fs/fs-writeback.c

   1 /*
   2  * fs/fs-writeback.c
   3  *
   4  * Copyright (C) 2002, Linus Torvalds.
   5  *
   6  * Contains all the functions related to writing back and waiting
   7  * upon dirty inodes against superblocks, and writing back dirty
   8  * pages against inodes.  ie: data writeback.  Writeout of the
   9  * inode itself is not handled here.
  10  *
  11  * 10Apr2002    Andrew Morton
  12  *              Split out of fs/inode.c
  13  *              Additions for address_space-based writeback
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/export.h>
  18 #include <linux/spinlock.h>
  19 #include <linux/slab.h>
  20 #include <linux/sched.h>
  21 #include <linux/fs.h>
  22 #include <linux/mm.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/kthread.h>
  25 #include <linux/freezer.h>
  26 #include <linux/writeback.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/tracepoint.h>
  30 #include "internal.h"
  31
  32 /*
  33  * 4MB minimal write chunk size
  34  */
  35 #define MIN_WRITEBACK_PAGES     (4096UL >> (PAGE_CACHE_SHIFT - 10))
  36
  37 /*
  38  * Passed into wb_writeback(), essentially a subset of writeback_control
  39  */
  40 struct wb_writeback_work {
  41         long nr_pages;
  42         struct super_block *sb;
  43         unsigned long *older_than_this;
  44         enum writeback_sync_modes sync_mode;
  45         unsigned int tagged_writepages:1;
  46         unsigned int for_kupdate:1;
  47         unsigned int range_cyclic:1;
  48         unsigned int for_background:1;
  49         enum wb_reason reason;          /* why was writeback initiated? */
  50
  51         struct list_head list;          /* pending work list */
  52         struct completion *done;        /* set if the caller waits */
  53 };
  54
  55 /*
  56  * We don't actually have pdflush, but this one is exported though /proc...
  57  */
  58 int nr_pdflush_threads;
  59
  60 /**
  61  * writeback_in_progress - determine whether there is writeback in progress
  62  * @bdi: the device's backing_dev_info structure.
  63  *
  64  * Determine whether there is writeback waiting to be handled against a
  65  * backing device.
  66  */
  67 int writeback_in_progress(struct backing_dev_info *bdi)
  68 {
  69         return test_bit(BDI_writeback_running, &bdi->state);
  70 }
  71
  72 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
  73 {
  74         struct super_block *sb = inode->i_sb;
  75
  76         if (strcmp(sb->s_type->name, "bdev") == 0)
  77                 return inode->i_mapping->backing_dev_info;
  78
  79         return sb->s_bdi;
  80 }
  81
  82 static inline struct inode *wb_inode(struct list_head *head)
  83 {
  84         return list_entry(head, struct inode, i_wb_list);
  85 }
  86
  87 /*
  88  * Include the creation of the trace points after defining the
  89  * wb_writeback_work structure and inline functions so that the definition
  90  * remains local to this file.
  91  */
  92 #define CREATE_TRACE_POINTS
  93 #include <trace/events/writeback.h>
  94
  95 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
  96 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
  97 {
  98         if (bdi->wb.task) {
  99                 wake_up_process(bdi->wb.task);
 100         } else {
 101                 /*
 102                  * The bdi thread isn't there, wake up the forker thread which
 103                  * will create and run it.
 104                  */
 105                 wake_up_process(default_backing_dev_info.wb.task);
 106         }
 107 }
 108
 109 static void bdi_queue_work(struct backing_dev_info *bdi,
 110                            struct wb_writeback_work *work)
 111 {
 112         trace_writeback_queue(bdi, work);
 113
 114         spin_lock_bh(&bdi->wb_lock);
 115         list_add_tail(&work->list, &bdi->work_list);
 116         if (!bdi->wb.task)
 117                 trace_writeback_nothread(bdi, work);
 118         bdi_wakeup_flusher(bdi);
 119         spin_unlock_bh(&bdi->wb_lock);
 120 }
 121
 122 static void
 123 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 124                       bool range_cyclic, enum wb_reason reason)
 125 {
 126         struct wb_writeback_work *work;
 127
 128         /*
 129          * This is WB_SYNC_NONE writeback, so if allocation fails just
 130          * wakeup the thread for old dirty data writeback
 131          */
 132         work = kzalloc(sizeof(*work), GFP_ATOMIC);
 133         if (!work) {
 134                 if (bdi->wb.task) {
 135                         trace_writeback_nowork(bdi);
 136                         wake_up_process(bdi->wb.task);
 137                 }
 138                 return;
 139         }
 140
 141         work->sync_mode = WB_SYNC_NONE;
 142         work->nr_pages  = nr_pages;
 143         work->range_cyclic = range_cyclic;
 144         work->reason    = reason;
 145
 146         bdi_queue_work(bdi, work);
 147 }
 148
 149 /**
 150  * bdi_start_writeback - start writeback
 151  * @bdi: the backing device to write from
 152  * @nr_pages: the number of pages to write
 153  * @reason: reason why some writeback work was initiated
 154  *
 155  * Description:
 156  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
 157  *   started when this function returns, we make no guarantees on
 158  *   completion. Caller need not hold sb s_umount semaphore.
 159  *
 160  */
 161 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 162                         enum wb_reason reason)
 163 {
 164         __bdi_start_writeback(bdi, nr_pages, true, reason);
 165 }
 166
 167 /**
 168  * bdi_start_background_writeback - start background writeback
 169  * @bdi: the backing device to write from
 170  *
 171  * Description:
 172  *   This makes sure WB_SYNC_NONE background writeback happens. When
 173  *   this function returns, it is only guaranteed that for given BDI
 174  *   some IO is happening if we are over background dirty threshold.
 175  *   Caller need not hold sb s_umount semaphore.
 176  */
 177 void bdi_start_background_writeback(struct backing_dev_info *bdi)
 178 {
 179         /*
 180          * We just wake up the flusher thread. It will perform background
 181          * writeback as soon as there is no other work to do.
