fs/nfs/direct.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/fs/nfs/direct.c
   4  *
   5  * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
   6  *
   7  * High-performance uncached I/O for the Linux NFS client
   8  *
   9  * There are important applications whose performance or correctness
  10  * depends on uncached access to file data.  Database clusters
  11  * (multiple copies of the same instance running on separate hosts)
  12  * implement their own cache coherency protocol that subsumes file
  13  * system cache protocols.  Applications that process datasets
  14  * considerably larger than the client's memory do not always benefit
  15  * from a local cache.  A streaming video server, for instance, has no
  16  * need to cache the contents of a file.
  17  *
  18  * When an application requests uncached I/O, all read and write requests
  19  * are made directly to the server; data stored or fetched via these
  20  * requests is not cached in the Linux page cache.  The client does not
  21  * correct unaligned requests from applications.  All requested bytes are
  22  * held on permanent storage before a direct write system call returns to
  23  * an application.
  24  *
  25  * Solaris implements an uncached I/O facility called directio() that
  26  * is used for backups and sequential I/O to very large files.  Solaris
  27  * also supports uncaching whole NFS partitions with "-o forcedirectio,"
  28  * an undocumented mount option.
  29  *
  30  * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
  31  * help from Andrew Morton.
  32  *
  33  * 18 Dec 2001  Initial implementation for 2.4  --cel
  34  * 08 Jul 2002  Version for 2.4.19, with bug fixes --trondmy
  35  * 08 Jun 2003  Port to 2.5 APIs  --cel
  36  * 31 Mar 2004  Handle direct I/O without VFS support  --cel
  37  * 15 Sep 2004  Parallel async reads  --cel
  38  * 04 May 2005  support O_DIRECT with aio  --cel
  39  *
  40  */
  41
  42 #include <linux/errno.h>
  43 #include <linux/sched.h>
  44 #include <linux/kernel.h>
  45 #include <linux/file.h>
  46 #include <linux/pagemap.h>
  47 #include <linux/kref.h>
  48 #include <linux/slab.h>
  49 #include <linux/task_io_accounting_ops.h>
  50 #include <linux/module.h>
  51
  52 #include <linux/nfs_fs.h>
  53 #include <linux/nfs_page.h>
  54 #include <linux/sunrpc/clnt.h>
  55
  56 #include <linux/uaccess.h>
  57 #include <linux/atomic.h>
  58
  59 #include "internal.h"
  60 #include "iostat.h"
  61 #include "pnfs.h"
  62
  63 #define NFSDBG_FACILITY         NFSDBG_VFS
  64
  65 static struct kmem_cache *nfs_direct_cachep;
  66
  67 struct nfs_direct_req {
  68         struct kref             kref;           /* release manager */
  69
  70         /* I/O parameters */
  71         struct nfs_open_context *ctx;           /* file open context info */
  72         struct nfs_lock_context *l_ctx;         /* Lock context info */
  73         struct kiocb *          iocb;           /* controlling i/o request */
  74         struct inode *          inode;          /* target file of i/o */
  75
  76         /* completion state */
  77         atomic_t                io_count;       /* i/os we're waiting for */
  78         spinlock_t              lock;           /* protect completion state */
  79
  80         loff_t                  io_start;       /* Start offset for I/O */
  81         ssize_t                 count,          /* bytes actually processed */
  82                                 max_count,      /* max expected count */
  83                                 bytes_left,     /* bytes left to be sent */
  84                                 error;          /* any reported error */
  85         struct completion       completion;     /* wait for i/o completion */
  86
  87         /* commit state */
  88         struct nfs_mds_commit_info mds_cinfo;   /* Storage for cinfo */
  89         struct pnfs_ds_commit_info ds_cinfo;    /* Storage for cinfo */
  90         struct work_struct      work;
  91         int                     flags;
  92         /* for write */
  93 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
  94 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
  95         /* for read */
  96 #define NFS_ODIRECT_SHOULD_DIRTY        (3)     /* dirty user-space page after read */
  97 #define NFS_ODIRECT_DONE                INT_MAX /* write verification failed */
  98 };
  99
 100 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
 101 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
 102 static void nfs_direct_write_complete(struct nfs_direct_req *dreq);
 103 static void nfs_direct_write_schedule_work(struct work_struct *work);
 104
