fs/nfs/direct.c

   1 /*
   2  * linux/fs/nfs/direct.c
   3  *
   4  * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
   5  *
   6  * High-performance uncached I/O for the Linux NFS client
   7  *
   8  * There are important applications whose performance or correctness
   9  * depends on uncached access to file data.  Database clusters
  10  * (multiple copies of the same instance running on separate hosts)
  11  * implement their own cache coherency protocol that subsumes file
  12  * system cache protocols.  Applications that process datasets
  13  * considerably larger than the client's memory do not always benefit
  14  * from a local cache.  A streaming video server, for instance, has no
  15  * need to cache the contents of a file.
  16  *
  17  * When an application requests uncached I/O, all read and write requests
  18  * are made directly to the server; data stored or fetched via these
  19  * requests is not cached in the Linux page cache.  The client does not
  20  * correct unaligned requests from applications.  All requested bytes are
  21  * held on permanent storage before a direct write system call returns to
  22  * an application.
  23  *
  24  * Solaris implements an uncached I/O facility called directio() that
  25  * is used for backups and sequential I/O to very large files.  Solaris
  26  * also supports uncaching whole NFS partitions with "-o forcedirectio,"
  27  * an undocumented mount option.
  28  *
  29  * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
  30  * help from Andrew Morton.
  31  *
  32  * 18 Dec 2001  Initial implementation for 2.4  --cel
  33  * 08 Jul 2002  Version for 2.4.19, with bug fixes --trondmy
  34  * 08 Jun 2003  Port to 2.5 APIs  --cel
  35  * 31 Mar 2004  Handle direct I/O without VFS support  --cel
  36  * 15 Sep 2004  Parallel async reads  --cel
  37  * 04 May 2005  support O_DIRECT with aio  --cel
  38  *
  39  */
  40
  41 #include <linux/errno.h>
  42 #include <linux/sched.h>
  43 #include <linux/kernel.h>
  44 #include <linux/file.h>
  45 #include <linux/pagemap.h>
  46 #include <linux/kref.h>
  47 #include <linux/slab.h>
  48 #include <linux/task_io_accounting_ops.h>
  49
  50 #include <linux/nfs_fs.h>
  51 #include <linux/nfs_page.h>
  52 #include <linux/sunrpc/clnt.h>
  53
  54 #include <asm/uaccess.h>
  55 #include <linux/atomic.h>
  56
  57 #include "internal.h"
  58 #include "iostat.h"
  59 #include "pnfs.h"
  60
  61 #define NFSDBG_FACILITY         NFSDBG_VFS
  62
  63 static struct kmem_cache *nfs_direct_cachep;
  64
  65 /*
  66  * This represents a set of asynchronous requests that we're waiting on
  67  */
  68 struct nfs_direct_req {
  69         struct kref             kref;           /* release manager */
  70
  71         /* I/O parameters */
  72         struct nfs_open_context *ctx;           /* file open context info */
  73         struct nfs_lock_context *l_ctx;         /* Lock context info */
  74         struct kiocb *          iocb;           /* controlling i/o request */
  75         struct inode *          inode;          /* target file of i/o */
  76
  77         /* completion state */
  78         atomic_t                io_count;       /* i/os we're waiting for */
  79         spinlock_t              lock;           /* protect completion state */
  80         ssize_t                 count,          /* bytes actually processed */
  81                                 error;          /* any reported error */
  82         struct completion       completion;     /* wait for i/o completion */
  83
  84         /* commit state */
  85         struct nfs_mds_commit_info mds_cinfo;   /* Storage for cinfo */
  86         struct pnfs_ds_commit_info ds_cinfo;    /* Storage for cinfo */
  87         struct work_struct      work;
  88         int                     flags;
  89 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
  90 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
  91         struct nfs_writeverf    verf;           /* unstable write verifier */
  92 };
  93
  94 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
  95 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
  96 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
  97 static void nfs_direct_write_schedule_work(struct work_struct *work);
  98
  99 static inline void get_dreq(struct nfs_direct_req *dreq)
 100 {
 101         atomic_inc(&dreq->io_count);
 102 }
 103
 104 static inline int put_dreq(struct nfs_direct_req *dreq)
 105 {
 106         return atomic_dec_and_test(&dreq->io_count);
 107 }
 108
 109 /**
 110  * nfs_direct_IO - NFS address space operation for direct I/O
 111  * @rw: direction (read or write)
 112  * @iocb: target I/O control block
 113  * @iov: array of vectors that define I/O buffer
 114  * @pos: offset in file to begin the operation
 115  * @nr_segs: size of iovec array
 116  *
 117  * The presence of this routine in the address space ops vector means
 118  * the NFS client supports direct I/O.  However, we shunt off direct
 119  * read and write requests before the VFS gets them, so this method
 120  * should never be called.
