drivers/staging/lustre/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, 2012, 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 <linux/uaccess.h>
  44
  45 #include <linux/migrate.h>
  46 #include <linux/fs.h>
  47 #include <linux/buffer_head.h>
  48 #include <linux/mpage.h>
  49 #include <linux/writeback.h>
  50 #include <linux/pagemap.h>
  51
  52 #define DEBUG_SUBSYSTEM S_LLITE
  53
  54 #include "llite_internal.h"
  55
  56 /**
  57  * Implements Linux VM address_space::invalidatepage() method. This method is
  58  * called when the page is truncate from a file, either as a result of
  59  * explicit truncate, or when inode is removed from memory (as a result of
  60  * final iput(), umount, or memory pressure induced icache shrinking).
  61  *
  62  * [0, offset] bytes of the page remain valid (this is for a case of not-page
  63  * aligned truncate). Lustre leaves partially truncated page in the cache,
  64  * relying on struct inode::i_size to limit further accesses.
  65  */
  66 static void ll_invalidatepage(struct page *vmpage, unsigned int offset,
  67                               unsigned int length)
  68 {
  69         struct inode     *inode;
  70         struct lu_env    *env;
  71         struct cl_page   *page;
  72         struct cl_object *obj;
  73
  74         int refcheck;
  75
  76         LASSERT(PageLocked(vmpage));
  77         LASSERT(!PageWriteback(vmpage));
  78
  79         /*
  80          * It is safe to not check anything in invalidatepage/releasepage
  81          * below because they are run with page locked and all our io is
  82          * happening with locked page too
  83          */
  84         if (offset == 0 && length == PAGE_SIZE) {
  85                 env = cl_env_get(&refcheck);
  86                 if (!IS_ERR(env)) {
  87                         inode = vmpage->mapping->host;
  88                         obj = ll_i2info(inode)->lli_clob;
  89                         if (obj) {
  90                                 page = cl_vmpage_page(vmpage, obj);
  91                                 if (page) {
  92                                         cl_page_delete(env, page);
  93                                         cl_page_put(env, page);
  94                                 }
  95                         } else {
  96                                 LASSERT(vmpage->private == 0);
  97                         }
  98                         cl_env_put(env, &refcheck);
  99                 }
 100         }
 101 }
 102
 103 static int ll_releasepage(struct page *vmpage, gfp_t gfp_mask)
 104 {
 105         struct lu_env     *env;
 106         void                    *cookie;
 107         struct cl_object  *obj;
 108         struct cl_page    *page;
 109         struct address_space *mapping;
 110         int result = 0;
 111
 112         LASSERT(PageLocked(vmpage));
 113         if (PageWriteback(vmpage) || PageDirty(vmpage))
 114                 return 0;
 115
 116         mapping = vmpage->mapping;
 117         if (!mapping)
 118                 return 1;
 119
 120         obj = ll_i2info(mapping->host)->lli_clob;
 121         if (!obj)
 122                 return 1;
 123
 124         /* 1 for caller, 1 for cl_page and 1 for page cache */
 125         if (page_count(vmpage) > 3)
 126                 return 0;
 127
 128         page = cl_vmpage_page(vmpage, obj);
 129         if (!page)
 130                 return 1;
 131
 132         cookie = cl_env_reenter();
 133         env = cl_env_percpu_get();
 134         LASSERT(!IS_ERR(env));
 135
 136         if (!cl_page_in_use(page)) {
 137                 result = 1;
 138                 cl_page_delete(env, page);
 139         }
 140
 141         /* To use percpu env array, the call path can not be rescheduled;
 142          * otherwise percpu array will be messed if ll_releaspage() called
 143          * again on the same CPU.
 144          *
 145          * If this page holds the last refc of cl_object, the following
 146          * call path may cause reschedule:
 147          *   cl_page_put -> cl_page_free -> cl_object_put ->
 148          *     lu_object_put -> lu_object_free -> lov_delete_raid0.