 105 static inline void get_dreq(struct nfs_direct_req *dreq)
 106 {
 107         atomic_inc(&dreq->io_count);
 108 }
 109
 110 static inline int put_dreq(struct nfs_direct_req *dreq)
 111 {
 112         return atomic_dec_and_test(&dreq->io_count);
 113 }
 114
 115 static void
 116 nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
 117                             const struct nfs_pgio_header *hdr,
 118                             ssize_t dreq_len)
 119 {
 120         if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
 121               test_bit(NFS_IOHDR_EOF, &hdr->flags)))
 122                 return;
 123         if (dreq->max_count >= dreq_len) {
 124                 dreq->max_count = dreq_len;
 125                 if (dreq->count > dreq_len)
 126                         dreq->count = dreq_len;
 127
 128                 if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
 129                         dreq->error = hdr->error;
 130                 else /* Clear outstanding error if this is EOF */
 131                         dreq->error = 0;
 132         }
 133 }
 134
 135 static void
 136 nfs_direct_count_bytes(struct nfs_direct_req *dreq,
 137                        const struct nfs_pgio_header *hdr)
 138 {
 139         loff_t hdr_end = hdr->io_start + hdr->good_bytes;
 140         ssize_t dreq_len = 0;
 141
 142         if (hdr_end > dreq->io_start)
 143                 dreq_len = hdr_end - dreq->io_start;
 144
 145         nfs_direct_handle_truncated(dreq, hdr, dreq_len);
 146
 147         if (dreq_len > dreq->max_count)
 148                 dreq_len = dreq->max_count;
 149
 150         if (dreq->count < dreq_len)
 151                 dreq->count = dreq_len;
 152 }
 153
 154 /**
 155  * nfs_direct_IO - NFS address space operation for direct I/O
 156  * @iocb: target I/O control block
 157  * @iter: I/O buffer
 158  *
 159  * The presence of this routine in the address space ops vector means
 160  * the NFS client supports direct I/O. However, for most direct IO, we
 161  * shunt off direct read and write requests before the VFS gets them,
 162  * so this method is only ever called for swap.
 163  */
 164 ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 165 {
 166         struct inode *inode = iocb->ki_filp->f_mapping->host;
 167
 168         /* we only support swap file calling nfs_direct_IO */
 169         if (!IS_SWAPFILE(inode))
 170                 return 0;
 171
 172         VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
 173
 174         if (iov_iter_rw(iter) == READ)
 175                 return nfs_file_direct_read(iocb, iter);
 176         return nfs_file_direct_write(iocb, iter);
 177 }
 178
 179 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
 180 {
 181         unsigned int i;
 182         for (i = 0; i < npages; i++)
 183                 put_page(pages[i]);
 184 }
 185
 186 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
 187                               struct nfs_direct_req *dreq)
 188 {
 189         cinfo->inode = dreq->inode;
 190         cinfo->mds = &dreq->mds_cinfo;
 191         cinfo->ds = &dreq->ds_cinfo;
 192         cinfo->dreq = dreq;
 193         cinfo->completion_ops = &nfs_direct_commit_completion_ops;
 194 }
 195
 196 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
 197 {
 198         struct nfs_direct_req *dreq;
 199
 200         dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
 201         if (!dreq)
 202                 return NULL;
 203
 204         kref_init(&dreq->kref);
 205         kref_get(&dreq->kref);
 206         init_completion(&dreq->completion);
 207         INIT_LIST_HEAD(&dreq->mds_cinfo.list);
 208         pnfs_init_ds_commit_info(&dreq->ds_cinfo);
 209         INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
 210         spin_lock_init(&dreq->lock);
 211
 212         return dreq;
 213 }
 214
 215 static void nfs_direct_req_free(struct kref *kref)
 216 {
 217         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
 218
 219         pnfs_release_ds_info(&dreq->ds_cinfo, dreq->inode);
 220         if (dreq->l_ctx != NULL)
 221                 nfs_put_lock_context(dreq->l_ctx);
 222         if (dreq->ctx != NULL)
 223                 put_nfs_open_context(dreq->ctx);
 224         kmem_cache_free(nfs_direct_cachep, dreq);
 225 }
 226
 227 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
 228 {
 229         kref_put(&dreq->kref, nfs_direct_req_free);
 230 }
 231
 232 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
 233 {
 234         return dreq->bytes_left;
 235 }
 236 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
 237
 238 /*
 239  * Collects and returns the final error value/byte-count.