 121  */
 122 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
 123 {
 124         dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
 125                         iocb->ki_filp->f_path.dentry->d_name.name,
 126                         (long long) pos, nr_segs);
 127
 128         return -EINVAL;
 129 }
 130
 131 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
 132 {
 133         unsigned int i;
 134         for (i = 0; i < npages; i++)
 135                 page_cache_release(pages[i]);
 136 }
 137
 138 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
 139                               struct nfs_direct_req *dreq)
 140 {
 141         cinfo->lock = &dreq->lock;
 142         cinfo->mds = &dreq->mds_cinfo;
 143         cinfo->ds = &dreq->ds_cinfo;
 144         cinfo->dreq = dreq;
 145         cinfo->completion_ops = &nfs_direct_commit_completion_ops;
 146 }
 147
 148 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
 149 {
 150         struct nfs_direct_req *dreq;
 151
 152         dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
 153         if (!dreq)
 154                 return NULL;
 155
 156         kref_init(&dreq->kref);
 157         kref_get(&dreq->kref);
 158         init_completion(&dreq->completion);
 159         INIT_LIST_HEAD(&dreq->mds_cinfo.list);
 160         INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
 161         spin_lock_init(&dreq->lock);
 162
 163         return dreq;
 164 }
 165
 166 static void nfs_direct_req_free(struct kref *kref)
 167 {
 168         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
 169
 170         if (dreq->l_ctx != NULL)
 171                 nfs_put_lock_context(dreq->l_ctx);
 172         if (dreq->ctx != NULL)
 173                 put_nfs_open_context(dreq->ctx);
 174         kmem_cache_free(nfs_direct_cachep, dreq);
 175 }
 176
 177 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
 178 {
 179         kref_put(&dreq->kref, nfs_direct_req_free);
 180 }
 181
 182 /*
 183  * Collects and returns the final error value/byte-count.
 184  */
 185 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
 186 {
 187         ssize_t result = -EIOCBQUEUED;
 188
 189         /* Async requests don't wait here */
 190         if (dreq->iocb)
 191                 goto out;
 192
 193         result = wait_for_completion_killable(&dreq->completion);
 194
 195         if (!result)
 196                 result = dreq->error;
 197         if (!result)
 198                 result = dreq->count;
 199
 200 out:
 201         return (ssize_t) result;
 202 }
 203
 204 /*
 205  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
 206  * the iocb is still valid here if this is a synchronous request.
 207  */
 208 static void nfs_direct_complete(struct nfs_direct_req *dreq)
 209 {
 210         if (dreq->iocb) {
 211                 long res = (long) dreq->error;
 212                 if (!res)
 213                         res = (long) dreq->count;
 214                 aio_complete(dreq->iocb, res, 0);
 215         }
 216         complete_all(&dreq->completion);
 217
 218         nfs_direct_req_release(dreq);
 219 }
 220
 221 static void nfs_direct_readpage_release(struct nfs_page *req)
 222 {
 223         dprintk("NFS: direct read done (%s/%lld %d@%lld)\n",
 224                 req->wb_context->dentry->d_inode->i_sb->s_id,
 225                 (long long)NFS_FILEID(req->wb_context->dentry->d_inode),
 226                 req->wb_bytes,
 227                 (long long)req_offset(req));
 228         nfs_release_request(req);
 229 }
 230
 231 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
 232 {
 233         unsigned long bytes = 0;
 234         struct nfs_direct_req *dreq = hdr->dreq;
 235
 236         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 237                 goto out_put;
 238
 239         spin_lock(&dreq->lock);
 240         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
 241                 dreq->error = hdr->error;
 242         else
 243                 dreq->count += hdr->good_bytes;
 244         spin_unlock(&dreq->lock);
 245
 246         while (!list_empty(&hdr->pages)) {
 247                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 248                 struct page *page = req->wb_page;
 249
 250                 if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 251                         if (bytes > hdr->good_bytes)
 252                                 zero_user(page, 0, PAGE_SIZE);
 253                         else if (hdr->good_bytes - bytes < PAGE_SIZE)
 254                                 zero_user_segment(page,
