linux/fs/fs-writeback.c
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   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 */
  40struct 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 * writeback_in_progress - determine whether there is writeback in progress
  57 * @bdi: the device's backing_dev_info structure.
  58 *
  59 * Determine whether there is writeback waiting to be handled against a
  60 * backing device.
  61 */
  62int writeback_in_progress(struct backing_dev_info *bdi)
  63{
  64        return test_bit(BDI_writeback_running, &bdi->state);
  65}
  66EXPORT_SYMBOL(writeback_in_progress);
  67
  68static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
  69{
  70        struct super_block *sb = inode->i_sb;
  71
  72        if (strcmp(sb->s_type->name, "bdev") == 0)
  73                return inode->i_mapping->backing_dev_info;
  74
  75        return sb->s_bdi;
  76}
  77
  78static inline struct inode *wb_inode(struct list_head *head)
  79{
  80        return list_entry(head, struct inode, i_wb_list);
  81}
  82
  83/*
  84 * Include the creation of the trace points after defining the
  85 * wb_writeback_work structure and inline functions so that the definition
  86 * remains local to this file.
  87 */
  88#define CREATE_TRACE_POINTS
  89#include <trace/events/writeback.h>
  90
  91/* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
  92static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
  93{
  94        if (bdi->wb.task) {
  95                wake_up_process(bdi->wb.task);
  96        } else {
  97                /*
  98                 * The bdi thread isn't there, wake up the forker thread which
  99                 * will create and run it.
 100                 */
 101                wake_up_process(default_backing_dev_info.wb.task);
 102        }
 103}
 104
 105static void bdi_queue_work(struct backing_dev_info *bdi,
 106                           struct wb_writeback_work *work)
 107{
 108        trace_writeback_queue(bdi, work);
 109
 110        spin_lock_bh(&bdi->wb_lock);
 111        list_add_tail(&work->list, &bdi->work_list);
 112        if (!bdi->wb.task)
 113                trace_writeback_nothread(bdi, work);
 114        bdi_wakeup_flusher(bdi);
 115        spin_unlock_bh(&bdi->wb_lock);
 116}
 117
 118static void
 119__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 120                      bool range_cyclic, enum wb_reason reason)
 121{
 122        struct wb_writeback_work *work;
 123
 124        /*
 125         * This is WB_SYNC_NONE writeback, so if allocation fails just
 126         * wakeup the thread for old dirty data writeback
 127         */
 128        work = kzalloc(sizeof(*work), GFP_ATOMIC);
 129        if (!work) {
 130                if (bdi->wb.task) {
 131                        trace_writeback_nowork(bdi);
 132                        wake_up_process(bdi->wb.task);
 133                }
 134                return;
 135        }
 136
 137        work->sync_mode = WB_SYNC_NONE;
 138        work->nr_pages  = nr_pages;
 139        work->range_cyclic = range_cyclic;
 140        work->reason    = reason;
 141
 142        bdi_queue_work(bdi, work);
 143}
 144
 145/**
 146 * bdi_start_writeback - start writeback
 147 * @bdi: the backing device to write from
 148 * @nr_pages: the number of pages to write
 149 * @reason: reason why some writeback work was initiated
 150 *
 151 * Description:
 152 *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
 153 *   started when this function returns, we make no guarantees on
 154 *   completion. Caller need not hold sb s_umount semaphore.
 155 *
 156 */
 157void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
 158                        enum wb_reason reason)
 159{
 160        __bdi_start_writeback(bdi, nr_pages, true, reason);
 161}
 162
 163/**
 164 * bdi_start_background_writeback - start background writeback
 165 * @bdi: the backing device to write from
 166 *
 167 * Description:
 168 *   This makes sure WB_SYNC_NONE background writeback happens. When
 169 *   this function returns, it is only guaranteed that for given BDI
 170 *   some IO is happening if we are over background dirty threshold.
 171 *   Caller need not hold sb s_umount semaphore.
 172 */
 173void bdi_start_background_writeback(struct backing_dev_info *bdi)
 174{
 175        /*
 176         * We just wake up the flusher thread. It will perform background
 177         * writeback as soon as there is no other work to do.
 178         */
 179        trace_writeback_wake_background(bdi);
 180        spin_lock_bh(&bdi->wb_lock);
 181        bdi_wakeup_flusher(bdi);
 182        spin_unlock_bh(&bdi->wb_lock);
 183}
 184
 185/*
 186 * Remove the inode from the writeback list it is on.
 187 */
 188void inode_wb_list_del(struct inode *inode)
 189{
 190        struct backing_dev_info *bdi = inode_to_bdi(inode);
 191
 192        spin_lock(&bdi->wb.list_lock);
 193        list_del_init(&inode->i_wb_list);
 194        spin_unlock(&bdi->wb.list_lock);
 195}
 196
 197/*
 198 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
 199 * furthest end of its superblock's dirty-inode list.
 200 *
 201 * Before stamping the inode's ->dirtied_when, we check to see whether it is
 202 * already the most-recently-dirtied inode on the b_dirty list.  If that is
 203 * the case then the inode must have been redirtied while it was being written
 204 * out and we don't reset its dirtied_when.
 205 */
 206static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
 207{
 208        assert_spin_locked(&wb->list_lock);
 209        if (!list_empty(&wb->b_dirty)) {
 210                struct inode *tail;
 211
 212                tail = wb_inode(wb->b_dirty.next);
 213                if (time_before(inode->dirtied_when, tail->dirtied_when))
 214                        inode->dirtied_when = jiffies;
 215        }
 216        list_move(&inode->i_wb_list, &wb->b_dirty);
 217}
 218
 219/*
 220 * requeue inode for re-scanning after bdi->b_io list is exhausted.
 221 */
 222static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
 223{
 224        assert_spin_locked(&wb->list_lock);
 225        list_move(&inode->i_wb_list, &wb->b_more_io);
 226}
 227
 228static void inode_sync_complete(struct inode *inode)
 229{
 230        inode->i_state &= ~I_SYNC;
 231        /* Waiters must see I_SYNC cleared before being woken up */
 232        smp_mb();
 233        wake_up_bit(&inode->i_state, __I_SYNC);
 234}
 235
 236static bool inode_dirtied_after(struct inode *inode, unsigned long t)
 237{
 238        bool ret = time_after(inode->dirtied_when, t);
 239#ifndef CONFIG_64BIT
 240        /*
 241         * For inodes being constantly redirtied, dirtied_when can get stuck.