 182          */
 183         trace_writeback_wake_background(bdi);
 184         spin_lock_bh(&bdi->wb_lock);
 185         bdi_wakeup_flusher(bdi);
 186         spin_unlock_bh(&bdi->wb_lock);
 187 }
 188
 189 /*
 190  * Remove the inode from the writeback list it is on.
 191  */
 192 void inode_wb_list_del(struct inode *inode)
 193 {
 194         struct backing_dev_info *bdi = inode_to_bdi(inode);
 195
 196         spin_lock(&bdi->wb.list_lock);
 197         list_del_init(&inode->i_wb_list);
 198         spin_unlock(&bdi->wb.list_lock);
 199 }
 200
 201 /*
 202  * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
 203  * furthest end of its superblock's dirty-inode list.
 204  *
 205  * Before stamping the inode's ->dirtied_when, we check to see whether it is
 206  * already the most-recently-dirtied inode on the b_dirty list.  If that is
 207  * the case then the inode must have been redirtied while it was being written
 208  * out and we don't reset its dirtied_when.
 209  */
 210 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
 211 {
 212         assert_spin_locked(&wb->list_lock);
 213         if (!list_empty(&wb->b_dirty)) {
 214                 struct inode *tail;
 215
 216                 tail = wb_inode(wb->b_dirty.next);
 217                 if (time_before(inode->dirtied_when, tail->dirtied_when))
 218                         inode->dirtied_when = jiffies;
 219         }
 220         list_move(&inode->i_wb_list, &wb->b_dirty);
 221 }
 222
 223 /*
 224  * requeue inode for re-scanning after bdi->b_io list is exhausted.
 225  */
 226 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
 227 {
 228         assert_spin_locked(&wb->list_lock);
 229         list_move(&inode->i_wb_list, &wb->b_more_io);
 230 }
 231
 232 static void inode_sync_complete(struct inode *inode)
 233 {
 234         /*
 235          * Prevent speculative execution through
 236          * spin_unlock(&wb->list_lock);
 237          */
 238
 239         smp_mb();
 240         wake_up_bit(&inode->i_state, __I_SYNC);
 241 }
 242
 243 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
 244 {
 245         bool ret = time_after(inode->dirtied_when, t);
 246 #ifndef CONFIG_64BIT
 247         /*
 248          * For inodes being constantly redirtied, dirtied_when can get stuck.
 249          * It _appears_ to be in the future, but is actually in distant past.
 250          * This test is necessary to prevent such wrapped-around relative times
 251          * from permanently stopping the whole bdi writeback.
 252          */
 253         ret = ret && time_before_eq(inode->dirtied_when, jiffies);
 254 #endif
 255         return ret;
 256 }
 257
 258 /*
 259  * Move expired (dirtied after work->older_than_this) dirty inodes from
 260  * @delaying_queue to @dispatch_queue.
 261  */
 262 static int move_expired_inodes(struct list_head *delaying_queue,
 263                                struct list_head *dispatch_queue,
 264                                struct wb_writeback_work *work)
 265 {
 266         LIST_HEAD(tmp);
 267         struct list_head *pos, *node;
 268         struct super_block *sb = NULL;
 269         struct inode *inode;
 270         int do_sb_sort = 0;
 271         int moved = 0;
 272
 273         while (!list_empty(delaying_queue)) {
 274                 inode = wb_inode(delaying_queue->prev);
 275                 if (work->older_than_this &&
 276                     inode_dirtied_after(inode, *work->older_than_this))
 277                         break;
 278                 if (sb && sb != inode->i_sb)
 279                         do_sb_sort = 1;
 280                 sb = inode->i_sb;
 281                 list_move(&inode->i_wb_list, &tmp);
 282                 moved++;
 283         }
 284
 285         /* just one sb in list, splice to dispatch_queue and we're done */
 286         if (!do_sb_sort) {
 287                 list_splice(&tmp, dispatch_queue);
 288                 goto out;
 289         }
 290
 291         /* Move inodes from one superblock together */
 292         while (!list_empty(&tmp)) {
 293                 sb = wb_inode(tmp.prev)->i_sb;
 294                 list_for_each_prev_safe(pos, node, &tmp) {
 295                         inode = wb_inode(pos);
 296                         if (inode->i_sb == sb)
 297                                 list_move(&inode->i_wb_list, dispatch_queue);
 298                 }
 299         }
 300 out:
 301         return moved;
 302 }
 303
 304 /*
 305  * Queue all expired dirty inodes for io, eldest first.
 306  * Before
 307  *         newly dirtied     b_dirty    b_io    b_more_io
 308  *         =============>    gf         edc     BA
 309  * After
 310  *         newly dirtied     b_dirty    b_io    b_more_io
 311  *         =============>    g          fBAedc
 312  *                                           |
 313  *                                           +--> dequeue for IO
 314  */
 315 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
 316 {
 317         int moved;
 318         assert_spin_locked(&wb->list_lock);
 319         list_splice_init(&wb->b_more_io, &wb->b_io);
 320         moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
 321         trace_writeback_queue_io(wb, work, moved);
 322 }
 323
 324 static int write_inode(struct inode *inode, struct writeback_control *wbc)
 325 {
 326         if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
 327                 return inode->i_sb->s_op->write_inode(inode, wbc);
 328         return 0;
 329 }
 330
 331 /*
 332  * Wait for writeback on an inode to complete.
 333  */
 334 static void inode_wait_for_writeback(struct inode *inode,
 335                                      struct bdi_writeback *wb)
 336 {
 337         DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
 338         wait_queue_head_t *wqh;
 339
 340         wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
 341         while (inode->i_state & I_SYNC) {
 342                 spin_unlock(&inode->i_lock);
 343                 spin_unlock(&wb->list_lock);
 344                 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
 345                 spin_lock(&wb->list_lock);
 346                 spin_lock(&inode->i_lock);
 347         }
 348 }
 349
 350 /*
 351  * Write out an inode's dirty pages.  Called under wb->list_lock and
 352  * inode->i_lock.  Either the caller has an active reference on the inode or
 353  * the inode has I_WILL_FREE set.
