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   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
  48 #include <linux/nfs_fs.h>
  49 #include <linux/nfs_page.h>
  50 #include <linux/sunrpc/clnt.h>
  51
  52 #include <asm/system.h>
  53 #include <asm/uaccess.h>
  54 #include <asm/atomic.h>
  55
  56 #include "internal.h"
  57 #include "iostat.h"
  58
  59 #define NFSDBG_FACILITY         NFSDBG_VFS
  60
  61 static struct kmem_cache *nfs_direct_cachep;
  62
  63 /*
  64  * This represents a set of asynchronous requests that we're waiting on
  65  */
  66 struct nfs_direct_req {
  67         struct kref             kref;           /* release manager */
  68
  69         /* I/O parameters */
  70         struct nfs_open_context *ctx;           /* file open context info */
  71         struct kiocb *          iocb;           /* controlling i/o request */
  72         struct inode *          inode;          /* target file of i/o */
  73
  74         /* completion state */
  75         atomic_t                io_count;       /* i/os we're waiting for */
  76         spinlock_t              lock;           /* protect completion state */
  77         ssize_t                 count,          /* bytes actually processed */
  78                                 error;          /* any reported error */
  79         struct completion       completion;     /* wait for i/o completion */
  80
  81         /* commit state */
  82         struct list_head        rewrite_list;   /* saved nfs_write_data structs */
  83         struct nfs_write_data * commit_data;    /* special write_data for commits */
  84         int                     flags;
  85 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
  86 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
  87         struct nfs_writeverf    verf;           /* unstable write verifier */
  88 };
  89
  90 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
  91 static const struct rpc_call_ops nfs_write_direct_ops;
  92
  93 static inline void get_dreq(struct nfs_direct_req *dreq)
  94 {
  95         atomic_inc(&dreq->io_count);
  96 }
  97
  98 static inline int put_dreq(struct nfs_direct_req *dreq)
  99 {
 100         return atomic_dec_and_test(&dreq->io_count);
 101 }
 102
 103 /**
 104  * nfs_direct_IO - NFS address space operation for direct I/O
 105  * @rw: direction (read or write)
 106  * @iocb: target I/O control block
 107  * @iov: array of vectors that define I/O buffer
 108  * @pos: offset in file to begin the operation
 109  * @nr_segs: size of iovec array
 110  *
 111  * The presence of this routine in the address space ops vector means
 112  * the NFS client supports direct I/O.  However, we shunt off direct
 113  * read and write requests before the VFS gets them, so this method
 114  * should never be called.
 115  */
 116 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
 117 {
 118         dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
 119                         iocb->ki_filp->f_path.dentry->d_name.name,
 120                         (long long) pos, nr_segs);
 121
 122         return -EINVAL;
 123 }
 124
 125 static void nfs_direct_dirty_pages(struct page **pages, unsigned int pgbase, size_t count)
 126 {
 127         unsigned int npages;
 128         unsigned int i;
 129
 130         if (count == 0)
 131                 return;
 132         pages += (pgbase >> PAGE_SHIFT);
 133         npages = (count + (pgbase & ~PAGE_MASK) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 134         for (i = 0; i < npages; i++) {
 135                 struct page *page = pages[i];
 136                 if (!PageCompound(page))
 137                         set_page_dirty(page);
 138         }
 139 }
 140
 141 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
 142 {
 143         unsigned int i;
 144         for (i = 0; i < npages; i++)
 145                 page_cache_release(pages[i]);
 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_alloc(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->rewrite_list);
 160         dreq->iocb = NULL;
 161         dreq->ctx = NULL;
 162         spin_lock_init(&dreq->lock);
 163         atomic_set(&dreq->io_count, 0);
 164         dreq->count = 0;
 165         dreq->error = 0;
 166         dreq->flags = 0;
 167
 168         return dreq;
 169 }
 170
 171 static void nfs_direct_req_release(struct kref *kref)
 172 {
 173         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
 174
 175         if (dreq->ctx != NULL)
 176                 put_nfs_open_context(dreq->ctx);
 177         kmem_cache_free(nfs_direct_cachep, dreq);
 178 }
 179
 180 /*
 181  * Collects and returns the final error value/byte-count.
