lustre/llite/rw26.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.gnu.org/licenses/gpl-2.0.html
  19  *
  20  * GPL HEADER END
  21  */
  22 /*
  23  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
  24  * Use is subject to license terms.
  25  *
  26  * Copyright (c) 2011, 2016, Intel Corporation.
  27  */
  28 /*
  29  * This file is part of Lustre, http://www.lustre.org/
  30  * Lustre is a trademark of Sun Microsystems, Inc.
  31  *
  32  * lustre/lustre/llite/rw26.c
  33  *
  34  * Lustre Lite I/O page cache routines for the 2.5/2.6 kernel version
  35  */
  36
  37 #include <linux/kernel.h>
  38 #include <linux/mm.h>
  39 #include <linux/string.h>
  40 #include <linux/stat.h>
  41 #include <linux/errno.h>
  42 #include <linux/unistd.h>
  43 #include <asm/uaccess.h>
  44
  45 #ifdef HAVE_MIGRATE_H
  46 #include <linux/migrate.h>
  47 #elif defined(HAVE_MIGRATE_MODE_H)
  48 #include <linux/migrate_mode.h>
  49 #endif
  50 #include <linux/fs.h>
  51 #include <linux/buffer_head.h>
  52 #include <linux/mpage.h>
  53 #include <linux/writeback.h>
  54 #include <linux/stat.h>
  55 #include <asm/uaccess.h>
  56 #include <linux/mm.h>
  57 #include <linux/pagemap.h>
  58
  59 #define DEBUG_SUBSYSTEM S_LLITE
  60
  61 #include "llite_internal.h"
  62 #include <lustre_compat.h>
  63
  64 /**
  65  * Implements Linux VM address_space::invalidatepage() method. This method is
  66  * called when the page is truncate from a file, either as a result of
  67  * explicit truncate, or when inode is removed from memory (as a result of
  68  * final iput(), umount, or memory pressure induced icache shrinking).
  69  *
  70  * [0, offset] bytes of the page remain valid (this is for a case of not-page
  71  * aligned truncate). Lustre leaves partially truncated page in the cache,
  72  * relying on struct inode::i_size to limit further accesses.
  73  */
  74 static void ll_invalidatepage(struct page *vmpage,
  75 #ifdef HAVE_INVALIDATE_RANGE
  76                                 unsigned int offset, unsigned int length
  77 #else
  78                                 unsigned long offset
  79 #endif
  80                              )
  81 {
  82         struct inode     *inode;
  83         struct lu_env    *env;
  84         struct cl_page   *page;
  85         struct cl_object *obj;
  86
  87         LASSERT(PageLocked(vmpage));
  88         LASSERT(!PageWriteback(vmpage));
  89
  90         /*
  91          * It is safe to not check anything in invalidatepage/releasepage
  92          * below because they are run with page locked and all our io is
  93          * happening with locked page too
  94          */
  95 #ifdef HAVE_INVALIDATE_RANGE
  96         if (offset == 0 && length == PAGE_SIZE) {
  97 #else
  98         if (offset == 0) {
  99 #endif
 100                 /* See the comment in ll_releasepage() */
 101                 env = cl_env_percpu_get();
 102                 LASSERT(!IS_ERR(env));
 103
 104                 inode = vmpage->mapping->host;
 105                 obj = ll_i2info(inode)->lli_clob;
 106                 if (obj != NULL) {
 107                         page = cl_vmpage_page(vmpage, obj);
 108                         if (page != NULL) {
 109                                 cl_page_delete(env, page);
 110                                 cl_page_put(env, page);
 111                         }
 112                 } else
 113                         LASSERT(vmpage->private == 0);
 114
 115                 cl_env_percpu_put(env);
 116         }
 117 }
 118
 119 #ifdef HAVE_RELEASEPAGE_WITH_INT
 120 #define RELEASEPAGE_ARG_TYPE int
 121 #else
 122 #define RELEASEPAGE_ARG_TYPE gfp_t
 123 #endif
 124 static int ll_releasepage(struct page *vmpage, RELEASEPAGE_ARG_TYPE gfp_mask)
 125 {
 126         struct lu_env           *env;
 127         struct cl_object        *obj;
 128         struct cl_page          *page;
 129         struct address_space    *mapping;
 130         int result = 0;
 131
 132         LASSERT(PageLocked(vmpage));
 133         if (PageWriteback(vmpage) || PageDirty(vmpage))
 134                 return 0;
 135
