backing-dev.c

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    1 
    2 #include <linux/wait.h>
    3 #include <linux/backing-dev.h>
    4 #include <linux/kthread.h>
    5 #include <linux/freezer.h>
    6 #include <linux/fs.h>
    7 #include <linux/pagemap.h>
    8 #include <linux/mm.h>
    9 #include <linux/sched.h>
   10 #include <linux/module.h>
   11 #include <linux/writeback.h>
   12 #include <linux/device.h>
   13 #include <trace/events/writeback.h>
   14 
   15 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
   16 
   17 struct backing_dev_info default_backing_dev_info = {
   18         .name           = "default",
   19         .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
   20         .state          = 0,
   21         .capabilities   = BDI_CAP_MAP_COPY,
   22 };
   23 EXPORT_SYMBOL_GPL(default_backing_dev_info);
   24 
   25 struct backing_dev_info noop_backing_dev_info = {
   26         .name           = "noop",
   27         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
   28 };
   29 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
   30 
   31 static struct class *bdi_class;
   32 
   33 /*
   34  * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
   35  * reader side protection for bdi_pending_list. bdi_list has RCU reader side
   36  * locking.
   37  */
   38 DEFINE_SPINLOCK(bdi_lock);
   39 LIST_HEAD(bdi_list);
   40 LIST_HEAD(bdi_pending_list);
   41 
   42 void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
   43 {
   44         if (wb1 < wb2) {
   45                 spin_lock(&wb1->list_lock);
   46                 spin_lock_nested(&wb2->list_lock, 1);
   47         } else {
   48                 spin_lock(&wb2->list_lock);
   49                 spin_lock_nested(&wb1->list_lock, 1);
   50         }
   51 }
   52 
   53 #ifdef CONFIG_DEBUG_FS
   54 #include <linux/debugfs.h>
   55 #include <linux/seq_file.h>
   56 
   57 static struct dentry *bdi_debug_root;
   58 
   59 static void bdi_debug_init(void)
   60 {
   61         bdi_debug_root = debugfs_create_dir("bdi", NULL);
   62 }
   63 
   64 static int bdi_debug_stats_show(struct seq_file *m, void *v)
   65 {
   66         struct backing_dev_info *bdi = m->private;
   67         struct bdi_writeback *wb = &bdi->wb;
   68         unsigned long background_thresh;
   69         unsigned long dirty_thresh;
   70         unsigned long bdi_thresh;
   71         unsigned long nr_dirty, nr_io, nr_more_io;
   72         struct inode *inode;
   73 
   74         nr_dirty = nr_io = nr_more_io = 0;
   75         spin_lock(&wb->list_lock);
   76         list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
   77                 nr_dirty++;
   78         list_for_each_entry(inode, &wb->b_io, i_wb_list)
   79                 nr_io++;
   80         list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
   81                 nr_more_io++;
   82         spin_unlock(&wb->list_lock);
   83 
   84         global_dirty_limits(&background_thresh, &dirty_thresh);
   85         bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
   86 
   87 #define K(x) ((x) << (PAGE_SHIFT - 10))
   88         seq_printf(m,
   89                    "BdiWriteback:       %10lu kB\n"
   90                    "BdiReclaimable:     %10lu kB\n"
   91                    "BdiDirtyThresh:     %10lu kB\n"
   92                    "DirtyThresh:        %10lu kB\n"
   93                    "BackgroundThresh:   %10lu kB\n"
   94                    "BdiDirtied:         %10lu kB\n"
   95                    "BdiWritten:         %10lu kB\n"
   96                    "BdiWriteBandwidth:  %10lu kBps\n"
   97                    "b_dirty:            %10lu\n"
   98                    "b_io:               %10lu\n"
   99                    "b_more_io:          %10lu\n"
  100                    "bdi_list:           %10u\n"
  101                    "state:              %10lx\n",
  102                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
  103                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
  104                    K(bdi_thresh),
  105                    K(dirty_thresh),
  106                    K(background_thresh),
  107                    (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
  108                    (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
  109                    (unsigned long) K(bdi->write_bandwidth),
  110                    nr_dirty,
  111                    nr_io,
  112                    nr_more_io,
  113                    !list_empty(&bdi->bdi_list), bdi->state);
  114 #undef K
  115 
  116         return 0;
  117 }
  118 
  119 static int bdi_debug_stats_open(struct inode *inode, struct file *file)
  120 {
  121         return single_open(file, bdi_debug_stats_show, inode->i_private);
  122 }
  123 
  124 static const struct file_operations bdi_debug_stats_fops = {
  125         .open           = bdi_debug_stats_open,
  126         .read           = seq_read,
  127         .llseek         = seq_lseek,