 182  */
 183 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
 184 {
 185         ssize_t result = -EIOCBQUEUED;
 186
 187         /* Async requests don't wait here */
 188         if (dreq->iocb)
 189                 goto out;
 190
 191         result = wait_for_completion_interruptible(&dreq->completion);
 192
 193         if (!result)
 194                 result = dreq->error;
 195         if (!result)
 196                 result = dreq->count;
 197
 198 out:
 199         kref_put(&dreq->kref, nfs_direct_req_release);
 200         return (ssize_t) result;
 201 }
 202
 203 /*
 204  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
 205  * the iocb is still valid here if this is a synchronous request.
 206  */
 207 static void nfs_direct_complete(struct nfs_direct_req *dreq)
 208 {
 209         if (dreq->iocb) {
 210                 long res = (long) dreq->error;
 211                 if (!res)
 212                         res = (long) dreq->count;
 213                 aio_complete(dreq->iocb, res, 0);
 214         }
 215         complete_all(&dreq->completion);
 216
 217         kref_put(&dreq->kref, nfs_direct_req_release);
 218 }
 219
 220 /*
 221  * We must hold a reference to all the pages in this direct read request
 222  * until the RPCs complete.  This could be long *after* we are woken up in
 223  * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
 224  */
 225 static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
 226 {
 227         struct nfs_read_data *data = calldata;
 228         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
 229
 230         if (nfs_readpage_result(task, data) != 0)
 231                 return;
 232
 233         spin_lock(&dreq->lock);
 234         if (unlikely(task->tk_status < 0)) {
 235                 dreq->error = task->tk_status;
 236                 spin_unlock(&dreq->lock);
 237         } else {
 238                 dreq->count += data->res.count;
 239                 spin_unlock(&dreq->lock);
 240                 nfs_direct_dirty_pages(data->pagevec,
 241                                 data->args.pgbase,
 242                                 data->res.count);
 243         }
 244         nfs_direct_release_pages(data->pagevec, data->npages);
 245
 246         if (put_dreq(dreq))
 247                 nfs_direct_complete(dreq);
 248 }
 249
 250 static const struct rpc_call_ops nfs_read_direct_ops = {
 251         .rpc_call_done = nfs_direct_read_result,
 252         .rpc_release = nfs_readdata_release,
 253 };
 254
 255 /*
 256  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
 257  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
 258  * bail and stop sending more reads.  Read length accounting is
 259  * handled automatically by nfs_direct_read_result().  Otherwise, if
 260  * no requests have been sent, just return an error.
 261  */
 262 static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos)
 263 {
 264         struct nfs_open_context *ctx = dreq->ctx;
 265         struct inode *inode = ctx->dentry->d_inode;
 266         size_t rsize = NFS_SERVER(inode)->rsize;
 267         unsigned int pgbase;
 268         int result;
 269         ssize_t started = 0;
 270
 271         get_dreq(dreq);
 272
 273         do {
 274                 struct nfs_read_data *data;
 275                 size_t bytes;
 276
 277                 pgbase = user_addr & ~PAGE_MASK;
 278                 bytes = min(rsize,count);
 279
 280                 result = -ENOMEM;
 281                 data = nfs_readdata_alloc(nfs_page_array_len(pgbase, bytes));
 282                 if (unlikely(!data))
 283                         break;
 284
 285                 down_read(&current->mm->mmap_sem);
 286                 result = get_user_pages(current, current->mm, user_addr,
 287                                         data->npages, 1, 0, data->pagevec, NULL);
 288                 up_read(&current->mm->mmap_sem);
 289                 if (result < 0) {
 290                         nfs_readdata_release(data);
 291                         break;
 292                 }
 293                 if ((unsigned)result < data->npages) {
 294                         nfs_direct_release_pages(data->pagevec, result);
 295                         nfs_readdata_release(data);
 296                         break;
 297                 }
 298
 299                 get_dreq(dreq);
 300
 301                 data->req = (struct nfs_page *) dreq;
 302                 data->inode = inode;
 303                 data->cred = ctx->cred;
 304                 data->args.fh = NFS_FH(inode);
