fs/ceph/addr.c

   1 #include <linux/ceph/ceph_debug.h>
   2
   3 #include <linux/backing-dev.h>
   4 #include <linux/fs.h>
   5 #include <linux/mm.h>
   6 #include <linux/pagemap.h>
   7 #include <linux/writeback.h>    /* generic_writepages */
   8 #include <linux/slab.h>
   9 #include <linux/pagevec.h>
  10 #include <linux/task_io_accounting_ops.h>
  11
  12 #include "super.h"
  13 #include "mds_client.h"
  14 #include <linux/ceph/osd_client.h>
  15
  16 /*
  17  * Ceph address space ops.
  18  *
  19  * There are a few funny things going on here.
  20  *
  21  * The page->private field is used to reference a struct
  22  * ceph_snap_context for _every_ dirty page.  This indicates which
  23  * snapshot the page was logically dirtied in, and thus which snap
  24  * context needs to be associated with the osd write during writeback.
  25  *
  26  * Similarly, struct ceph_inode_info maintains a set of counters to
  27  * count dirty pages on the inode.  In the absence of snapshots,
  28  * i_wrbuffer_ref == i_wrbuffer_ref_head == the dirty page count.
  29  *
  30  * When a snapshot is taken (that is, when the client receives
  31  * notification that a snapshot was taken), each inode with caps and
  32  * with dirty pages (dirty pages implies there is a cap) gets a new
  33  * ceph_cap_snap in the i_cap_snaps list (which is sorted in ascending
  34  * order, new snaps go to the tail).  The i_wrbuffer_ref_head count is
  35  * moved to capsnap->dirty. (Unless a sync write is currently in
  36  * progress.  In that case, the capsnap is said to be "pending", new
  37  * writes cannot start, and the capsnap isn't "finalized" until the
  38  * write completes (or fails) and a final size/mtime for the inode for
  39  * that snap can be settled upon.)  i_wrbuffer_ref_head is reset to 0.
  40  *
  41  * On writeback, we must submit writes to the osd IN SNAP ORDER.  So,
  42  * we look for the first capsnap in i_cap_snaps and write out pages in
  43  * that snap context _only_.  Then we move on to the next capsnap,
  44  * eventually reaching the "live" or "head" context (i.e., pages that
  45  * are not yet snapped) and are writing the most recently dirtied
  46  * pages.
  47  *
  48  * Invalidate and so forth must take care to ensure the dirty page
  49  * accounting is preserved.
  50  */
  51
  52 #define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
  53 #define CONGESTION_OFF_THRESH(congestion_kb)                            \
  54         (CONGESTION_ON_THRESH(congestion_kb) -                          \
  55          (CONGESTION_ON_THRESH(congestion_kb) >> 2))
  56
  57 static inline struct ceph_snap_context *page_snap_context(struct page *page)
  58 {
  59         if (PagePrivate(page))
  60                 return (void *)page->private;
  61         return NULL;
  62 }
  63
  64 /*
  65  * Dirty a page.  Optimistically adjust accounting, on the assumption
  66  * that we won't race with invalidate.  If we do, readjust.
  67  */
  68 static int ceph_set_page_dirty(struct page *page)
  69 {
  70         struct address_space *mapping = page->mapping;
  71         struct inode *inode;
  72         struct ceph_inode_info *ci;
  73         int undo = 0;
  74         struct ceph_snap_context *snapc;
  75
  76         if (unlikely(!mapping))
  77                 return !TestSetPageDirty(page);
  78
  79         if (TestSetPageDirty(page)) {
  80                 dout("%p set_page_dirty %p idx %lu -- already dirty\n",
  81                      mapping->host, page, page->index);
  82                 return 0;
  83         }
  84
  85         inode = mapping->host;
  86         ci = ceph_inode(inode);
  87
  88         /*
  89          * Note that we're grabbing a snapc ref here without holding
  90          * any locks!
  91          */
  92         snapc = ceph_get_snap_context(ci->i_snap_realm->cached_context);
  93
  94         /* dirty the head */
  95         spin_lock(&ci->i_ceph_lock);
  96         if (ci->i_head_snapc == NULL)
  97                 ci->i_head_snapc = ceph_get_snap_context(snapc);
  98         ++ci->i_wrbuffer_ref_head;
  99         if (ci->i_wrbuffer_ref == 0)
 100                 ihold(inode);
 101         ++ci->i_wrbuffer_ref;
 102         dout("%p set_page_dirty %p idx %lu head %d/%d -> %d/%d "
 103              "snapc %p seq %lld (%d snaps)\n",
 104              mapping->host, page, page->index,
 105              ci->i_wrbuffer_ref-1, ci->i_wrbuffer_ref_head-1,
 106              ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
 107              snapc, snapc->seq, snapc->num_snaps);
 108         spin_unlock(&ci->i_ceph_lock);
 109
 110         /* now adjust page */
 111         spin_lock_irq(&mapping->tree_lock);
 112         if (page->mapping) {    /* Race with truncate? */
 113                 WARN_ON_ONCE(!PageUptodate(page));
 114                 account_page_dirtied(page, page->mapping);
 115                 radix_tree_tag_set(&mapping->page_tree,
 116                                 page_index(page), PAGECACHE_TAG_DIRTY);
 117
 118                 /*
 119                  * Reference snap context in page->private.  Also set
 120                  * PagePrivate so that we get invalidatepage callback.
 121                  */
 122                 page->private = (unsigned long)snapc;
 123                 SetPagePrivate(page);
 124         } else {
 125                 dout("ANON set_page_dirty %p (raced truncate?)\n", page);
 126                 undo = 1;
 127         }
 128
 129         spin_unlock_irq(&mapping->tree_lock);
 130
 131         if (undo)
 132                 /* whoops, we failed to dirty the page */
 133                 ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
 134
 135         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 136
 137         BUG_ON(!PageDirty(page));
 138         return 1;
 139 }
 140
 141 /*
 142  * If we are truncating the full page (i.e. offset == 0), adjust the
 143  * dirty page counters appropriately.  Only called if there is private
 144  * data on the page.