 242         * It _appears_ to be in the future, but is actually in distant past.
 243         * This test is necessary to prevent such wrapped-around relative times
 244         * from permanently stopping the whole bdi writeback.
 245         */
 246        ret = ret && time_before_eq(inode->dirtied_when, jiffies);
 247#endif
 248        return ret;
 249}
 250
 251/*
 252 * Move expired (dirtied after work->older_than_this) dirty inodes from
 253 * @delaying_queue to @dispatch_queue.
 254 */
 255static int move_expired_inodes(struct list_head *delaying_queue,
 256                               struct list_head *dispatch_queue,
 257                               struct wb_writeback_work *work)
 258{
 259        LIST_HEAD(tmp);
 260        struct list_head *pos, *node;
 261        struct super_block *sb = NULL;
 262        struct inode *inode;
 263        int do_sb_sort = 0;
 264        int moved = 0;
 265
 266        while (!list_empty(delaying_queue)) {
 267                inode = wb_inode(delaying_queue->prev);
 268                if (work->older_than_this &&
 269                    inode_dirtied_after(inode, *work->older_than_this))
 270                        break;
 271                if (sb && sb != inode->i_sb)
 272                        do_sb_sort = 1;
 273                sb = inode->i_sb;
 274                list_move(&inode->i_wb_list, &tmp);
 275                moved++;
 276        }
 277
 278        /* just one sb in list, splice to dispatch_queue and we're done */
 279        if (!do_sb_sort) {
 280                list_splice(&tmp, dispatch_queue);
 281                goto out;
 282        }
 283
 284        /* Move inodes from one superblock together */
 285        while (!list_empty(&tmp)) {
 286                sb = wb_inode(tmp.prev)->i_sb;
 287                list_for_each_prev_safe(pos, node, &tmp) {
 288                        inode = wb_inode(pos);
 289                        if (inode->i_sb == sb)
 290                                list_move(&inode->i_wb_list, dispatch_queue);
 291                }
 292        }
 293out:
 294        return moved;
 295}
 296
 297/*
 298 * Queue all expired dirty inodes for io, eldest first.
 299 * Before
 300 *         newly dirtied     b_dirty    b_io    b_more_io
 301 *         =============>    gf         edc     BA
 302 * After
 303 *         newly dirtied     b_dirty    b_io    b_more_io
 304 *         =============>    g          fBAedc
 305 *                                           |
 306 *                                           +--> dequeue for IO
 307 */
 308static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
 309{
 310        int moved;
 311        assert_spin_locked(&wb->list_lock);
 312        list_splice_init(&wb->b_more_io, &wb->b_io);
 313        moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
 314        trace_writeback_queue_io(wb, work, moved);
 315}
 316
 317static int write_inode(struct inode *inode, struct writeback_control *wbc)
 318{
 319        if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
 320                return inode->i_sb->s_op->write_inode(inode, wbc);
 321        return 0;
 322}
 323
 324/*
 325 * Wait for writeback on an inode to complete. Called with i_lock held.
 326 * Caller must make sure inode cannot go away when we drop i_lock.
 327 */
 328static void __inode_wait_for_writeback(struct inode *inode)
 329        __releases(inode->i_lock)
 330        __acquires(inode->i_lock)
 331{
 332        DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
 333        wait_queue_head_t *wqh;
 334
 335        wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
 336        while (inode->i_state & I_SYNC) {
 337                spin_unlock(&inode->i_lock);
 338                __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
 339                spin_lock(&inode->i_lock);
 340        }
 341}
 342
 343/*
 344 * Wait for writeback on an inode to complete. Caller must have inode pinned.
 345 */
 346void inode_wait_for_writeback(struct inode *inode)
 347{
 348        spin_lock(&inode->i_lock);
 349        __inode_wait_for_writeback(inode);
 350        spin_unlock(&inode->i_lock);
 351}
 352
 353/*
 354 * Sleep until I_SYNC is cleared. This function must be called with i_lock
 355 * held and drops it. It is aimed for callers not holding any inode reference
 356 * so once i_lock is dropped, inode can go away.
 357 */
 358static void inode_sleep_on_writeback(struct inode *inode)
 359        __releases(inode->i_lock)
 360{
 361        DEFINE_WAIT(wait);
 362        wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
 363        int sleep;
 364
 365        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
 366        sleep = inode->i_state & I_SYNC;
 367        spin_unlock(&inode->i_lock);
 368        if (sleep)
 369                schedule();
 370        finish_wait(wqh, &wait);
 371}
 372
 373/*
 374 * Find proper writeback list for the inode depending on its current state and
 375 * possibly also change of its state while we were doing writeback.  Here we
 376 * handle things such as livelock prevention or fairness of writeback among
 377 * inodes. This function can be called only by flusher thread - noone else
 378 * processes all inodes in writeback lists and requeueing inodes behind flusher
 379 * thread's back can have unexpected consequences.
 380 */
 381static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
 382                          struct writeback_control *wbc)
 383{
 384        if (inode->i_state & I_FREEING)
 385                return;
 386
 387        /*
 388         * Sync livelock prevention. Each inode is tagged and synced in one
 389         * shot. If still dirty, it will be redirty_tail()'ed below.  Update
 390         * the dirty time to prevent enqueue and sync it again.
 391         */
 392        if ((inode->i_state & I_DIRTY) &&
 393            (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
 394                inode->dirtied_when = jiffies;
 395
 396        if (wbc->pages_skipped) {
 397                /*
 398                 * writeback is not making progress due to locked
 399                 * buffers. Skip this inode for now.
 400                 */
 401                redirty_tail(inode, wb);
 402                return;
 403        }
 404
 405        if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
 406                /*
 407                 * We didn't write back all the pages.  nfs_writepages()
 408                 * sometimes bales out without doing anything.