 305                 data->args.context = ctx;
 306                 data->args.offset = pos;
 307                 data->args.pgbase = pgbase;
 308                 data->args.pages = data->pagevec;
 309                 data->args.count = bytes;
 310                 data->res.fattr = &data->fattr;
 311                 data->res.eof = 0;
 312                 data->res.count = bytes;
 313
 314                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
 315                                 &nfs_read_direct_ops, data);
 316                 NFS_PROTO(inode)->read_setup(data);
 317
 318                 data->task.tk_cookie = (unsigned long) inode;
 319
 320                 rpc_execute(&data->task);
 321
 322                 dprintk("NFS: %5u initiated direct read call "
 323                         "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
 324                                 data->task.tk_pid,
 325                                 inode->i_sb->s_id,
 326                                 (long long)NFS_FILEID(inode),
 327                                 bytes,
 328                                 (unsigned long long)data->args.offset);
 329
 330                 started += bytes;
 331                 user_addr += bytes;
 332                 pos += bytes;
 333                 /* FIXME: Remove this unnecessary math from final patch */
 334                 pgbase += bytes;
 335                 pgbase &= ~PAGE_MASK;
 336                 BUG_ON(pgbase != (user_addr & ~PAGE_MASK));
 337
 338                 count -= bytes;
 339         } while (count != 0);
 340
 341         if (put_dreq(dreq))
 342                 nfs_direct_complete(dreq);
 343
 344         if (started)
 345                 return 0;
 346         return result < 0 ? (ssize_t) result : -EFAULT;
 347 }
 348
 349 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 350 {
 351         ssize_t result = 0;
 352         sigset_t oldset;
 353         struct inode *inode = iocb->ki_filp->f_mapping->host;
 354         struct rpc_clnt *clnt = NFS_CLIENT(inode);
 355         struct nfs_direct_req *dreq;
 356
 357         dreq = nfs_direct_req_alloc();
 358         if (!dreq)
 359                 return -ENOMEM;
 360
 361         dreq->inode = inode;
 362         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
 363         if (!is_sync_kiocb(iocb))
 364                 dreq->iocb = iocb;
 365
 366         nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
 367         rpc_clnt_sigmask(clnt, &oldset);
 368         result = nfs_direct_read_schedule(dreq, user_addr, count, pos);
 369         if (!result)
 370                 result = nfs_direct_wait(dreq);
 371         rpc_clnt_sigunmask(clnt, &oldset);
 372
 373         return result;
 374 }
 375
 376 static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
 377 {
 378         while (!list_empty(&dreq->rewrite_list)) {
 379                 struct nfs_write_data *data = list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
 380                 list_del(&data->pages);
 381                 nfs_direct_release_pages(data->pagevec, data->npages);
 382                 nfs_writedata_release(data);
 383         }
 384 }
 385
 386 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
 387 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
 388 {
 389         struct inode *inode = dreq->inode;
 390         struct list_head *p;
 391         struct nfs_write_data *data;
 392
 393         dreq->count = 0;
 394         get_dreq(dreq);
 395
 396         list_for_each(p, &dreq->rewrite_list) {
 397                 data = list_entry(p, struct nfs_write_data, pages);
 398
 399                 get_dreq(dreq);
 400
 401                 /*
 402                  * Reset data->res.
 403                  */
 404                 nfs_fattr_init(&data->fattr);
 405                 data->res.count = data->args.count;
 406                 memset(&data->verf, 0, sizeof(data->verf));
 407
 408                 /*
 409                  * Reuse data->task; data->args should not have changed
 410                  * since the original request was sent.
 411                  */
 412                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
 413                                 &nfs_write_direct_ops, data);
 414                 NFS_PROTO(inode)->write_setup(data, FLUSH_STABLE);
 415
 416                 data->task.tk_priority = RPC_PRIORITY_NORMAL;
 417                 data->task.tk_cookie = (unsigned long) inode;
 418
 419                 /*
 420                  * We're called via an RPC callback, so BKL is already held.