 149          *
 150          * However, the kernel can't get rid of this inode until all pages have
 151          * been cleaned up. Now that we hold page lock here, it's pretty safe
 152          * that we won't get into object delete path.
 153          */
 154         LASSERT(cl_object_refc(obj) > 1);
 155         cl_page_put(env, page);
 156
 157         cl_env_percpu_put(env);
 158         cl_env_reexit(cookie);
 159         return result;
 160 }
 161
 162 #define MAX_DIRECTIO_SIZE (2 * 1024 * 1024 * 1024UL)
 163
 164 static inline int ll_get_user_pages(int rw, unsigned long user_addr,
 165                                     size_t size, struct page ***pages,
 166                                     int *max_pages)
 167 {
 168         int result = -ENOMEM;
 169
 170         /* set an arbitrary limit to prevent arithmetic overflow */
 171         if (size > MAX_DIRECTIO_SIZE) {
 172                 *pages = NULL;
 173                 return -EFBIG;
 174         }
 175
 176         *max_pages = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 177         *max_pages -= user_addr >> PAGE_SHIFT;
 178
 179         *pages = libcfs_kvzalloc(*max_pages * sizeof(**pages), GFP_NOFS);
 180         if (*pages) {
 181                 result = get_user_pages_fast(user_addr, *max_pages,
 182                                              (rw == READ), *pages);
 183                 if (unlikely(result <= 0))
 184                         kvfree(*pages);
 185         }
 186
 187         return result;
 188 }
 189
 190 /*  ll_free_user_pages - tear down page struct array
 191  *  @pages: array of page struct pointers underlying target buffer
 192  */
 193 static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
 194 {
 195         int i;
 196
 197         for (i = 0; i < npages; i++) {
 198                 if (do_dirty)
 199                         set_page_dirty_lock(pages[i]);
 200                 put_page(pages[i]);
 201         }
 202         kvfree(pages);
 203 }
 204
 205 ssize_t ll_direct_rw_pages(const struct lu_env *env, struct cl_io *io,
 206                            int rw, struct inode *inode,
 207                            struct ll_dio_pages *pv)
 208 {
 209         struct cl_page    *clp;
 210         struct cl_2queue  *queue;
 211         struct cl_object  *obj = io->ci_obj;
 212         int i;
 213         ssize_t rc = 0;
 214         loff_t file_offset  = pv->ldp_start_offset;
 215         size_t size = pv->ldp_size;
 216         int page_count      = pv->ldp_nr;
 217         struct page **pages = pv->ldp_pages;
 218         size_t page_size = cl_page_size(obj);
 219         bool do_io;
 220         int  io_pages       = 0;
 221
 222         queue = &io->ci_queue;
 223         cl_2queue_init(queue);
 224         for (i = 0; i < page_count; i++) {
 225                 if (pv->ldp_offsets)
 226                         file_offset = pv->ldp_offsets[i];
 227
 228                 LASSERT(!(file_offset & (page_size - 1)));
 229                 clp = cl_page_find(env, obj, cl_index(obj, file_offset),
 230                                    pv->ldp_pages[i], CPT_TRANSIENT);
 231                 if (IS_ERR(clp)) {
 232                         rc = PTR_ERR(clp);
 233                         break;
 234                 }
 235
 236                 rc = cl_page_own(env, io, clp);
 237                 if (rc) {
 238                         LASSERT(clp->cp_state == CPS_FREEING);
 239                         cl_page_put(env, clp);
 240                         break;
 241                 }
 242
 243                 do_io = true;
 244
 245                 /* check the page type: if the page is a host page, then do
 246                  * write directly
 247                  */
 248                 if (clp->cp_type == CPT_CACHEABLE) {
 249                         struct page *vmpage = cl_page_vmpage(clp);
 250                         struct page *src_page;
 251                         struct page *dst_page;
 252                         void       *src;
 253                         void       *dst;
 254
 255                         src_page = (rw == WRITE) ? pages[i] : vmpage;
 256                         dst_page = (rw == WRITE) ? vmpage : pages[i];
 257
 258                         src = kmap_atomic(src_page);
 259                         dst = kmap_atomic(dst_page);
 260                         memcpy(dst, src, min(page_size, size));
 261                         kunmap_atomic(dst);
 262                         kunmap_atomic(src);
 263
 264                         /* make sure page will be added to the transfer by
 265                          * cl_io_submit()->...->vvp_page_prep_write().