 409                 */
 410                if (wbc->nr_to_write <= 0) {
 411                        /* Slice used up. Queue for next turn. */
 412                        requeue_io(inode, wb);
 413                } else {
 414                        /*
 415                         * Writeback blocked by something other than
 416                         * congestion. Delay the inode for some time to
 417                         * avoid spinning on the CPU (100% iowait)
 418                         * retrying writeback of the dirty page/inode
 419                         * that cannot be performed immediately.
 420                         */
 421                        redirty_tail(inode, wb);
 422                }
 423        } else if (inode->i_state & I_DIRTY) {
 424                /*
 425                 * Filesystems can dirty the inode during writeback operations,
 426                 * such as delayed allocation during submission or metadata
 427                 * updates after data IO completion.
 428                 */
 429                redirty_tail(inode, wb);
 430        } else {
 431                /* The inode is clean. Remove from writeback lists. */
 432                list_del_init(&inode->i_wb_list);
 433        }
 434}
 435
 436/*
 437 * Write out an inode and its dirty pages. Do not update the writeback list
 438 * linkage. That is left to the caller. The caller is also responsible for
 439 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
 440 */
 441static int
 442__writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 443                         struct writeback_control *wbc)
 444{
 445        struct address_space *mapping = inode->i_mapping;
 446        long nr_to_write = wbc->nr_to_write;
 447        unsigned dirty;
 448        int ret;
 449
 450        WARN_ON(!(inode->i_state & I_SYNC));
 451
 452        ret = do_writepages(mapping, wbc);
 453
 454        /*
 455         * Make sure to wait on the data before writing out the metadata.
 456         * This is important for filesystems that modify metadata on data
 457         * I/O completion.
 458         */
 459        if (wbc->sync_mode == WB_SYNC_ALL) {
 460                int err = filemap_fdatawait(mapping);
 461                if (ret == 0)
 462                        ret = err;
 463        }
 464
 465        /*
 466         * Some filesystems may redirty the inode during the writeback
 467         * due to delalloc, clear dirty metadata flags right before
 468         * write_inode()
 469         */
 470        spin_lock(&inode->i_lock);
 471        /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
 472        if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
 473                inode->i_state &= ~I_DIRTY_PAGES;
 474        dirty = inode->i_state & I_DIRTY;
 475        inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
 476        spin_unlock(&inode->i_lock);
 477        /* Don't write the inode if only I_DIRTY_PAGES was set */
 478        if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
 479                int err = write_inode(inode, wbc);
 480                if (ret == 0)
 481                        ret = err;
 482        }
 483        trace_writeback_single_inode(inode, wbc, nr_to_write);
 484        return ret;
 485}
 486
 487/*
 488 * Write out an inode's dirty pages. Either the caller has an active reference
 489 * on the inode or the inode has I_WILL_FREE set.
 490 *
 491 * This function is designed to be called for writing back one inode which
 492 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
 493 * and does more profound writeback list handling in writeback_sb_inodes().
 494 */
 495static int
 496writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 497                       struct writeback_control *wbc)
 498{
 499        int ret = 0;
 500
 501        spin_lock(&inode->i_lock);
 502        if (!atomic_read(&inode->i_count))
 503                WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
 504        else
 505                WARN_ON(inode->i_state & I_WILL_FREE);
 506
 507        if (inode->i_state & I_SYNC) {
 508                if (wbc->sync_mode != WB_SYNC_ALL)
 509                        goto out;
 510                /*
 511                 * It's a data-integrity sync. We must wait. Since callers hold
 512                 * inode reference or inode has I_WILL_FREE set, it cannot go
 513                 * away under us.
 514                 */
 515                __inode_wait_for_writeback(inode);
 516        }
 517        WARN_ON(inode->i_state & I_SYNC);
 518        /*
 519         * Skip inode if it is clean. We don't want to mess with writeback
 520         * lists in this function since flusher thread may be doing for example
 521         * sync in parallel and if we move the inode, it could get skipped. So
 522         * here we make sure inode is on some writeback list and leave it there
 523         * unless we have completely cleaned the inode.
 524         */
 525        if (!(inode->i_state & I_DIRTY))
 526                goto out;
 527        inode->i_state |= I_SYNC;
 528        spin_unlock(&inode->i_lock);
 529
 530        ret = __writeback_single_inode(inode, wb, wbc);
 531
 532        spin_lock(&wb->list_lock);
 533        spin_lock(&inode->i_lock);
 534        /*
 535         * If inode is clean, remove it from writeback lists. Otherwise don't
 536         * touch it. See comment above for explanation.
 537         */
 538        if (!(inode->i_state & I_DIRTY))
 539                list_del_init(&inode->i_wb_list);
 540        spin_unlock(&wb->list_lock);
 541        inode_sync_complete(inode);
 542out:
 543        spin_unlock(&inode->i_lock);
 544        return ret;
 545}
 546
 547static long writeback_chunk_size(struct backing_dev_info *bdi,
 548                                 struct wb_writeback_work *work)
 549{
 550        long pages;
 551
 552        /*
 553         * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
 554         * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
 555         * here avoids calling into writeback_inodes_wb() more than once.
 556         *
 557         * The intended call sequence for WB_SYNC_ALL writeback is:
 558         *
 559         *      wb_writeback()
 560         *          writeback_sb_inodes()       <== called only once
 561         *              write_cache_pages()     <== called once for each inode
 562         *                   (quickly) tag currently dirty pages
 563         *                   (maybe slowly) sync all tagged pages
 564         */
 565        if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
 566                pages = LONG_MAX;
 567        else {
 568                pages = min(bdi->avg_write_bandwidth / 2,
 569                            global_dirty_limit / DIRTY_SCOPE);
 570                pages = min(pages, work->nr_pages);
 571                pages = round_down(pages + MIN_WRITEBACK_PAGES,
 572                                   MIN_WRITEBACK_PAGES);
 573        }
 574
 575        return pages;
 576}
 577
 578/*
 579 * Write a portion of b_io inodes which belong to @sb.
 580 *
 581 * If @only_this_sb is true, then find and write all such
 582 * inodes. Otherwise write only ones which go sequentially
 583 * in reverse order.
