 145 {
 146         unsigned long bytes = 0;
 147
 148         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 149                 goto out;
 150         while (!list_empty(&hdr->pages)) {
 151                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 152                 struct page *page = req->wb_page;
 153                 unsigned long start = req->wb_pgbase;
 154                 unsigned long end = req->wb_pgbase + req->wb_bytes;
 155
 156                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 157                         /* note: regions of the page not covered by a
 158                          * request are zeroed in nfs_readpage_async /
 159                          * readpage_async_filler */
 160                         if (bytes > hdr->good_bytes) {
 161                                 /* nothing in this request was good, so zero
 162                                  * the full extent of the request */
 163                                 zero_user_segment(page, start, end);
 164
 165                         } else if (hdr->good_bytes - bytes < req->wb_bytes) {
 166                                 /* part of this request has good bytes, but
 167                                  * not all. zero the bad bytes */
 168                                 start += hdr->good_bytes - bytes;
 169                                 WARN_ON(start < req->wb_pgbase);
 170                                 zero_user_segment(page, start, end);
 171                         }
 172                 }
 173                 bytes += req->wb_bytes;
 174                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 175                         if (bytes <= hdr->good_bytes)
 176                                 nfs_page_group_set_uptodate(req);
 177                 } else
 178                         nfs_page_group_set_uptodate(req);
 179                 nfs_list_remove_request(req);
 180                 nfs_readpage_release(req);
 181         }
 182 out:
 183         hdr->release(hdr);
 184 }
 185
 186 static void nfs_initiate_read(struct nfs_pgio_header *hdr,
 187                               struct rpc_message *msg,
 188                               const struct nfs_rpc_ops *rpc_ops,
 189                               struct rpc_task_setup *task_setup_data, int how)
 190 {
 191         struct inode *inode = hdr->inode;
 192         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 193
 194         task_setup_data->flags |= swap_flags;
 195         rpc_ops->read_setup(hdr, msg);
 196 }
 197
 198 static void
 199 nfs_async_read_error(struct list_head *head)
 200 {
 201         struct nfs_page *req;
 202
 203         while (!list_empty(head)) {
 204                 req = nfs_list_entry(head->next);
 205                 nfs_list_remove_request(req);
 206                 nfs_readpage_release(req);
 207         }
 208 }
 209
 210 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 211         .error_cleanup = nfs_async_read_error,
 212         .completion = nfs_read_completion,
 213 };
 214
 215 /*
 216  * This is the callback from RPC telling us whether a reply was
 217  * received or some error occurred (timeout or socket shutdown).
 218  */
 219 static int nfs_readpage_done(struct rpc_task *task,
 220                              struct nfs_pgio_header *hdr,
 221                              struct inode *inode)
 222 {
 223         int status = NFS_PROTO(inode)->read_done(task, hdr);
 224         if (status != 0)
 225                 return status;
 226
 227         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
 228
 229         if (task->tk_status == -ESTALE) {
 230                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 231                 nfs_mark_for_revalidate(inode);
 232         }
 233         return 0;
 234 }
 235
 236 static void nfs_readpage_retry(struct rpc_task *task,
 237                                struct nfs_pgio_header *hdr)
 238 {
 239         struct nfs_pgio_args *argp = &hdr->args;
 240         struct nfs_pgio_res  *resp = &hdr->res;
 241
 242         /* This is a short read! */
 243         nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
 244         /* Has the server at least made some progress? */
 245         if (resp->count == 0) {
 246                 nfs_set_pgio_error(hdr, -EIO, argp->offset);
 247                 return;
 248         }
 249         /* Yes, so retry the read at the end of the hdr */
 250         hdr->mds_offset += resp->count;
 251         argp->offset += resp->count;
 252         argp->pgbase += resp->count;
 253         argp->count -= resp->count;
 254         rpc_restart_call_prepare(task);
 255 }
 256
 257 static void nfs_readpage_result(struct rpc_task *task,
 258                                 struct nfs_pgio_header *hdr)
 259 {
 260         if (hdr->res.eof) {
 261                 loff_t bound;
 262
 263                 bound = hdr->args.offset + hdr->res.count;
 264                 spin_lock(&hdr->lock);
 265                 if (bound < hdr->io_start + hdr->good_bytes) {
 266                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 267                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 268                         hdr->good_bytes = bound - hdr->io_start;
 269                 }
 270                 spin_unlock(&hdr->lock);
 271         } else if (hdr->res.count != hdr->args.count)
 272                 nfs_readpage_retry(task, hdr);
 273 }
 274
 275 /*
 276  * Read a page over NFS.
 277  * We read the page synchronously in the following case:
 278  *  -   The error flag is set for this page. This happens only when a
 279  *      previous async read operation failed.
 280  */
 281 int nfs_readpage(struct file *file, struct page *page)
 282 {
 283         struct nfs_open_context *ctx;
 284         struct inode *inode = page_file_mapping(page)->host;
 285         int             error;
 286
 287         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 288                 page, PAGE_CACHE_SIZE, page_file_index(page));
 289         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 290         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 291
 292         /*
 293          * Try to flush any pending writes to the file..