 136         mapping = vmpage->mapping;
 137         if (mapping == NULL)
 138                 return 1;
 139
 140         obj = ll_i2info(mapping->host)->lli_clob;
 141         if (obj == NULL)
 142                 return 1;
 143
 144         /* 1 for caller, 1 for cl_page and 1 for page cache */
 145         if (page_count(vmpage) > 3)
 146                 return 0;
 147
 148         page = cl_vmpage_page(vmpage, obj);
 149         if (page == NULL)
 150                 return 1;
 151
 152         env = cl_env_percpu_get();
 153         LASSERT(!IS_ERR(env));
 154
 155         if (!cl_page_in_use(page)) {
 156                 result = 1;
 157                 cl_page_delete(env, page);
 158         }
 159
 160         /* To use percpu env array, the call path can not be rescheduled;
 161          * otherwise percpu array will be messed if ll_releaspage() called
 162          * again on the same CPU.
 163          *
 164          * If this page holds the last refc of cl_object, the following
 165          * call path may cause reschedule:
 166          *   cl_page_put -> cl_page_free -> cl_object_put ->
 167          *     lu_object_put -> lu_object_free -> lov_delete_raid0.
 168          *
 169          * However, the kernel can't get rid of this inode until all pages have
 170          * been cleaned up. Now that we hold page lock here, it's pretty safe
 171          * that we won't get into object delete path.
 172          */
 173         LASSERT(cl_object_refc(obj) > 1);
 174         cl_page_put(env, page);
 175
 176         cl_env_percpu_put(env);
 177         return result;
 178 }
 179
 180 #define MAX_DIRECTIO_SIZE 2*1024*1024*1024UL
 181
 182 static ssize_t
 183 ll_direct_IO_seg(const struct lu_env *env, struct cl_io *io, int rw,
 184                  struct inode *inode, size_t size, loff_t file_offset,
 185                  struct page **pages, int page_count)
 186 {
 187         struct cl_page *clp;
 188         struct cl_2queue *queue;
 189         struct cl_object *obj = io->ci_obj;
 190         int i;
 191         ssize_t rc = 0;
 192         size_t page_size = cl_page_size(obj);
 193         size_t orig_size = size;
 194         bool do_io;
 195         int io_pages = 0;
 196
 197         ENTRY;
 198         queue = &io->ci_queue;
 199         cl_2queue_init(queue);
 200         for (i = 0; i < page_count; i++) {
 201                 LASSERT(!(file_offset & (page_size - 1)));
 202                 clp = cl_page_find(env, obj, cl_index(obj, file_offset),
 203                                    pages[i], CPT_TRANSIENT);
 204                 if (IS_ERR(clp)) {
 205                         rc = PTR_ERR(clp);
 206                         break;
 207                 }
 208
 209                 rc = cl_page_own(env, io, clp);
 210                 if (rc) {
 211                         LASSERT(clp->cp_state == CPS_FREEING);
 212                         cl_page_put(env, clp);
 213                         break;
 214                 }
 215
 216                 do_io = true;
 217
 218                 /* check the page type: if the page is a host page, then do
 219                  * write directly
 220                  */
 221                 if (clp->cp_type == CPT_CACHEABLE) {
 222                         struct page *vmpage = cl_page_vmpage(clp);
 223                         struct page *src_page;
 224                         struct page *dst_page;
 225                         void *src;
 226                         void *dst;
 227
 228                         src_page = (rw == WRITE) ? pages[i] : vmpage;
 229                         dst_page = (rw == WRITE) ? vmpage : pages[i];
 230
 231                         src = ll_kmap_atomic(src_page, KM_USER0);
 232                         dst = ll_kmap_atomic(dst_page, KM_USER1);
 233                         memcpy(dst, src, min(page_size, size));
 234                         ll_kunmap_atomic(dst, KM_USER1);
 235                         ll_kunmap_atomic(src, KM_USER0);
 236
 237                         /* make sure page will be added to the transfer by
 238                          * cl_io_submit()->...->vvp_page_prep_write().