 145  */
 146 static void ceph_invalidatepage(struct page *page, unsigned long offset)
 147 {
 148         struct inode *inode;
 149         struct ceph_inode_info *ci;
 150         struct ceph_snap_context *snapc = page_snap_context(page);
 151
 152         BUG_ON(!PageLocked(page));
 153         BUG_ON(!PagePrivate(page));
 154         BUG_ON(!page->mapping);
 155
 156         inode = page->mapping->host;
 157
 158         /*
 159          * We can get non-dirty pages here due to races between
 160          * set_page_dirty and truncate_complete_page; just spit out a
 161          * warning, in case we end up with accounting problems later.
 162          */
 163         if (!PageDirty(page))
 164                 pr_err("%p invalidatepage %p page not dirty\n", inode, page);
 165
 166         if (offset == 0)
 167                 ClearPageChecked(page);
 168
 169         ci = ceph_inode(inode);
 170         if (offset == 0) {
 171                 dout("%p invalidatepage %p idx %lu full dirty page %lu\n",
 172                      inode, page, page->index, offset);
 173                 ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
 174                 ceph_put_snap_context(snapc);
 175                 page->private = 0;
 176                 ClearPagePrivate(page);
 177         } else {
 178                 dout("%p invalidatepage %p idx %lu partial dirty page\n",
 179                      inode, page, page->index);
 180         }
 181 }
 182
 183 /* just a sanity check */
 184 static int ceph_releasepage(struct page *page, gfp_t g)
 185 {
 186         struct inode *inode = page->mapping ? page->mapping->host : NULL;
 187         dout("%p releasepage %p idx %lu\n", inode, page, page->index);
 188         WARN_ON(PageDirty(page));
 189         WARN_ON(PagePrivate(page));
 190         return 0;
 191 }
 192
 193 /*
 194  * read a single page, without unlocking it.
 195  */
 196 static int readpage_nounlock(struct file *filp, struct page *page)
 197 {
 198         struct inode *inode = filp->f_dentry->d_inode;
 199         struct ceph_inode_info *ci = ceph_inode(inode);
 200         struct ceph_osd_client *osdc =
 201                 &ceph_inode_to_client(inode)->client->osdc;
 202         int err = 0;
 203         u64 len = PAGE_CACHE_SIZE;
 204
 205         dout("readpage inode %p file %p page %p index %lu\n",
 206              inode, filp, page, page->index);
 207         err = ceph_osdc_readpages(osdc, ceph_vino(inode), &ci->i_layout,
 208                                   (u64) page_offset(page), &len,
 209                                   ci->i_truncate_seq, ci->i_truncate_size,
 210                                   &page, 1, 0);
 211         if (err == -ENOENT)
 212                 err = 0;
 213         if (err < 0) {
 214                 SetPageError(page);
 215                 goto out;
 216         } else if (err < PAGE_CACHE_SIZE) {
 217                 /* zero fill remainder of page */
 218                 zero_user_segment(page, err, PAGE_CACHE_SIZE);
 219         }
 220         SetPageUptodate(page);
 221
 222 out:
 223         return err < 0 ? err : 0;
 224 }
 225
 226 static int ceph_readpage(struct file *filp, struct page *page)
 227 {
 228         int r = readpage_nounlock(filp, page);
 229         unlock_page(page);
 230         return r;
 231 }
 232
 233 /*
 234  * Finish an async read(ahead) op.
 235  */
 236 static void finish_read(struct ceph_osd_request *req, struct ceph_msg *msg)
 237 {
 238         struct inode *inode = req->r_inode;
 239         struct ceph_osd_reply_head *replyhead;
 240         int rc, bytes;
 241         int i;
 242
 243         /* parse reply */
 244         replyhead = msg->front.iov_base;
 245         WARN_ON(le32_to_cpu(replyhead->num_ops) == 0);
 246         rc = le32_to_cpu(replyhead->result);
 247         bytes = le32_to_cpu(msg->hdr.data_len);
 248
 249         dout("finish_read %p req %p rc %d bytes %d\n", inode, req, rc, bytes);
 250
 251         /* unlock all pages, zeroing any data we didn't read */
 252         for (i = 0; i < req->r_num_pages; i++, bytes -= PAGE_CACHE_SIZE) {
 253                 struct page *page = req->r_pages[i];
 254
 255                 if (bytes < (int)PAGE_CACHE_SIZE) {
 256                         /* zero (remainder of) page */
 257                         int s = bytes < 0 ? 0 : bytes;
 258                         zero_user_segment(page, s, PAGE_CACHE_SIZE);
 259                 }
 260                 dout("finish_read %p uptodate %p idx %lu\n", inode, page,
 261                      page->index);
 262                 flush_dcache_page(page);
 263                 SetPageUptodate(page);
 264                 unlock_page(page);
 265                 page_cache_release(page);
 266         }
 267         kfree(req->r_pages);
 268 }
 269
 270 static void ceph_unlock_page_vector(struct page **pages, int num_pages)
 271 {
 272         int i;
 273
 274         for (i = 0; i < num_pages; i++)
 275                 unlock_page(pages[i]);
 276 }
 277
 278 /*
 279  * start an async read(ahead) operation.  return nr_pages we submitted
 280  * a read for on success, or negative error code.
