root/fs/nfs/read.c

DEFINITIONS

1. nfs_readhdr_alloc
2. nfs_readhdr_free
3. nfs_return_empty_page
4. nfs_pageio_init_read
5. nfs_pageio_reset_read_mds
6. nfs_readpage_release
7. nfs_readpage_async
8. nfs_page_group_set_uptodate
9. nfs_read_completion
10. nfs_initiate_read
11. nfs_async_read_error
12. nfs_readpage_done
13. nfs_readpage_retry
14. nfs_readpage_result
15. nfs_readpage
16. readpage_async_filler
17. nfs_readpages
18. nfs_init_readpagecache
19. nfs_destroy_readpagecache

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/fs/nfs/read.c
   4  *
   5  * Block I/O for NFS
   6  *
   7  * Partial copy of Linus' read cache modifications to fs/nfs/file.c
   8  * modified for async RPC by okir@monad.swb.de
   9  */
  10 
  11 #include <linux/time.h>
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/fcntl.h>
  15 #include <linux/stat.h>
  16 #include <linux/mm.h>
  17 #include <linux/slab.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/sunrpc/clnt.h>
  20 #include <linux/nfs_fs.h>
  21 #include <linux/nfs_page.h>
  22 #include <linux/module.h>
  23 
  24 #include "nfs4_fs.h"
  25 #include "internal.h"
  26 #include "iostat.h"
  27 #include "fscache.h"
  28 #include "pnfs.h"
  29 #include "nfstrace.h"
  30 
  31 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  32 
  33 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  34 static const struct nfs_rw_ops nfs_rw_read_ops;
  35 
  36 static struct kmem_cache *nfs_rdata_cachep;
  37 
  38 static struct nfs_pgio_header *nfs_readhdr_alloc(void)
  39 {
  40         struct nfs_pgio_header *p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  41 
  42         if (p)
  43                 p->rw_mode = FMODE_READ;
  44         return p;
  45 }
  46 
  47 static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
  48 {
  49         kmem_cache_free(nfs_rdata_cachep, rhdr);
  50 }
  51 
  52 static
  53 int nfs_return_empty_page(struct page *page)
  54 {
  55         zero_user(page, 0, PAGE_SIZE);
  56         SetPageUptodate(page);
  57         unlock_page(page);
  58         return 0;
  59 }
  60 
  61 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
  62                               struct inode *inode, bool force_mds,
  63                               const struct nfs_pgio_completion_ops *compl_ops)
  64 {
  65         struct nfs_server *server = NFS_SERVER(inode);
  66         const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
  67 
  68 #ifdef CONFIG_NFS_V4_1
  69         if (server->pnfs_curr_ld && !force_mds)
  70                 pg_ops = server->pnfs_curr_ld->pg_read_ops;
  71 #endif
  72         nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
  73                         server->rsize, 0);
  74 }
  75 EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
  76 
  77 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
  78 {
  79         struct nfs_pgio_mirror *mirror;
  80 
  81         if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
  82                 pgio->pg_ops->pg_cleanup(pgio);
  83 
  84         pgio->pg_ops = &nfs_pgio_rw_ops;
  85 
  86         /* read path should never have more than one mirror */
  87         WARN_ON_ONCE(pgio->pg_mirror_count != 1);
  88 
  89         mirror = &pgio->pg_mirrors[0];
  90         mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
  91 }
  92 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
  93 
  94 static void nfs_readpage_release(struct nfs_page *req, int error)
  95 {
  96         struct inode *inode = d_inode(nfs_req_openctx(req)->dentry);
  97         struct page *page = req->wb_page;
  98 
  99         dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
 100                 (unsigned long long)NFS_FILEID(inode), req->wb_bytes,
 101                 (long long)req_offset(req));
 102 
 103         if (nfs_error_is_fatal_on_server(error) && error != -ETIMEDOUT)
 104                 SetPageError(page);
 105         if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
 106                 struct address_space *mapping = page_file_mapping(page);
 107 
 108                 if (PageUptodate(page))
 109                         nfs_readpage_to_fscache(inode, page, 0);
 110                 else if (!PageError(page) && !PagePrivate(page))
 111                         generic_error_remove_page(mapping, page);
 112                 unlock_page(page);
 113         }
 114         nfs_release_request(req);
 115 }
 116 
 117 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 118                        struct page *page)
 119 {
 120         struct nfs_page *new;
 121         unsigned int len;
 122         struct nfs_pageio_descriptor pgio;
 123         struct nfs_pgio_mirror *pgm;
 124 
 125         len = nfs_page_length(page);
 126         if (len == 0)
 127                 return nfs_return_empty_page(page);