 354  *
 355  * If `wait' is set, wait on the writeout.
 356  *
 357  * The whole writeout design is quite complex and fragile.  We want to avoid
 358  * starvation of particular inodes when others are being redirtied, prevent
 359  * livelocks, etc.
 360  */
 361 static int
 362 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 363                        struct writeback_control *wbc)
 364 {
 365         struct address_space *mapping = inode->i_mapping;
 366         long nr_to_write = wbc->nr_to_write;
 367         unsigned dirty;
 368         int ret;
 369
 370         assert_spin_locked(&wb->list_lock);
 371         assert_spin_locked(&inode->i_lock);
 372
 373         if (!atomic_read(&inode->i_count))
 374                 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
 375         else
 376                 WARN_ON(inode->i_state & I_WILL_FREE);
 377
 378         if (inode->i_state & I_SYNC) {
 379                 /*
 380                  * If this inode is locked for writeback and we are not doing
 381                  * writeback-for-data-integrity, move it to b_more_io so that
 382                  * writeback can proceed with the other inodes on s_io.
 383                  *
 384                  * We'll have another go at writing back this inode when we
 385                  * completed a full scan of b_io.
 386                  */
 387                 if (wbc->sync_mode != WB_SYNC_ALL) {
 388                         requeue_io(inode, wb);
 389                         trace_writeback_single_inode_requeue(inode, wbc,
 390                                                              nr_to_write);
 391                         return 0;
 392                 }
 393
 394                 /*
 395                  * It's a data-integrity sync.  We must wait.
 396                  */
 397                 inode_wait_for_writeback(inode, wb);
 398         }
 399
 400         BUG_ON(inode->i_state & I_SYNC);
 401
 402         /* Set I_SYNC, reset I_DIRTY_PAGES */
 403         inode->i_state |= I_SYNC;
 404         inode->i_state &= ~I_DIRTY_PAGES;
 405         spin_unlock(&inode->i_lock);
 406         spin_unlock(&wb->list_lock);
 407
 408         ret = do_writepages(mapping, wbc);
 409
 410         /*
 411          * Make sure to wait on the data before writing out the metadata.
 412          * This is important for filesystems that modify metadata on data
 413          * I/O completion.
 414          */
 415         if (wbc->sync_mode == WB_SYNC_ALL) {
 416                 int err = filemap_fdatawait(mapping);
 417                 if (ret == 0)
 418                         ret = err;
 419         }
 420
 421         /*
 422          * Some filesystems may redirty the inode during the writeback
 423          * due to delalloc, clear dirty metadata flags right before
 424          * write_inode()
 425          */
 426         spin_lock(&inode->i_lock);
 427         dirty = inode->i_state & I_DIRTY;
 428         inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
 429         spin_unlock(&inode->i_lock);
 430         /* Don't write the inode if only I_DIRTY_PAGES was set */
 431         if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
 432                 int err = write_inode(inode, wbc);
 433                 if (ret == 0)
 434                         ret = err;
 435         }
 436
 437         spin_lock(&wb->list_lock);
 438         spin_lock(&inode->i_lock);
 439         inode->i_state &= ~I_SYNC;
 440         if (!(inode->i_state & I_FREEING)) {
 441                 /*
 442                  * Sync livelock prevention. Each inode is tagged and synced in
 443                  * one shot. If still dirty, it will be redirty_tail()'ed below.
 444                  * Update the dirty time to prevent enqueue and sync it again.
 445                  */
 446                 if ((inode->i_state & I_DIRTY) &&
 447                     (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
 448                         inode->dirtied_when = jiffies;
 449
 450                 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 451                         /*
 452                          * We didn't write back all the pages.  nfs_writepages()
 453                          * sometimes bales out without doing anything.
 454                          */
 455                         inode->i_state |= I_DIRTY_PAGES;
 456                         if (wbc->nr_to_write <= 0) {
 457                                 /*
 458                                  * slice used up: queue for next turn
 459                                  */
 460                                 requeue_io(inode, wb);
 461                         } else {
 462                                 /*
 463                                  * Writeback blocked by something other than
 464                                  * congestion. Delay the inode for some time to
 465                                  * avoid spinning on the CPU (100% iowait)
 466                                  * retrying writeback of the dirty page/inode
 467                                  * that cannot be performed immediately.
 468                                  */
 469                                 redirty_tail(inode, wb);
 470                         }
 471                 } else if (inode->i_state & I_DIRTY) {
 472                         /*
 473                          * Filesystems can dirty the inode during writeback
 474                          * operations, such as delayed allocation during
 475                          * submission or metadata updates after data IO
 476                          * completion.
 477                          */
 478                         redirty_tail(inode, wb);
 479                 } else {
 480                         /*
 481                          * The inode is clean.  At this point we either have
 482                          * a reference to the inode or it's on it's way out.
 483                          * No need to add it back to the LRU.
 484                          */
 485                         list_del_init(&inode->i_wb_list);
 486                 }
 487         }
 488         inode_sync_complete(inode);
 489         trace_writeback_single_inode(inode, wbc, nr_to_write);
 490         return ret;
 491 }
 492
 493 static long writeback_chunk_size(struct backing_dev_info *bdi,
 494                                  struct wb_writeback_work *work)
 495 {
 496         long pages;
 497
 498         /*
 499          * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
 500          * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
 501          * here avoids calling into writeback_inodes_wb() more than once.
 502          *
 503          * The intended call sequence for WB_SYNC_ALL writeback is:
 504          *
 505          *      wb_writeback()
 506          *          writeback_sb_inodes()       <== called only once
 507          *              write_cache_pages()     <== called once for each inode
 508          *                   (quickly) tag currently dirty pages
 509          *                   (maybe slowly) sync all tagged pages
 510          */
 511         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
 512                 pages = LONG_MAX;
 513         else {
 514                 pages = min(bdi->avg_write_bandwidth / 2,
 515                             global_dirty_limit / DIRTY_SCOPE);
 516                 pages = min(pages, work->nr_pages);
 517                 pages = round_down(pages + MIN_WRITEBACK_PAGES,
 518                                    MIN_WRITEBACK_PAGES);
 519         }
 520
 521         return pages;
 522 }
 523
 524 /*
 525  * Write a portion of b_io inodes which belong to @sb.