 281  */
 282 static int start_read(struct inode *inode, struct list_head *page_list, int max)
 283 {
 284         struct ceph_osd_client *osdc =
 285                 &ceph_inode_to_client(inode)->client->osdc;
 286         struct ceph_inode_info *ci = ceph_inode(inode);
 287         struct page *page = list_entry(page_list->prev, struct page, lru);
 288         struct ceph_osd_request *req;
 289         u64 off;
 290         u64 len;
 291         int i;
 292         struct page **pages;
 293         pgoff_t next_index;
 294         int nr_pages = 0;
 295         int ret;
 296
 297         off = (u64) page_offset(page);
 298
 299         /* count pages */
 300         next_index = page->index;
 301         list_for_each_entry_reverse(page, page_list, lru) {
 302                 if (page->index != next_index)
 303                         break;
 304                 nr_pages++;
 305                 next_index++;
 306                 if (max && nr_pages == max)
 307                         break;
 308         }
 309         len = nr_pages << PAGE_CACHE_SHIFT;
 310         dout("start_read %p nr_pages %d is %lld~%lld\n", inode, nr_pages,
 311              off, len);
 312
 313         req = ceph_osdc_new_request(osdc, &ci->i_layout, ceph_vino(inode),
 314                                     off, &len,
 315                                     CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ,
 316                                     NULL, 0,
 317                                     ci->i_truncate_seq, ci->i_truncate_size,
 318                                     NULL, false, 1, 0);
 319         if (IS_ERR(req))
 320                 return PTR_ERR(req);
 321
 322         /* build page vector */
 323         nr_pages = len >> PAGE_CACHE_SHIFT;
 324         pages = kmalloc(sizeof(*pages) * nr_pages, GFP_NOFS);
 325         ret = -ENOMEM;
 326         if (!pages)
 327                 goto out;
 328         for (i = 0; i < nr_pages; ++i) {
 329                 page = list_entry(page_list->prev, struct page, lru);
 330                 BUG_ON(PageLocked(page));
 331                 list_del(&page->lru);
 332
 333                 dout("start_read %p adding %p idx %lu\n", inode, page,
 334                      page->index);
 335                 if (add_to_page_cache_lru(page, &inode->i_data, page->index,
 336                                           GFP_NOFS)) {
 337                         page_cache_release(page);
 338                         dout("start_read %p add_to_page_cache failed %p\n",
 339                              inode, page);
 340                         nr_pages = i;
 341                         goto out_pages;
 342                 }
 343                 pages[i] = page;
 344         }
 345         req->r_pages = pages;
 346         req->r_num_pages = nr_pages;
 347         req->r_callback = finish_read;
 348         req->r_inode = inode;
 349
 350         dout("start_read %p starting %p %lld~%lld\n", inode, req, off, len);
 351         ret = ceph_osdc_start_request(osdc, req, false);
 352         if (ret < 0)
 353                 goto out_pages;
 354         ceph_osdc_put_request(req);
 355         return nr_pages;
 356
 357 out_pages:
 358         ceph_unlock_page_vector(pages, nr_pages);
 359         ceph_release_page_vector(pages, nr_pages);
 360 out:
 361         ceph_osdc_put_request(req);
 362         return ret;
 363 }
 364
 365
 366 /*
 367  * Read multiple pages.  Leave pages we don't read + unlock in page_list;
 368  * the caller (VM) cleans them up.
 369  */
 370 static int ceph_readpages(struct file *file, struct address_space *mapping,
 371                           struct list_head *page_list, unsigned nr_pages)
 372 {
 373         struct inode *inode = file->f_dentry->d_inode;
 374         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
 375         int rc = 0;
 376         int max = 0;
 377
 378         if (fsc->mount_options->rsize >= PAGE_CACHE_SIZE)
 379                 max = (fsc->mount_options->rsize + PAGE_CACHE_SIZE - 1)
 380                         >> PAGE_SHIFT;
 381
 382         dout("readpages %p file %p nr_pages %d max %d\n", inode, file, nr_pages,
 383              max);
 384         while (!list_empty(page_list)) {
 385                 rc = start_read(inode, page_list, max);
 386                 if (rc < 0)
 387                         goto out;
 388                 BUG_ON(rc == 0);
 389         }
 390 out:
 391         dout("readpages %p file %p ret %d\n", inode, file, rc);
 392         return rc;
 393 }
 394
 395 /*
 396  * Get ref for the oldest snapc for an inode with dirty data... that is, the
 397  * only snap context we are allowed to write back.
 398  */
 399 static struct ceph_snap_context *get_oldest_context(struct inode *inode,
 400                                                     u64 *snap_size)
 401 {
 402         struct ceph_inode_info *ci = ceph_inode(inode);
 403         struct ceph_snap_context *snapc = NULL;
 404         struct ceph_cap_snap *capsnap = NULL;
 405
 406         spin_lock(&ci->i_ceph_lock);
 407         list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
 408                 dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
 409                      capsnap->context, capsnap->dirty_pages);
 410                 if (capsnap->dirty_pages) {
 411                         snapc = ceph_get_snap_context(capsnap->context);
 412                         if (snap_size)
 413                                 *snap_size = capsnap->size;
 414                         break;
 415                 }
 416         }
 417         if (!snapc && ci->i_wrbuffer_ref_head) {
 418                 snapc = ceph_get_snap_context(ci->i_head_snapc);
 419                 dout(" head snapc %p has %d dirty pages\n",
 420                      snapc, ci->i_wrbuffer_ref_head);
 421         }
 422         spin_unlock(&ci->i_ceph_lock);
 423         return snapc;
 424 }
 425
 426 /*
 427  * Write a single page, but leave the page locked.
 428  *
 429  * If we get a write error, set the page error bit, but still adjust the
 430  * dirty page accounting (i.e., page is no longer dirty).