 255                                         hdr->good_bytes & ~PAGE_MASK,
 256                                         PAGE_SIZE);
 257                 }
 258                 if (!PageCompound(page)) {
 259                         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 260                                 if (bytes < hdr->good_bytes)
 261                                         set_page_dirty(page);
 262                         } else
 263                                 set_page_dirty(page);
 264                 }
 265                 bytes += req->wb_bytes;
 266                 nfs_list_remove_request(req);
 267                 nfs_direct_readpage_release(req);
 268         }
 269 out_put:
 270         if (put_dreq(dreq))
 271                 nfs_direct_complete(dreq);
 272         hdr->release(hdr);
 273 }
 274
 275 static void nfs_read_sync_pgio_error(struct list_head *head)
 276 {
 277         struct nfs_page *req;
 278
 279         while (!list_empty(head)) {
 280                 req = nfs_list_entry(head->next);
 281                 nfs_list_remove_request(req);
 282                 nfs_release_request(req);
 283         }
 284 }
 285
 286 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
 287 {
 288         get_dreq(hdr->dreq);
 289 }
 290
 291 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
 292         .error_cleanup = nfs_read_sync_pgio_error,
 293         .init_hdr = nfs_direct_pgio_init,
 294         .completion = nfs_direct_read_completion,
 295 };
 296
 297 /*
 298  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
 299  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
 300  * bail and stop sending more reads.  Read length accounting is
 301  * handled automatically by nfs_direct_read_result().  Otherwise, if
 302  * no requests have been sent, just return an error.
 303  */
 304 static ssize_t nfs_direct_read_schedule_segment(struct nfs_pageio_descriptor *desc,
 305                                                 const struct iovec *iov,
 306                                                 loff_t pos)
 307 {
 308         struct nfs_direct_req *dreq = desc->pg_dreq;
 309         struct nfs_open_context *ctx = dreq->ctx;
 310         struct inode *inode = ctx->dentry->d_inode;
 311         unsigned long user_addr = (unsigned long)iov->iov_base;
 312         size_t count = iov->iov_len;
 313         size_t rsize = NFS_SERVER(inode)->rsize;
 314         unsigned int pgbase;
 315         int result;
 316         ssize_t started = 0;
 317         struct page **pagevec = NULL;
 318         unsigned int npages;
 319
 320         do {
 321                 size_t bytes;
 322                 int i;
 323
 324                 pgbase = user_addr & ~PAGE_MASK;
 325                 bytes = min(max_t(size_t, rsize, PAGE_SIZE), count);
 326
 327                 result = -ENOMEM;
 328                 npages = nfs_page_array_len(pgbase, bytes);
 329                 if (!pagevec)
 330                         pagevec = kmalloc(npages * sizeof(struct page *),
 331                                           GFP_KERNEL);
 332                 if (!pagevec)
 333                         break;
 334                 down_read(&current->mm->mmap_sem);
 335                 result = get_user_pages(current, current->mm, user_addr,
 336                                         npages, 1, 0, pagevec, NULL);
 337                 up_read(&current->mm->mmap_sem);
 338                 if (result < 0)
 339                         break;
 340                 if ((unsigned)result < npages) {
 341                         bytes = result * PAGE_SIZE;
 342                         if (bytes <= pgbase) {
 343                                 nfs_direct_release_pages(pagevec, result);
 344                                 break;
 345                         }
 346                         bytes -= pgbase;
 347                         npages = result;
 348                 }
 349
 350                 for (i = 0; i < npages; i++) {
 351                         struct nfs_page *req;
 352                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
 353                         /* XXX do we need to do the eof zeroing found in async_filler? */
 354                         req = nfs_create_request(dreq->ctx, dreq->inode,
 355                                                  pagevec[i],
 356                                                  pgbase, req_len);
 357                         if (IS_ERR(req)) {
 358                                 result = PTR_ERR(req);
 359                                 break;
 360                         }