 526  *
 527  * If @only_this_sb is true, then find and write all such
 528  * inodes. Otherwise write only ones which go sequentially
 529  * in reverse order.
 530  *
 531  * Return the number of pages and/or inodes written.
 532  */
 533 static long writeback_sb_inodes(struct super_block *sb,
 534                                 struct bdi_writeback *wb,
 535                                 struct wb_writeback_work *work)
 536 {
 537         struct writeback_control wbc = {
 538                 .sync_mode              = work->sync_mode,
 539                 .tagged_writepages      = work->tagged_writepages,
 540                 .for_kupdate            = work->for_kupdate,
 541                 .for_background         = work->for_background,
 542                 .range_cyclic           = work->range_cyclic,
 543                 .range_start            = 0,
 544                 .range_end              = LLONG_MAX,
 545         };
 546         unsigned long start_time = jiffies;
 547         long write_chunk;
 548         long wrote = 0;  /* count both pages and inodes */
 549
 550         while (!list_empty(&wb->b_io)) {
 551                 struct inode *inode = wb_inode(wb->b_io.prev);
 552
 553                 if (inode->i_sb != sb) {
 554                         if (work->sb) {
 555                                 /*
 556                                  * We only want to write back data for this
 557                                  * superblock, move all inodes not belonging
 558                                  * to it back onto the dirty list.
 559                                  */
 560                                 redirty_tail(inode, wb);
 561                                 continue;
 562                         }
 563
 564                         /*
 565                          * The inode belongs to a different superblock.
 566                          * Bounce back to the caller to unpin this and
 567                          * pin the next superblock.
 568                          */
 569                         break;
 570                 }
 571
 572                 /*
 573                  * Don't bother with new inodes or inodes beeing freed, first
 574                  * kind does not need peridic writeout yet, and for the latter
 575                  * kind writeout is handled by the freer.
 576                  */
 577                 spin_lock(&inode->i_lock);
 578                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
 579                         spin_unlock(&inode->i_lock);
 580                         redirty_tail(inode, wb);
 581                         continue;
 582                 }
 583                 __iget(inode);
 584                 write_chunk = writeback_chunk_size(wb->bdi, work);
 585                 wbc.nr_to_write = write_chunk;
 586                 wbc.pages_skipped = 0;
 587
 588                 writeback_single_inode(inode, wb, &wbc);
 589
 590                 work->nr_pages -= write_chunk - wbc.nr_to_write;
 591                 wrote += write_chunk - wbc.nr_to_write;
 592                 if (!(inode->i_state & I_DIRTY))
 593                         wrote++;
 594                 if (wbc.pages_skipped) {
 595                         /*
 596                          * writeback is not making progress due to locked
 597                          * buffers.  Skip this inode for now.
 598                          */
 599                         redirty_tail(inode, wb);
 600                 }
 601                 spin_unlock(&inode->i_lock);
 602                 spin_unlock(&wb->list_lock);
 603                 iput(inode);
 604                 cond_resched();
 605                 spin_lock(&wb->list_lock);
 606                 /*
 607                  * bail out to wb_writeback() often enough to check
 608                  * background threshold and other termination conditions.
 609                  */
 610                 if (wrote) {
 611                         if (time_is_before_jiffies(start_time + HZ / 10UL))
 612                                 break;
 613                         if (work->nr_pages <= 0)
 614                                 break;
 615                 }
 616         }
 617         return wrote;
 618 }
 619
 620 static long __writeback_inodes_wb(struct bdi_writeback *wb,
 621                                   struct wb_writeback_work *work)
 622 {
 623         unsigned long start_time = jiffies;
 624         long wrote = 0;
 625
 626         while (!list_empty(&wb->b_io)) {
 627                 struct inode *inode = wb_inode(wb->b_io.prev);
 628                 struct super_block *sb = inode->i_sb;
 629
 630                 if (!grab_super_passive(sb)) {
 631                         /*
 632                          * grab_super_passive() may fail consistently due to
 633                          * s_umount being grabbed by someone else. Don't use
 634                          * requeue_io() to avoid busy retrying the inode/sb.
 635                          */
 636                         redirty_tail(inode, wb);
 637                         continue;
 638                 }
 639                 wrote += writeback_sb_inodes(sb, wb, work);
 640                 drop_super(sb);
 641
 642                 /* refer to the same tests at the end of writeback_sb_inodes */
 643                 if (wrote) {
 644                         if (time_is_before_jiffies(start_time + HZ / 10UL))
 645                                 break;
 646                         if (work->nr_pages <= 0)
 647                                 break;
 648                 }
 649         }
 650         /* Leave any unwritten inodes on b_io */
 651         return wrote;
 652 }
 653
 654 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
 655                                 enum wb_reason reason)
 656 {
 657         struct wb_writeback_work work = {
 658                 .nr_pages       = nr_pages,
 659                 .sync_mode      = WB_SYNC_NONE,
 660                 .range_cyclic   = 1,
 661                 .reason         = reason,
 662         };
 663
 664         spin_lock(&wb->list_lock);
 665         if (list_empty(&wb->b_io))
 666                 queue_io(wb, &work);
 667         __writeback_inodes_wb(wb, &work);
 668         spin_unlock(&wb->list_lock);
 669
 670         return nr_pages - work.nr_pages;
 671 }
 672
 673 static bool over_bground_thresh(struct backing_dev_info *bdi)
 674 {
 675         unsigned long background_thresh, dirty_thresh;
 676
 677         global_dirty_limits(&background_thresh, &dirty_thresh);
 678
 679         if (global_page_state(NR_FILE_DIRTY) +
 680             global_page_state(NR_UNSTABLE_NFS) > background_thresh)
 681                 return true;
 682
 683         if (bdi_stat(bdi, BDI_RECLAIMABLE) >
 684                                 bdi_dirty_limit(bdi, background_thresh))
 685                 return true;
 686
 687         return false;
 688 }
 689
 690 /*
 691  * Called under wb->list_lock. If there are multiple wb per bdi,
 692  * only the flusher working on the first wb should do it.