 128         new = nfs_create_request(ctx, page, 0, len);
 129         if (IS_ERR(new)) {
 130                 unlock_page(page);
 131                 return PTR_ERR(new);
 132         }
 133         if (len < PAGE_SIZE)
 134                 zero_user_segment(page, len, PAGE_SIZE);
 135 
 136         nfs_pageio_init_read(&pgio, inode, false,
 137                              &nfs_async_read_completion_ops);
 138         if (!nfs_pageio_add_request(&pgio, new)) {
 139                 nfs_list_remove_request(new);
 140                 nfs_readpage_release(new, pgio.pg_error);
 141         }
 142         nfs_pageio_complete(&pgio);
 143 
 144         /* It doesn't make sense to do mirrored reads! */
 145         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 146 
 147         pgm = &pgio.pg_mirrors[0];
 148         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 149 
 150         return pgio.pg_error < 0 ? pgio.pg_error : 0;
 151 }
 152 
 153 static void nfs_page_group_set_uptodate(struct nfs_page *req)
 154 {
 155         if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
 156                 SetPageUptodate(req->wb_page);
 157 }
 158 
 159 static void nfs_read_completion(struct nfs_pgio_header *hdr)
 160 {
 161         unsigned long bytes = 0;
 162         int error;
 163 
 164         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 165                 goto out;
 166         while (!list_empty(&hdr->pages)) {
 167                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 168                 struct page *page = req->wb_page;
 169                 unsigned long start = req->wb_pgbase;
 170                 unsigned long end = req->wb_pgbase + req->wb_bytes;
 171 
 172                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 173                         /* note: regions of the page not covered by a
 174                          * request are zeroed in nfs_readpage_async /
 175                          * readpage_async_filler */
 176                         if (bytes > hdr->good_bytes) {
 177                                 /* nothing in this request was good, so zero
 178                                  * the full extent of the request */
 179                                 zero_user_segment(page, start, end);
 180 
 181                         } else if (hdr->good_bytes - bytes < req->wb_bytes) {
 182                                 /* part of this request has good bytes, but
 183                                  * not all. zero the bad bytes */
 184                                 start += hdr->good_bytes - bytes;
 185                                 WARN_ON(start < req->wb_pgbase);
 186                                 zero_user_segment(page, start, end);
 187                         }
 188                 }
 189                 error = 0;
 190                 bytes += req->wb_bytes;
 191                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 192                         if (bytes <= hdr->good_bytes)
 193                                 nfs_page_group_set_uptodate(req);
 194                         else {
 195                                 error = hdr->error;
 196                                 xchg(&nfs_req_openctx(req)->error, error);
 197                         }
 198                 } else
 199                         nfs_page_group_set_uptodate(req);
 200                 nfs_list_remove_request(req);
 201                 nfs_readpage_release(req, error);
 202         }
 203 out:
 204         hdr->release(hdr);
 205 }
 206 
 207 static void nfs_initiate_read(struct nfs_pgio_header *hdr,
 208                               struct rpc_message *msg,
 209                               const struct nfs_rpc_ops *rpc_ops,
 210                               struct rpc_task_setup *task_setup_data, int how)
 211 {
 212         struct inode *inode = hdr->inode;
 213         int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 214 
 215         task_setup_data->flags |= swap_flags;
 216         rpc_ops->read_setup(hdr, msg);
 217         trace_nfs_initiate_read(inode, hdr->io_start, hdr->good_bytes);
 218 }
 219 
 220 static void
 221 nfs_async_read_error(struct list_head *head, int error)
 222 {
 223         struct nfs_page *req;
 224 
 225         while (!list_empty(head)) {
 226                 req = nfs_list_entry(head->next);
 227                 nfs_list_remove_request(req);
 228                 nfs_readpage_release(req, error);
 229         }
 230 }
 231 
 232 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 233         .error_cleanup = nfs_async_read_error,
 234         .completion = nfs_read_completion,
 235 };
 236 
 237 /*
 238  * This is the callback from RPC telling us whether a reply was
 239  * received or some error occurred (timeout or socket shutdown).