 239                          */
 240                         if (rw == WRITE)
 241                                 set_page_dirty(vmpage);
 242
 243                         if (rw == READ) {
 244                                 /* do not issue the page for read, since it
 245                                  * may reread a ra page which has NOT uptodate
 246                                  * bit set.
 247                                  */
 248                                 cl_page_disown(env, io, clp);
 249                                 do_io = false;
 250                         }
 251                 }
 252
 253                 if (likely(do_io)) {
 254                         cl_2queue_add(queue, clp);
 255
 256                         /*
 257                          * Set page clip to tell transfer formation engine
 258                          * that page has to be sent even if it is beyond KMS.
 259                          */
 260                         cl_page_clip(env, clp, 0, min(size, page_size));
 261
 262                         ++io_pages;
 263                 }
 264
 265                 /* drop the reference count for cl_page_find */
 266                 cl_page_put(env, clp);
 267                 size -= page_size;
 268                 file_offset += page_size;
 269         }
 270
 271         if (rc == 0 && io_pages) {
 272                 rc = cl_io_submit_sync(env, io,
 273                                        rw == READ ? CRT_READ : CRT_WRITE,
 274                                        queue, 0);
 275         }
 276         if (rc == 0)
 277                 rc = orig_size;
 278
 279         cl_2queue_discard(env, io, queue);
 280         cl_2queue_disown(env, io, queue);
 281         cl_2queue_fini(env, queue);
 282         RETURN(rc);
 283 }
 284
 285 /*  ll_free_user_pages - tear down page struct array
 286  *  @pages: array of page struct pointers underlying target buffer */
 287 static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
 288 {
 289         int i;
 290
 291         for (i = 0; i < npages; i++) {
 292                 if (pages[i] == NULL)
 293                         break;
 294                 if (do_dirty)
 295                         set_page_dirty_lock(pages[i]);
 296                 put_page(pages[i]);
 297         }
 298
 299 #if defined(HAVE_DIRECTIO_ITER) || defined(HAVE_IOV_ITER_RW)
 300         kvfree(pages);
 301 #else
 302         OBD_FREE_LARGE(pages, npages * sizeof(*pages));
 303 #endif
 304 }
 305
 306 #ifdef KMALLOC_MAX_SIZE
 307 #define MAX_MALLOC KMALLOC_MAX_SIZE
 308 #else
 309 #define MAX_MALLOC (128 * 1024)
 310 #endif
 311
 312 /* This is the maximum size of a single O_DIRECT request, based on the
 313  * kmalloc limit.  We need to fit all of the brw_page structs, each one
 314  * representing PAGE_SIZE worth of user data, into a single buffer, and
 315  * then truncate this to be a full-sized RPC.  For 4kB PAGE_SIZE this is
 316  * up to 22MB for 128kB kmalloc and up to 682MB for 4MB kmalloc. */
 317 #define MAX_DIO_SIZE ((MAX_MALLOC / sizeof(struct brw_page) * PAGE_SIZE) & \
 318                       ~(DT_MAX_BRW_SIZE - 1))
 319
 320 #ifndef HAVE_IOV_ITER_RW
 321 # define iov_iter_rw(iter)      rw
 322 #endif
 323
 324 #if defined(HAVE_DIRECTIO_ITER) || defined(HAVE_IOV_ITER_RW)
 325 static ssize_t
 326 ll_direct_IO(
 327 # ifndef HAVE_IOV_ITER_RW
 328              int rw,
 329 # endif
