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
 250         /* For non rpc-based layout drivers, retry-through-MDS */
 251         if (!task->tk_ops) {
 252                 hdr->pnfs_error = -EAGAIN;
 253                 return;
 254         }
 255
 256         /* Yes, so retry the read at the end of the hdr */
 257         hdr->mds_offset += resp->count;
 258         argp->offset += resp->count;
 259         argp->pgbase += resp->count;
 260         argp->count -= resp->count;
 261         rpc_restart_call_prepare(task);
 262 }
 263
 264 static void nfs_readpage_result(struct rpc_task *task,
 265                                 struct nfs_pgio_header *hdr)
 266 {
 267         if (hdr->res.eof) {
 268                 loff_t bound;
 269
 270                 bound = hdr->args.offset + hdr->res.count;
 271                 spin_lock(&hdr->lock);
 272                 if (bound < hdr->io_start + hdr->good_bytes) {
 273                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 274                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 275                         hdr->good_bytes = bound - hdr->io_start;
 276                 }
 277                 spin_unlock(&hdr->lock);
 278         } else if (hdr->res.count < hdr->args.count)
 279                 nfs_readpage_retry(task, hdr);
 280 }
 281
 282 /*
 283  * Read a page over NFS.
 284  * We read the page synchronously in the following case:
 285  *  -   The error flag is set for this page. This happens only when a
 286  *      previous async read operation failed.
 287  */
 288 int nfs_readpage(struct file *file, struct page *page)
 289 {
 290         struct nfs_open_context *ctx;
 291         struct inode *inode = page_file_mapping(page)->host;
 292         int             error;
 293
 294         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 295                 page, PAGE_CACHE_SIZE, page_file_index(page));
 296         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 297         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 298
 299         /*
 300          * Try to flush any pending writes to the file..
 301          *
 302          * NOTE! Because we own the page lock, there cannot
 303          * be any new pending writes generated at this point
 304          * for this page (other pages can be written to).
 305          */
 306         error = nfs_wb_page(inode, page);
 307         if (error)
 308                 goto out_unlock;
 309         if (PageUptodate(page))
 310                 goto out_unlock;
 311
 312         error = -ESTALE;
 313         if (NFS_STALE(inode))
 314                 goto out_unlock;
 315
 316         if (file == NULL) {
 317                 error = -EBADF;
 318                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 319                 if (ctx == NULL)
 320                         goto out_unlock;
 321         } else
 322                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 323
 324         if (!IS_SYNC(inode)) {
 325                 error = nfs_readpage_from_fscache(ctx, inode, page);
 326                 if (error == 0)
 327                         goto out;
 328         }
 329
 330         error = nfs_readpage_async(ctx, inode, page);
 331
 332 out:
 333         put_nfs_open_context(ctx);
 334         return error;
 335 out_unlock:
 336         unlock_page(page);
 337         return error;
 338 }
 339
 340 struct nfs_readdesc {
 341         struct nfs_pageio_descriptor *pgio;
 342         struct nfs_open_context *ctx;
 343 };
 344
 345 static int
 346 readpage_async_filler(void *data, struct page *page)
 347 {
 348         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 349         struct nfs_page *new;
 350         unsigned int len;
 351         int error;
 352
 353         len = nfs_page_length(page);
 354         if (len == 0)
 355                 return nfs_return_empty_page(page);
 356
 357         new = nfs_create_request(desc->ctx, page, NULL, 0, len);
 358         if (IS_ERR(new))
 359                 goto out_error;
 360
 361         if (len < PAGE_CACHE_SIZE)
 362                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 363         if (!nfs_pageio_add_request(desc->pgio, new)) {
 364                 error = desc->pgio->pg_error;
 365                 goto out_unlock;
 366         }
 367         return 0;
 368 out_error:
 369         error = PTR_ERR(new);
 370 out_unlock:
 371         unlock_page(page);
 372         return error;
 373 }
 374
 375 int nfs_readpages(struct file *filp, struct address_space *mapping,
 376                 struct list_head *pages, unsigned nr_pages)
 377 {
 378         struct nfs_pageio_descriptor pgio;
 379         struct nfs_pgio_mirror *pgm;
 380         struct nfs_readdesc desc = {
 381                 .pgio = &pgio,
 382         };
 383         struct inode *inode = mapping->host;
 384         unsigned long npages;
 385         int ret = -ESTALE;
 386
 387         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 388                         inode->i_sb->s_id,
 389                         (unsigned long long)NFS_FILEID(inode),
 390                         nr_pages);
 391         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 392
 393         if (NFS_STALE(inode))
 394                 goto out;
 395
 396         if (filp == NULL) {
 397                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 398                 if (desc.ctx == NULL)
 399                         return -EBADF;
 400         } else
 401                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 402
 403         /* attempt to read as many of the pages as possible from the cache
 404          * - this returns -ENOBUFS immediately if the cookie is negative
 405          */
 406         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 407                                          pages, &nr_pages);
 408         if (ret == 0)
 409                 goto read_complete; /* all pages were read */
 410
 411         nfs_pageio_init_read(&pgio, inode, false,
 412                              &nfs_async_read_completion_ops);
 413
 414         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 415         nfs_pageio_complete(&pgio);
 416
 417         /* It doesn't make sense to do mirrored reads! */
 418         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 419
 420         pgm = &pgio.pg_mirrors[0];
 421         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 422         npages = (pgm->pg_bytes_written + PAGE_CACHE_SIZE - 1) >>
 423                  PAGE_CACHE_SHIFT;
 424         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 425 read_complete:
 426         put_nfs_open_context(desc.ctx);
 427 out:
 428         return ret;
 429 }
 430
 431 int __init nfs_init_readpagecache(void)
 432 {
 433         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 434                                              sizeof(struct nfs_pgio_header),
 435                                              0, SLAB_HWCACHE_ALIGN,
 436                                              NULL);
 437         if (nfs_rdata_cachep == NULL)
 438                 return -ENOMEM;
 439
 440         return 0;
 441 }
 442
 443 void nfs_destroy_readpagecache(void)
 444 {
 445         kmem_cache_destroy(nfs_rdata_cachep);
 446 }
 447
 448 static const struct nfs_rw_ops nfs_rw_read_ops = {
 449         .rw_mode                = FMODE_READ,
 450         .rw_alloc_header        = nfs_readhdr_alloc,
 451         .rw_free_header         = nfs_readhdr_free,
 452         .rw_done                = nfs_readpage_done,
 453         .rw_result              = nfs_readpage_result,
 454         .rw_initiate            = nfs_initiate_read,
 455 };