 421                  */
 422                 rpc_execute(&data->task);
 423
 424                 dprintk("NFS: %5u rescheduled direct write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
 425                                 data->task.tk_pid,
 426                                 inode->i_sb->s_id,
 427                                 (long long)NFS_FILEID(inode),
 428                                 data->args.count,
 429                                 (unsigned long long)data->args.offset);
 430         }
 431
 432         if (put_dreq(dreq))
 433                 nfs_direct_write_complete(dreq, inode);
 434 }
 435
 436 static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
 437 {
 438         struct nfs_write_data *data = calldata;
 439         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
 440
 441         /* Call the NFS version-specific code */
 442         if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
 443                 return;
 444         if (unlikely(task->tk_status < 0)) {
 445                 dprintk("NFS: %5u commit failed with error %d.\n",
 446                                 task->tk_pid, task->tk_status);
 447                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 448         } else if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
 449                 dprintk("NFS: %5u commit verify failed\n", task->tk_pid);
 450                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 451         }
 452
 453         dprintk("NFS: %5u commit returned %d\n", task->tk_pid, task->tk_status);
 454         nfs_direct_write_complete(dreq, data->inode);
 455 }
 456
 457 static const struct rpc_call_ops nfs_commit_direct_ops = {
 458         .rpc_call_done = nfs_direct_commit_result,
 459         .rpc_release = nfs_commit_release,
 460 };
 461
 462 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
 463 {
 464         struct nfs_write_data *data = dreq->commit_data;
 465
 466         data->inode = dreq->inode;
 467         data->cred = dreq->ctx->cred;
 468
 469         data->args.fh = NFS_FH(data->inode);
 470         data->args.offset = 0;
 471         data->args.count = 0;
 472         data->res.count = 0;
 473         data->res.fattr = &data->fattr;
 474         data->res.verf = &data->verf;
 475
 476         rpc_init_task(&data->task, NFS_CLIENT(dreq->inode), RPC_TASK_ASYNC,
 477                                 &nfs_commit_direct_ops, data);
 478         NFS_PROTO(data->inode)->commit_setup(data, 0);
 479
 480         data->task.tk_priority = RPC_PRIORITY_NORMAL;
 481         data->task.tk_cookie = (unsigned long)data->inode;
 482         /* Note: task.tk_ops->rpc_release will free dreq->commit_data */
 483         dreq->commit_data = NULL;
 484
 485         dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);
 486
 487         rpc_execute(&data->task);
 488 }
 489
 490 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
 491 {
 492         int flags = dreq->flags;
 493
 494         dreq->flags = 0;
 495         switch (flags) {
 496                 case NFS_ODIRECT_DO_COMMIT:
 497                         nfs_direct_commit_schedule(dreq);
 498                         break;
 499                 case NFS_ODIRECT_RESCHED_WRITES:
 500                         nfs_direct_write_reschedule(dreq);
 501                         break;
 502                 default:
 503                         nfs_end_data_update(inode);
 504                         if (dreq->commit_data != NULL)
 505                                 nfs_commit_free(dreq->commit_data);
 506                         nfs_direct_free_writedata(dreq);
 507                         nfs_zap_mapping(inode, inode->i_mapping);
 508                         nfs_direct_complete(dreq);
 509         }
 510 }
 511
 512 static void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
 513 {
 514         dreq->commit_data = nfs_commit_alloc();
 515         if (dreq->commit_data != NULL)
 516                 dreq->commit_data->req = (struct nfs_page *) dreq;
 517 }
 518 #else
 519 static inline void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
 520 {
 521         dreq->commit_data = NULL;
 522 }
 523
 524 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
 525 {
 526         nfs_end_data_update(inode);
 527         nfs_direct_free_writedata(dreq);