 330              struct kiocb *iocb, struct iov_iter *iter
 331 # ifndef HAVE_DIRECTIO_2ARGS
 332              , loff_t file_offset
 333 # endif
 334              )
 335 {
 336 #ifdef HAVE_DIRECTIO_2ARGS
 337         loff_t file_offset = iocb->ki_pos;
 338 #endif
 339         struct ll_cl_context *lcc;
 340         const struct lu_env *env;
 341         struct cl_io *io;
 342         struct file *file = iocb->ki_filp;
 343         struct inode *inode = file->f_mapping->host;
 344         ssize_t count = iov_iter_count(iter);
 345         ssize_t tot_bytes = 0, result = 0;
 346         size_t size = MAX_DIO_SIZE;
 347
 348         /* Check EOF by ourselves */
 349         if (iov_iter_rw(iter) == READ && file_offset >= i_size_read(inode))
 350                 return 0;
 351         /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
 352         if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
 353                 return -EINVAL;
 354
 355         CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), "
 356                "offset=%lld=%llx, pages %zd (max %lu)\n",
 357                PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
 358                file_offset, file_offset, count >> PAGE_SHIFT,
 359                MAX_DIO_SIZE >> PAGE_SHIFT);
 360
 361         /* Check that all user buffers are aligned as well */
 362         if (iov_iter_alignment(iter) & ~PAGE_MASK)
 363                 return -EINVAL;
 364
 365         lcc = ll_cl_find(file);
 366         if (lcc == NULL)
 367                 RETURN(-EIO);
 368
 369         env = lcc->lcc_env;
 370         LASSERT(!IS_ERR(env));
 371         io = lcc->lcc_io;
 372         LASSERT(io != NULL);
 373
 374         /* 0. Need locking between buffered and direct access. and race with
 375          *    size changing by concurrent truncates and writes.
 376          * 1. Need inode mutex to operate transient pages.
 377          */
 378         if (iov_iter_rw(iter) == READ)
 379                 inode_lock(inode);
 380
 381         while (iov_iter_count(iter)) {
 382                 struct page **pages;
 383                 size_t offs;
 384
 385                 count = min_t(size_t, iov_iter_count(iter), size);
 386                 if (iov_iter_rw(iter) == READ) {
 387                         if (file_offset >= i_size_read(inode))
 388                                 break;
 389
 390                         if (file_offset + count > i_size_read(inode))
 391                                 count = i_size_read(inode) - file_offset;
 392                 }
 393
 394                 result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
 395                 if (likely(result > 0)) {
 396                         int n = DIV_ROUND_UP(result + offs, PAGE_SIZE);
 397
 398                         result = ll_direct_IO_seg(env, io, iov_iter_rw(iter),
 399                                                   inode, result, file_offset,
 400                                                   pages, n);
 401                         ll_free_user_pages(pages, n,
 402                                            iov_iter_rw(iter) == READ);
 403
 404                 }
 405                 if (unlikely(result <= 0)) {
 406                         /* If we can't allocate a large enough buffer
 407                          * for the request, shrink it to a smaller
 408                          * PAGE_SIZE multiple and try again.