 431  */
 432 static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 433 {
 434         struct inode *inode;
 435         struct ceph_inode_info *ci;
 436         struct ceph_fs_client *fsc;
 437         struct ceph_osd_client *osdc;
 438         loff_t page_off = page_offset(page);
 439         int len = PAGE_CACHE_SIZE;
 440         loff_t i_size;
 441         int err = 0;
 442         struct ceph_snap_context *snapc, *oldest;
 443         u64 snap_size = 0;
 444         long writeback_stat;
 445
 446         dout("writepage %p idx %lu\n", page, page->index);
 447
 448         if (!page->mapping || !page->mapping->host) {
 449                 dout("writepage %p - no mapping\n", page);
 450                 return -EFAULT;
 451         }
 452         inode = page->mapping->host;
 453         ci = ceph_inode(inode);
 454         fsc = ceph_inode_to_client(inode);
 455         osdc = &fsc->client->osdc;
 456
 457         /* verify this is a writeable snap context */
 458         snapc = page_snap_context(page);
 459         if (snapc == NULL) {
 460                 dout("writepage %p page %p not dirty?\n", inode, page);
 461                 goto out;
 462         }
 463         oldest = get_oldest_context(inode, &snap_size);
 464         if (snapc->seq > oldest->seq) {
 465                 dout("writepage %p page %p snapc %p not writeable - noop\n",
 466                      inode, page, snapc);
 467                 /* we should only noop if called by kswapd */
 468                 WARN_ON((current->flags & PF_MEMALLOC) == 0);
 469                 ceph_put_snap_context(oldest);
 470                 goto out;
 471         }
 472         ceph_put_snap_context(oldest);
 473
 474         /* is this a partial page at end of file? */
 475         if (snap_size)
 476                 i_size = snap_size;
 477         else
 478                 i_size = i_size_read(inode);
 479         if (i_size < page_off + len)
 480                 len = i_size - page_off;
 481
 482         dout("writepage %p page %p index %lu on %llu~%u snapc %p\n",
 483              inode, page, page->index, page_off, len, snapc);
 484
 485         writeback_stat = atomic_long_inc_return(&fsc->writeback_count);
 486         if (writeback_stat >
 487             CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb))
 488                 set_bdi_congested(&fsc->backing_dev_info, BLK_RW_ASYNC);
 489
 490         set_page_writeback(page);
 491         err = ceph_osdc_writepages(osdc, ceph_vino(inode),
 492                                    &ci->i_layout, snapc,
 493                                    page_off, len,
 494                                    ci->i_truncate_seq, ci->i_truncate_size,
 495                                    &inode->i_mtime,
 496                                    &page, 1, 0, 0, true);
 497         if (err < 0) {
 498                 dout("writepage setting page/mapping error %d %p\n", err, page);
 499                 SetPageError(page);
 500                 mapping_set_error(&inode->i_data, err);
 501                 if (wbc)
 502                         wbc->pages_skipped++;
 503         } else {
 504                 dout("writepage cleaned page %p\n", page);
 505                 err = 0;  /* vfs expects us to return 0 */
 506         }
 507         page->private = 0;
 508         ClearPagePrivate(page);
 509         end_page_writeback(page);
 510         ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
 511         ceph_put_snap_context(snapc);  /* page's reference */
 512 out:
 513         return err;
 514 }
 515
 516 static int ceph_writepage(struct page *page, struct writeback_control *wbc)
 517 {
 518         int err;
 519         struct inode *inode = page->mapping->host;
 520         BUG_ON(!inode);
 521         ihold(inode);
 522         err = writepage_nounlock(page, wbc);
 523         unlock_page(page);
 524         iput(inode);
 525         return err;
 526 }
 527
 528
 529 /*
 530  * lame release_pages helper.  release_pages() isn't exported to
 531  * modules.
 532  */
 533 static void ceph_release_pages(struct page **pages, int num)
 534 {
 535         struct pagevec pvec;
 536         int i;
 537
 538         pagevec_init(&pvec, 0);
 539         for (i = 0; i < num; i++) {
 540                 if (pagevec_add(&pvec, pages[i]) == 0)
 541                         pagevec_release(&pvec);
 542         }
 543         pagevec_release(&pvec);
 544 }
 545
 546
 547 /*
 548  * async writeback completion handler.
 549  *
 550  * If we get an error, set the mapping error bit, but not the individual
 551  * page error bits.
 552  */
 553 static void writepages_finish(struct ceph_osd_request *req,
 554                               struct ceph_msg *msg)
 555 {
 556         struct inode *inode = req->r_inode;
 557         struct ceph_osd_reply_head *replyhead;
 558         struct ceph_osd_op *op;
 559         struct ceph_inode_info *ci = ceph_inode(inode);
 560         unsigned wrote;
 561         struct page *page;
 562         int i;
 563         struct ceph_snap_context *snapc = req->r_snapc;
 564         struct address_space *mapping = inode->i_mapping;
 565         __s32 rc = -EIO;
 566         u64 bytes = 0;
 567         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
 568         long writeback_stat;
 569         unsigned issued = ceph_caps_issued(ci);
 570
 571         /* parse reply */
 572         replyhead = msg->front.iov_base;
 573         WARN_ON(le32_to_cpu(replyhead->num_ops) == 0);
 574         op = (void *)(replyhead + 1);
 575         rc = le32_to_cpu(replyhead->result);
 576         bytes = le64_to_cpu(op->extent.length);
 577
 578         if (rc >= 0) {
 579                 /*
 580                  * Assume we wrote the pages we originally sent.  The
 581                  * osd might reply with fewer pages if our writeback
 582                  * raced with a truncation and was adjusted at the osd,
 583                  * so don't believe the reply.
 584                  */
 585                 wrote = req->r_num_pages;
 586         } else {
 587                 wrote = 0;
 588                 mapping_set_error(mapping, rc);
 589         }
 590         dout("writepages_finish %p rc %d bytes %llu wrote %d (pages)\n",
 591              inode, rc, bytes, wrote);
 592
 593         /* clean all pages */
 594         for (i = 0; i < req->r_num_pages; i++) {
 595                 page = req->r_pages[i];
 596                 BUG_ON(!page);
 597                 WARN_ON(!PageUptodate(page));
 598
 599                 writeback_stat =
 600                         atomic_long_dec_return(&fsc->writeback_count);
 601                 if (writeback_stat <
 602                     CONGESTION_OFF_THRESH(fsc->mount_options->congestion_kb))
 603                         clear_bdi_congested(&fsc->backing_dev_info,
 604                                             BLK_RW_ASYNC);
 605
 606                 ceph_put_snap_context(page_snap_context(page));
 607                 page->private = 0;
 608                 ClearPagePrivate(page);
 609                 dout("unlocking %d %p\n", i, page);
 610                 end_page_writeback(page);
 611
 612                 /*
 613                  * We lost the cache cap, need to truncate the page before
 614                  * it is unlocked, otherwise we'd truncate it later in the
 615                  * page truncation thread, possibly losing some data that
 616                  * raced its way in
 617                  */
 618                 if ((issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0)
 619                         generic_error_remove_page(inode->i_mapping, page);
 620
 621                 unlock_page(page);
 622         }
 623         dout("%p wrote+cleaned %d pages\n", inode, wrote);
 624         ceph_put_wrbuffer_cap_refs(ci, req->r_num_pages, snapc);
 625
 626         ceph_release_pages(req->r_pages, req->r_num_pages);
 627         if (req->r_pages_from_pool)
 628                 mempool_free(req->r_pages,
 629                              ceph_sb_to_client(inode->i_sb)->wb_pagevec_pool);
 630         else
 631                 kfree(req->r_pages);
 632         ceph_osdc_put_request(req);
 633 }
 634
 635 /*
 636  * allocate a page vec, either directly, or if necessary, via a the
 637  * mempool.  we avoid the mempool if we can because req->r_num_pages
 638  * may be less than the maximum write size.