 361                         req->wb_index = pos >> PAGE_SHIFT;
 362                         req->wb_offset = pos & ~PAGE_MASK;
 363                         if (!nfs_pageio_add_request(desc, req)) {
 364                                 result = desc->pg_error;
 365                                 nfs_release_request(req);
 366                                 break;
 367                         }
 368                         pgbase = 0;
 369                         bytes -= req_len;
 370                         started += req_len;
 371                         user_addr += req_len;
 372                         pos += req_len;
 373                         count -= req_len;
 374                 }
 375                 /* The nfs_page now hold references to these pages */
 376                 nfs_direct_release_pages(pagevec, npages);
 377         } while (count != 0 && result >= 0);
 378
 379         kfree(pagevec);
 380
 381         if (started)
 382                 return started;
 383         return result < 0 ? (ssize_t) result : -EFAULT;
 384 }
 385
 386 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 387                                               const struct iovec *iov,
 388                                               unsigned long nr_segs,
 389                                               loff_t pos)
 390 {
 391         struct nfs_pageio_descriptor desc;
 392         ssize_t result = -EINVAL;
 393         size_t requested_bytes = 0;
 394         unsigned long seg;
 395
 396         nfs_pageio_init_read(&desc, dreq->inode,
 397                              &nfs_direct_read_completion_ops);
 398         get_dreq(dreq);
 399         desc.pg_dreq = dreq;
 400
 401         for (seg = 0; seg < nr_segs; seg++) {
 402                 const struct iovec *vec = &iov[seg];
 403                 result = nfs_direct_read_schedule_segment(&desc, vec, pos);
 404                 if (result < 0)
 405                         break;
 406                 requested_bytes += result;
 407                 if ((size_t)result < vec->iov_len)
 408                         break;
 409                 pos += vec->iov_len;
 410         }
 411
 412         nfs_pageio_complete(&desc);
 413
 414         /*
 415          * If no bytes were started, return the error, and let the
 416          * generic layer handle the completion.
 417          */
 418         if (requested_bytes == 0) {
 419                 nfs_direct_req_release(dreq);
 420                 return result < 0 ? result : -EIO;
 421         }
 422
 423         if (put_dreq(dreq))
 424                 nfs_direct_complete(dreq);
 425         return 0;
 426 }
 427
 428 static ssize_t nfs_direct_read(struct kiocb *iocb, const struct iovec *iov,
 429                                unsigned long nr_segs, loff_t pos)
 430 {
 431         ssize_t result = -ENOMEM;
 432         struct inode *inode = iocb->ki_filp->f_mapping->host;
 433         struct nfs_direct_req *dreq;
 434
 435         dreq = nfs_direct_req_alloc();
 436         if (dreq == NULL)
 437                 goto out;
 438
 439         dreq->inode = inode;
 440         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
 441         dreq->l_ctx = nfs_get_lock_context(dreq->ctx);
 442         if (dreq->l_ctx == NULL)
 443                 goto out_release;
 444         if (!is_sync_kiocb(iocb))
 445                 dreq->iocb = iocb;
 446
 447         result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos);
 448         if (!result)
 449                 result = nfs_direct_wait(dreq);
 450         NFS_I(inode)->read_io += result;
 451 out_release:
 452         nfs_direct_req_release(dreq);
 453 out:
 454         return result;
 455 }
 456
 457 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
 458 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
 459 {
 460         struct nfs_pageio_descriptor desc;
 461         struct nfs_page *req, *tmp;
 462         LIST_HEAD(reqs);
 463         struct nfs_commit_info cinfo;
 464         LIST_HEAD(failed);
 465
 466         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 467         pnfs_recover_commit_reqs(dreq->inode, &reqs, &cinfo);
 468         spin_lock(cinfo.lock);
 469         nfs_scan_commit_list(&cinfo.mds->list, &reqs, &cinfo, 0);
 470         spin_unlock(cinfo.lock);
 471
 472         dreq->count = 0;
 473         get_dreq(dreq);
 474
 475         nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE,
 476                               &nfs_direct_write_completion_ops);
 477         desc.pg_dreq = dreq;
 478
 479         list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