 584 *
 585 * Return the number of pages and/or inodes written.
 586 */
 587static long writeback_sb_inodes(struct super_block *sb,
 588                                struct bdi_writeback *wb,
 589                                struct wb_writeback_work *work)
 590{
 591        struct writeback_control wbc = {
 592                .sync_mode              = work->sync_mode,
 593                .tagged_writepages      = work->tagged_writepages,
 594                .for_kupdate            = work->for_kupdate,
 595                .for_background         = work->for_background,
 596                .range_cyclic           = work->range_cyclic,
 597                .range_start            = 0,
 598                .range_end              = LLONG_MAX,
 599        };
 600        unsigned long start_time = jiffies;
 601        long write_chunk;
 602        long wrote = 0;  /* count both pages and inodes */
 603
 604        while (!list_empty(&wb->b_io)) {
 605                struct inode *inode = wb_inode(wb->b_io.prev);
 606
 607                if (inode->i_sb != sb) {
 608                        if (work->sb) {
 609                                /*
 610                                 * We only want to write back data for this
 611                                 * superblock, move all inodes not belonging
 612                                 * to it back onto the dirty list.
 613                                 */
 614                                redirty_tail(inode, wb);
 615                                continue;
 616                        }
 617
 618                        /*
 619                         * The inode belongs to a different superblock.
 620                         * Bounce back to the caller to unpin this and
 621                         * pin the next superblock.
 622                         */
 623                        break;
 624                }
 625
 626                /*
 627                 * Don't bother with new inodes or inodes being freed, first
 628                 * kind does not need periodic writeout yet, and for the latter
 629                 * kind writeout is handled by the freer.
 630                 */
 631                spin_lock(&inode->i_lock);
 632                if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
 633                        spin_unlock(&inode->i_lock);
 634                        redirty_tail(inode, wb);
 635                        continue;
 636                }
 637                if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
 638                        /*
 639                         * If this inode is locked for writeback and we are not
 640                         * doing writeback-for-data-integrity, move it to
 641                         * b_more_io so that writeback can proceed with the
 642                         * other inodes on s_io.
 643                         *
 644                         * We'll have another go at writing back this inode
 645                         * when we completed a full scan of b_io.
 646                         */
 647                        spin_unlock(&inode->i_lock);
 648                        requeue_io(inode, wb);
 649                        trace_writeback_sb_inodes_requeue(inode);
 650                        continue;
 651                }
 652                spin_unlock(&wb->list_lock);
 653
 654                /*
 655                 * We already requeued the inode if it had I_SYNC set and we
 656                 * are doing WB_SYNC_NONE writeback. So this catches only the
 657                 * WB_SYNC_ALL case.
 658                 */
 659                if (inode->i_state & I_SYNC) {
 660                        /* Wait for I_SYNC. This function drops i_lock... */
 661                        inode_sleep_on_writeback(inode);
 662                        /* Inode may be gone, start again */
 663                        spin_lock(&wb->list_lock);
 664                        continue;
 665                }
 666                inode->i_state |= I_SYNC;
 667                spin_unlock(&inode->i_lock);
 668
 669                write_chunk = writeback_chunk_size(wb->bdi, work);
 670                wbc.nr_to_write = write_chunk;
 671                wbc.pages_skipped = 0;
 672
 673                /*
 674                 * We use I_SYNC to pin the inode in memory. While it is set
 675                 * evict_inode() will wait so the inode cannot be freed.
 676                 */
 677                __writeback_single_inode(inode, wb, &wbc);
 678
 679                work->nr_pages -= write_chunk - wbc.nr_to_write;
 680                wrote += write_chunk - wbc.nr_to_write;
 681                spin_lock(&wb->list_lock);
 682                spin_lock(&inode->i_lock);
 683                if (!(inode->i_state & I_DIRTY))
 684                        wrote++;
 685                requeue_inode(inode, wb, &wbc);
 686                inode_sync_complete(inode);
 687                spin_unlock(&inode->i_lock);
 688                cond_resched_lock(&wb->list_lock);
 689                /*
 690                 * bail out to wb_writeback() often enough to check
 691                 * background threshold and other termination conditions.
 692                 */
 693                if (wrote) {
 694                        if (time_is_before_jiffies(start_time + HZ / 10UL))
 695                                break;
 696                        if (work->nr_pages <= 0)
 697                                break;
 698                }
 699        }
 700        return wrote;
 701}
 702
 703static long __writeback_inodes_wb(struct bdi_writeback *wb,
 704                                  struct wb_writeback_work *work)
 705{
 706        unsigned long start_time = jiffies;
 707        long wrote = 0;
 708
 709        while (!list_empty(&wb->b_io)) {
 710                struct inode *inode = wb_inode(wb->b_io.prev);
 711                struct super_block *sb = inode->i_sb;
 712
 713                if (!grab_super_passive(sb)) {
 714                        /*
 715                         * grab_super_passive() may fail consistently due to
 716                         * s_umount being grabbed by someone else. Don't use
 717                         * requeue_io() to avoid busy retrying the inode/sb.
 718                         */
 719                        redirty_tail(inode, wb);
 720                        continue;
 721                }
 722                wrote += writeback_sb_inodes(sb, wb, work);
 723                drop_super(sb);
 724
 725                /* refer to the same tests at the end of writeback_sb_inodes */
 726                if (wrote) {
 727                        if (time_is_before_jiffies(start_time + HZ / 10UL))
 728                                break;
 729                        if (work->nr_pages <= 0)
 730                                break;
 731                }
 732        }
 733        /* Leave any unwritten inodes on b_io */
 734        return wrote;
 735}
 736
 737long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
 738                                enum wb_reason reason)
 739{
 740        struct wb_writeback_work work = {
 741                .nr_pages       = nr_pages,
 742                .sync_mode      = WB_SYNC_NONE,
 743                .range_cyclic   = 1,
 744                .reason         = reason,
 745        };
 746
 747        spin_lock(&wb->list_lock);
 748        if (list_empty(&wb->b_io))
 749                queue_io(wb, &work);
 750        __writeback_inodes_wb(wb, &work);
 751        spin_unlock(&wb->list_lock);
 752
 753        return nr_pages - work.nr_pages;
 754}
 755
 756static bool over_bground_thresh(struct backing_dev_info *bdi)
 757{
 758        unsigned long background_thresh, dirty_thresh;
 759
 760        global_dirty_limits(&background_thresh, &dirty_thresh);
 761
 762        if (global_page_state(NR_FILE_DIRTY) +
 763            global_page_state(NR_UNSTABLE_NFS) > background_thresh)
 764                return true;
 765
 766        if (bdi_stat(bdi, BDI_RECLAIMABLE) >
 767                                bdi_dirty_limit(bdi, background_thresh))
 768                return true;
 769
 770        return false;
 771}
 772
 773/*
 774 * Called under wb->list_lock. If there are multiple wb per bdi,
 775 * only the flusher working on the first wb should do it.