 528         nfs_zap_mapping(inode, inode->i_mapping);
 529         nfs_direct_complete(dreq);
 530 }
 531 #endif
 532
 533 static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
 534 {
 535         struct nfs_write_data *data = calldata;
 536         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
 537         int status = task->tk_status;
 538
 539         if (nfs_writeback_done(task, data) != 0)
 540                 return;
 541
 542         spin_lock(&dreq->lock);
 543
 544         if (unlikely(dreq->error != 0))
 545                 goto out_unlock;
 546         if (unlikely(status < 0)) {
 547                 /* An error has occured, so we should not commit */
 548                 dreq->flags = 0;
 549                 dreq->error = status;
 550         }
 551
 552         dreq->count += data->res.count;
 553
 554         if (data->res.verf->committed != NFS_FILE_SYNC) {
 555                 switch (dreq->flags) {
 556                         case 0:
 557                                 memcpy(&dreq->verf, &data->verf, sizeof(dreq->verf));
 558                                 dreq->flags = NFS_ODIRECT_DO_COMMIT;
 559                                 break;
 560                         case NFS_ODIRECT_DO_COMMIT:
 561                                 if (memcmp(&dreq->verf, &data->verf, sizeof(dreq->verf))) {
 562                                         dprintk("NFS: %5u write verify failed\n", task->tk_pid);
 563                                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
 564                                 }
 565                 }
 566         }
 567 out_unlock:
 568         spin_unlock(&dreq->lock);
 569 }
 570
 571 /*
 572  * NB: Return the value of the first error return code.  Subsequent
 573  *     errors after the first one are ignored.
 574  */
 575 static void nfs_direct_write_release(void *calldata)
 576 {
 577         struct nfs_write_data *data = calldata;
 578         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
 579
 580         if (put_dreq(dreq))
 581                 nfs_direct_write_complete(dreq, data->inode);
 582 }
 583
 584 static const struct rpc_call_ops nfs_write_direct_ops = {
 585         .rpc_call_done = nfs_direct_write_result,
 586         .rpc_release = nfs_direct_write_release,
 587 };
 588
 589 /*
 590  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
 591  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
 592  * bail and stop sending more writes.  Write length accounting is
 593  * handled automatically by nfs_direct_write_result().  Otherwise, if
 594  * no requests have been sent, just return an error.
 595  */
 596 static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync)
 597 {
 598         struct nfs_open_context *ctx = dreq->ctx;
 599         struct inode *inode = ctx->dentry->d_inode;
 600         size_t wsize = NFS_SERVER(inode)->wsize;
 601         unsigned int pgbase;
 602         int result;
 603         ssize_t started = 0;
 604
 605         get_dreq(dreq);
 606
 607         do {
 608                 struct nfs_write_data *data;
 609                 size_t bytes;
 610
 611                 pgbase = user_addr & ~PAGE_MASK;
 612                 bytes = min(wsize,count);
 613
 614                 result = -ENOMEM;
 615                 data = nfs_writedata_alloc(nfs_page_array_len(pgbase, bytes));
 616                 if (unlikely(!data))
 617                         break;
 618
 619                 down_read(&current->mm->mmap_sem);
 620                 result = get_user_pages(current, current->mm, user_addr,
 621                                         data->npages, 0, 0, data->pagevec, NULL);
 622                 up_read(&current->mm->mmap_sem);
 623                 if (result < 0) {
 624                         nfs_writedata_release(data);
 625                         break;
 626                 }
 627                 if ((unsigned)result < data->npages) {
 628                         nfs_direct_release_pages(data->pagevec, result);
 629                         nfs_writedata_release(data);
 630                         break;
 631                 }
 632
 633                 get_dreq(dreq);
 634
 635                 list_move_tail(&data->pages, &dreq->rewrite_list);
 636
 637                 data->req = (struct nfs_page *) dreq;
 638                 data->inode = inode;