 480                 if (!nfs_pageio_add_request(&desc, req)) {
 481                         nfs_list_add_request(req, &failed);
 482                         spin_lock(cinfo.lock);
 483                         dreq->flags = 0;
 484                         dreq->error = -EIO;
 485                         spin_unlock(cinfo.lock);
 486                 }
 487         }
 488         nfs_pageio_complete(&desc);
 489
 490         while (!list_empty(&failed))
 491                 nfs_unlock_and_release_request(req);
 492
 493         if (put_dreq(dreq))
 494                 nfs_direct_write_complete(dreq, dreq->inode);
 495 }
 496
 497 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
 498 {
 499         struct nfs_direct_req *dreq = data->dreq;
 500         struct nfs_commit_info cinfo;
 501         struct nfs_page *req;
 502         int status = data->task.tk_status;
 503
 504         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 505         if (status < 0) {
 506                 dprintk("NFS: %5u commit failed with error %d.\n",
 507                         data->task.tk_pid, status);
 508                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 509         } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
 510                 dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid);
 511                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 512         }
 513
 514         dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status);
 515         while (!list_empty(&data->pages)) {
 516                 req = nfs_list_entry(data->pages.next);
 517                 nfs_list_remove_request(req);
 518                 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) {
 519                         /* Note the rewrite will go through mds */
 520                         kref_get(&req->wb_kref);
 521                         nfs_mark_request_commit(req, NULL, &cinfo);
 522                 }
 523                 nfs_unlock_and_release_request(req);
 524         }
 525
 526         if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
 527                 nfs_direct_write_complete(dreq, data->inode);
 528 }
 529
 530 static void nfs_direct_error_cleanup(struct nfs_inode *nfsi)
 531 {
 532         /* There is no lock to clear */
 533 }
 534
 535 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
 536         .completion = nfs_direct_commit_complete,
 537         .error_cleanup = nfs_direct_error_cleanup,
 538 };
 539
 540 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
 541 {
 542         int res;
 543         struct nfs_commit_info cinfo;
 544         LIST_HEAD(mds_list);
 545
 546         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 547         nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
 548         res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
 549         if (res < 0) /* res == -ENOMEM */
 550                 nfs_direct_write_reschedule(dreq);
 551 }
 552
 553 static void nfs_direct_write_schedule_work(struct work_struct *work)
 554 {
 555         struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
 556         int flags = dreq->flags;
 557
 558         dreq->flags = 0;
 559         switch (flags) {
 560                 case NFS_ODIRECT_DO_COMMIT:
 561                         nfs_direct_commit_schedule(dreq);
 562                         break;
 563                 case NFS_ODIRECT_RESCHED_WRITES:
 564                         nfs_direct_write_reschedule(dreq);
 565                         break;
 566                 default:
 567                         nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
 568                         nfs_direct_complete(dreq);
 569         }
 570 }
 571
 572 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
 573 {
 574         schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
 575 }
 576
 577 #else
 578 static void nfs_direct_write_schedule_work(struct work_struct *work)
 579 {
 580 }
 581
 582 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
 583 {
 584         nfs_zap_mapping(inode, inode->i_mapping);
 585         nfs_direct_complete(dreq);
 586 }
 587 #endif
 588
 589 /*
 590  * NB: Return the value of the first error return code.  Subsequent
 591  *     errors after the first one are ignored.
 592  */
 593 /*
 594  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
 595  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
 596  * bail and stop sending more writes.  Write length accounting is
 597  * handled automatically by nfs_direct_write_result().  Otherwise, if
 598  * no requests have been sent, just return an error.