 776 */
 777static void wb_update_bandwidth(struct bdi_writeback *wb,
 778                                unsigned long start_time)
 779{
 780        __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
 781}
 782
 783/*
 784 * Explicit flushing or periodic writeback of "old" data.
 785 *
 786 * Define "old": the first time one of an inode's pages is dirtied, we mark the
 787 * dirtying-time in the inode's address_space.  So this periodic writeback code
 788 * just walks the superblock inode list, writing back any inodes which are
 789 * older than a specific point in time.
 790 *
 791 * Try to run once per dirty_writeback_interval.  But if a writeback event
 792 * takes longer than a dirty_writeback_interval interval, then leave a
 793 * one-second gap.
 794 *
 795 * older_than_this takes precedence over nr_to_write.  So we'll only write back
 796 * all dirty pages if they are all attached to "old" mappings.
 797 */
 798static long wb_writeback(struct bdi_writeback *wb,
 799                         struct wb_writeback_work *work)
 800{
 801        unsigned long wb_start = jiffies;
 802        long nr_pages = work->nr_pages;
 803        unsigned long oldest_jif;
 804        struct inode *inode;
 805        long progress;
 806
 807        oldest_jif = jiffies;
 808        work->older_than_this = &oldest_jif;
 809
 810        spin_lock(&wb->list_lock);
 811        for (;;) {
 812                /*
 813                 * Stop writeback when nr_pages has been consumed
 814                 */
 815                if (work->nr_pages <= 0)
 816                        break;
 817
 818                /*
 819                 * Background writeout and kupdate-style writeback may
 820                 * run forever. Stop them if there is other work to do
 821                 * so that e.g. sync can proceed. They'll be restarted
 822                 * after the other works are all done.
 823                 */
 824                if ((work->for_background || work->for_kupdate) &&
 825                    !list_empty(&wb->bdi->work_list))
 826                        break;
 827
 828                /*
 829                 * For background writeout, stop when we are below the
 830                 * background dirty threshold
 831                 */
 832                if (work->for_background && !over_bground_thresh(wb->bdi))
 833                        break;
 834
 835                /*
 836                 * Kupdate and background works are special and we want to
 837                 * include all inodes that need writing. Livelock avoidance is
 838                 * handled by these works yielding to any other work so we are
 839                 * safe.
 840                 */
 841                if (work->for_kupdate) {
 842                        oldest_jif = jiffies -
 843                                msecs_to_jiffies(dirty_expire_interval * 10);
 844                } else if (work->for_background)
 845                        oldest_jif = jiffies;
 846
 847                trace_writeback_start(wb->bdi, work);
 848                if (list_empty(&wb->b_io))
 849                        queue_io(wb, work);
 850                if (work->sb)
 851                        progress = writeback_sb_inodes(work->sb, wb, work);
 852                else
 853                        progress = __writeback_inodes_wb(wb, work);
 854                trace_writeback_written(wb->bdi, work);
 855
 856                wb_update_bandwidth(wb, wb_start);
 857
 858                /*
 859                 * Did we write something? Try for more
 860                 *
 861                 * Dirty inodes are moved to b_io for writeback in batches.
 862                 * The completion of the current batch does not necessarily
 863                 * mean the overall work is done. So we keep looping as long
 864                 * as made some progress on cleaning pages or inodes.
 865                 */
 866                if (progress)
 867                        continue;
 868                /*
 869                 * No more inodes for IO, bail
 870                 */
 871                if (list_empty(&wb->b_more_io))
 872                        break;
 873                /*
 874                 * Nothing written. Wait for some inode to
 875                 * become available for writeback. Otherwise
 876                 * we'll just busyloop.
 877                 */
 878                if (!list_empty(&wb->b_more_io))  {
 879                        trace_writeback_wait(wb->bdi, work);
 880                        inode = wb_inode(wb->b_more_io.prev);
 881                        spin_lock(&inode->i_lock);
 882                        spin_unlock(&wb->list_lock);
 883                        /* This function drops i_lock... */
 884                        inode_sleep_on_writeback(inode);
 885                        spin_lock(&wb->list_lock);
 886                }
 887        }
 888        spin_unlock(&wb->list_lock);
 889
 890        return nr_pages - work->nr_pages;
 891}
 892
 893/*
 894 * Return the next wb_writeback_work struct that hasn't been processed yet.
 895 */
 896static struct wb_writeback_work *
 897get_next_work_item(struct backing_dev_info *bdi)
 898{
 899        struct wb_writeback_work *work = NULL;
 900
 901        spin_lock_bh(&bdi->wb_lock);
 902        if (!list_empty(&bdi->work_list)) {
 903                work = list_entry(bdi->work_list.next,
 904                                  struct wb_writeback_work, list);
 905                list_del_init(&work->list);
 906        }
 907        spin_unlock_bh(&bdi->wb_lock);
 908        return work;
 909}
 910
 911/*
 912 * Add in the number of potentially dirty inodes, because each inode
 913 * write can dirty pagecache in the underlying blockdev.