  128         .release        = single_release,
  129 };
  130 
  131 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
  132 {
  133         bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
  134         bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
  135                                                bdi, &bdi_debug_stats_fops);
  136 }
  137 
  138 static void bdi_debug_unregister(struct backing_dev_info *bdi)
  139 {
  140         debugfs_remove(bdi->debug_stats);
  141         debugfs_remove(bdi->debug_dir);
  142 }
  143 #else
  144 static inline void bdi_debug_init(void)
  145 {
  146 }
  147 static inline void bdi_debug_register(struct backing_dev_info *bdi,
  148                                       const char *name)
  149 {
  150 }
  151 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
  152 {
  153 }
  154 #endif
  155 
  156 static ssize_t read_ahead_kb_store(struct device *dev,
  157                                   struct device_attribute *attr,
  158                                   const char *buf, size_t count)
  159 {
  160         struct backing_dev_info *bdi = dev_get_drvdata(dev);
  161         unsigned long read_ahead_kb;
  162         ssize_t ret;
  163 
  164         ret = kstrtoul(buf, 10, &read_ahead_kb);
  165         if (ret < 0)
  166                 return ret;
  167 
  168         bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
  169 
  170         return count;
  171 }
  172 
  173 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
  174 
  175 #define BDI_SHOW(name, expr)                                            \
  176 static ssize_t name##_show(struct device *dev,                          \
  177                            struct device_attribute *attr, char *page)   \
  178 {                                                                       \
  179         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
  180                                                                         \
  181         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
  182 }
  183 
  184 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
  185 
  186 static ssize_t min_ratio_store(struct device *dev,
  187                 struct device_attribute *attr, const char *buf, size_t count)
  188 {
  189         struct backing_dev_info *bdi = dev_get_drvdata(dev);
  190         unsigned int ratio;
  191         ssize_t ret;
  192 
  193         ret = kstrtouint(buf, 10, &ratio);
  194         if (ret < 0)
  195                 return ret;
  196 
  197         ret = bdi_set_min_ratio(bdi, ratio);
  198         if (!ret)
  199                 ret = count;
  200 
  201         return ret;
  202 }
  203 BDI_SHOW(min_ratio, bdi->min_ratio)
  204 
  205 static ssize_t max_ratio_store(struct device *dev,
  206                 struct device_attribute *attr, const char *buf, size_t count)
  207 {
  208         struct backing_dev_info *bdi = dev_get_drvdata(dev);
  209         unsigned int ratio;
  210         ssize_t ret;
  211 
  212         ret = kstrtouint(buf, 10, &ratio);
  213         if (ret < 0)
  214                 return ret;
  215 
  216         ret = bdi_set_max_ratio(bdi, ratio);
  217         if (!ret)
  218                 ret = count;
  219 
  220         return ret;
  221 }
  222 BDI_SHOW(max_ratio, bdi->max_ratio)
  223 
  224 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
  225 
  226 static struct device_attribute bdi_dev_attrs[] = {
  227         __ATTR_RW(read_ahead_kb),
  228         __ATTR_RW(min_ratio),
  229         __ATTR_RW(max_ratio),
  230         __ATTR_NULL,
  231 };
  232 
  233 static __init int bdi_class_init(void)
  234 {
  235         bdi_class = class_create(THIS_MODULE, "bdi");
  236         if (IS_ERR(bdi_class))
  237                 return PTR_ERR(bdi_class);
  238 
  239         bdi_class->dev_attrs = bdi_dev_attrs;
  240         bdi_debug_init();
  241         return 0;
  242 }
  243 postcore_initcall(bdi_class_init);
  244 
  245 static int __init default_bdi_init(void)
  246 {
  247         int err;
  248 
  249         err = bdi_init(&default_backing_dev_info);
  250         if (!err)
  251                 bdi_register(&default_backing_dev_info, NULL, "default");
  252         err = bdi_init(&noop_backing_dev_info);
  253 
  254         return err;
  255 }
  256 subsys_initcall(default_bdi_init);
  257 
  258 int bdi_has_dirty_io(struct backing_dev_info *bdi)
  259 {
  260         return wb_has_dirty_io(&bdi->wb);
  261 }
  262 
  263 static void wakeup_timer_fn(unsigned long data)
  264 {
  265         struct backing_dev_info *bdi = (struct backing_dev_info *)data;
  266 
  267         spin_lock_bh(&bdi->wb_lock);
  268         if (bdi->wb.task) {
  269                 trace_writeback_wake_thread(bdi);
  270                 wake_up_process(bdi->wb.task);
  271         } else if (bdi->dev) {
  272                 /*
  273                  * When bdi tasks are inactive for long time, they are killed.