 693  */
 694 static void wb_update_bandwidth(struct bdi_writeback *wb,
 695                                 unsigned long start_time)
 696 {
 697         __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
 698 }
 699
 700 /*
 701  * Explicit flushing or periodic writeback of "old" data.
 702  *
 703  * Define "old": the first time one of an inode's pages is dirtied, we mark the
 704  * dirtying-time in the inode's address_space.  So this periodic writeback code
 705  * just walks the superblock inode list, writing back any inodes which are
 706  * older than a specific point in time.
 707  *
 708  * Try to run once per dirty_writeback_interval.  But if a writeback event
 709  * takes longer than a dirty_writeback_interval interval, then leave a
 710  * one-second gap.
 711  *
 712  * older_than_this takes precedence over nr_to_write.  So we'll only write back
 713  * all dirty pages if they are all attached to "old" mappings.
 714  */
 715 static long wb_writeback(struct bdi_writeback *wb,
 716                          struct wb_writeback_work *work)
 717 {
 718         unsigned long wb_start = jiffies;
 719         long nr_pages = work->nr_pages;
 720         unsigned long oldest_jif;
 721         struct inode *inode;
 722         long progress;
 723
 724         oldest_jif = jiffies;
 725         work->older_than_this = &oldest_jif;
 726
 727         spin_lock(&wb->list_lock);
 728         for (;;) {
 729                 /*
 730                  * Stop writeback when nr_pages has been consumed
 731                  */
 732                 if (work->nr_pages <= 0)
 733                         break;
 734
 735                 /*
 736                  * Background writeout and kupdate-style writeback may
 737                  * run forever. Stop them if there is other work to do
 738                  * so that e.g. sync can proceed. They'll be restarted
 739                  * after the other works are all done.
 740                  */
 741                 if ((work->for_background || work->for_kupdate) &&
 742                     !list_empty(&wb->bdi->work_list))
 743                         break;
 744
 745                 /*
 746                  * For background writeout, stop when we are below the
 747                  * background dirty threshold
 748                  */
 749                 if (work->for_background && !over_bground_thresh(wb->bdi))
 750                         break;
 751
 752                 /*
 753                  * Kupdate and background works are special and we want to
 754                  * include all inodes that need writing. Livelock avoidance is
 755                  * handled by these works yielding to any other work so we are
 756                  * safe.
 757                  */
 758                 if (work->for_kupdate) {
 759                         oldest_jif = jiffies -
 760                                 msecs_to_jiffies(dirty_expire_interval * 10);
 761                 } else if (work->for_background)
 762                         oldest_jif = jiffies;
 763
 764                 trace_writeback_start(wb->bdi, work);
 765                 if (list_empty(&wb->b_io))
 766                         queue_io(wb, work);
 767                 if (work->sb)
 768                         progress = writeback_sb_inodes(work->sb, wb, work);
 769                 else
 770                         progress = __writeback_inodes_wb(wb, work);
 771                 trace_writeback_written(wb->bdi, work);
 772
 773                 wb_update_bandwidth(wb, wb_start);
 774
 775                 /*
 776                  * Did we write something? Try for more
 777                  *
 778                  * Dirty inodes are moved to b_io for writeback in batches.
 779                  * The completion of the current batch does not necessarily
 780                  * mean the overall work is done. So we keep looping as long
 781                  * as made some progress on cleaning pages or inodes.
 782                  */
 783                 if (progress)
 784                         continue;
 785                 /*
 786                  * No more inodes for IO, bail
 787                  */
 788                 if (list_empty(&wb->b_more_io))
 789                         break;
 790                 /*
 791                  * Nothing written. Wait for some inode to
 792                  * become available for writeback. Otherwise
 793                  * we'll just busyloop.
 794                  */
 795                 if (!list_empty(&wb->b_more_io))  {
 796                         trace_writeback_wait(wb->bdi, work);
 797                         inode = wb_inode(wb->b_more_io.prev);
 798                         spin_lock(&inode->i_lock);
 799                         inode_wait_for_writeback(inode, wb);
 800                         spin_unlock(&inode->i_lock);
 801                 }
 802         }
 803         spin_unlock(&wb->list_lock);
 804
 805         return nr_pages - work->nr_pages;
 806 }
 807
 808 /*
 809  * Return the next wb_writeback_work struct that hasn't been processed yet.
 810  */
 811 static struct wb_writeback_work *
 812 get_next_work_item(struct backing_dev_info *bdi)
 813 {
 814         struct wb_writeback_work *work = NULL;
 815
 816         spin_lock_bh(&bdi->wb_lock);
 817         if (!list_empty(&bdi->work_list)) {
 818                 work = list_entry(bdi->work_list.next,
 819                                   struct wb_writeback_work, list);
 820                 list_del_init(&work->list);
 821         }
 822         spin_unlock_bh(&bdi->wb_lock);
 823         return work;
 824 }
 825
 826 /*
 827  * Add in the number of potentially dirty inodes, because each inode
 828  * write can dirty pagecache in the underlying blockdev.