 409                          * We should always be able to kmalloc for a
 410                          * page worth of page pointers = 4MB on i386. */
 411                         if (result == -ENOMEM &&
 412                             size > (PAGE_SIZE / sizeof(*pages)) *
 413                                     PAGE_SIZE) {
 414                                 size = ((((size / 2) - 1) |
 415                                         ~PAGE_MASK) + 1) & PAGE_MASK;
 416                                 CDEBUG(D_VFSTRACE, "DIO size now %zu\n",
 417                                        size);
 418                                 continue;
 419                         }
 420
 421                         GOTO(out, result);
 422                 }
 423
 424                 iov_iter_advance(iter, result);
 425                 tot_bytes += result;
 426                 file_offset += result;
 427         }
 428 out:
 429         if (iov_iter_rw(iter) == READ)
 430                 inode_unlock(inode);
 431
 432         if (tot_bytes > 0) {
 433                 struct vvp_io *vio = vvp_env_io(env);
 434
 435                 /* no commit async for direct IO */
 436                 vio->u.write.vui_written += tot_bytes;
 437         }
 438
 439         return tot_bytes ? : result;
 440 }
 441 #else /* !HAVE_DIRECTIO_ITER && !HAVE_IOV_ITER_RW */
 442
 443 static inline int ll_get_user_pages(int rw, unsigned long user_addr,
 444                                     size_t size, struct page ***pages,
 445                                     int *max_pages)
 446 {
 447         int result = -ENOMEM;
 448
 449         /* set an arbitrary limit to prevent arithmetic overflow */
 450         if (size > MAX_DIRECTIO_SIZE) {
 451                 *pages = NULL;
 452                 return -EFBIG;
 453         }
 454
 455         *max_pages = (user_addr + size + PAGE_SIZE - 1) >>
 456                       PAGE_SHIFT;
 457         *max_pages -= user_addr >> PAGE_SHIFT;
 458
 459         OBD_ALLOC_LARGE(*pages, *max_pages * sizeof(**pages));
 460         if (*pages) {
 461                 down_read(&current->mm->mmap_sem);
 462                 result = get_user_pages(current, current->mm, user_addr,
 463                                         *max_pages, (rw == READ), 0, *pages,
 464                                         NULL);
 465                 up_read(&current->mm->mmap_sem);
 466                 if (unlikely(result <= 0))
 467                         OBD_FREE_LARGE(*pages, *max_pages * sizeof(**pages));
 468         }
 469
 470         return result;
 471 }
 472
 473 static ssize_t
 474 ll_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 475              loff_t file_offset, unsigned long nr_segs)
 476 {
 477         struct ll_cl_context *lcc;
 478         const struct lu_env *env;
 479         struct cl_io *io;
 480         struct file *file = iocb->ki_filp;
 481         struct inode *inode = file->f_mapping->host;
 482         ssize_t count = iov_length(iov, nr_segs);
 483         ssize_t tot_bytes = 0, result = 0;
 484         unsigned long seg = 0;
 485         size_t size = MAX_DIO_SIZE;
 486         ENTRY;
 487
 488         /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
 489         if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
 490                 RETURN(-EINVAL);
 491
 492         CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), "
 493                "offset=%lld=%llx, pages %zd (max %lu)\n",
 494                PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
 495                file_offset, file_offset, count >> PAGE_SHIFT,
 496                MAX_DIO_SIZE >> PAGE_SHIFT);
 497
 498         /* Check that all user buffers are aligned as well */
 499         for (seg = 0; seg < nr_segs; seg++) {
 500                 if (((unsigned long)iov[seg].iov_base & ~PAGE_MASK) ||
 501                     (iov[seg].iov_len & ~PAGE_MASK))
 502                         RETURN(-EINVAL);
 503         }
 504
 505         lcc = ll_cl_find(file);
 506         if (lcc == NULL)
 507                 RETURN(-EIO);
 508
 509         env = lcc->lcc_env;
 510         LASSERT(!IS_ERR(env));
 511         io = lcc->lcc_io;
 512         LASSERT(io != NULL);
 513
 514         for (seg = 0; seg < nr_segs; seg++) {
 515                 size_t iov_left = iov[seg].iov_len;
 516                 unsigned long user_addr = (unsigned long)iov[seg].iov_base;
 517
 518                 if (rw == READ) {
 519                         if (file_offset >= i_size_read(inode))
 520                                 break;
 521                         if (file_offset + iov_left > i_size_read(inode))
 522                                 iov_left = i_size_read(inode) - file_offset;
 523                 }
 524
 525                 while (iov_left > 0) {
 526                         struct page **pages;
 527                         int page_count, max_pages = 0;
 528                         size_t bytes;
 529
 530                         bytes = min(size, iov_left);
 531                         page_count = ll_get_user_pages(rw, user_addr, bytes,
 532                                                        &pages, &max_pages);
 533                         if (likely(page_count > 0)) {
 534                                 if (unlikely(page_count <  max_pages))
 535                                         bytes = page_count << PAGE_SHIFT;
 536                                 result = ll_direct_IO_seg(env, io, rw, inode,
 537                                                           bytes, file_offset,
 538                                                           pages, page_count);
 539                                 ll_free_user_pages(pages, max_pages, rw==READ);
 540                         } else if (page_count == 0) {
 541                                 GOTO(out, result = -EFAULT);
 542                         } else {
 543                                 result = page_count;
 544                         }
 545                         if (unlikely(result <= 0)) {
 546                                 /* If we can't allocate a large enough buffer
 547                                  * for the request, shrink it to a smaller
 548                                  * PAGE_SIZE multiple and try again.