 240  */
 241 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
 242 {
 243         ssize_t result = -EIOCBQUEUED;
 244
 245         /* Async requests don't wait here */
 246         if (dreq->iocb)
 247                 goto out;
 248
 249         result = wait_for_completion_killable(&dreq->completion);
 250
 251         if (!result) {
 252                 result = dreq->count;
 253                 WARN_ON_ONCE(dreq->count < 0);
 254         }
 255         if (!result)
 256                 result = dreq->error;
 257
 258 out:
 259         return (ssize_t) result;
 260 }
 261
 262 /*
 263  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
 264  * the iocb is still valid here if this is a synchronous request.
 265  */
 266 static void nfs_direct_complete(struct nfs_direct_req *dreq)
 267 {
 268         struct inode *inode = dreq->inode;
 269
 270         inode_dio_end(inode);
 271
 272         if (dreq->iocb) {
 273                 long res = (long) dreq->error;
 274                 if (dreq->count != 0) {
 275                         res = (long) dreq->count;
 276                         WARN_ON_ONCE(dreq->count < 0);
 277                 }
 278                 dreq->iocb->ki_complete(dreq->iocb, res, 0);
 279         }
 280
 281         complete(&dreq->completion);
 282
 283         nfs_direct_req_release(dreq);
 284 }
 285
 286 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
 287 {
 288         unsigned long bytes = 0;
 289         struct nfs_direct_req *dreq = hdr->dreq;
 290
 291         spin_lock(&dreq->lock);
 292         if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
 293                 spin_unlock(&dreq->lock);
 294                 goto out_put;
 295         }
 296
 297         nfs_direct_count_bytes(dreq, hdr);
 298         spin_unlock(&dreq->lock);
 299
 300         while (!list_empty(&hdr->pages)) {
 301                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 302                 struct page *page = req->wb_page;
 303
 304                 if (!PageCompound(page) && bytes < hdr->good_bytes &&
 305                     (dreq->flags == NFS_ODIRECT_SHOULD_DIRTY))
 306                         set_page_dirty(page);
 307                 bytes += req->wb_bytes;
 308                 nfs_list_remove_request(req);
 309                 nfs_release_request(req);
 310         }
 311 out_put:
 312         if (put_dreq(dreq))
 313                 nfs_direct_complete(dreq);
 314         hdr->release(hdr);
 315 }
 316
 317 static void nfs_read_sync_pgio_error(struct list_head *head, int error)
 318 {
 319         struct nfs_page *req;
 320
 321         while (!list_empty(head)) {
 322                 req = nfs_list_entry(head->next);
 323                 nfs_list_remove_request(req);
 324                 nfs_release_request(req);
 325         }
 326 }
 327
 328 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
 329 {
 330         get_dreq(hdr->dreq);
 331 }
 332
 333 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
 334         .error_cleanup = nfs_read_sync_pgio_error,
 335         .init_hdr = nfs_direct_pgio_init,
 336         .completion = nfs_direct_read_completion,
 337 };
 338
 339 /*
 340  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
 341  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
 342  * bail and stop sending more reads.  Read length accounting is
 343  * handled automatically by nfs_direct_read_result().  Otherwise, if
 344  * no requests have been sent, just return an error.