 266                          */
 267                         if (rw == WRITE)
 268                                 set_page_dirty(vmpage);
 269
 270                         if (rw == READ) {
 271                                 /* do not issue the page for read, since it
 272                                  * may reread a ra page which has NOT uptodate
 273                                  * bit set.
 274                                  */
 275                                 cl_page_disown(env, io, clp);
 276                                 do_io = false;
 277                         }
 278                 }
 279
 280                 if (likely(do_io)) {
 281                         /*
 282                          * Add a page to the incoming page list of 2-queue.
 283                          */
 284                         cl_page_list_add(&queue->c2_qin, clp);
 285
 286                         /*
 287                          * Set page clip to tell transfer formation engine
 288                          * that page has to be sent even if it is beyond KMS.
 289                          */
 290                         cl_page_clip(env, clp, 0, min(size, page_size));
 291
 292                         ++io_pages;
 293                 }
 294
 295                 /* drop the reference count for cl_page_find */
 296                 cl_page_put(env, clp);
 297                 size -= page_size;
 298                 file_offset += page_size;
 299         }
 300
 301         if (rc == 0 && io_pages) {
 302                 rc = cl_io_submit_sync(env, io,
 303                                        rw == READ ? CRT_READ : CRT_WRITE,
 304                                        queue, 0);
 305         }
 306         if (rc == 0)
 307                 rc = pv->ldp_size;
 308
 309         cl_2queue_discard(env, io, queue);
 310         cl_2queue_disown(env, io, queue);
 311         cl_2queue_fini(env, queue);
 312         return rc;
 313 }
 314 EXPORT_SYMBOL(ll_direct_rw_pages);
 315
 316 static ssize_t ll_direct_IO_26_seg(const struct lu_env *env, struct cl_io *io,
 317                                    int rw, struct inode *inode,
 318                                    struct address_space *mapping,
 319                                    size_t size, loff_t file_offset,
 320                                    struct page **pages, int page_count)
 321 {
 322         struct ll_dio_pages pvec = {
 323                 .ldp_pages      = pages,
 324                 .ldp_nr         = page_count,
 325                 .ldp_size       = size,
 326                 .ldp_offsets    = NULL,
 327                 .ldp_start_offset = file_offset
 328         };
 329
 330         return ll_direct_rw_pages(env, io, rw, inode, &pvec);
 331 }
 332
 333 /* This is the maximum size of a single O_DIRECT request, based on the
 334  * kmalloc limit.  We need to fit all of the brw_page structs, each one
 335  * representing PAGE_SIZE worth of user data, into a single buffer, and
 336  * then truncate this to be a full-sized RPC.  For 4kB PAGE_SIZE this is
 337  * up to 22MB for 128kB kmalloc and up to 682MB for 4MB kmalloc.