 549                                  * We should always be able to kmalloc for a
 550                                  * page worth of page pointers = 4MB on i386. */
 551                                 if (result == -ENOMEM &&
 552                                     size > (PAGE_SIZE / sizeof(*pages)) *
 553                                            PAGE_SIZE) {
 554                                         size = ((((size / 2) - 1) |
 555                                                  ~PAGE_MASK) + 1) &
 556                                                 PAGE_MASK;
 557                                         CDEBUG(D_VFSTRACE, "DIO size now %zu\n",
 558                                                size);
 559                                         continue;
 560                                 }
 561
 562                                 GOTO(out, result);
 563                         }
 564
 565                         tot_bytes += result;
 566                         file_offset += result;
 567                         iov_left -= result;
 568                         user_addr += result;
 569                 }
 570         }
 571 out:
 572         if (tot_bytes > 0) {
 573                 struct vvp_io *vio = vvp_env_io(env);
 574
 575                 /* no commit async for direct IO */
 576                 vio->u.write.vui_written += tot_bytes;
 577         }
 578
 579         RETURN(tot_bytes ? tot_bytes : result);
 580 }
 581 #endif /* HAVE_DIRECTIO_ITER || HAVE_IOV_ITER_RW */
 582
 583 /**
 584  * Prepare partially written-to page for a write.
 585  */
 586 static int ll_prepare_partial_page(const struct lu_env *env, struct cl_io *io,
 587                                    struct cl_page *pg)
 588 {
 589         struct cl_attr *attr   = vvp_env_thread_attr(env);
 590         struct cl_object *obj  = io->ci_obj;
 591         struct vvp_page *vpg   = cl_object_page_slice(obj, pg);
 592         loff_t          offset = cl_offset(obj, vvp_index(vpg));
 593         int             result;
 594
 595         cl_object_attr_lock(obj);
 596         result = cl_object_attr_get(env, obj, attr);
 597         cl_object_attr_unlock(obj);
 598         if (result == 0) {
 599                 /*
 600                  * If are writing to a new page, no need to read old data.
 601                  * The extent locking will have updated the KMS, and for our
 602                  * purposes here we can treat it like i_size.