 345  */
 346
 347 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 348                                               struct iov_iter *iter,
 349                                               loff_t pos)
 350 {
 351         struct nfs_pageio_descriptor desc;
 352         struct inode *inode = dreq->inode;
 353         ssize_t result = -EINVAL;
 354         size_t requested_bytes = 0;
 355         size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
 356
 357         nfs_pageio_init_read(&desc, dreq->inode, false,
 358                              &nfs_direct_read_completion_ops);
 359         get_dreq(dreq);
 360         desc.pg_dreq = dreq;
 361         inode_dio_begin(inode);
 362
 363         while (iov_iter_count(iter)) {
 364                 struct page **pagevec;
 365                 size_t bytes;
 366                 size_t pgbase;
 367                 unsigned npages, i;
 368
 369                 result = iov_iter_get_pages_alloc(iter, &pagevec,
 370                                                   rsize, &pgbase);
 371                 if (result < 0)
 372                         break;
 373
 374                 bytes = result;
 375                 iov_iter_advance(iter, bytes);
 376                 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
 377                 for (i = 0; i < npages; i++) {
 378                         struct nfs_page *req;
 379                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
 380                         /* XXX do we need to do the eof zeroing found in async_filler? */
 381                         req = nfs_create_request(dreq->ctx, pagevec[i],
 382                                                  pgbase, req_len);
 383                         if (IS_ERR(req)) {
 384                                 result = PTR_ERR(req);
 385                                 break;
 386                         }
 387                         req->wb_index = pos >> PAGE_SHIFT;
 388                         req->wb_offset = pos & ~PAGE_MASK;
 389                         if (!nfs_pageio_add_request(&desc, req)) {
 390                                 result = desc.pg_error;
 391                                 nfs_release_request(req);
 392                                 break;
 393                         }
 394                         pgbase = 0;
 395                         bytes -= req_len;
 396                         requested_bytes += req_len;
 397                         pos += req_len;
 398                         dreq->bytes_left -= req_len;
 399                 }
 400                 nfs_direct_release_pages(pagevec, npages);
 401                 kvfree(pagevec);
 402                 if (result < 0)
 403                         break;
 404         }
 405
 406         nfs_pageio_complete(&desc);
 407
 408         /*
 409          * If no bytes were started, return the error, and let the
 410          * generic layer handle the completion.
 411          */
 412         if (requested_bytes == 0) {
 413                 inode_dio_end(inode);
 414                 nfs_direct_req_release(dreq);
 415                 return result < 0 ? result : -EIO;
 416         }
 417
 418         if (put_dreq(dreq))
 419                 nfs_direct_complete(dreq);
 420         return requested_bytes;
 421 }
 422
 423 /**
 424  * nfs_file_direct_read - file direct read operation for NFS files
 425  * @iocb: target I/O control block
 426  * @iter: vector of user buffers into which to read data
 427  *
 428  * We use this function for direct reads instead of calling
 429  * generic_file_aio_read() in order to avoid gfar's check to see if
 430  * the request starts before the end of the file.  For that check
 431  * to work, we must generate a GETATTR before each direct read, and
 432  * even then there is a window between the GETATTR and the subsequent
 433  * READ where the file size could change.  Our preference is simply
 434  * to do all reads the application wants, and the server will take
 435  * care of managing the end of file boundary.
 436  *
 437  * This function also eliminates unnecessarily updating the file's
 438  * atime locally, as the NFS server sets the file's atime, and this
 439  * client must read the updated atime from the server back into its
 440  * cache.
 441  */
 442 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
 443 {
 444         struct file *file = iocb->ki_filp;
 445         struct address_space *mapping = file->f_mapping;
 446         struct inode *inode = mapping->host;
 447         struct nfs_direct_req *dreq;
 448         struct nfs_lock_context *l_ctx;
 449         ssize_t result, requested;
 450         size_t count = iov_iter_count(iter);
 451         nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
 452
 453         dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
 454                 file, count, (long long) iocb->ki_pos);
 455
 456         result = 0;
 457         if (!count)
 458                 goto out;
 459
 460         task_io_account_read(count);
 461
 462         result = -ENOMEM;
 463         dreq = nfs_direct_req_alloc();
 464         if (dreq == NULL)
 465                 goto out;
 466
 467         dreq->inode = inode;
 468         dreq->bytes_left = dreq->max_count = count;
 469         dreq->io_start = iocb->ki_pos;
 470         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
 471         l_ctx = nfs_get_lock_context(dreq->ctx);
 472         if (IS_ERR(l_ctx)) {
 473                 result = PTR_ERR(l_ctx);