 639  */
 640 static void alloc_page_vec(struct ceph_fs_client *fsc,
 641                            struct ceph_osd_request *req)
 642 {
 643         req->r_pages = kmalloc(sizeof(struct page *) * req->r_num_pages,
 644                                GFP_NOFS);
 645         if (!req->r_pages) {
 646                 req->r_pages = mempool_alloc(fsc->wb_pagevec_pool, GFP_NOFS);
 647                 req->r_pages_from_pool = 1;
 648                 WARN_ON(!req->r_pages);
 649         }
 650 }
 651
 652 /*
 653  * initiate async writeback
 654  */
 655 static int ceph_writepages_start(struct address_space *mapping,
 656                                  struct writeback_control *wbc)
 657 {
 658         struct inode *inode = mapping->host;
 659         struct ceph_inode_info *ci = ceph_inode(inode);
 660         struct ceph_fs_client *fsc;
 661         pgoff_t index, start, end;
 662         int range_whole = 0;
 663         int should_loop = 1;
 664         pgoff_t max_pages = 0, max_pages_ever = 0;
 665         struct ceph_snap_context *snapc = NULL, *last_snapc = NULL, *pgsnapc;
 666         struct pagevec pvec;
 667         int done = 0;
 668         int rc = 0;
 669         unsigned wsize = 1 << inode->i_blkbits;
 670         struct ceph_osd_request *req = NULL;
 671         int do_sync;
 672         u64 snap_size = 0;
 673
 674         /*
 675          * Include a 'sync' in the OSD request if this is a data
 676          * integrity write (e.g., O_SYNC write or fsync()), or if our
 677          * cap is being revoked.
 678          */
 679         do_sync = wbc->sync_mode == WB_SYNC_ALL;
 680         if (ceph_caps_revoking(ci, CEPH_CAP_FILE_BUFFER))
 681                 do_sync = 1;
 682         dout("writepages_start %p dosync=%d (mode=%s)\n",
 683              inode, do_sync,
 684              wbc->sync_mode == WB_SYNC_NONE ? "NONE" :
 685              (wbc->sync_mode == WB_SYNC_ALL ? "ALL" : "HOLD"));
 686
 687         fsc = ceph_inode_to_client(inode);
 688         if (fsc->mount_state == CEPH_MOUNT_SHUTDOWN) {
 689                 pr_warning("writepage_start %p on forced umount\n", inode);
 690                 return -EIO; /* we're in a forced umount, don't write! */
 691         }
 692         if (fsc->mount_options->wsize && fsc->mount_options->wsize < wsize)
 693                 wsize = fsc->mount_options->wsize;
 694         if (wsize < PAGE_CACHE_SIZE)
 695                 wsize = PAGE_CACHE_SIZE;
 696         max_pages_ever = wsize >> PAGE_CACHE_SHIFT;
 697
 698         pagevec_init(&pvec, 0);
 699
 700         /* where to start/end? */
 701         if (wbc->range_cyclic) {
 702                 start = mapping->writeback_index; /* Start from prev offset */
 703                 end = -1;
 704                 dout(" cyclic, start at %lu\n", start);
 705         } else {
 706                 start = wbc->range_start >> PAGE_CACHE_SHIFT;
 707                 end = wbc->range_end >> PAGE_CACHE_SHIFT;
 708                 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
 709                         range_whole = 1;
 710                 should_loop = 0;
 711                 dout(" not cyclic, %lu to %lu\n", start, end);
 712         }
 713         index = start;
 714
 715 retry:
 716         /* find oldest snap context with dirty data */
 717         ceph_put_snap_context(snapc);
 718         snapc = get_oldest_context(inode, &snap_size);
 719         if (!snapc) {
 720                 /* hmm, why does writepages get called when there
 721                    is no dirty data? */
 722                 dout(" no snap context with dirty data?\n");
 723                 goto out;
 724         }
 725         dout(" oldest snapc is %p seq %lld (%d snaps)\n",
 726              snapc, snapc->seq, snapc->num_snaps);
 727         if (last_snapc && snapc != last_snapc) {
 728                 /* if we switched to a newer snapc, restart our scan at the
 729                  * start of the original file range. */
 730                 dout("  snapc differs from last pass, restarting at %lu\n",
 731                      index);
 732                 index = start;
 733         }
 734         last_snapc = snapc;
 735
 736         while (!done && index <= end) {
 737                 unsigned i;
 738                 int first;
 739                 pgoff_t next;
 740                 int pvec_pages, locked_pages;
 741                 struct page *page;
 742                 int want;
 743                 u64 offset, len;
 744                 struct ceph_osd_request_head *reqhead;
 745                 struct ceph_osd_op *op;
 746                 long writeback_stat;
 747
 748                 next = 0;
 749                 locked_pages = 0;
 750                 max_pages = max_pages_ever;
 751
 752 get_more_pages:
 753                 first = -1;
 754                 want = min(end - index,
 755                            min((pgoff_t)PAGEVEC_SIZE,
 756                                max_pages - (pgoff_t)locked_pages) - 1)
 757                         + 1;
 758                 pvec_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 759                                                 PAGECACHE_TAG_DIRTY,
 760                                                 want);
 761                 dout("pagevec_lookup_tag got %d\n", pvec_pages);
 762                 if (!pvec_pages && !locked_pages)
 763                         break;
 764                 for (i = 0; i < pvec_pages && locked_pages < max_pages; i++) {
 765                         page = pvec.pages[i];
 766                         dout("? %p idx %lu\n", page, page->index);
 767                         if (locked_pages == 0)
 768                                 lock_page(page);  /* first page */
 769                         else if (!trylock_page(page))
 770                                 break;
 771
 772                         /* only dirty pages, or our accounting breaks */
 773                         if (unlikely(!PageDirty(page)) ||
 774                             unlikely(page->mapping != mapping)) {
 775                                 dout("!dirty or !mapping %p\n", page);
 776                                 unlock_page(page);
 777                                 break;
 778                         }
 779                         if (!wbc->range_cyclic && page->index > end) {
 780                                 dout("end of range %p\n", page);
 781                                 done = 1;
 782                                 unlock_page(page);
 783                                 break;
 784                         }
 785                         if (next && (page->index != next)) {
 786                                 dout("not consecutive %p\n", page);
 787                                 unlock_page(page);
 788                                 break;
 789                         }
 790                         if (wbc->sync_mode != WB_SYNC_NONE) {
 791                                 dout("waiting on writeback %p\n", page);
 792                                 wait_on_page_writeback(page);
 793                         }
 794                         if ((snap_size && page_offset(page) > snap_size) ||
 795                             (!snap_size &&
 796                              page_offset(page) > i_size_read(inode))) {
 797                                 dout("%p page eof %llu\n", page, snap_size ?