 639                 data->cred = ctx->cred;
 640                 data->args.fh = NFS_FH(inode);
 641                 data->args.context = ctx;
 642                 data->args.offset = pos;
 643                 data->args.pgbase = pgbase;
 644                 data->args.pages = data->pagevec;
 645                 data->args.count = bytes;
 646                 data->res.fattr = &data->fattr;
 647                 data->res.count = bytes;
 648                 data->res.verf = &data->verf;
 649
 650                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
 651                                 &nfs_write_direct_ops, data);
 652                 NFS_PROTO(inode)->write_setup(data, sync);
 653
 654                 data->task.tk_priority = RPC_PRIORITY_NORMAL;
 655                 data->task.tk_cookie = (unsigned long) inode;
 656
 657                 rpc_execute(&data->task);
 658
 659                 dprintk("NFS: %5u initiated direct write call "
 660                         "(req %s/%Ld, %zu bytes @ offset %Lu)\n",
 661                                 data->task.tk_pid,
 662                                 inode->i_sb->s_id,
 663                                 (long long)NFS_FILEID(inode),
 664                                 bytes,
 665                                 (unsigned long long)data->args.offset);
 666
 667                 started += bytes;
 668                 user_addr += bytes;
 669                 pos += bytes;
 670
 671                 /* FIXME: Remove this useless math from the final patch */
 672                 pgbase += bytes;
 673                 pgbase &= ~PAGE_MASK;
 674                 BUG_ON(pgbase != (user_addr & ~PAGE_MASK));
 675
 676                 count -= bytes;
 677         } while (count != 0);
 678
 679         if (put_dreq(dreq))
 680                 nfs_direct_write_complete(dreq, inode);
 681
 682         if (started)
 683                 return 0;
 684         return result < 0 ? (ssize_t) result : -EFAULT;
 685 }
 686
 687 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos)
 688 {
 689         ssize_t result = 0;
 690         sigset_t oldset;
 691         struct inode *inode = iocb->ki_filp->f_mapping->host;
 692         struct rpc_clnt *clnt = NFS_CLIENT(inode);
 693         struct nfs_direct_req *dreq;
 694         size_t wsize = NFS_SERVER(inode)->wsize;
 695         int sync = 0;
 696
 697         dreq = nfs_direct_req_alloc();
 698         if (!dreq)
 699                 return -ENOMEM;
 700         nfs_alloc_commit_data(dreq);
 701
 702         if (dreq->commit_data == NULL || count < wsize)
 703                 sync = FLUSH_STABLE;
 704
 705         dreq->inode = inode;
 706         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
 707         if (!is_sync_kiocb(iocb))
 708                 dreq->iocb = iocb;
 709
 710         nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
 711
 712         nfs_begin_data_update(inode);
 713
 714         rpc_clnt_sigmask(clnt, &oldset);
 715         result = nfs_direct_write_schedule(dreq, user_addr, count, pos, sync);
 716         if (!result)
 717                 result = nfs_direct_wait(dreq);
 718         rpc_clnt_sigunmask(clnt, &oldset);
 719
 720         return result;
 721 }
 722
 723 /**
 724  * nfs_file_direct_read - file direct read operation for NFS files
 725  * @iocb: target I/O control block
 726  * @iov: vector of user buffers into which to read data
 727  * @nr_segs: size of iov vector
 728  * @pos: byte offset in file where reading starts
 729  *
 730  * We use this function for direct reads instead of calling
 731  * generic_file_aio_read() in order to avoid gfar's check to see if
 732  * the request starts before the end of the file.  For that check
 733  * to work, we must generate a GETATTR before each direct read, and
 734  * even then there is a window between the GETATTR and the subsequent
 735  * READ where the file size could change.  Our preference is simply
 736  * to do all reads the application wants, and the server will take
 737  * care of managing the end of file boundary.
 738  *
 739  * This function also eliminates unnecessarily updating the file's
 740  * atime locally, as the NFS server sets the file's atime, and this
 741  * client must read the updated atime from the server back into its
 742  * cache.