 603                  */
 604                 if (attr->cat_kms <= offset) {
 605                         char *kaddr = ll_kmap_atomic(vpg->vpg_page, KM_USER0);
 606
 607                         memset(kaddr, 0, cl_page_size(obj));
 608                         ll_kunmap_atomic(kaddr, KM_USER0);
 609                 } else if (vpg->vpg_defer_uptodate)
 610                         vpg->vpg_ra_used = 1;
 611                 else
 612                         result = ll_page_sync_io(env, io, pg, CRT_READ);
 613         }
 614         return result;
 615 }
 616
 617 static int ll_write_begin(struct file *file, struct address_space *mapping,
 618                           loff_t pos, unsigned len, unsigned flags,
 619                           struct page **pagep, void **fsdata)
 620 {
 621         struct ll_cl_context *lcc;
 622         const struct lu_env  *env = NULL;
 623         struct cl_io   *io;
 624         struct cl_page *page = NULL;
 625
 626         struct cl_object *clob = ll_i2info(mapping->host)->lli_clob;
 627         pgoff_t index = pos >> PAGE_SHIFT;
 628         struct page *vmpage = NULL;
 629         unsigned from = pos & (PAGE_SIZE - 1);
 630         unsigned to = from + len;
 631         int result = 0;
 632         ENTRY;
 633
 634         CDEBUG(D_PAGE, "Writing %lu of %d to %d bytes\n", index, from, len);
 635
 636         lcc = ll_cl_find(file);
 637         if (lcc == NULL) {
 638                 io = NULL;
 639                 GOTO(out, result = -EIO);
 640         }
 641
 642         env = lcc->lcc_env;
 643         io  = lcc->lcc_io;
 644
 645         /* To avoid deadlock, try to lock page first. */
 646         vmpage = grab_cache_page_nowait(mapping, index);
 647
 648         if (unlikely(vmpage == NULL ||
 649                      PageDirty(vmpage) || PageWriteback(vmpage))) {
 650                 struct vvp_io *vio = vvp_env_io(env);
 651                 struct cl_page_list *plist = &vio->u.write.vui_queue;
 652
 653                 /* if the page is already in dirty cache, we have to commit
 654                  * the pages right now; otherwise, it may cause deadlock
 655                  * because it holds page lock of a dirty page and request for
 656                  * more grants. It's okay for the dirty page to be the first
 657                  * one in commit page list, though. */
 658                 if (vmpage != NULL && plist->pl_nr > 0) {
 659                         unlock_page(vmpage);
 660                         put_page(vmpage);
 661                         vmpage = NULL;
 662                 }
 663
 664                 /* commit pages and then wait for page lock */
 665                 result = vvp_io_write_commit(env, io);
 666                 if (result < 0)
 667                         GOTO(out, result);
 668
 669                 if (vmpage == NULL) {
 670                         vmpage = grab_cache_page_write_begin(mapping, index,
 671                                                              flags);
 672                         if (vmpage == NULL)
 673                                 GOTO(out, result = -ENOMEM);
 674                 }
 675         }
 676
 677         page = cl_page_find(env, clob, vmpage->index, vmpage, CPT_CACHEABLE);
 678         if (IS_ERR(page))
 679                 GOTO(out, result = PTR_ERR(page));
 680
 681         lcc->lcc_page = page;
 682         lu_ref_add(&page->cp_reference, "cl_io", io);
 683
 684         cl_page_assume(env, io, page);
 685         if (!PageUptodate(vmpage)) {
 686                 /*
 687                  * We're completely overwriting an existing page,
 688                  * so _don't_ set it up to date until commit_write
 689                  */
 690                 if (from == 0 && to == PAGE_SIZE) {
 691                         CL_PAGE_HEADER(D_PAGE, env, page, "full page write\n");
 692                         POISON_PAGE(vmpage, 0x11);
 693                 } else {
 694                         /* TODO: can be optimized at OSC layer to check if it
 695                          * is a lockless IO. In that case, it's not necessary
 696                          * to read the data. */
 697                         result = ll_prepare_partial_page(env, io, page);
 698                         if (result == 0)
 699                                 SetPageUptodate(vmpage);