 240  */
 241 static int nfs_readpage_done(struct rpc_task *task,
 242                              struct nfs_pgio_header *hdr,
 243                              struct inode *inode)
 244 {
 245         int status = NFS_PROTO(inode)->read_done(task, hdr);
 246         if (status != 0)
 247                 return status;
 248 
 249         nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
 250         trace_nfs_readpage_done(inode, task->tk_status,
 251                                 hdr->args.offset, hdr->res.eof);
 252 
 253         if (task->tk_status == -ESTALE) {
 254                 set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 255                 nfs_mark_for_revalidate(inode);
 256         }
 257         return 0;
 258 }
 259 
 260 static void nfs_readpage_retry(struct rpc_task *task,
 261                                struct nfs_pgio_header *hdr)
 262 {
 263         struct nfs_pgio_args *argp = &hdr->args;
 264         struct nfs_pgio_res  *resp = &hdr->res;
 265 
 266         /* This is a short read! */
 267         nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
 268         /* Has the server at least made some progress? */
 269         if (resp->count == 0) {
 270                 nfs_set_pgio_error(hdr, -EIO, argp->offset);
 271                 return;
 272         }
 273 
 274         /* For non rpc-based layout drivers, retry-through-MDS */
 275         if (!task->tk_ops) {
 276                 hdr->pnfs_error = -EAGAIN;
 277                 return;
 278         }
 279 
 280         /* Yes, so retry the read at the end of the hdr */
 281         hdr->mds_offset += resp->count;
 282         argp->offset += resp->count;
 283         argp->pgbase += resp->count;
 284         argp->count -= resp->count;
 285         rpc_restart_call_prepare(task);
 286 }
 287 
 288 static void nfs_readpage_result(struct rpc_task *task,
 289                                 struct nfs_pgio_header *hdr)
 290 {
 291         if (hdr->res.eof) {
 292                 loff_t pos = hdr->args.offset + hdr->res.count;
 293                 unsigned int new = pos - hdr->io_start;
 294 
 295                 if (hdr->good_bytes > new) {
 296                         hdr->good_bytes = new;
 297                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
 298                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 299                 }
 300         } else if (hdr->res.count < hdr->args.count)
 301                 nfs_readpage_retry(task, hdr);
 302 }
 303 
 304 /*
 305  * Read a page over NFS.
 306  * We read the page synchronously in the following case:
 307  *  -   The error flag is set for this page. This happens only when a
 308  *      previous async read operation failed.
 309  */
 310 int nfs_readpage(struct file *file, struct page *page)
 311 {
 312         struct nfs_open_context *ctx;
 313         struct inode *inode = page_file_mapping(page)->host;
 314         int             error;
 315 
 316         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 317                 page, PAGE_SIZE, page_index(page));
 318         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 319         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 320 
 321         /*
 322          * Try to flush any pending writes to the file..
 323          *
 324          * NOTE! Because we own the page lock, there cannot
 325          * be any new pending writes generated at this point
 326          * for this page (other pages can be written to).