  274                  * In this case we have to wake-up the forker thread which
  275                  * should create and run the bdi thread.
  276                  */
  277                 trace_writeback_wake_forker_thread(bdi);
  278                 wake_up_process(default_backing_dev_info.wb.task);
  279         }
  280         spin_unlock_bh(&bdi->wb_lock);
  281 }
  282 
  283 /*
  284  * This function is used when the first inode for this bdi is marked dirty. It
  285  * wakes-up the corresponding bdi thread which should then take care of the
  286  * periodic background write-out of dirty inodes. Since the write-out would
  287  * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
  288  * set up a timer which wakes the bdi thread up later.
  289  *
  290  * Note, we wouldn't bother setting up the timer, but this function is on the
  291  * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
  292  * by delaying the wake-up.
  293  */
  294 void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
  295 {
  296         unsigned long timeout;
  297 
  298         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
  299         mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
  300 }
  301 
  302 /*
  303  * Calculate the longest interval (jiffies) bdi threads are allowed to be
  304  * inactive.
  305  */
  306 static unsigned long bdi_longest_inactive(void)
  307 {
  308         unsigned long interval;
  309 
  310         interval = msecs_to_jiffies(dirty_writeback_interval * 10);
  311         return max(5UL * 60 * HZ, interval);
  312 }
  313 
  314 /*
  315  * Clear pending bit and wakeup anybody waiting for flusher thread creation or
  316  * shutdown
  317  */
  318 static void bdi_clear_pending(struct backing_dev_info *bdi)
  319 {
  320         clear_bit(BDI_pending, &bdi->state);
  321         smp_mb__after_clear_bit();
  322         wake_up_bit(&bdi->state, BDI_pending);
  323 }
  324 
  325 static int bdi_forker_thread(void *ptr)
  326 {
  327         struct bdi_writeback *me = ptr;
  328 
  329         current->flags |= PF_SWAPWRITE;
  330         set_freezable();
  331 
  332         /*
  333          * Our parent may run at a different priority, just set us to normal
  334          */
  335         set_user_nice(current, 0);
  336 
  337         for (;;) {
  338                 struct task_struct *task = NULL;
  339                 struct backing_dev_info *bdi;
  340                 enum {
  341                         NO_ACTION,   /* Nothing to do */
  342                         FORK_THREAD, /* Fork bdi thread */
  343                         KILL_THREAD, /* Kill inactive bdi thread */
  344                 } action = NO_ACTION;
  345 
  346                 /*
  347                  * Temporary measure, we want to make sure we don't see
  348                  * dirty data on the default backing_dev_info
  349                  */
  350                 if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
  351                         del_timer(&me->wakeup_timer);
  352                         wb_do_writeback(me, 0);
  353                 }
  354 
  355                 spin_lock_bh(&bdi_lock);
  356                 /*
  357                  * In the following loop we are going to check whether we have
  358                  * some work to do without any synchronization with tasks
  359                  * waking us up to do work for them. Set the task state here
  360                  * so that we don't miss wakeups after verifying conditions.