 829  */
 830 static unsigned long get_nr_dirty_pages(void)
 831 {
 832         return global_page_state(NR_FILE_DIRTY) +
 833                 global_page_state(NR_UNSTABLE_NFS) +
 834                 get_nr_dirty_inodes();
 835 }
 836
 837 static long wb_check_background_flush(struct bdi_writeback *wb)
 838 {
 839         if (over_bground_thresh(wb->bdi)) {
 840
 841                 struct wb_writeback_work work = {
 842                         .nr_pages       = LONG_MAX,
 843                         .sync_mode      = WB_SYNC_NONE,
 844                         .for_background = 1,
 845                         .range_cyclic   = 1,
 846                         .reason         = WB_REASON_BACKGROUND,
 847                 };
 848
 849                 return wb_writeback(wb, &work);
 850         }
 851
 852         return 0;
 853 }
 854
 855 static long wb_check_old_data_flush(struct bdi_writeback *wb)
 856 {
 857         unsigned long expired;
 858         long nr_pages;
 859
 860         /*
 861          * When set to zero, disable periodic writeback
 862          */
 863         if (!dirty_writeback_interval)
 864                 return 0;
 865
 866         expired = wb->last_old_flush +
 867                         msecs_to_jiffies(dirty_writeback_interval * 10);
 868         if (time_before(jiffies, expired))
 869                 return 0;
 870
 871         wb->last_old_flush = jiffies;
 872         nr_pages = get_nr_dirty_pages();
 873
 874         if (nr_pages) {
 875                 struct wb_writeback_work work = {
 876                         .nr_pages       = nr_pages,
 877                         .sync_mode      = WB_SYNC_NONE,
 878                         .for_kupdate    = 1,
 879                         .range_cyclic   = 1,
 880                         .reason         = WB_REASON_PERIODIC,
 881                 };
 882
 883                 return wb_writeback(wb, &work);
 884         }
 885
 886         return 0;
 887 }
 888
 889 /*
 890  * Retrieve work items and do the writeback they describe
 891  */
 892 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
 893 {
 894         struct backing_dev_info *bdi = wb->bdi;
 895         struct wb_writeback_work *work;
 896         long wrote = 0;
 897
 898         set_bit(BDI_writeback_running, &wb->bdi->state);
 899         while ((work = get_next_work_item(bdi)) != NULL) {
 900                 /*
 901                  * Override sync mode, in case we must wait for completion
 902                  * because this thread is exiting now.
 903                  */
 904                 if (force_wait)
 905                         work->sync_mode = WB_SYNC_ALL;
 906
 907                 trace_writeback_exec(bdi, work);
 908
 909                 wrote += wb_writeback(wb, work);
 910
 911                 /*
 912                  * Notify the caller of completion if this is a synchronous
 913                  * work item, otherwise just free it.
 914                  */
 915                 if (work->done)
 916                         complete(work->done);
 917                 else
 918                         kfree(work);
 919         }
 920
 921         /*
 922          * Check for periodic writeback, kupdated() style
 923          */
 924         wrote += wb_check_old_data_flush(wb);
 925         wrote += wb_check_background_flush(wb);
 926         clear_bit(BDI_writeback_running, &wb->bdi->state);
 927
 928         return wrote;
 929 }
 930
 931 /*
 932  * Handle writeback of dirty data for the device backed by this bdi. Also
 933  * wakes up periodically and does kupdated style flushing.
 934  */
 935 int bdi_writeback_thread(void *data)
 936 {
 937         struct bdi_writeback *wb = data;
 938         struct backing_dev_info *bdi = wb->bdi;
 939         long pages_written;
 940
 941         current->flags |= PF_SWAPWRITE;
 942         set_freezable();
 943         wb->last_active = jiffies;
 944
 945         /*
 946          * Our parent may run at a different priority, just set us to normal
 947          */
 948         set_user_nice(current, 0);
 949
 950         trace_writeback_thread_start(bdi);
 951
 952         while (!kthread_freezable_should_stop(NULL)) {
 953                 /*
 954                  * Remove own delayed wake-up timer, since we are already awake
 955                  * and we'll take care of the preriodic write-back.
 956                  */
 957                 del_timer(&wb->wakeup_timer);
 958
 959                 pages_written = wb_do_writeback(wb, 0);
 960
 961                 trace_writeback_pages_written(pages_written);
 962
 963                 if (pages_written)
 964                         wb->last_active = jiffies;
 965
 966                 set_current_state(TASK_INTERRUPTIBLE);
 967                 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
 968                         __set_current_state(TASK_RUNNING);
 969                         continue;
 970                 }
 971
 972                 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
 973                         schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
 974                 else {
 975                         /*
 976                          * We have nothing to do, so can go sleep without any
 977                          * timeout and save power. When a work is queued or
 978                          * something is made dirty - we will be woken up.
 979                          */
 980                         schedule();
 981                 }
 982         }
 983
 984         /* Flush any work that raced with us exiting */
 985         if (!list_empty(&bdi->work_list))
 986                 wb_do_writeback(wb, 1);
 987
 988         trace_writeback_thread_stop(bdi);
 989         return 0;
 990 }
 991
 992
 993 /*
 994  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
 995  * the whole world.
 996  */
 997 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
 998 {
 999         struct backing_dev_info *bdi;
1000
1001         if (!nr_pages) {
1002                 nr_pages = global_page_state(NR_FILE_DIRTY) +
1003                                 global_page_state(NR_UNSTABLE_NFS);
1004         }
1005
1006         rcu_read_lock();
1007         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1008                 if (!bdi_has_dirty_io(bdi))
1009                         continue;
1010                 __bdi_start_writeback(bdi, nr_pages, false, reason);
1011         }
1012         rcu_read_unlock();
1013 }
1014
1015 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1016 {
1017         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1018                 struct dentry *dentry;
1019                 const char *name = "?";
1020
1021                 dentry = d_find_alias(inode);
1022                 if (dentry) {
1023                         spin_lock(&dentry->d_lock);
1024                         name = (const char *) dentry->d_name.name;
1025                 }
1026                 printk(KERN_DEBUG
1027                        "%s(%d): dirtied inode %lu (%s) on %s\n",
1028                        current->comm, task_pid_nr(current), inode->i_ino,
1029                        name, inode->i_sb->s_id);
1030                 if (dentry) {
1031                         spin_unlock(&dentry->d_lock);
1032                         dput(dentry);
1033                 }
1034         }
1035 }
1036
1037 /**
1038  *      __mark_inode_dirty -    internal function
1039  *      @inode: inode to mark
1040  *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1041  *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1042  *      mark_inode_dirty_sync.
1043  *
1044  * Put the inode on the super block's dirty list.
1045  *
1046  * CAREFUL! We mark it dirty unconditionally, but move it onto the
1047  * dirty list only if it is hashed or if it refers to a blockdev.