 338  */
 339 #define MAX_DIO_SIZE ((KMALLOC_MAX_SIZE / sizeof(struct brw_page) *       \
 340                        PAGE_SIZE) & ~(DT_MAX_BRW_SIZE - 1))
 341 static ssize_t ll_direct_IO_26(struct kiocb *iocb, struct iov_iter *iter)
 342 {
 343         struct lu_env *env;
 344         struct cl_io *io;
 345         struct file *file = iocb->ki_filp;
 346         struct inode *inode = file->f_mapping->host;
 347         loff_t file_offset = iocb->ki_pos;
 348         ssize_t count = iov_iter_count(iter);
 349         ssize_t tot_bytes = 0, result = 0;
 350         struct ll_inode_info *lli = ll_i2info(inode);
 351         long size = MAX_DIO_SIZE;
 352         int refcheck;
 353
 354         if (!lli->lli_has_smd)
 355                 return -EBADF;
 356
 357         /* Check EOF by ourselves */
 358         if (iov_iter_rw(iter) == READ && file_offset >= i_size_read(inode))
 359                 return 0;
 360
 361         /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
 362         if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
 363                 return -EINVAL;
 364
 365         CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), offset=%lld=%llx, pages %zd (max %lu)\n",
 366                PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
 367                file_offset, file_offset, count >> PAGE_SHIFT,
 368                MAX_DIO_SIZE >> PAGE_SHIFT);
 369
 370         /* Check that all user buffers are aligned as well */
 371         if (iov_iter_alignment(iter) & ~PAGE_MASK)
 372                 return -EINVAL;
 373
 374         env = cl_env_get(&refcheck);
 375         LASSERT(!IS_ERR(env));
 376         io = vvp_env_io(env)->vui_cl.cis_io;
 377         LASSERT(io);
 378
 379         while (iov_iter_count(iter)) {
 380                 struct page **pages;
 381                 size_t offs;
 382
 383                 count = min_t(size_t, iov_iter_count(iter), size);
 384                 if (iov_iter_rw(iter) == READ) {
 385                         if (file_offset >= i_size_read(inode))
 386                                 break;
 387                         if (file_offset + count > i_size_read(inode))
 388                                 count = i_size_read(inode) - file_offset;
 389                 }
 390
 391                 result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
 392                 if (likely(result > 0)) {
 393                         int n = DIV_ROUND_UP(result + offs, PAGE_SIZE);
 394
 395                         result = ll_direct_IO_26_seg(env, io, iov_iter_rw(iter),
 396                                                      inode, file->f_mapping,
 397                                                      result, file_offset, pages,
 398                                                      n);
 399                         ll_free_user_pages(pages, n, iov_iter_rw(iter) == READ);
 400                 }
 401                 if (unlikely(result <= 0)) {
 402                         /* If we can't allocate a large enough buffer
 403                          * for the request, shrink it to a smaller
 404                          * PAGE_SIZE multiple and try again.
 405                          * We should always be able to kmalloc for a
 406                          * page worth of page pointers = 4MB on i386.
 407                          */
 408                         if (result == -ENOMEM &&
 409                             size > (PAGE_SIZE / sizeof(*pages)) *
 410                             PAGE_SIZE) {
 411                                 size = ((((size / 2) - 1) |
 412                                          ~PAGE_MASK) + 1) &
 413                                         PAGE_MASK;
 414                                 CDEBUG(D_VFSTRACE, "DIO size now %lu\n",
 415                                        size);
 416                                 continue;
 417                         }
 418
 419                         goto out;
 420                 }
 421                 iov_iter_advance(iter, result);
 422                 tot_bytes += result;
 423                 file_offset += result;
 424         }
 425 out:
 426         if (tot_bytes > 0) {
 427                 struct vvp_io *vio = vvp_env_io(env);
 428
 429                 /* no commit async for direct IO */
 430                 vio->u.write.vui_written += tot_bytes;
 431         }
 432
 433         cl_env_put(env, &refcheck);
 434         return tot_bytes ? tot_bytes : result;
 435 }
 436
 437 /**
 438  * Prepare partially written-to page for a write.
 439  */
 440 static int ll_prepare_partial_page(const struct lu_env *env, struct cl_io *io,
 441                                    struct cl_page *pg)
 442 {
 443         struct cl_attr *attr   = vvp_env_thread_attr(env);
 444         struct cl_object *obj  = io->ci_obj;
 445         struct vvp_page *vpg   = cl_object_page_slice(obj, pg);
 446         loff_t          offset = cl_offset(obj, vvp_index(vpg));
 447         int             result;
 448
 449         cl_object_attr_lock(obj);
 450         result = cl_object_attr_get(env, obj, attr);
 451         cl_object_attr_unlock(obj);
 452         if (result == 0) {
 453                 /*
 454                  * If are writing to a new page, no need to read old data.