 294          *
 295          * NOTE! Because we own the page lock, there cannot
 296          * be any new pending writes generated at this point
 297          * for this page (other pages can be written to).
 298          */
 299         error = nfs_wb_page(inode, page);
 300         if (error)
 301                 goto out_unlock;
 302         if (PageUptodate(page))
 303                 goto out_unlock;
 304
 305         error = -ESTALE;
 306         if (NFS_STALE(inode))
 307                 goto out_unlock;
 308
 309         if (file == NULL) {
 310                 error = -EBADF;
 311                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 312                 if (ctx == NULL)
 313                         goto out_unlock;
 314         } else
 315                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 316
 317         if (!IS_SYNC(inode)) {
 318                 error = nfs_readpage_from_fscache(ctx, inode, page);
 319                 if (error == 0)
 320                         goto out;
 321         }
 322
 323         error = nfs_readpage_async(ctx, inode, page);
 324
 325 out:
 326         put_nfs_open_context(ctx);
 327         return error;
 328 out_unlock:
 329         unlock_page(page);
 330         return error;
 331 }
 332
 333 struct nfs_readdesc {
 334         struct nfs_pageio_descriptor *pgio;
 335         struct nfs_open_context *ctx;
 336 };
 337
 338 static int
 339 readpage_async_filler(void *data, struct page *page)
 340 {
 341         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 342         struct nfs_page *new;
 343         unsigned int len;
 344         int error;
 345
 346         len = nfs_page_length(page);
 347         if (len == 0)
 348                 return nfs_return_empty_page(page);
 349
 350         new = nfs_create_request(desc->ctx, page, NULL, 0, len);
 351         if (IS_ERR(new))
 352                 goto out_error;
 353
 354         if (len < PAGE_CACHE_SIZE)
 355                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 356         if (!nfs_pageio_add_request(desc->pgio, new)) {
 357                 error = desc->pgio->pg_error;
 358                 goto out_unlock;
 359         }
 360         return 0;
 361 out_error:
 362         error = PTR_ERR(new);
 363 out_unlock:
 364         unlock_page(page);
 365         return error;
 366 }
 367
 368 int nfs_readpages(struct file *filp, struct address_space *mapping,
 369                 struct list_head *pages, unsigned nr_pages)
 370 {
 371         struct nfs_pageio_descriptor pgio;
 372         struct nfs_pgio_mirror *pgm;
 373         struct nfs_readdesc desc = {
 374                 .pgio = &pgio,
 375         };
 376         struct inode *inode = mapping->host;
 377         unsigned long npages;
 378         int ret = -ESTALE;
 379
 380         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 381                         inode->i_sb->s_id,
 382                         (unsigned long long)NFS_FILEID(inode),
 383                         nr_pages);
 384         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 385
 386         if (NFS_STALE(inode))
 387                 goto out;
 388
 389         if (filp == NULL) {
 390                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 391                 if (desc.ctx == NULL)
 392                         return -EBADF;
 393         } else
 394                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 395
 396         /* attempt to read as many of the pages as possible from the cache
 397          * - this returns -ENOBUFS immediately if the cookie is negative
 398          */
 399         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 400                                          pages, &nr_pages);
 401         if (ret == 0)
 402                 goto read_complete; /* all pages were read */
 403
 404         nfs_pageio_init_read(&pgio, inode, false,
 405                              &nfs_async_read_completion_ops);
 406
 407         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 408         nfs_pageio_complete(&pgio);
 409
 410         /* It doesn't make sense to do mirrored reads! */
 411         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 412
 413         pgm = &pgio.pg_mirrors[0];
 414         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 415         npages = (pgm->pg_bytes_written + PAGE_CACHE_SIZE - 1) >>
 416                  PAGE_CACHE_SHIFT;
 417         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 418 read_complete:
 419         put_nfs_open_context(desc.ctx);
 420 out:
 421         return ret;
 422 }
 423
 424 int __init nfs_init_readpagecache(void)
 425 {
 426         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 427                                              sizeof(struct nfs_pgio_header),
 428                                              0, SLAB_HWCACHE_ALIGN,
 429                                              NULL);
 430         if (nfs_rdata_cachep == NULL)
 431                 return -ENOMEM;
 432
 433         return 0;
 434 }
 435
 436 void nfs_destroy_readpagecache(void)
 437 {
 438         kmem_cache_destroy(nfs_rdata_cachep);
 439 }
 440
 441 static const struct nfs_rw_ops nfs_rw_read_ops = {
 442         .rw_mode                = FMODE_READ,
 443         .rw_alloc_header        = nfs_readhdr_alloc,
 444         .rw_free_header         = nfs_readhdr_free,
 445         .rw_done                = nfs_readpage_done,
 446         .rw_result              = nfs_readpage_result,
 447         .rw_initiate            = nfs_initiate_read,
 448 };