1048  * If it was not hashed, it will never be added to the dirty list
1049  * even if it is later hashed, as it will have been marked dirty already.
1050  *
1051  * In short, make sure you hash any inodes _before_ you start marking
1052  * them dirty.
1053  *
1054  * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1055  * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1056  * the kernel-internal blockdev inode represents the dirtying time of the
1057  * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1058  * page->mapping->host, so the page-dirtying time is recorded in the internal
1059  * blockdev inode.
1060  */
1061 void __mark_inode_dirty(struct inode *inode, int flags)
1062 {
1063         struct super_block *sb = inode->i_sb;
1064         struct backing_dev_info *bdi = NULL;
1065
1066         /*
1067          * Don't do this for I_DIRTY_PAGES - that doesn't actually
1068          * dirty the inode itself
1069          */
1070         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1071                 if (sb->s_op->dirty_inode)
1072                         sb->s_op->dirty_inode(inode, flags);
1073         }
1074
1075         /*
1076          * make sure that changes are seen by all cpus before we test i_state
1077          * -- mikulas
1078          */
1079         smp_mb();
1080
1081         /* avoid the locking if we can */
1082         if ((inode->i_state & flags) == flags)
1083                 return;
1084
1085         if (unlikely(block_dump))
1086                 block_dump___mark_inode_dirty(inode);
1087
1088         spin_lock(&inode->i_lock);
1089         if ((inode->i_state & flags) != flags) {
1090                 const int was_dirty = inode->i_state & I_DIRTY;
1091
1092                 inode->i_state |= flags;
1093
1094                 /*
1095                  * If the inode is being synced, just update its dirty state.
1096                  * The unlocker will place the inode on the appropriate
1097                  * superblock list, based upon its state.
1098                  */
1099                 if (inode->i_state & I_SYNC)
1100                         goto out_unlock_inode;
1101
1102                 /*
1103                  * Only add valid (hashed) inodes to the superblock's
1104                  * dirty list.  Add blockdev inodes as well.
1105                  */
1106                 if (!S_ISBLK(inode->i_mode)) {
1107                         if (inode_unhashed(inode))
1108                                 goto out_unlock_inode;
1109                 }
1110                 if (inode->i_state & I_FREEING)
1111                         goto out_unlock_inode;
1112
1113                 /*
1114                  * If the inode was already on b_dirty/b_io/b_more_io, don't
1115                  * reposition it (that would break b_dirty time-ordering).
1116                  */
1117                 if (!was_dirty) {
1118                         bool wakeup_bdi = false;
1119                         bdi = inode_to_bdi(inode);
1120
1121                         if (bdi_cap_writeback_dirty(bdi)) {
1122                                 WARN(!test_bit(BDI_registered, &bdi->state),
1123                                      "bdi-%s not registered\n", bdi->name);
1124
1125                                 /*
1126                                  * If this is the first dirty inode for this
1127                                  * bdi, we have to wake-up the corresponding
1128                                  * bdi thread to make sure background
1129                                  * write-back happens later.
1130                                  */
1131                                 if (!wb_has_dirty_io(&bdi->wb))
1132                                         wakeup_bdi = true;
1133                         }
1134
1135                         spin_unlock(&inode->i_lock);
1136                         spin_lock(&bdi->wb.list_lock);
1137                         inode->dirtied_when = jiffies;
1138                         list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1139                         spin_unlock(&bdi->wb.list_lock);
1140
1141                         if (wakeup_bdi)
1142                                 bdi_wakeup_thread_delayed(bdi);
1143                         return;
1144                 }
1145         }
1146 out_unlock_inode:
1147         spin_unlock(&inode->i_lock);
1148
1149 }
1150 EXPORT_SYMBOL(__mark_inode_dirty);
1151
1152 static void wait_sb_inodes(struct super_block *sb)
1153 {
1154         struct inode *inode, *old_inode = NULL;
1155
1156         /*
1157          * We need to be protected against the filesystem going from
1158          * r/o to r/w or vice versa.
1159          */
1160         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1161
1162         spin_lock(&inode_sb_list_lock);
1163
1164         /*
1165          * Data integrity sync. Must wait for all pages under writeback,
1166          * because there may have been pages dirtied before our sync
1167          * call, but which had writeout started before we write it out.
1168          * In which case, the inode may not be on the dirty list, but
1169          * we still have to wait for that writeout.
1170          */
1171         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1172                 struct address_space *mapping = inode->i_mapping;
1173
1174                 spin_lock(&inode->i_lock);
1175                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1176                     (mapping->nrpages == 0)) {
1177                         spin_unlock(&inode->i_lock);
1178                         continue;
1179                 }
1180                 __iget(inode);
1181                 spin_unlock(&inode->i_lock);
1182                 spin_unlock(&inode_sb_list_lock);
1183
1184                 /*
1185                  * We hold a reference to 'inode' so it couldn't have been
1186                  * removed from s_inodes list while we dropped the
1187                  * inode_sb_list_lock.  We cannot iput the inode now as we can
1188                  * be holding the last reference and we cannot iput it under
1189                  * inode_sb_list_lock. So we keep the reference and iput it
1190                  * later.
1191                  */
1192                 iput(old_inode);
1193                 old_inode = inode;
1194
1195                 filemap_fdatawait(mapping);
1196
1197                 cond_resched();
1198
1199                 spin_lock(&inode_sb_list_lock);
1200         }
1201         spin_unlock(&inode_sb_list_lock);
1202         iput(old_inode);
1203 }
1204
1205 /**
1206  * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1207  * @sb: the superblock
1208  * @nr: the number of pages to write
1209  * @reason: reason why some writeback work initiated
1210  *
1211  * Start writeback on some inodes on this super_block. No guarantees are made
1212  * on how many (if any) will be written, and this function does not wait
1213  * for IO completion of submitted IO.