 455                  * The extent locking will have updated the KMS, and for our
 456                  * purposes here we can treat it like i_size.
 457                  */
 458                 if (attr->cat_kms <= offset) {
 459                         char *kaddr = kmap_atomic(vpg->vpg_page);
 460
 461                         memset(kaddr, 0, cl_page_size(obj));
 462                         kunmap_atomic(kaddr);
 463                 } else if (vpg->vpg_defer_uptodate) {
 464                         vpg->vpg_ra_used = 1;
 465                 } else {
 466                         result = ll_page_sync_io(env, io, pg, CRT_READ);
 467                 }
 468         }
 469         return result;
 470 }
 471
 472 static int ll_write_begin(struct file *file, struct address_space *mapping,
 473                           loff_t pos, unsigned len, unsigned flags,
 474                           struct page **pagep, void **fsdata)
 475 {
 476         struct ll_cl_context *lcc;
 477         const struct lu_env  *env;
 478         struct cl_io   *io;
 479         struct cl_page *page;
 480         struct cl_object *clob = ll_i2info(mapping->host)->lli_clob;
 481         pgoff_t index = pos >> PAGE_SHIFT;
 482         struct page *vmpage = NULL;
 483         unsigned int from = pos & (PAGE_SIZE - 1);
 484         unsigned int to = from + len;
 485         int result = 0;
 486
 487         CDEBUG(D_VFSTRACE, "Writing %lu of %d to %d bytes\n", index, from, len);
 488
 489         lcc = ll_cl_find(file);
 490         if (!lcc) {
 491                 result = -EIO;
 492                 goto out;
 493         }
 494
 495         env = lcc->lcc_env;
 496         io  = lcc->lcc_io;
 497
 498         /* To avoid deadlock, try to lock page first. */
 499         vmpage = grab_cache_page_nowait(mapping, index);
 500         if (unlikely(!vmpage || PageDirty(vmpage) || PageWriteback(vmpage))) {
 501                 struct vvp_io *vio = vvp_env_io(env);
 502                 struct cl_page_list *plist = &vio->u.write.vui_queue;
 503
 504                 /* if the page is already in dirty cache, we have to commit
 505                  * the pages right now; otherwise, it may cause deadlock
 506                  * because it holds page lock of a dirty page and request for
 507                  * more grants. It's okay for the dirty page to be the first
 508                  * one in commit page list, though.
 509                  */
 510                 if (vmpage && plist->pl_nr > 0) {
 511                         unlock_page(vmpage);
 512                         put_page(vmpage);
 513                         vmpage = NULL;
 514                 }
 515
 516                 /* commit pages and then wait for page lock */
 517                 result = vvp_io_write_commit(env, io);
 518                 if (result < 0)
 519                         goto out;
 520
 521                 if (!vmpage) {
 522                         vmpage = grab_cache_page_write_begin(mapping, index,
 523                                                              flags);
 524                         if (!vmpage) {
 525                                 result = -ENOMEM;
 526                                 goto out;
 527                         }
 528                 }
 529         }
 530
 531         page = cl_page_find(env, clob, vmpage->index, vmpage, CPT_CACHEABLE);
 532         if (IS_ERR(page)) {
 533                 result = PTR_ERR(page);
 534                 goto out;
 535         }
 536
 537         lcc->lcc_page = page;
 538         lu_ref_add(&page->cp_reference, "cl_io", io);
 539
 540         cl_page_assume(env, io, page);
 541         if (!PageUptodate(vmpage)) {
 542                 /*
 543                  * We're completely overwriting an existing page,
 544                  * so _don't_ set it up to date until commit_write
 545                  */
 546                 if (from == 0 && to == PAGE_SIZE) {
 547                         CL_PAGE_HEADER(D_PAGE, env, page, "full page write\n");
 548                         POISON_PAGE(vmpage, 0x11);
 549                 } else {
 550                         /* TODO: can be optimized at OSC layer to check if it
 551                          * is a lockless IO. In that case, it's not necessary
 552                          * to read the data.