 599  */
 600 static ssize_t nfs_direct_write_schedule_segment(struct nfs_pageio_descriptor *desc,
 601                                                  const struct iovec *iov,
 602                                                  loff_t pos)
 603 {
 604         struct nfs_direct_req *dreq = desc->pg_dreq;
 605         struct nfs_open_context *ctx = dreq->ctx;
 606         struct inode *inode = ctx->dentry->d_inode;
 607         unsigned long user_addr = (unsigned long)iov->iov_base;
 608         size_t count = iov->iov_len;
 609         size_t wsize = NFS_SERVER(inode)->wsize;
 610         unsigned int pgbase;
 611         int result;
 612         ssize_t started = 0;
 613         struct page **pagevec = NULL;
 614         unsigned int npages;
 615
 616         do {
 617                 size_t bytes;
 618                 int i;
 619
 620                 pgbase = user_addr & ~PAGE_MASK;
 621                 bytes = min(max_t(size_t, wsize, PAGE_SIZE), count);
 622
 623                 result = -ENOMEM;
 624                 npages = nfs_page_array_len(pgbase, bytes);
 625                 if (!pagevec)
 626                         pagevec = kmalloc(npages * sizeof(struct page *), GFP_KERNEL);
 627                 if (!pagevec)
 628                         break;
 629
 630                 down_read(&current->mm->mmap_sem);
 631                 result = get_user_pages(current, current->mm, user_addr,
 632                                         npages, 0, 0, pagevec, NULL);
 633                 up_read(&current->mm->mmap_sem);
 634                 if (result < 0)
 635                         break;
 636
 637                 if ((unsigned)result < npages) {
 638                         bytes = result * PAGE_SIZE;
 639                         if (bytes <= pgbase) {
 640                                 nfs_direct_release_pages(pagevec, result);
 641                                 break;
 642                         }
 643                         bytes -= pgbase;
 644                         npages = result;
 645                 }
 646
 647                 for (i = 0; i < npages; i++) {
 648                         struct nfs_page *req;
 649                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
 650
 651                         req = nfs_create_request(dreq->ctx, dreq->inode,
 652                                                  pagevec[i],
 653                                                  pgbase, req_len);
 654                         if (IS_ERR(req)) {
 655                                 result = PTR_ERR(req);
 656                                 break;
 657                         }
 658                         nfs_lock_request(req);
 659                         req->wb_index = pos >> PAGE_SHIFT;
 660                         req->wb_offset = pos & ~PAGE_MASK;
 661                         if (!nfs_pageio_add_request(desc, req)) {
 662                                 result = desc->pg_error;
 663                                 nfs_unlock_and_release_request(req);
 664                                 break;
 665                         }
 666                         pgbase = 0;
 667                         bytes -= req_len;
 668                         started += req_len;
 669                         user_addr += req_len;
 670                         pos += req_len;
 671                         count -= req_len;
 672                 }
 673                 /* The nfs_page now hold references to these pages */
 674                 nfs_direct_release_pages(pagevec, npages);
 675         } while (count != 0 && result >= 0);
 676
 677         kfree(pagevec);
 678
 679         if (started)
 680                 return started;
 681         return result < 0 ? (ssize_t) result : -EFAULT;
 682 }
 683
 684 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
 685 {
 686         struct nfs_direct_req *dreq = hdr->dreq;
 687         struct nfs_commit_info cinfo;
 688         int bit = -1;
 689         struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 690
 691         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 692                 goto out_put;
 693
 694         nfs_init_cinfo_from_dreq(&cinfo, dreq);
 695
 696         spin_lock(&dreq->lock);
 697
 698         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 699                 dreq->flags = 0;
 700                 dreq->error = hdr->error;
 701         }
 702         if (dreq->error != 0)
 703                 bit = NFS_IOHDR_ERROR;
 704         else {
 705                 dreq->count += hdr->good_bytes;
 706                 if (test_bit(NFS_IOHDR_NEED_RESCHED, &hdr->flags)) {
 707                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 708                         bit = NFS_IOHDR_NEED_RESCHED;
 709                 } else if (test_bit(NFS_IOHDR_NEED_COMMIT, &hdr->flags)) {
 710                         if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
 711                                 bit = NFS_IOHDR_NEED_RESCHED;
 712                         else if (dreq->flags == 0) {
 713                                 memcpy(&dreq->verf, &req->wb_verf,
 714                                        sizeof(dreq->verf));
 715                                 bit = NFS_IOHDR_NEED_COMMIT;
 716                                 dreq->flags = NFS_ODIRECT_DO_COMMIT;
 717                         } else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) {
 718                                 if (memcmp(&dreq->verf, &req->wb_verf, sizeof(dreq->verf))) {