 798                                      snap_size : i_size_read(inode));
 799                                 done = 1;
 800                                 unlock_page(page);
 801                                 break;
 802                         }
 803                         if (PageWriteback(page)) {
 804                                 dout("%p under writeback\n", page);
 805                                 unlock_page(page);
 806                                 break;
 807                         }
 808
 809                         /* only if matching snap context */
 810                         pgsnapc = page_snap_context(page);
 811                         if (pgsnapc->seq > snapc->seq) {
 812                                 dout("page snapc %p %lld > oldest %p %lld\n",
 813                                      pgsnapc, pgsnapc->seq, snapc, snapc->seq);
 814                                 unlock_page(page);
 815                                 if (!locked_pages)
 816                                         continue; /* keep looking for snap */
 817                                 break;
 818                         }
 819
 820                         if (!clear_page_dirty_for_io(page)) {
 821                                 dout("%p !clear_page_dirty_for_io\n", page);
 822                                 unlock_page(page);
 823                                 break;
 824                         }
 825
 826                         /* ok */
 827                         if (locked_pages == 0) {
 828                                 /* prepare async write request */
 829                                 offset = (u64) page_offset(page);
 830                                 len = wsize;
 831                                 req = ceph_osdc_new_request(&fsc->client->osdc,
 832                                             &ci->i_layout,
 833                                             ceph_vino(inode),
 834                                             offset, &len,
 835                                             CEPH_OSD_OP_WRITE,
 836                                             CEPH_OSD_FLAG_WRITE |
 837                                                     CEPH_OSD_FLAG_ONDISK,
 838                                             snapc, do_sync,
 839                                             ci->i_truncate_seq,
 840                                             ci->i_truncate_size,
 841                                             &inode->i_mtime, true, 1, 0);
 842
 843                                 if (IS_ERR(req)) {
 844                                         rc = PTR_ERR(req);
 845                                         unlock_page(page);
 846                                         break;
 847                                 }
 848
 849                                 max_pages = req->r_num_pages;
 850
 851                                 alloc_page_vec(fsc, req);
 852                                 req->r_callback = writepages_finish;
 853                                 req->r_inode = inode;
 854                         }
 855
 856                         /* note position of first page in pvec */
 857                         if (first < 0)
 858                                 first = i;
 859                         dout("%p will write page %p idx %lu\n",
 860                              inode, page, page->index);
 861
 862                         writeback_stat =
 863                                atomic_long_inc_return(&fsc->writeback_count);
 864                         if (writeback_stat > CONGESTION_ON_THRESH(
 865                                     fsc->mount_options->congestion_kb)) {
 866                                 set_bdi_congested(&fsc->backing_dev_info,
 867                                                   BLK_RW_ASYNC);
 868                         }
 869
 870                         set_page_writeback(page);
 871                         req->r_pages[locked_pages] = page;
 872                         locked_pages++;
 873                         next = page->index + 1;
 874                 }
 875
 876                 /* did we get anything? */
 877                 if (!locked_pages)
 878                         goto release_pvec_pages;
 879                 if (i) {
 880                         int j;
 881                         BUG_ON(!locked_pages || first < 0);
 882
 883                         if (pvec_pages && i == pvec_pages &&
 884                             locked_pages < max_pages) {
 885                                 dout("reached end pvec, trying for more\n");
 886                                 pagevec_reinit(&pvec);
 887                                 goto get_more_pages;
 888                         }
 889
 890                         /* shift unused pages over in the pvec...  we
 891                          * will need to release them below. */
 892                         for (j = i; j < pvec_pages; j++) {
 893                                 dout(" pvec leftover page %p\n",
 894                                      pvec.pages[j]);
 895                                 pvec.pages[j-i+first] = pvec.pages[j];
 896                         }
 897                         pvec.nr -= i-first;
 898                 }
 899
 900                 /* submit the write */
 901                 offset = req->r_pages[0]->index << PAGE_CACHE_SHIFT;
 902                 len = min((snap_size ? snap_size : i_size_read(inode)) - offset,
 903                           (u64)locked_pages << PAGE_CACHE_SHIFT);
 904                 dout("writepages got %d pages at %llu~%llu\n",
 905                      locked_pages, offset, len);
 906
 907                 /* revise final length, page count */
 908                 req->r_num_pages = locked_pages;
 909                 reqhead = req->r_request->front.iov_base;
 910                 op = (void *)(reqhead + 1);
 911                 op->extent.length = cpu_to_le64(len);
 912                 op->payload_len = cpu_to_le32(len);
 913                 req->r_request->hdr.data_len = cpu_to_le32(len);
 914
 915                 rc = ceph_osdc_start_request(&fsc->client->osdc, req, true);
 916                 BUG_ON(rc);
 917                 req = NULL;
 918
 919                 /* continue? */
 920                 index = next;
 921                 wbc->nr_to_write -= locked_pages;
 922                 if (wbc->nr_to_write <= 0)
 923                         done = 1;
 924
 925 release_pvec_pages:
 926                 dout("pagevec_release on %d pages (%p)\n", (int)pvec.nr,
 927                      pvec.nr ? pvec.pages[0] : NULL);
 928                 pagevec_release(&pvec);
 929
 930                 if (locked_pages && !done)
 931                         goto retry;
 932         }
 933
 934         if (should_loop && !done) {
 935                 /* more to do; loop back to beginning of file */
 936                 dout("writepages looping back to beginning of file\n");
 937                 should_loop = 0;
 938                 index = 0;
 939                 goto retry;
 940         }
 941
 942         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
 943                 mapping->writeback_index = index;
 944
 945 out:
 946         if (req)
 947                 ceph_osdc_put_request(req);
 948         ceph_put_snap_context(snapc);
 949         dout("writepages done, rc = %d\n", rc);
 950         return rc;
 951 }
 952
 953
 954
 955 /*
 956  * See if a given @snapc is either writeable, or already written.