  361                  */
  362                 set_current_state(TASK_INTERRUPTIBLE);
  363 
  364                 list_for_each_entry(bdi, &bdi_list, bdi_list) {
  365                         bool have_dirty_io;
  366 
  367                         if (!bdi_cap_writeback_dirty(bdi) ||
  368                              bdi_cap_flush_forker(bdi))
  369                                 continue;
  370 
  371                         WARN(!test_bit(BDI_registered, &bdi->state),
  372                              "bdi %p/%s is not registered!\n", bdi, bdi->name);
  373 
  374                         have_dirty_io = !list_empty(&bdi->work_list) ||
  375                                         wb_has_dirty_io(&bdi->wb);
  376 
  377                         /*
  378                          * If the bdi has work to do, but the thread does not
  379                          * exist - create it.
  380                          */
  381                         if (!bdi->wb.task && have_dirty_io) {
  382                                 /*
  383                                  * Set the pending bit - if someone will try to
  384                                  * unregister this bdi - it'll wait on this bit.
  385                                  */
  386                                 set_bit(BDI_pending, &bdi->state);
  387                                 action = FORK_THREAD;
  388                                 break;
  389                         }
  390 
  391                         spin_lock(&bdi->wb_lock);
  392 
  393                         /*
  394                          * If there is no work to do and the bdi thread was
  395                          * inactive long enough - kill it. The wb_lock is taken
  396                          * to make sure no-one adds more work to this bdi and
  397                          * wakes the bdi thread up.
  398                          */
  399                         if (bdi->wb.task && !have_dirty_io &&
  400                             time_after(jiffies, bdi->wb.last_active +
  401                                                 bdi_longest_inactive())) {
  402                                 task = bdi->wb.task;
  403                                 bdi->wb.task = NULL;
  404                                 spin_unlock(&bdi->wb_lock);
  405                                 set_bit(BDI_pending, &bdi->state);
  406                                 action = KILL_THREAD;
  407                                 break;
  408                         }
  409                         spin_unlock(&bdi->wb_lock);
  410                 }
  411                 spin_unlock_bh(&bdi_lock);
  412 
  413                 /* Keep working if default bdi still has things to do */
  414                 if (!list_empty(&me->bdi->work_list))
  415                         __set_current_state(TASK_RUNNING);
  416 
  417                 switch (action) {
  418                 case FORK_THREAD:
  419                         __set_current_state(TASK_RUNNING);
  420                         task = kthread_create(bdi_writeback_thread, &bdi->wb,
  421                                               "flush-%s", dev_name(bdi->dev));
  422                         if (IS_ERR(task)) {
  423                                 /*
  424                                  * If thread creation fails, force writeout of
  425                                  * the bdi from the thread. Hopefully 1024 is
  426                                  * large enough for efficient IO.
  427                                  */
  428                                 writeback_inodes_wb(&bdi->wb, 1024,
  429                                                     WB_REASON_FORKER_THREAD);
  430                         } else {
  431                                 /*
  432                                  * The spinlock makes sure we do not lose
  433                                  * wake-ups when racing with 'bdi_queue_work()'.
  434                                  * And as soon as the bdi thread is visible, we
  435                                  * can start it.
  436                                  */
  437                                 spin_lock_bh(&bdi->wb_lock);
  438                                 bdi->wb.task = task;
  439                                 spin_unlock_bh(&bdi->wb_lock);
  440                                 wake_up_process(task);
  441                         }
  442                         bdi_clear_pending(bdi);
  443                         break;
  444 
  445                 case KILL_THREAD:
  446                         __set_current_state(TASK_RUNNING);
  447                         kthread_stop(task);
  448                         bdi_clear_pending(bdi);
  449                         break;
  450 
  451                 case NO_ACTION:
  452                         if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
  453                                 /*
  454                                  * There are no dirty data. The only thing we
  455                                  * should now care about is checking for
  456                                  * inactive bdi threads and killing them. Thus,
  457                                  * let's sleep for longer time, save energy and
  458                                  * be friendly for battery-driven devices.