 719                                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 720                                         bit = NFS_IOHDR_NEED_RESCHED;
 721                                 } else
 722                                         bit = NFS_IOHDR_NEED_COMMIT;
 723                         }
 724                 }
 725         }
 726         spin_unlock(&dreq->lock);
 727
 728         while (!list_empty(&hdr->pages)) {
 729                 req = nfs_list_entry(hdr->pages.next);
 730                 nfs_list_remove_request(req);
 731                 switch (bit) {
 732                 case NFS_IOHDR_NEED_RESCHED:
 733                 case NFS_IOHDR_NEED_COMMIT:
 734                         kref_get(&req->wb_kref);
 735                         nfs_mark_request_commit(req, hdr->lseg, &cinfo);
 736                 }
 737                 nfs_unlock_and_release_request(req);
 738         }
 739
 740 out_put:
 741         if (put_dreq(dreq))
 742                 nfs_direct_write_complete(dreq, hdr->inode);
 743         hdr->release(hdr);
 744 }
 745
 746 static void nfs_write_sync_pgio_error(struct list_head *head)
 747 {
 748         struct nfs_page *req;
 749
 750         while (!list_empty(head)) {
 751                 req = nfs_list_entry(head->next);
 752                 nfs_list_remove_request(req);
 753                 nfs_unlock_and_release_request(req);
 754         }
 755 }
 756
 757 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
 758         .error_cleanup = nfs_write_sync_pgio_error,
 759         .init_hdr = nfs_direct_pgio_init,
 760         .completion = nfs_direct_write_completion,
 761 };
 762
 763 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 764                                                const struct iovec *iov,
 765                                                unsigned long nr_segs,
 766                                                loff_t pos)
 767 {
 768         struct nfs_pageio_descriptor desc;
 769         ssize_t result = 0;
 770         size_t requested_bytes = 0;
 771         unsigned long seg;
 772
 773         nfs_pageio_init_write(&desc, dreq->inode, FLUSH_COND_STABLE,
 774                               &nfs_direct_write_completion_ops);
 775         desc.pg_dreq = dreq;
 776         get_dreq(dreq);
 777
 778         for (seg = 0; seg < nr_segs; seg++) {
 779                 const struct iovec *vec = &iov[seg];
 780                 result = nfs_direct_write_schedule_segment(&desc, vec, pos);
 781                 if (result < 0)
 782                         break;
 783                 requested_bytes += result;
 784                 if ((size_t)result < vec->iov_len)
 785                         break;
 786                 pos += vec->iov_len;
 787         }
 788         nfs_pageio_complete(&desc);
 789         NFS_I(dreq->inode)->write_io += desc.pg_bytes_written;
 790
 791         /*
 792          * If no bytes were started, return the error, and let the
 793          * generic layer handle the completion.
 794          */
 795         if (requested_bytes == 0) {
 796                 nfs_direct_req_release(dreq);
 797                 return result < 0 ? result : -EIO;
 798         }
 799
 800         if (put_dreq(dreq))
 801                 nfs_direct_write_complete(dreq, dreq->inode);
 802         return 0;
 803 }
 804
 805 static ssize_t nfs_direct_write(struct kiocb *iocb, const struct iovec *iov,
 806                                 unsigned long nr_segs, loff_t pos,
 807                                 size_t count)
 808 {
 809         ssize_t result = -ENOMEM;
 810         struct inode *inode = iocb->ki_filp->f_mapping->host;
 811         struct nfs_direct_req *dreq;
 812
 813         dreq = nfs_direct_req_alloc();
 814         if (!dreq)
 815                 goto out;
 816
 817         dreq->inode = inode;
 818         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
 819         dreq->l_ctx = nfs_get_lock_context(dreq->ctx);
 820         if (dreq->l_ctx == NULL)
 821                 goto out_release;
 822         if (!is_sync_kiocb(iocb))
 823                 dreq->iocb = iocb;
 824
 825         result = nfs_direct_write_schedule_iovec(dreq, iov, nr_segs, pos);
 826         if (!result)
 827                 result = nfs_direct_wait(dreq);
 828 out_release:
 829         nfs_direct_req_release(dreq);
 830 out:
 831         return result;
 832 }
 833
 834 /**
 835  * nfs_file_direct_read - file direct read operation for NFS files
 836  * @iocb: target I/O control block
 837  * @iov: vector of user buffers into which to read data
 838  * @nr_segs: size of iov vector
 839  * @pos: byte offset in file where reading starts
 840  *
 841  * We use this function for direct reads instead of calling
 842  * generic_file_aio_read() in order to avoid gfar's check to see if
 843  * the request starts before the end of the file.  For that check
 844  * to work, we must generate a GETATTR before each direct read, and
 845  * even then there is a window between the GETATTR and the subsequent
 846  * READ where the file size could change.  Our preference is simply
 847  * to do all reads the application wants, and the server will take
 848  * care of managing the end of file boundary.
 849  *
 850  * This function also eliminates unnecessarily updating the file's
 851  * atime locally, as the NFS server sets the file's atime, and this
 852  * client must read the updated atime from the server back into its
 853  * cache.