 957  */
 958 static int context_is_writeable_or_written(struct inode *inode,
 959                                            struct ceph_snap_context *snapc)
 960 {
 961         struct ceph_snap_context *oldest = get_oldest_context(inode, NULL);
 962         int ret = !oldest || snapc->seq <= oldest->seq;
 963
 964         ceph_put_snap_context(oldest);
 965         return ret;
 966 }
 967
 968 /*
 969  * We are only allowed to write into/dirty the page if the page is
 970  * clean, or already dirty within the same snap context.
 971  *
 972  * called with page locked.
 973  * return success with page locked,
 974  * or any failure (incl -EAGAIN) with page unlocked.
 975  */
 976 static int ceph_update_writeable_page(struct file *file,
 977                             loff_t pos, unsigned len,
 978                             struct page *page)
 979 {
 980         struct inode *inode = file->f_dentry->d_inode;
 981         struct ceph_inode_info *ci = ceph_inode(inode);
 982         struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
 983         loff_t page_off = pos & PAGE_CACHE_MASK;
 984         int pos_in_page = pos & ~PAGE_CACHE_MASK;
 985         int end_in_page = pos_in_page + len;
 986         loff_t i_size;
 987         int r;
 988         struct ceph_snap_context *snapc, *oldest;
 989
 990 retry_locked:
 991         /* writepages currently holds page lock, but if we change that later, */
 992         wait_on_page_writeback(page);
 993
 994         /* check snap context */
 995         BUG_ON(!ci->i_snap_realm);
 996         down_read(&mdsc->snap_rwsem);
 997         BUG_ON(!ci->i_snap_realm->cached_context);
 998         snapc = page_snap_context(page);
 999         if (snapc && snapc != ci->i_head_snapc) {
1000                 /*
1001                  * this page is already dirty in another (older) snap
1002                  * context!  is it writeable now?
1003                  */
1004                 oldest = get_oldest_context(inode, NULL);
1005                 up_read(&mdsc->snap_rwsem);
1006
1007                 if (snapc->seq > oldest->seq) {
1008                         ceph_put_snap_context(oldest);
1009                         dout(" page %p snapc %p not current or oldest\n",
1010                              page, snapc);
1011                         /*
1012                          * queue for writeback, and wait for snapc to
1013                          * be writeable or written
1014                          */
1015                         snapc = ceph_get_snap_context(snapc);
1016                         unlock_page(page);
1017                         ceph_queue_writeback(inode);
1018                         r = wait_event_interruptible(ci->i_cap_wq,
1019                                context_is_writeable_or_written(inode, snapc));
1020                         ceph_put_snap_context(snapc);
1021                         if (r == -ERESTARTSYS)
1022                                 return r;
1023                         return -EAGAIN;
1024                 }
1025                 ceph_put_snap_context(oldest);
1026
1027                 /* yay, writeable, do it now (without dropping page lock) */
1028                 dout(" page %p snapc %p not current, but oldest\n",
1029                      page, snapc);
1030                 if (!clear_page_dirty_for_io(page))
1031                         goto retry_locked;
1032                 r = writepage_nounlock(page, NULL);
1033                 if (r < 0)
1034                         goto fail_nosnap;
1035                 goto retry_locked;
1036         }
1037
1038         if (PageUptodate(page)) {
1039                 dout(" page %p already uptodate\n", page);
1040                 return 0;
1041         }
1042
1043         /* full page? */
1044         if (pos_in_page == 0 && len == PAGE_CACHE_SIZE)
1045                 return 0;
1046
1047         /* past end of file? */
1048         i_size = inode->i_size;   /* caller holds i_mutex */
1049
1050         if (i_size + len > inode->i_sb->s_maxbytes) {
1051                 /* file is too big */
1052                 r = -EINVAL;
1053                 goto fail;
1054         }
1055
1056         if (page_off >= i_size ||
1057             (pos_in_page == 0 && (pos+len) >= i_size &&
1058              end_in_page - pos_in_page != PAGE_CACHE_SIZE)) {
1059                 dout(" zeroing %p 0 - %d and %d - %d\n",
1060                      page, pos_in_page, end_in_page, (int)PAGE_CACHE_SIZE);
1061                 zero_user_segments(page,
1062                                    0, pos_in_page,
1063                                    end_in_page, PAGE_CACHE_SIZE);
1064                 return 0;
1065         }
1066
1067         /* we need to read it. */
1068         up_read(&mdsc->snap_rwsem);
1069         r = readpage_nounlock(file, page);
1070         if (r < 0)
1071                 goto fail_nosnap;
1072         goto retry_locked;
1073
1074 fail:
1075         up_read(&mdsc->snap_rwsem);
1076 fail_nosnap:
1077         unlock_page(page);
1078         return r;
1079 }
1080
1081 /*
1082  * We are only allowed to write into/dirty the page if the page is
1083  * clean, or already dirty within the same snap context.
1084  */
1085 static int ceph_write_begin(struct file *file, struct address_space *mapping,
1086                             loff_t pos, unsigned len, unsigned flags,
1087                             struct page **pagep, void **fsdata)
1088 {
1089         struct inode *inode = file->f_dentry->d_inode;
1090         struct ceph_inode_info *ci = ceph_inode(inode);
1091         struct ceph_file_info *fi = file->private_data;
1092         struct page *page;
1093         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1094         int r, want, got = 0;
1095
1096         if (fi->fmode & CEPH_FILE_MODE_LAZY)
1097                 want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
1098         else
1099                 want = CEPH_CAP_FILE_BUFFER;
1100
1101         dout("write_begin %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
1102              inode, ceph_vinop(inode), pos, len, inode->i_size);
1103         r = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, &got, pos+len);
1104         if (r < 0)
1105                 return r;
1106         dout("write_begin %p %llx.%llx %llu~%u  got cap refs on %s\n",
1107              inode, ceph_vinop(inode), pos, len, ceph_cap_string(got));
1108         if (!(got & (CEPH_CAP_FILE_BUFFER|CEPH_CAP_FILE_LAZYIO))) {
1109                 ceph_put_cap_refs(ci, got);
1110                 return -EAGAIN;
1111         }
1112
1113         do {
1114                 /* get a page */
1115                 page = grab_cache_page_write_begin(mapping, index, 0);
1116                 if (!page) {
1117                         r = -ENOMEM;
1118                         break;
1119                 }
1120
1121                 dout("write_begin file %p inode %p page %p %d~%d\n", file,
1122                      inode, page, (int)pos, (int)len);
1123
1124                 r = ceph_update_writeable_page(file, pos, len, page);
1125                 if (r)
1126                         page_cache_release(page);
1127         } while (r == -EAGAIN);
1128
1129         if (r) {
1130                 ceph_put_cap_refs(ci, got);
1131         } else {
1132                 *pagep = page;
1133                 *(int *)fsdata = got;
1134         }
1135         return r;
1136 }
1137
1138 /*
1139  * we don't do anything in here that simple_write_end doesn't do
1140  * except adjust dirty page accounting and drop read lock on
1141  * mdsc->snap_rwsem.