 474                 nfs_direct_req_release(dreq);
 475                 goto out_release;
 476         }
 477         dreq->l_ctx = l_ctx;
 478         if (!is_sync_kiocb(iocb))
 479                 dreq->iocb = iocb;
 480
 481         if (iter_is_iovec(iter))
 482                 dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
 483
 484         nfs_start_io_direct(inode);
 485
 486         NFS_I(inode)->read_io += count;
 487         requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
 488
 489         nfs_end_io_direct(inode);
 490
 491         if (requested > 0) {
 492                 result = nfs_direct_wait(dreq);
 493                 if (result > 0) {
 494                         requested -= result;
 495                         iocb->ki_pos += result;
 496                 }
 497                 iov_iter_revert(iter, requested);
 498         } else {
 499                 result = requested;
 500         }
 501
 502 out_release:
 503         nfs_direct_req_release(dreq);
 504 out:
 505         return result;
 506 }
 507
 508 static void
 509 nfs_direct_join_group(struct list_head *list, struct inode *inode)
 510 {
 511         struct nfs_page *req, *next;
 512
 513         list_for_each_entry(req, list, wb_list) {
 514                 if (req->wb_head != req || req->wb_this_page == req)
 515                         continue;
 516                 for (next = req->wb_this_page;
 517                                 next != req->wb_head;
 518                                 next = next->wb_this_page) {
 519                         nfs_list_remove_request(next);
 520                         nfs_release_request(next);
 521                 }
 522                 nfs_join_page_group(req, inode);
 523         }
 524 }
 525
 526 static void
 527 nfs_direct_write_scan_commit_list(struct inode *inode,
 528                                   struct list_head *list,
 529                                   struct nfs_commit_info *cinfo)
 530 {
 531         mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
 532         pnfs_recover_commit_reqs(list, cinfo);
 533         nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
 534         mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
 535 }
 536
 537 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
 538 {
 539         struct nfs_pageio_descriptor desc;
 540         struct nfs_page *req, *tmp;
 541         LIST_HEAD(reqs);
 542         struct nfs_commit_info cinfo;
 543         LIST_HEAD(failed);
 544
 545         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 546         nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 547
 548         nfs_direct_join_group(&reqs, dreq->inode);
 549
 550         dreq->count = 0;
 551         dreq->max_count = 0;
 552         list_for_each_entry(req, &reqs, wb_list)
 553                 dreq->max_count += req->wb_bytes;
 554         nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
 555         get_dreq(dreq);
 556
 557         nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
 558                               &nfs_direct_write_completion_ops);
 559         desc.pg_dreq = dreq;
 560
 561         list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
 562                 /* Bump the transmission count */
 563                 req->wb_nio++;
 564                 if (!nfs_pageio_add_request(&desc, req)) {
 565                         nfs_list_move_request(req, &failed);
 566                         spin_lock(&cinfo.inode->i_lock);
 567                         dreq->flags = 0;
 568                         if (desc.pg_error < 0)
 569                                 dreq->error = desc.pg_error;
 570                         else
 571                                 dreq->error = -EIO;
 572                         spin_unlock(&cinfo.inode->i_lock);
 573                 }
 574                 nfs_release_request(req);
 575         }
 576         nfs_pageio_complete(&desc);
 577
 578         while (!list_empty(&failed)) {
 579                 req = nfs_list_entry(failed.next);
 580                 nfs_list_remove_request(req);
 581                 nfs_unlock_and_release_request(req);
 582         }
 583
 584         if (put_dreq(dreq))
 585                 nfs_direct_write_complete(dreq);
 586 }
 587
 588 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
 589 {
 590         const struct nfs_writeverf *verf = data->res.verf;
 591         struct nfs_direct_req *dreq = data->dreq;
 592         struct nfs_commit_info cinfo;
 593         struct nfs_page *req;
 594         int status = data->task.tk_status;
 595
 596         if (status < 0) {
 597                 /* Errors in commit are fatal */
 598                 dreq->error = status;
 599                 dreq->max_count = 0;
 600                 dreq->count = 0;
 601                 dreq->flags = NFS_ODIRECT_DONE;
 602         } else if (dreq->flags == NFS_ODIRECT_DONE)
 603                 status = dreq->error;
 604
 605         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 606
 607         while (!list_empty(&data->pages)) {
 608                 req = nfs_list_entry(data->pages.next);
 609                 nfs_list_remove_request(req);
 610                 if (status >= 0 && !nfs_write_match_verf(verf, req)) {
 611                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 612                         /*
 613                          * Despite the reboot, the write was successful,
 614                          * so reset wb_nio.