 553                          */
 554                         result = ll_prepare_partial_page(env, io, page);
 555                         if (result == 0)
 556                                 SetPageUptodate(vmpage);
 557                 }
 558         }
 559         if (result < 0)
 560                 cl_page_unassume(env, io, page);
 561 out:
 562         if (result < 0) {
 563                 if (vmpage) {
 564                         unlock_page(vmpage);
 565                         put_page(vmpage);
 566                 }
 567         } else {
 568                 *pagep = vmpage;
 569                 *fsdata = lcc;
 570         }
 571         return result;
 572 }
 573
 574 static int ll_write_end(struct file *file, struct address_space *mapping,
 575                         loff_t pos, unsigned len, unsigned copied,
 576                         struct page *vmpage, void *fsdata)
 577 {
 578         struct ll_cl_context *lcc = fsdata;
 579         const struct lu_env *env;
 580         struct cl_io *io;
 581         struct vvp_io *vio;
 582         struct cl_page *page;
 583         unsigned from = pos & (PAGE_SIZE - 1);
 584         bool unplug = false;
 585         int result = 0;
 586
 587         put_page(vmpage);
 588
 589         env  = lcc->lcc_env;
 590         page = lcc->lcc_page;
 591         io   = lcc->lcc_io;
 592         vio  = vvp_env_io(env);
 593
 594         LASSERT(cl_page_is_owned(page, io));
 595         if (copied > 0) {
 596                 struct cl_page_list *plist = &vio->u.write.vui_queue;
 597
 598                 lcc->lcc_page = NULL; /* page will be queued */
 599
 600                 /* Add it into write queue */
 601                 cl_page_list_add(plist, page);
 602                 if (plist->pl_nr == 1) /* first page */
 603                         vio->u.write.vui_from = from;
 604                 else
 605                         LASSERT(from == 0);
 606                 vio->u.write.vui_to = from + copied;
 607
 608                 /*
 609                  * To address the deadlock in balance_dirty_pages() where
 610                  * this dirty page may be written back in the same thread.
 611                  */
 612                 if (PageDirty(vmpage))
 613                         unplug = true;
 614
 615                 /* We may have one full RPC, commit it soon */
 616                 if (plist->pl_nr >= PTLRPC_MAX_BRW_PAGES)
 617                         unplug = true;
 618
 619                 CL_PAGE_DEBUG(D_VFSTRACE, env, page,
 620                               "queued page: %d.\n", plist->pl_nr);
 621         } else {
 622                 cl_page_disown(env, io, page);
 623
 624                 lcc->lcc_page = NULL;
 625                 lu_ref_del(&page->cp_reference, "cl_io", io);
 626                 cl_page_put(env, page);
 627
 628                 /* page list is not contiguous now, commit it now */
 629                 unplug = true;
 630         }
 631
 632         if (unplug ||
 633             file->f_flags & O_SYNC || IS_SYNC(file_inode(file)))
 634                 result = vvp_io_write_commit(env, io);
 635
 636         return result >= 0 ? copied : result;
 637 }
 638
 639 #ifdef CONFIG_MIGRATION
 640 static int ll_migratepage(struct address_space *mapping,
 641                           struct page *newpage, struct page *page,
 642                           enum migrate_mode mode
 643                 )
 644 {
 645         /* Always fail page migration until we have a proper implementation */
 646         return -EIO;
 647 }
 648 #endif
 649
 650 const struct address_space_operations ll_aops = {
 651         .readpage       = ll_readpage,
 652         .direct_IO      = ll_direct_IO_26,
 653         .writepage      = ll_writepage,
 654         .writepages     = ll_writepages,
 655         .set_page_dirty = __set_page_dirty_nobuffers,
 656         .write_begin    = ll_write_begin,
 657         .write_end      = ll_write_end,
 658         .invalidatepage = ll_invalidatepage,
 659         .releasepage    = (void *)ll_releasepage,
 660 #ifdef CONFIG_MIGRATION
 661         .migratepage    = ll_migratepage,
 662 #endif
 663 };