 914 */
 915static unsigned long get_nr_dirty_pages(void)
 916{
 917        return global_page_state(NR_FILE_DIRTY) +
 918                global_page_state(NR_UNSTABLE_NFS) +
 919                get_nr_dirty_inodes();
 920}
 921
 922static long wb_check_background_flush(struct bdi_writeback *wb)
 923{
 924        if (over_bground_thresh(wb->bdi)) {
 925
 926                struct wb_writeback_work work = {
 927                        .nr_pages       = LONG_MAX,
 928                        .sync_mode      = WB_SYNC_NONE,
 929                        .for_background = 1,
 930                        .range_cyclic   = 1,
 931                        .reason         = WB_REASON_BACKGROUND,
 932                };
 933
 934                return wb_writeback(wb, &work);
 935        }
 936
 937        return 0;
 938}
 939
 940static long wb_check_old_data_flush(struct bdi_writeback *wb)
 941{
 942        unsigned long expired;
 943        long nr_pages;
 944
 945        /*
 946         * When set to zero, disable periodic writeback
 947         */
 948        if (!dirty_writeback_interval)
 949                return 0;
 950
 951        expired = wb->last_old_flush +
 952                        msecs_to_jiffies(dirty_writeback_interval * 10);
 953        if (time_before(jiffies, expired))
 954                return 0;
 955
 956        wb->last_old_flush = jiffies;
 957        nr_pages = get_nr_dirty_pages();
 958
 959        if (nr_pages) {
 960                struct wb_writeback_work work = {
 961                        .nr_pages       = nr_pages,
 962                        .sync_mode      = WB_SYNC_NONE,
 963                        .for_kupdate    = 1,
 964                        .range_cyclic   = 1,
 965                        .reason         = WB_REASON_PERIODIC,
 966                };
 967
 968                return wb_writeback(wb, &work);
 969        }
 970
 971        return 0;
 972}
 973
 974/*
 975 * Retrieve work items and do the writeback they describe
 976 */
 977long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
 978{
 979        struct backing_dev_info *bdi = wb->bdi;
 980        struct wb_writeback_work *work;
 981        long wrote = 0;
 982
 983        set_bit(BDI_writeback_running, &wb->bdi->state);
 984        while ((work = get_next_work_item(bdi)) != NULL) {
 985                /*
 986                 * Override sync mode, in case we must wait for completion
 987                 * because this thread is exiting now.
 988                 */
 989                if (force_wait)
 990                        work->sync_mode = WB_SYNC_ALL;
 991
 992                trace_writeback_exec(bdi, work);
 993
 994                wrote += wb_writeback(wb, work);
 995
 996                /*
 997                 * Notify the caller of completion if this is a synchronous
 998                 * work item, otherwise just free it.
 999                 */
1000                if (work->done)
1001                        complete(work->done);
1002                else
1003                        kfree(work);
1004        }
1005
1006        /*
1007         * Check for periodic writeback, kupdated() style
1008         */
1009        wrote += wb_check_old_data_flush(wb);
1010        wrote += wb_check_background_flush(wb);
1011        clear_bit(BDI_writeback_running, &wb->bdi->state);
1012
1013        return wrote;
1014}
1015
1016/*
1017 * Handle writeback of dirty data for the device backed by this bdi. Also
1018 * wakes up periodically and does kupdated style flushing.
1019 */
1020int bdi_writeback_thread(void *data)
1021{
1022        struct bdi_writeback *wb = data;
1023        struct backing_dev_info *bdi = wb->bdi;
1024        long pages_written;
1025
1026        current->flags |= PF_SWAPWRITE;
1027        set_freezable();
1028        wb->last_active = jiffies;
1029
1030        /*
1031         * Our parent may run at a different priority, just set us to normal
1032         */
1033        set_user_nice(current, 0);
1034
1035        trace_writeback_thread_start(bdi);
1036
1037        while (!kthread_freezable_should_stop(NULL)) {
1038                /*
1039                 * Remove own delayed wake-up timer, since we are already awake
1040                 * and we'll take care of the preriodic write-back.
1041                 */
1042                del_timer(&wb->wakeup_timer);
1043
1044                pages_written = wb_do_writeback(wb, 0);
1045
1046                trace_writeback_pages_written(pages_written);
1047
1048                if (pages_written)
1049                        wb->last_active = jiffies;
1050
1051                set_current_state(TASK_INTERRUPTIBLE);
1052                if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
1053                        __set_current_state(TASK_RUNNING);
1054                        continue;
1055                }
1056
1057                if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1058                        schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
1059                else {
1060                        /*
1061                         * We have nothing to do, so can go sleep without any
1062                         * timeout and save power. When a work is queued or
1063                         * something is made dirty - we will be woken up.
1064                         */
1065                        schedule();
1066                }
1067        }
1068
1069        /* Flush any work that raced with us exiting */
1070        if (!list_empty(&bdi->work_list))
1071                wb_do_writeback(wb, 1);
1072
1073        trace_writeback_thread_stop(bdi);
1074        return 0;
1075}
1076
1077
1078/*
1079 * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
1080 * the whole world.
1081 */
1082void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1083{
1084        struct backing_dev_info *bdi;
1085
1086        if (!nr_pages) {
1087                nr_pages = global_page_state(NR_FILE_DIRTY) +
1088                                global_page_state(NR_UNSTABLE_NFS);
1089        }
1090
1091        rcu_read_lock();
1092        list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1093                if (!bdi_has_dirty_io(bdi))
1094                        continue;
1095                __bdi_start_writeback(bdi, nr_pages, false, reason);
1096        }
1097        rcu_read_unlock();
1098}
1099
1100static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1101{
1102        if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1103                struct dentry *dentry;
1104                const char *name = "?";
1105
1106                dentry = d_find_alias(inode);
1107                if (dentry) {
1108                        spin_lock(&dentry->d_lock);
1109                        name = (const char *) dentry->d_name.name;
1110                }
1111                printk(KERN_DEBUG
1112                       "%s(%d): dirtied inode %lu (%s) on %s\n",
1113                       current->comm, task_pid_nr(current), inode->i_ino,
1114                       name, inode->i_sb->s_id);
1115                if (dentry) {
1116                        spin_unlock(&dentry->d_lock);
1117                        dput(dentry);
1118                }
1119        }
1120}
1121
1122/**
1123 *      __mark_inode_dirty -    internal function
1124 *      @inode: inode to mark
1125 *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1126 *      Mark an inode as dirty. Callers should use mark_inode_dirty or
1127 *      mark_inode_dirty_sync.