 615                          */
 616                         req->wb_nio = 0;
 617                         nfs_mark_request_commit(req, NULL, &cinfo, 0);
 618                 } else /* Error or match */
 619                         nfs_release_request(req);
 620                 nfs_unlock_and_release_request(req);
 621         }
 622
 623         if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
 624                 nfs_direct_write_complete(dreq);
 625 }
 626
 627 static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
 628                 struct nfs_page *req)
 629 {
 630         struct nfs_direct_req *dreq = cinfo->dreq;
 631
 632         spin_lock(&dreq->lock);
 633         if (dreq->flags != NFS_ODIRECT_DONE)
 634                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 635         spin_unlock(&dreq->lock);
 636         nfs_mark_request_commit(req, NULL, cinfo, 0);
 637 }
 638
 639 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
 640         .completion = nfs_direct_commit_complete,
 641         .resched_write = nfs_direct_resched_write,
 642 };
 643
 644 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
 645 {
 646         int res;
 647         struct nfs_commit_info cinfo;
 648         LIST_HEAD(mds_list);
 649
 650         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 651         nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
 652         res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
 653         if (res < 0) /* res == -ENOMEM */
 654                 nfs_direct_write_reschedule(dreq);
 655 }
 656
 657 static void nfs_direct_write_clear_reqs(struct nfs_direct_req *dreq)
 658 {
 659         struct nfs_commit_info cinfo;
 660         struct nfs_page *req;
 661         LIST_HEAD(reqs);
 662
 663         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 664         nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 665
 666         while (!list_empty(&reqs)) {
 667                 req = nfs_list_entry(reqs.next);
 668                 nfs_list_remove_request(req);
 669                 nfs_release_request(req);
 670                 nfs_unlock_and_release_request(req);
 671         }
 672 }
 673
 674 static void nfs_direct_write_schedule_work(struct work_struct *work)
 675 {
 676         struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
 677         int flags = dreq->flags;
 678
 679         dreq->flags = 0;
 680         switch (flags) {
 681                 case NFS_ODIRECT_DO_COMMIT:
 682                         nfs_direct_commit_schedule(dreq);
 683                         break;
 684                 case NFS_ODIRECT_RESCHED_WRITES:
 685                         nfs_direct_write_reschedule(dreq);
 686                         break;
 687                 default:
 688                         nfs_direct_write_clear_reqs(dreq);
 689                         nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
 690                         nfs_direct_complete(dreq);
 691         }
 692 }
 693
 694 static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
 695 {
 696         queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
 697 }
 698
 699 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
 700 {
 701         struct nfs_direct_req *dreq = hdr->dreq;
 702         struct nfs_commit_info cinfo;
 703         struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 704         int flags = NFS_ODIRECT_DONE;
 705
 706         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 707
 708         spin_lock(&dreq->lock);
 709         if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
 710                 spin_unlock(&dreq->lock);
 711                 goto out_put;
 712         }
 713
 714         nfs_direct_count_bytes(dreq, hdr);
 715         if (hdr->good_bytes != 0 && nfs_write_need_commit(hdr)) {
 716                 if (!dreq->flags)
 717                         dreq->flags = NFS_ODIRECT_DO_COMMIT;
 718                 flags = dreq->flags;
 719         }
 720         spin_unlock(&dreq->lock);
 721
 722         while (!list_empty(&hdr->pages)) {
 723
 724                 req = nfs_list_entry(hdr->pages.next);
 725                 nfs_list_remove_request(req);
 726                 if (flags == NFS_ODIRECT_DO_COMMIT) {
 727                         kref_get(&req->wb_kref);
 728                         memcpy(&req->wb_verf, &hdr->verf.verifier,
 729                                sizeof(req->wb_verf));
 730                         nfs_mark_request_commit(req, hdr->lseg, &cinfo,
 731                                 hdr->ds_commit_idx);
 732                 } else if (flags == NFS_ODIRECT_RESCHED_WRITES) {
 733                         kref_get(&req->wb_kref);
 734                         nfs_mark_request_commit(req, NULL, &cinfo, 0);
 735                 }
 736                 nfs_unlock_and_release_request(req);
 737         }
 738
 739 out_put:
 740         if (put_dreq(dreq))
 741                 nfs_direct_write_complete(dreq);