  459                                  */
  460                                 schedule_timeout(bdi_longest_inactive());
  461                         else
  462                                 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
  463                         try_to_freeze();
  464                         break;
  465                 }
  466         }
  467 
  468         return 0;
  469 }
  470 
  471 /*
  472  * Remove bdi from bdi_list, and ensure that it is no longer visible
  473  */
  474 static void bdi_remove_from_list(struct backing_dev_info *bdi)
  475 {
  476         spin_lock_bh(&bdi_lock);
  477         list_del_rcu(&bdi->bdi_list);
  478         spin_unlock_bh(&bdi_lock);
  479 
  480         synchronize_rcu_expedited();
  481 }
  482 
  483 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
  484                 const char *fmt, ...)
  485 {
  486         va_list args;
  487         struct device *dev;
  488 
  489         if (bdi->dev)   /* The driver needs to use separate queues per device */
  490                 return 0;
  491 
  492         va_start(args, fmt);
  493         dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
  494         va_end(args);
  495         if (IS_ERR(dev))
  496                 return PTR_ERR(dev);
  497 
  498         bdi->dev = dev;
  499 
  500         /*
  501          * Just start the forker thread for our default backing_dev_info,
  502          * and add other bdi's to the list. They will get a thread created
  503          * on-demand when they need it.
  504          */
  505         if (bdi_cap_flush_forker(bdi)) {
  506                 struct bdi_writeback *wb = &bdi->wb;
  507 
  508                 wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
  509                                                 dev_name(dev));
  510                 if (IS_ERR(wb->task))
  511                         return PTR_ERR(wb->task);
  512         }
  513 
  514         bdi_debug_register(bdi, dev_name(dev));
  515         set_bit(BDI_registered, &bdi->state);
  516 
  517         spin_lock_bh(&bdi_lock);
  518         list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
  519         spin_unlock_bh(&bdi_lock);
  520 
  521         trace_writeback_bdi_register(bdi);
  522         return 0;
  523 }
  524 EXPORT_SYMBOL(bdi_register);
  525 
  526 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
  527 {
  528         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
  529 }
  530 EXPORT_SYMBOL(bdi_register_dev);
  531 
  532 /*
  533  * Remove bdi from the global list and shutdown any threads we have running
  534  */
  535 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
  536 {
  537         struct task_struct *task;
  538 
  539         if (!bdi_cap_writeback_dirty(bdi))
  540                 return;
  541 
  542         /*
  543          * Make sure nobody finds us on the bdi_list anymore
  544          */
  545         bdi_remove_from_list(bdi);
  546 
  547         /*
  548          * If setup is pending, wait for that to complete first
  549          */
  550         wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
  551                         TASK_UNINTERRUPTIBLE);
  552 
  553         /*
  554          * Finally, kill the kernel thread. We don't need to be RCU
  555          * safe anymore, since the bdi is gone from visibility.
  556          */
  557         spin_lock_bh(&bdi->wb_lock);
  558         task = bdi->wb.task;
  559         bdi->wb.task = NULL;
  560         spin_unlock_bh(&bdi->wb_lock);
  561 
  562         if (task)
  563                 kthread_stop(task);
  564 }
  565 
  566 /*
  567  * This bdi is going away now, make sure that no super_blocks point to it
  568  */
  569 static void bdi_prune_sb(struct backing_dev_info *bdi)
  570 {
  571         struct super_block *sb;
  572 
  573         spin_lock(&sb_lock);
  574         list_for_each_entry(sb, &super_blocks, s_list) {
  575                 if (sb->s_bdi == bdi)
  576                         sb->s_bdi = &default_backing_dev_info;
  577         }
  578         spin_unlock(&sb_lock);
  579 }
  580 
  581 void bdi_unregister(struct backing_dev_info *bdi)
  582 {
  583         struct device *dev = bdi->dev;
  584 
  585         if (dev) {
  586                 bdi_set_min_ratio(bdi, 0);
  587                 trace_writeback_bdi_unregister(bdi);