 327          */
 328         error = nfs_wb_page(inode, page);
 329         if (error)
 330                 goto out_unlock;
 331         if (PageUptodate(page))
 332                 goto out_unlock;
 333 
 334         error = -ESTALE;
 335         if (NFS_STALE(inode))
 336                 goto out_unlock;
 337 
 338         if (file == NULL) {
 339                 error = -EBADF;
 340                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 341                 if (ctx == NULL)
 342                         goto out_unlock;
 343         } else
 344                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 345 
 346         if (!IS_SYNC(inode)) {
 347                 error = nfs_readpage_from_fscache(ctx, inode, page);
 348                 if (error == 0)
 349                         goto out;
 350         }
 351 
 352         xchg(&ctx->error, 0);
 353         error = nfs_readpage_async(ctx, inode, page);
 354         if (!error) {
 355                 error = wait_on_page_locked_killable(page);
 356                 if (!PageUptodate(page) && !error)
 357                         error = xchg(&ctx->error, 0);
 358         }
 359 out:
 360         put_nfs_open_context(ctx);
 361         return error;
 362 out_unlock:
 363         unlock_page(page);
 364         return error;
 365 }
 366 
 367 struct nfs_readdesc {
 368         struct nfs_pageio_descriptor *pgio;
 369         struct nfs_open_context *ctx;
 370 };
 371 
 372 static int
 373 readpage_async_filler(void *data, struct page *page)
 374 {
 375         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 376         struct nfs_page *new;
 377         unsigned int len;
 378         int error;
 379 
 380         len = nfs_page_length(page);
 381         if (len == 0)
 382                 return nfs_return_empty_page(page);
 383 
 384         new = nfs_create_request(desc->ctx, page, 0, len);
 385         if (IS_ERR(new))
 386                 goto out_error;
 387 
 388         if (len < PAGE_SIZE)
 389                 zero_user_segment(page, len, PAGE_SIZE);
 390         if (!nfs_pageio_add_request(desc->pgio, new)) {
 391                 nfs_list_remove_request(new);
 392                 error = desc->pgio->pg_error;
 393                 nfs_readpage_release(new, error);
 394                 goto out;
 395         }
 396         return 0;
 397 out_error:
 398         error = PTR_ERR(new);
 399         unlock_page(page);
 400 out:
 401         return error;
 402 }
 403 
 404 int nfs_readpages(struct file *filp, struct address_space *mapping,
 405                 struct list_head *pages, unsigned nr_pages)
 406 {
 407         struct nfs_pageio_descriptor pgio;
 408         struct nfs_pgio_mirror *pgm;
 409         struct nfs_readdesc desc = {
 410                 .pgio = &pgio,
 411         };
 412         struct inode *inode = mapping->host;
 413         unsigned long npages;
 414         int ret = -ESTALE;
 415 
 416         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 417                         inode->i_sb->s_id,
 418                         (unsigned long long)NFS_FILEID(inode),
 419                         nr_pages);
 420         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 421 
 422         if (NFS_STALE(inode))
 423                 goto out;
 424 
 425         if (filp == NULL) {
 426                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 427                 if (desc.ctx == NULL)
 428                         return -EBADF;
 429         } else
 430                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 431 
 432         /* attempt to read as many of the pages as possible from the cache
 433          * - this returns -ENOBUFS immediately if the cookie is negative
 434          */
 435         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 436                                          pages, &nr_pages);
 437         if (ret == 0)
 438                 goto read_complete; /* all pages were read */
 439 
 440         nfs_pageio_init_read(&pgio, inode, false,
 441                              &nfs_async_read_completion_ops);
 442 
 443         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 444         nfs_pageio_complete(&pgio);
 445 
 446         /* It doesn't make sense to do mirrored reads! */
 447         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 448 
 449         pgm = &pgio.pg_mirrors[0];
 450         NFS_I(inode)->read_io += pgm->pg_bytes_written;
 451         npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >>
 452                  PAGE_SHIFT;
 453         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 454 read_complete:
 455         put_nfs_open_context(desc.ctx);
 456 out:
 457         return ret;
 458 }
 459 
 460 int __init nfs_init_readpagecache(void)
 461 {
 462         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 463                                              sizeof(struct nfs_pgio_header),
 464                                              0, SLAB_HWCACHE_ALIGN,
 465                                              NULL);
 466         if (nfs_rdata_cachep == NULL)
 467                 return -ENOMEM;
 468 
 469         return 0;
 470 }
 471 
 472 void nfs_destroy_readpagecache(void)
 473 {
 474         kmem_cache_destroy(nfs_rdata_cachep);
 475 }
 476 
 477 static const struct nfs_rw_ops nfs_rw_read_ops = {
 478         .rw_alloc_header        = nfs_readhdr_alloc,
 479         .rw_free_header         = nfs_readhdr_free,
 480         .rw_done                = nfs_readpage_done,
 481         .rw_result              = nfs_readpage_result,
 482         .rw_initiate            = nfs_initiate_read,
 483 };