 742         hdr->release(hdr);
 743 }
 744
 745 static void nfs_write_sync_pgio_error(struct list_head *head, int error)
 746 {
 747         struct nfs_page *req;
 748
 749         while (!list_empty(head)) {
 750                 req = nfs_list_entry(head->next);
 751                 nfs_list_remove_request(req);
 752                 nfs_unlock_and_release_request(req);
 753         }
 754 }
 755
 756 static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
 757 {
 758         struct nfs_direct_req *dreq = hdr->dreq;
 759
 760         spin_lock(&dreq->lock);
 761         if (dreq->error == 0) {
 762                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 763                 /* fake unstable write to let common nfs resend pages */
 764                 hdr->verf.committed = NFS_UNSTABLE;
 765                 hdr->good_bytes = hdr->args.offset + hdr->args.count -
 766                         hdr->io_start;
 767         }
 768         spin_unlock(&dreq->lock);
 769 }
 770
 771 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
 772         .error_cleanup = nfs_write_sync_pgio_error,
 773         .init_hdr = nfs_direct_pgio_init,
 774         .completion = nfs_direct_write_completion,
 775         .reschedule_io = nfs_direct_write_reschedule_io,
 776 };
 777
 778
 779 /*
 780  * NB: Return the value of the first error return code.  Subsequent
 781  *     errors after the first one are ignored.
 782  */
 783 /*
 784  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
 785  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
 786  * bail and stop sending more writes.  Write length accounting is
 787  * handled automatically by nfs_direct_write_result().  Otherwise, if
 788  * no requests have been sent, just return an error.
 789  */
 790 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 791                                                struct iov_iter *iter,
 792                                                loff_t pos)
 793 {
 794         struct nfs_pageio_descriptor desc;
 795         struct inode *inode = dreq->inode;
 796         ssize_t result = 0;
 797         size_t requested_bytes = 0;
 798         size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
 799
 800         nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false,
 801                               &nfs_direct_write_completion_ops);
 802         desc.pg_dreq = dreq;
 803         get_dreq(dreq);
 804         inode_dio_begin(inode);
 805
 806         NFS_I(inode)->write_io += iov_iter_count(iter);
 807         while (iov_iter_count(iter)) {
 808                 struct page **pagevec;
 809                 size_t bytes;
 810                 size_t pgbase;
 811                 unsigned npages, i;
 812
 813                 result = iov_iter_get_pages_alloc(iter, &pagevec,
 814                                                   wsize, &pgbase);
 815                 if (result < 0)
 816                         break;
 817
 818                 bytes = result;
 819                 iov_iter_advance(iter, bytes);
 820                 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
 821                 for (i = 0; i < npages; i++) {
 822                         struct nfs_page *req;
 823                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
 824
 825                         req = nfs_create_request(dreq->ctx, pagevec[i],
 826                                                  pgbase, req_len);
 827                         if (IS_ERR(req)) {
 828                                 result = PTR_ERR(req);
 829                                 break;
 830                         }
 831
 832                         if (desc.pg_error < 0) {
 833                                 nfs_free_request(req);
 834                                 result = desc.pg_error;
 835                                 break;
 836                         }
 837
 838                         nfs_lock_request(req);
 839                         req->wb_index = pos >> PAGE_SHIFT;
 840                         req->wb_offset = pos & ~PAGE_MASK;
 841                         if (!nfs_pageio_add_request(&desc, req)) {
 842                                 result = desc.pg_error;
 843                                 nfs_unlock_and_release_request(req);
 844                                 break;
 845                         }
 846                         pgbase = 0;
 847                         bytes -= req_len;
 848                         requested_bytes += req_len;
 849                         pos += req_len;
 850                         dreq->bytes_left -= req_len;
 851                 }
 852                 nfs_direct_release_pages(pagevec, npages);
 853                 kvfree(pagevec);
 854                 if (result < 0)
 855                         break;
 856         }
 857         nfs_pageio_complete(&desc);
 858
 859         /*
 860          * If no bytes were started, return the error, and let the
 861          * generic layer handle the completion.