1142  */
1143 static int ceph_write_end(struct file *file, struct address_space *mapping,
1144                           loff_t pos, unsigned len, unsigned copied,
1145                           struct page *page, void *fsdata)
1146 {
1147         struct inode *inode = file->f_dentry->d_inode;
1148         struct ceph_inode_info *ci = ceph_inode(inode);
1149         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
1150         struct ceph_mds_client *mdsc = fsc->mdsc;
1151         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1152         int check_cap = 0;
1153         int got = (unsigned long)fsdata;
1154
1155         dout("write_end file %p inode %p page %p %d~%d (%d)\n", file,
1156              inode, page, (int)pos, (int)copied, (int)len);
1157
1158         /* zero the stale part of the page if we did a short copy */
1159         if (copied < len)
1160                 zero_user_segment(page, from+copied, len);
1161
1162         /* did file size increase? */
1163         /* (no need for i_size_read(); we caller holds i_mutex */
1164         if (pos+copied > inode->i_size)
1165                 check_cap = ceph_inode_set_size(inode, pos+copied);
1166
1167         if (!PageUptodate(page))
1168                 SetPageUptodate(page);
1169
1170         set_page_dirty(page);
1171
1172         unlock_page(page);
1173         up_read(&mdsc->snap_rwsem);
1174         page_cache_release(page);
1175
1176         if (copied > 0) {
1177                 int dirty;
1178                 spin_lock(&ci->i_ceph_lock);
1179                 dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);
1180                 spin_unlock(&ci->i_ceph_lock);
1181                 if (dirty)
1182                         __mark_inode_dirty(inode, dirty);
1183         }
1184
1185         dout("write_end %p %llx.%llx %llu~%u  dropping cap refs on %s\n",
1186              inode, ceph_vinop(inode), pos, len, ceph_cap_string(got));
1187         ceph_put_cap_refs(ci, got);
1188
1189         if (check_cap)
1190                 ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY, NULL);
1191
1192         return copied;
1193 }
1194
1195 /*
1196  * we set .direct_IO to indicate direct io is supported, but since we
1197  * intercept O_DIRECT reads and writes early, this function should
1198  * never get called.
1199  */
1200 static ssize_t ceph_direct_io(int rw, struct kiocb *iocb,
1201                               const struct iovec *iov,
1202                               loff_t pos, unsigned long nr_segs)
1203 {
1204         WARN_ON(1);
1205         return -EINVAL;
1206 }
1207
1208 const struct address_space_operations ceph_aops = {
1209         .readpage = ceph_readpage,
1210         .readpages = ceph_readpages,
1211         .writepage = ceph_writepage,
1212         .writepages = ceph_writepages_start,
1213         .write_begin = ceph_write_begin,
1214         .write_end = ceph_write_end,
1215         .set_page_dirty = ceph_set_page_dirty,
1216         .invalidatepage = ceph_invalidatepage,
1217         .releasepage = ceph_releasepage,
1218         .direct_IO = ceph_direct_io,
1219 };
1220
1221
1222 /*
1223  * vm ops
1224  */
1225
1226 /*
1227  * Reuse write_begin here for simplicity.
1228  */
1229 static int ceph_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1230 {
1231         struct inode *inode = vma->vm_file->f_dentry->d_inode;
1232         struct page *page = vmf->page;
1233         struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
1234         loff_t off = page_offset(page);
1235         loff_t size, len;
1236         int ret;
1237
1238         /* Update time before taking page lock */
1239         file_update_time(vma->vm_file);
1240
1241         size = i_size_read(inode);
1242         if (off + PAGE_CACHE_SIZE <= size)
1243                 len = PAGE_CACHE_SIZE;
1244         else
1245                 len = size & ~PAGE_CACHE_MASK;
1246
1247         dout("page_mkwrite %p %llu~%llu page %p idx %lu\n", inode,
1248              off, len, page, page->index);
1249
1250         lock_page(page);
1251
1252         ret = VM_FAULT_NOPAGE;
1253         if ((off > size) ||
1254             (page->mapping != inode->i_mapping))
1255                 goto out;
1256
1257         ret = ceph_update_writeable_page(vma->vm_file, off, len, page);
1258         if (ret == 0) {
1259                 /* success.  we'll keep the page locked. */
1260                 set_page_dirty(page);
1261                 up_read(&mdsc->snap_rwsem);
1262                 ret = VM_FAULT_LOCKED;
1263         } else {
1264                 if (ret == -ENOMEM)
1265                         ret = VM_FAULT_OOM;
1266                 else
1267                         ret = VM_FAULT_SIGBUS;
1268         }
1269 out:
1270         dout("page_mkwrite %p %llu~%llu = %d\n", inode, off, len, ret);
1271         if (ret != VM_FAULT_LOCKED)
1272                 unlock_page(page);
1273         return ret;
1274 }
1275
1276 static struct vm_operations_struct ceph_vmops = {
1277         .fault          = filemap_fault,
1278         .page_mkwrite   = ceph_page_mkwrite,
1279         .remap_pages    = generic_file_remap_pages,
1280 };
1281
1282 int ceph_mmap(struct file *file, struct vm_area_struct *vma)
1283 {
1284         struct address_space *mapping = file->f_mapping;
1285
1286         if (!mapping->a_ops->readpage)
1287                 return -ENOEXEC;
1288         file_accessed(file);
1289         vma->vm_ops = &ceph_vmops;
1290         return 0;
1291 }