 700                 }
 701         }
 702         if (result < 0)
 703                 cl_page_unassume(env, io, page);
 704         EXIT;
 705 out:
 706         if (result < 0) {
 707                 if (vmpage != NULL) {
 708                         unlock_page(vmpage);
 709                         put_page(vmpage);
 710                 }
 711                 if (!IS_ERR_OR_NULL(page)) {
 712                         lu_ref_del(&page->cp_reference, "cl_io", io);
 713                         cl_page_put(env, page);
 714                 }
 715                 if (io)
 716                         io->ci_result = result;
 717         } else {
 718                 *pagep = vmpage;
 719                 *fsdata = lcc;
 720         }
 721         RETURN(result);
 722 }
 723
 724 static int ll_write_end(struct file *file, struct address_space *mapping,
 725                         loff_t pos, unsigned len, unsigned copied,
 726                         struct page *vmpage, void *fsdata)
 727 {
 728         struct ll_cl_context *lcc = fsdata;
 729         const struct lu_env *env;
 730         struct cl_io *io;
 731         struct vvp_io *vio;
 732         struct cl_page *page;
 733         unsigned from = pos & (PAGE_SIZE - 1);
 734         bool unplug = false;
 735         int result = 0;
 736         ENTRY;
 737
 738         put_page(vmpage);
 739
 740         LASSERT(lcc != NULL);
 741         env  = lcc->lcc_env;
 742         page = lcc->lcc_page;
 743         io   = lcc->lcc_io;
 744         vio  = vvp_env_io(env);
 745
 746         LASSERT(cl_page_is_owned(page, io));
 747         if (copied > 0) {
 748                 struct cl_page_list *plist = &vio->u.write.vui_queue;
 749
 750                 lcc->lcc_page = NULL; /* page will be queued */
 751
 752                 /* Add it into write queue */
 753                 cl_page_list_add(plist, page);
 754                 if (plist->pl_nr == 1) /* first page */
 755                         vio->u.write.vui_from = from;
 756                 else
 757                         LASSERT(from == 0);
 758                 vio->u.write.vui_to = from + copied;
 759
 760                 /* To address the deadlock in balance_dirty_pages() where
 761                  * this dirty page may be written back in the same thread. */
 762                 if (PageDirty(vmpage))
 763                         unplug = true;
 764
 765                 /* We may have one full RPC, commit it soon */
 766                 if (plist->pl_nr >= PTLRPC_MAX_BRW_PAGES)
 767                         unplug = true;
 768
 769                 CL_PAGE_DEBUG(D_PAGE, env, page,
 770                               "queued page: %d.\n", plist->pl_nr);
 771         } else {
 772                 cl_page_disown(env, io, page);
 773
 774                 lcc->lcc_page = NULL;
 775                 lu_ref_del(&page->cp_reference, "cl_io", io);
 776                 cl_page_put(env, page);
 777
 778                 /* page list is not contiguous now, commit it now */
 779                 unplug = true;
 780         }
 781         if (unplug ||
 782             file->f_flags & O_SYNC || IS_SYNC(file_inode(file)))
 783                 result = vvp_io_write_commit(env, io);
 784
 785         if (result < 0)
 786                 io->ci_result = result;
 787         RETURN(result >= 0 ? copied : result);
 788 }
 789
 790 #ifdef CONFIG_MIGRATION
 791 static int ll_migratepage(struct address_space *mapping,
 792                           struct page *newpage, struct page *page
 793 #ifdef HAVE_MIGRATEPAGE_4ARGS
 794                           , enum migrate_mode mode
 795 #endif
 796         )
 797 {
 798         /* Always fail page migration until we have a proper implementation */
 799         return -EIO;
 800 }
 801 #endif
 802
 803 const struct address_space_operations ll_aops = {
 804         .readpage       = ll_readpage,
 805         .direct_IO      = ll_direct_IO,
 806         .writepage      = ll_writepage,
 807         .writepages     = ll_writepages,
 808         .set_page_dirty = __set_page_dirty_nobuffers,
 809         .write_begin    = ll_write_begin,
 810         .write_end      = ll_write_end,
 811         .invalidatepage = ll_invalidatepage,
 812         .releasepage    = (void *)ll_releasepage,
 813 #ifdef CONFIG_MIGRATION
 814         .migratepage    = ll_migratepage,
 815 #endif
 816 };