 862          */
 863         if (requested_bytes == 0) {
 864                 inode_dio_end(inode);
 865                 nfs_direct_req_release(dreq);
 866                 return result < 0 ? result : -EIO;
 867         }
 868
 869         if (put_dreq(dreq))
 870                 nfs_direct_write_complete(dreq);
 871         return requested_bytes;
 872 }
 873
 874 /**
 875  * nfs_file_direct_write - file direct write operation for NFS files
 876  * @iocb: target I/O control block
 877  * @iter: vector of user buffers from which to write data
 878  *
 879  * We use this function for direct writes instead of calling
 880  * generic_file_aio_write() in order to avoid taking the inode
 881  * semaphore and updating the i_size.  The NFS server will set
 882  * the new i_size and this client must read the updated size
 883  * back into its cache.  We let the server do generic write
 884  * parameter checking and report problems.
 885  *
 886  * We eliminate local atime updates, see direct read above.
 887  *
 888  * We avoid unnecessary page cache invalidations for normal cached
 889  * readers of this file.
 890  *
 891  * Note that O_APPEND is not supported for NFS direct writes, as there
 892  * is no atomic O_APPEND write facility in the NFS protocol.
 893  */
 894 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
 895 {
 896         ssize_t result, requested;
 897         size_t count;
 898         struct file *file = iocb->ki_filp;
 899         struct address_space *mapping = file->f_mapping;
 900         struct inode *inode = mapping->host;
 901         struct nfs_direct_req *dreq;
 902         struct nfs_lock_context *l_ctx;
 903         loff_t pos, end;
 904
 905         dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
 906                 file, iov_iter_count(iter), (long long) iocb->ki_pos);
 907
 908         result = generic_write_checks(iocb, iter);
 909         if (result <= 0)
 910                 return result;
 911         count = result;
 912         nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 913
 914         pos = iocb->ki_pos;
 915         end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
 916
 917         task_io_account_write(count);
 918
 919         result = -ENOMEM;
 920         dreq = nfs_direct_req_alloc();
 921         if (!dreq)
 922                 goto out;
 923
 924         dreq->inode = inode;
 925         dreq->bytes_left = dreq->max_count = count;
 926         dreq->io_start = pos;
 927         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
 928         l_ctx = nfs_get_lock_context(dreq->ctx);
 929         if (IS_ERR(l_ctx)) {
 930                 result = PTR_ERR(l_ctx);
 931                 nfs_direct_req_release(dreq);
 932                 goto out_release;
 933         }
 934         dreq->l_ctx = l_ctx;
 935         if (!is_sync_kiocb(iocb))
 936                 dreq->iocb = iocb;
 937         pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
 938
 939         nfs_start_io_direct(inode);
 940
 941         requested = nfs_direct_write_schedule_iovec(dreq, iter, pos);
 942
 943         if (mapping->nrpages) {
 944                 invalidate_inode_pages2_range(mapping,
 945                                               pos >> PAGE_SHIFT, end);
 946         }
 947
 948         nfs_end_io_direct(inode);
 949
 950         if (requested > 0) {
 951                 result = nfs_direct_wait(dreq);
 952                 if (result > 0) {
 953                         requested -= result;
 954                         iocb->ki_pos = pos + result;
 955                         /* XXX: should check the generic_write_sync retval */
 956                         generic_write_sync(iocb, result);
 957                 }
 958                 iov_iter_revert(iter, requested);
 959         } else {
 960                 result = requested;
 961         }
 962 out_release:
 963         nfs_direct_req_release(dreq);
 964 out:
 965         return result;
 966 }
 967
 968 /**
 969  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
 970  *
 971  */
 972 int __init nfs_init_directcache(void)
 973 {
 974         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
 975                                                 sizeof(struct nfs_direct_req),
 976                                                 0, (SLAB_RECLAIM_ACCOUNT|
 977                                                         SLAB_MEM_SPREAD),
 978                                                 NULL);
 979         if (nfs_direct_cachep == NULL)
 980                 return -ENOMEM;
 981
 982         return 0;
 983 }
 984
 985 /**
 986  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
 987  *
 988  */
 989 void nfs_destroy_directcache(void)
 990 {
 991         kmem_cache_destroy(nfs_direct_cachep);
 992 }