1214  */
1215 void writeback_inodes_sb_nr(struct super_block *sb,
1216                             unsigned long nr,
1217                             enum wb_reason reason)
1218 {
1219         DECLARE_COMPLETION_ONSTACK(done);
1220         struct wb_writeback_work work = {
1221                 .sb                     = sb,
1222                 .sync_mode              = WB_SYNC_NONE,
1223                 .tagged_writepages      = 1,
1224                 .done                   = &done,
1225                 .nr_pages               = nr,
1226                 .reason                 = reason,
1227         };
1228
1229         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1230         bdi_queue_work(sb->s_bdi, &work);
1231         wait_for_completion(&done);
1232 }
1233 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1234
1235 /**
1236  * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1237  * @sb: the superblock
1238  * @reason: reason why some writeback work was initiated
1239  *
1240  * Start writeback on some inodes on this super_block. No guarantees are made
1241  * on how many (if any) will be written, and this function does not wait
1242  * for IO completion of submitted IO.
1243  */
1244 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1245 {
1246         return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1247 }
1248 EXPORT_SYMBOL(writeback_inodes_sb);
1249
1250 /**
1251  * writeback_inodes_sb_if_idle  -       start writeback if none underway
1252  * @sb: the superblock
1253  * @reason: reason why some writeback work was initiated
1254  *
1255  * Invoke writeback_inodes_sb if no writeback is currently underway.
1256  * Returns 1 if writeback was started, 0 if not.
1257  */
1258 int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
1259 {
1260         if (!writeback_in_progress(sb->s_bdi)) {
1261                 down_read(&sb->s_umount);
1262                 writeback_inodes_sb(sb, reason);
1263                 up_read(&sb->s_umount);
1264                 return 1;
1265         } else
1266                 return 0;
1267 }
1268 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1269
1270 /**
1271  * writeback_inodes_sb_nr_if_idle       -       start writeback if none underway
1272  * @sb: the superblock
1273  * @nr: the number of pages to write
1274  * @reason: reason why some writeback work was initiated
1275  *
1276  * Invoke writeback_inodes_sb if no writeback is currently underway.
1277  * Returns 1 if writeback was started, 0 if not.
1278  */
1279 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1280                                    unsigned long nr,
1281                                    enum wb_reason reason)
1282 {
1283         if (!writeback_in_progress(sb->s_bdi)) {
1284                 down_read(&sb->s_umount);
1285                 writeback_inodes_sb_nr(sb, nr, reason);
1286                 up_read(&sb->s_umount);
1287                 return 1;
1288         } else
1289                 return 0;
1290 }
1291 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1292
1293 /**
1294  * sync_inodes_sb       -       sync sb inode pages
1295  * @sb: the superblock
1296  *
1297  * This function writes and waits on any dirty inode belonging to this
1298  * super_block.
1299  */
1300 void sync_inodes_sb(struct super_block *sb)
1301 {
1302         DECLARE_COMPLETION_ONSTACK(done);
1303         struct wb_writeback_work work = {
1304                 .sb             = sb,
1305                 .sync_mode      = WB_SYNC_ALL,
1306                 .nr_pages       = LONG_MAX,
1307                 .range_cyclic   = 0,
1308                 .done           = &done,
1309                 .reason         = WB_REASON_SYNC,
1310         };
1311
1312         WARN_ON(!rwsem_is_locked(&sb->s_umount));
1313
1314         bdi_queue_work(sb->s_bdi, &work);
1315         wait_for_completion(&done);
1316
1317         wait_sb_inodes(sb);
1318 }
1319 EXPORT_SYMBOL(sync_inodes_sb);
1320
1321 /**
1322  * write_inode_now      -       write an inode to disk
1323  * @inode: inode to write to disk
1324  * @sync: whether the write should be synchronous or not
1325  *
1326  * This function commits an inode to disk immediately if it is dirty. This is
1327  * primarily needed by knfsd.
1328  *
1329  * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1330  */
1331 int write_inode_now(struct inode *inode, int sync)
1332 {
1333         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1334         int ret;
1335         struct writeback_control wbc = {
1336                 .nr_to_write = LONG_MAX,
1337                 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1338                 .range_start = 0,
1339                 .range_end = LLONG_MAX,
1340         };
1341
1342         if (!mapping_cap_writeback_dirty(inode->i_mapping))
1343                 wbc.nr_to_write = 0;
1344
1345         might_sleep();
1346         spin_lock(&wb->list_lock);
1347         spin_lock(&inode->i_lock);
1348         ret = writeback_single_inode(inode, wb, &wbc);
1349         spin_unlock(&inode->i_lock);
1350         spin_unlock(&wb->list_lock);
1351         return ret;
1352 }
1353 EXPORT_SYMBOL(write_inode_now);
1354
1355 /**
1356  * sync_inode - write an inode and its pages to disk.
1357  * @inode: the inode to sync
1358  * @wbc: controls the writeback mode
1359  *
1360  * sync_inode() will write an inode and its pages to disk.  It will also
1361  * correctly update the inode on its superblock's dirty inode lists and will
1362  * update inode->i_state.
1363  *
1364  * The caller must have a ref on the inode.
1365  */
1366 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1367 {
1368         struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1369         int ret;
1370
1371         spin_lock(&wb->list_lock);
1372         spin_lock(&inode->i_lock);
1373         ret = writeback_single_inode(inode, wb, wbc);
1374         spin_unlock(&inode->i_lock);
1375         spin_unlock(&wb->list_lock);
1376         return ret;
1377 }
1378 EXPORT_SYMBOL(sync_inode);
1379
1380 /**
1381  * sync_inode_metadata - write an inode to disk
1382  * @inode: the inode to sync
1383  * @wait: wait for I/O to complete.
1384  *
1385  * Write an inode to disk and adjust its dirty state after completion.
1386  *
1387  * Note: only writes the actual inode, no associated data or other metadata.
1388  */
1389 int sync_inode_metadata(struct inode *inode, int wait)
1390 {
1391         struct writeback_control wbc = {
1392                 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1393                 .nr_to_write = 0, /* metadata-only */
1394         };
1395
1396         return sync_inode(inode, &wbc);
1397 }
1398 EXPORT_SYMBOL(sync_inode_metadata);