 854  */
 855 ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
 856                                 unsigned long nr_segs, loff_t pos)
 857 {
 858         ssize_t retval = -EINVAL;
 859         struct file *file = iocb->ki_filp;
 860         struct address_space *mapping = file->f_mapping;
 861         size_t count;
 862
 863         count = iov_length(iov, nr_segs);
 864         nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
 865
 866         dfprintk(FILE, "NFS: direct read(%s/%s, %zd@%Ld)\n",
 867                 file->f_path.dentry->d_parent->d_name.name,
 868                 file->f_path.dentry->d_name.name,
 869                 count, (long long) pos);
 870
 871         retval = 0;
 872         if (!count)
 873                 goto out;
 874
 875         retval = nfs_sync_mapping(mapping);
 876         if (retval)
 877                 goto out;
 878
 879         task_io_account_read(count);
 880
 881         retval = nfs_direct_read(iocb, iov, nr_segs, pos);
 882         if (retval > 0)
 883                 iocb->ki_pos = pos + retval;
 884
 885 out:
 886         return retval;
 887 }
 888
 889 /**
 890  * nfs_file_direct_write - file direct write operation for NFS files
 891  * @iocb: target I/O control block
 892  * @iov: vector of user buffers from which to write data
 893  * @nr_segs: size of iov vector
 894  * @pos: byte offset in file where writing starts
 895  *
 896  * We use this function for direct writes instead of calling
 897  * generic_file_aio_write() in order to avoid taking the inode
 898  * semaphore and updating the i_size.  The NFS server will set
 899  * the new i_size and this client must read the updated size
 900  * back into its cache.  We let the server do generic write
 901  * parameter checking and report problems.
 902  *
 903  * We eliminate local atime updates, see direct read above.
 904  *
 905  * We avoid unnecessary page cache invalidations for normal cached
 906  * readers of this file.
 907  *
 908  * Note that O_APPEND is not supported for NFS direct writes, as there
 909  * is no atomic O_APPEND write facility in the NFS protocol.
 910  */
 911 ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
 912                                 unsigned long nr_segs, loff_t pos)
 913 {
 914         ssize_t retval = -EINVAL;
 915         struct file *file = iocb->ki_filp;
 916         struct address_space *mapping = file->f_mapping;
 917         size_t count;
 918
 919         count = iov_length(iov, nr_segs);
 920         nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 921
 922         dfprintk(FILE, "NFS: direct write(%s/%s, %zd@%Ld)\n",
 923                 file->f_path.dentry->d_parent->d_name.name,
 924                 file->f_path.dentry->d_name.name,
 925                 count, (long long) pos);
 926
 927         retval = generic_write_checks(file, &pos, &count, 0);
 928         if (retval)
 929                 goto out;
 930
 931         retval = -EINVAL;
 932         if ((ssize_t) count < 0)
 933                 goto out;
 934         retval = 0;
 935         if (!count)
 936                 goto out;
 937
 938         retval = nfs_sync_mapping(mapping);
 939         if (retval)
 940                 goto out;
 941
 942         task_io_account_write(count);
 943
 944         retval = nfs_direct_write(iocb, iov, nr_segs, pos, count);
 945         if (retval > 0) {
 946                 struct inode *inode = mapping->host;
 947
 948                 iocb->ki_pos = pos + retval;
 949                 spin_lock(&inode->i_lock);
 950                 if (i_size_read(inode) < iocb->ki_pos)
 951                         i_size_write(inode, iocb->ki_pos);
 952                 spin_unlock(&inode->i_lock);
 953         }
 954 out:
 955         return retval;
 956 }
 957
 958 /**
 959  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
 960  *
 961  */
 962 int __init nfs_init_directcache(void)
 963 {
 964         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
 965                                                 sizeof(struct nfs_direct_req),
 966                                                 0, (SLAB_RECLAIM_ACCOUNT|
 967                                                         SLAB_MEM_SPREAD),
 968                                                 NULL);
 969         if (nfs_direct_cachep == NULL)
 970                 return -ENOMEM;
 971
 972         return 0;
 973 }
 974
 975 /**
 976  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
 977  *
 978  */
 979 void nfs_destroy_directcache(void)
 980 {
 981         kmem_cache_destroy(nfs_direct_cachep);
 982 }