 743  */
 744 ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
 745                                 unsigned long nr_segs, loff_t pos)
 746 {
 747         ssize_t retval = -EINVAL;
 748         struct file *file = iocb->ki_filp;
 749         struct address_space *mapping = file->f_mapping;
 750         /* XXX: temporary */
 751         const char __user *buf = iov[0].iov_base;
 752         size_t count = iov[0].iov_len;
 753
 754         dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
 755                 file->f_path.dentry->d_parent->d_name.name,
 756                 file->f_path.dentry->d_name.name,
 757                 (unsigned long) count, (long long) pos);
 758
 759         if (nr_segs != 1)
 760                 return -EINVAL;
 761
 762         if (count < 0)
 763                 goto out;
 764         retval = -EFAULT;
 765         if (!access_ok(VERIFY_WRITE, buf, count))
 766                 goto out;
 767         retval = 0;
 768         if (!count)
 769                 goto out;
 770
 771         retval = nfs_sync_mapping(mapping);
 772         if (retval)
 773                 goto out;
 774
 775         retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos);
 776         if (retval > 0)
 777                 iocb->ki_pos = pos + retval;
 778
 779 out:
 780         return retval;
 781 }
 782
 783 /**
 784  * nfs_file_direct_write - file direct write operation for NFS files
 785  * @iocb: target I/O control block
 786  * @iov: vector of user buffers from which to write data
 787  * @nr_segs: size of iov vector
 788  * @pos: byte offset in file where writing starts
 789  *
 790  * We use this function for direct writes instead of calling
 791  * generic_file_aio_write() in order to avoid taking the inode
 792  * semaphore and updating the i_size.  The NFS server will set
 793  * the new i_size and this client must read the updated size
 794  * back into its cache.  We let the server do generic write
 795  * parameter checking and report problems.
 796  *
 797  * We also avoid an unnecessary invocation of generic_osync_inode(),
 798  * as it is fairly meaningless to sync the metadata of an NFS file.
 799  *
 800  * We eliminate local atime updates, see direct read above.
 801  *
 802  * We avoid unnecessary page cache invalidations for normal cached
 803  * readers of this file.
 804  *
 805  * Note that O_APPEND is not supported for NFS direct writes, as there
 806  * is no atomic O_APPEND write facility in the NFS protocol.
 807  */
 808 ssize_t nfs_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
 809                                 unsigned long nr_segs, loff_t pos)
 810 {
 811         ssize_t retval;
 812         struct file *file = iocb->ki_filp;
 813         struct address_space *mapping = file->f_mapping;
 814         /* XXX: temporary */
 815         const char __user *buf = iov[0].iov_base;
 816         size_t count = iov[0].iov_len;
 817
 818         dprintk("nfs: direct write(%s/%s, %lu@%Ld)\n",
 819                 file->f_path.dentry->d_parent->d_name.name,
 820                 file->f_path.dentry->d_name.name,
 821                 (unsigned long) count, (long long) pos);
 822
 823         if (nr_segs != 1)
 824                 return -EINVAL;
 825
 826         retval = generic_write_checks(file, &pos, &count, 0);
 827         if (retval)
 828                 goto out;
 829
 830         retval = -EINVAL;
 831         if ((ssize_t) count < 0)
 832                 goto out;
 833         retval = 0;
 834         if (!count)
 835                 goto out;
 836
 837         retval = -EFAULT;
 838         if (!access_ok(VERIFY_READ, buf, count))
 839                 goto out;
 840
 841         retval = nfs_sync_mapping(mapping);
 842         if (retval)
 843                 goto out;
 844
 845         retval = nfs_direct_write(iocb, (unsigned long) buf, count, pos);
 846
 847         if (retval > 0)
 848                 iocb->ki_pos = pos + retval;
 849
 850 out:
 851         return retval;
 852 }
 853
 854 /**
 855  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
 856  *
 857  */
 858 int __init nfs_init_directcache(void)
 859 {
 860         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
 861                                                 sizeof(struct nfs_direct_req),
 862                                                 0, (SLAB_RECLAIM_ACCOUNT|
 863                                                         SLAB_MEM_SPREAD),
 864                                                 NULL, NULL);
 865         if (nfs_direct_cachep == NULL)
 866                 return -ENOMEM;
 867
 868         return 0;
 869 }
 870
 871 /**
 872  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
 873  *
 874  */
 875 void nfs_destroy_directcache(void)
 876 {
 877         kmem_cache_destroy(nfs_direct_cachep);
 878 }