1128 *
1129 * Put the inode on the super block's dirty list.
1130 *
1131 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1132 * dirty list only if it is hashed or if it refers to a blockdev.
1133 * If it was not hashed, it will never be added to the dirty list
1134 * even if it is later hashed, as it will have been marked dirty already.
1135 *
1136 * In short, make sure you hash any inodes _before_ you start marking
1137 * them dirty.
1138 *
1139 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1140 * the block-special inode (/dev/hda1) itself.  And the ->dirtied_when field of
1141 * the kernel-internal blockdev inode represents the dirtying time of the
1142 * blockdev's pages.  This is why for I_DIRTY_PAGES we always use
1143 * page->mapping->host, so the page-dirtying time is recorded in the internal
1144 * blockdev inode.
1145 */
1146void __mark_inode_dirty(struct inode *inode, int flags)
1147{
1148        struct super_block *sb = inode->i_sb;
1149        struct backing_dev_info *bdi = NULL;
1150
1151        /*
1152         * Don't do this for I_DIRTY_PAGES - that doesn't actually
1153         * dirty the inode itself
1154         */
1155        if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1156                if (sb->s_op->dirty_inode)
1157                        sb->s_op->dirty_inode(inode, flags);
1158        }
1159
1160        /*
1161         * make sure that changes are seen by all cpus before we test i_state
1162         * -- mikulas
1163         */
1164        smp_mb();
1165
1166        /* avoid the locking if we can */
1167        if ((inode->i_state & flags) == flags)
1168                return;
1169
1170        if (unlikely(block_dump))
1171                block_dump___mark_inode_dirty(inode);
1172
1173        spin_lock(&inode->i_lock);
1174        if ((inode->i_state & flags) != flags) {
1175                const int was_dirty = inode->i_state & I_DIRTY;
1176
1177                inode->i_state |= flags;
1178
1179                /*
1180                 * If the inode is being synced, just update its dirty state.
1181                 * The unlocker will place the inode on the appropriate
1182                 * superblock list, based upon its state.
1183                 */
1184                if (inode->i_state & I_SYNC)
1185                        goto out_unlock_inode;
1186
1187                /*
1188                 * Only add valid (hashed) inodes to the superblock's
1189                 * dirty list.  Add blockdev inodes as well.
1190                 */
1191                if (!S_ISBLK(inode->i_mode)) {
1192                        if (inode_unhashed(inode))
1193                                goto out_unlock_inode;
1194                }
1195                if (inode->i_state & I_FREEING)
1196                        goto out_unlock_inode;
1197
1198                /*
1199                 * If the inode was already on b_dirty/b_io/b_more_io, don't
1200                 * reposition it (that would break b_dirty time-ordering).
1201                 */
1202                if (!was_dirty) {
1203                        bool wakeup_bdi = false;
1204                        bdi = inode_to_bdi(inode);
1205
1206                        if (bdi_cap_writeback_dirty(bdi)) {
1207                                WARN(!test_bit(BDI_registered, &bdi->state),
1208                                     "bdi-%s not registered\n", bdi->name);
1209
1210                                /*
1211                                 * If this is the first dirty inode for this
1212                                 * bdi, we have to wake-up the corresponding
1213                                 * bdi thread to make sure background
1214                                 * write-back happens later.
1215                                 */
1216                                if (!wb_has_dirty_io(&bdi->wb))
1217                                        wakeup_bdi = true;
1218                        }
1219
1220                        spin_unlock(&inode->i_lock);
1221                        spin_lock(&bdi->wb.list_lock);
1222                        inode->dirtied_when = jiffies;
1223                        list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1224                        spin_unlock(&bdi->wb.list_lock);
1225
1226                        if (wakeup_bdi)
1227                                bdi_wakeup_thread_delayed(bdi);
1228                        return;
1229                }
1230        }
1231out_unlock_inode:
1232        spin_unlock(&inode->i_lock);
1233
1234}
1235EXPORT_SYMBOL(__mark_inode_dirty);
1236
1237static void wait_sb_inodes(struct super_block *sb)
1238{
1239        struct inode *inode, *old_inode = NULL;
1240
1241        /*
1242         * We need to be protected against the filesystem going from
1243         * r/o to r/w or vice versa.
1244         */
1245        WARN_ON(!rwsem_is_locked(&sb->s_umount));
1246
1247        spin_lock(&inode_sb_list_lock);
1248
1249        /*
1250         * Data integrity sync. Must wait for all pages under writeback,
1251         * because there may have been pages dirtied before our sync
1252         * call, but which had writeout started before we write it out.
1253         * In which case, the inode may not be on the dirty list, but
1254         * we still have to wait for that writeout.
1255         */
1256        list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1257                struct address_space *mapping = inode->i_mapping;
1258
1259                spin_lock(&inode->i_lock);
1260                if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1261                    (mapping->nrpages == 0)) {
1262                        spin_unlock(&inode->i_lock);
1263                        continue;
1264                }
1265                __iget(inode);
1266                spin_unlock(&inode->i_lock);
1267                spin_unlock(&inode_sb_list_lock);
1268
1269                /*
1270                 * We hold a reference to 'inode' so it couldn't have been
1271                 * removed from s_inodes list while we dropped the
1272                 * inode_sb_list_lock.  We cannot iput the inode now as we can
1273                 * be holding the last reference and we cannot iput it under
1274                 * inode_sb_list_lock. So we keep the reference and iput it
1275                 * later.
1276                 */
1277                iput(old_inode);
1278                old_inode = inode;
1279
1280                filemap_fdatawait(mapping);
1281
1282                cond_resched();
1283
1284                spin_lock(&inode_sb_list_lock);
1285        }
1286        spin_unlock(&inode_sb_list_lock);
1287        iput(old_inode);
1288}
1289
1290/**
1291 * writeback_inodes_sb_nr -     writeback dirty inodes from given super_block
1292 * @sb: the superblock
1293 * @nr: the number of pages to write
1294 * @reason: reason why some writeback work initiated
1295 *
1296 * Start writeback on some inodes on this super_block. No guarantees are made
1297 * on how many (if any) will be written, and this function does not wait
1298 * for IO completion of submitted IO.
1299 */
1300void writeback_inodes_sb_nr(struct super_block *sb,
1301                            unsigned long nr,
1302                            enum wb_reason reason)
1303{
1304        DECLARE_COMPLETION_ONSTACK(done);
1305        struct wb_writeback_work work = {
1306                .sb                     = sb,
1307                .sync_mode              = WB_SYNC_NONE,
1308                .tagged_writepages      = 1,
1309                .done                   = &done,
1310                .nr_pages               = nr,
1311                .reason                 = reason,
1312        };
1313
1314        if (sb->s_bdi == &noop_backing_dev_info)
1315                return;
1316        WARN_ON(!rwsem_is_locked(&sb->s_umount));
1317        bdi_queue_work(sb->s_bdi, &work);
1318        wait_for_completion(&done);
1319}
1320EXPORT_SYMBOL(writeback_inodes_sb_nr);
1321
1322/**
1323 * writeback_inodes_sb  -       writeback dirty inodes from given super_block
1324 * @sb: the superblock
1325 * @reason: reason why some writeback work was initiated
1326 *
1327 * Start writeback on some inodes on this super_block. No guarantees are made
1328 * on how many (if any) will be written, and this function does not wait
1329 * for IO completion of submitted IO.
1330 */
1331void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1332{
1333        return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1334}
1335EXPORT_SYMBOL(writeback_inodes_sb);
1336
1337/**
1338 * writeback_inodes_sb_if_idle  -       start writeback if none underway
1339 * @sb: the superblock
1340 * @reason: reason why some writeback work was initiated
1341 *
1342 * Invoke writeback_inodes_sb if no writeback is currently underway.
1343 * Returns 1 if writeback was started, 0 if not.
1344 */
1345int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
1346{
1347        if (!writeback_in_progress(sb->s_bdi)) {
1348                down_read(&sb->s_umount);
1349                writeback_inodes_sb(sb, reason);
1350                up_read(&sb->s_umount);
1351                return 1;
1352        } else
1353                return 0;
1354}
1355EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1356
1357/**
1358 * writeback_inodes_sb_nr_if_idle       -       start writeback if none underway
1359 * @sb: the superblock
1360 * @nr: the number of pages to write
1361 * @reason: reason why some writeback work was initiated
1362 *
1363 * Invoke writeback_inodes_sb if no writeback is currently underway.
1364 * Returns 1 if writeback was started, 0 if not.
1365 */
1366int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1367                                   unsigned long nr,
1368                                   enum wb_reason reason)
1369{
1370        if (!writeback_in_progress(sb->s_bdi)) {
1371                down_read(&sb->s_umount);
1372                writeback_inodes_sb_nr(sb, nr, reason);
1373                up_read(&sb->s_umount);
1374                return 1;
1375        } else
1376                return 0;
1377}
1378EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1379
1380/**
1381 * sync_inodes_sb       -       sync sb inode pages
1382 * @sb: the superblock
1383 *
1384 * This function writes and waits on any dirty inode belonging to this
1385 * super_block.
1386 */
1387void sync_inodes_sb(struct super_block *sb)
1388{
1389        DECLARE_COMPLETION_ONSTACK(done);
1390        struct wb_writeback_work work = {
1391                .sb             = sb,
1392                .sync_mode      = WB_SYNC_ALL,
1393                .nr_pages       = LONG_MAX,
1394                .range_cyclic   = 0,
1395                .done           = &done,
1396                .reason         = WB_REASON_SYNC,
1397        };
1398
1399        /* Nothing to do? */
1400        if (sb->s_bdi == &noop_backing_dev_info)
1401                return;
1402        WARN_ON(!rwsem_is_locked(&sb->s_umount));
1403
1404        bdi_queue_work(sb->s_bdi, &work);
1405        wait_for_completion(&done);
1406
1407        wait_sb_inodes(sb);
1408}
1409EXPORT_SYMBOL(sync_inodes_sb);
1410
1411/**
1412 * write_inode_now      -       write an inode to disk
1413 * @inode: inode to write to disk
1414 * @sync: whether the write should be synchronous or not
1415 *
1416 * This function commits an inode to disk immediately if it is dirty. This is
1417 * primarily needed by knfsd.
1418 *
1419 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1420 */
1421int write_inode_now(struct inode *inode, int sync)
1422{
1423        struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1424        struct writeback_control wbc = {
1425                .nr_to_write = LONG_MAX,
1426                .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1427                .range_start = 0,
1428                .range_end = LLONG_MAX,
1429        };
1430
1431        if (!mapping_cap_writeback_dirty(inode->i_mapping))
1432                wbc.nr_to_write = 0;
1433
1434        might_sleep();
1435        return writeback_single_inode(inode, wb, &wbc);
1436}
1437EXPORT_SYMBOL(write_inode_now);
1438
1439/**
1440 * sync_inode - write an inode and its pages to disk.
1441 * @inode: the inode to sync
1442 * @wbc: controls the writeback mode
1443 *
1444 * sync_inode() will write an inode and its pages to disk.  It will also
1445 * correctly update the inode on its superblock's dirty inode lists and will
1446 * update inode->i_state.
1447 *
1448 * The caller must have a ref on the inode.
1449 */
1450int sync_inode(struct inode *inode, struct writeback_control *wbc)
1451{
1452        return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1453}
1454EXPORT_SYMBOL(sync_inode);
1455
1456/**
1457 * sync_inode_metadata - write an inode to disk
1458 * @inode: the inode to sync
1459 * @wait: wait for I/O to complete.
1460 *
1461 * Write an inode to disk and adjust its dirty state after completion.
1462 *
1463 * Note: only writes the actual inode, no associated data or other metadata.
1464 */
1465int sync_inode_metadata(struct inode *inode, int wait)
1466{
1467        struct writeback_control wbc = {
1468                .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1469                .nr_to_write = 0, /* metadata-only */
1470        };
1471
1472        return sync_inode(inode, &wbc);
1473}
1474EXPORT_SYMBOL(sync_inode_metadata);
1475
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