  588                 bdi_prune_sb(bdi);
  589                 del_timer_sync(&bdi->wb.wakeup_timer);
  590 
  591                 if (!bdi_cap_flush_forker(bdi))
  592                         bdi_wb_shutdown(bdi);
  593                 bdi_debug_unregister(bdi);
  594 
  595                 spin_lock_bh(&bdi->wb_lock);
  596                 bdi->dev = NULL;
  597                 spin_unlock_bh(&bdi->wb_lock);
  598 
  599                 device_unregister(dev);
  600         }
  601 }
  602 EXPORT_SYMBOL(bdi_unregister);
  603 
  604 static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
  605 {
  606         memset(wb, 0, sizeof(*wb));
  607 
  608         wb->bdi = bdi;
  609         wb->last_old_flush = jiffies;
  610         INIT_LIST_HEAD(&wb->b_dirty);
  611         INIT_LIST_HEAD(&wb->b_io);
  612         INIT_LIST_HEAD(&wb->b_more_io);
  613         spin_lock_init(&wb->list_lock);
  614         setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
  615 }
  616 
  617 /*
  618  * Initial write bandwidth: 100 MB/s
  619  */
  620 #define INIT_BW         (100 << (20 - PAGE_SHIFT))
  621 
  622 int bdi_init(struct backing_dev_info *bdi)
  623 {
  624         int i, err;
  625 
  626         bdi->dev = NULL;
  627 
  628         bdi->min_ratio = 0;
  629         bdi->max_ratio = 100;
  630         bdi->max_prop_frac = FPROP_FRAC_BASE;
  631         spin_lock_init(&bdi->wb_lock);
  632         INIT_LIST_HEAD(&bdi->bdi_list);
  633         INIT_LIST_HEAD(&bdi->work_list);
  634 
  635         bdi_wb_init(&bdi->wb, bdi);
  636 
  637         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
  638                 err = percpu_counter_init(&bdi->bdi_stat[i], 0);
  639                 if (err)
  640                         goto err;
  641         }
  642 
  643         bdi->dirty_exceeded = 0;
  644 
  645         bdi->bw_time_stamp = jiffies;
  646         bdi->written_stamp = 0;
  647 
  648         bdi->balanced_dirty_ratelimit = INIT_BW;
  649         bdi->dirty_ratelimit = INIT_BW;
  650         bdi->write_bandwidth = INIT_BW;
  651         bdi->avg_write_bandwidth = INIT_BW;
  652 
  653         err = fprop_local_init_percpu(&bdi->completions);
  654 
  655         if (err) {
  656 err:
  657                 while (i--)
  658                         percpu_counter_destroy(&bdi->bdi_stat[i]);
  659         }
  660 
  661         return err;
  662 }
  663 EXPORT_SYMBOL(bdi_init);
  664 
  665 void bdi_destroy(struct backing_dev_info *bdi)
  666 {
  667         int i;
  668 
  669         /*
  670          * Splice our entries to the default_backing_dev_info, if this
  671          * bdi disappears
  672          */
  673         if (bdi_has_dirty_io(bdi)) {
  674                 struct bdi_writeback *dst = &default_backing_dev_info.wb;
  675 
  676                 bdi_lock_two(&bdi->wb, dst);
  677                 list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
  678                 list_splice(&bdi->wb.b_io, &dst->b_io);
  679                 list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
  680                 spin_unlock(&bdi->wb.list_lock);
  681                 spin_unlock(&dst->list_lock);
  682         }
  683 
  684         bdi_unregister(bdi);
  685 
  686         /*
  687          * If bdi_unregister() had already been called earlier, the
  688          * wakeup_timer could still be armed because bdi_prune_sb()
  689          * can race with the bdi_wakeup_thread_delayed() calls from
  690          * __mark_inode_dirty().
  691          */
  692         del_timer_sync(&bdi->wb.wakeup_timer);
  693 
  694         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
  695                 percpu_counter_destroy(&bdi->bdi_stat[i]);
  696 
  697         fprop_local_destroy_percpu(&bdi->completions);
  698 }
  699 EXPORT_SYMBOL(bdi_destroy);
  700 
  701 /*
  702  * For use from filesystems to quickly init and register a bdi associated
  703  * with dirty writeback
  704  */
  705 int bdi_setup_and_register(struct backing_dev_info *bdi, char *name,
  706                            unsigned int cap)
  707 {
  708         char tmp[32];
  709         int err;
  710 
  711         bdi->name = name;
  712         bdi->capabilities = cap;
  713         err = bdi_init(bdi);
  714         if (err)
  715                 return err;
  716 
  717         sprintf(tmp, "%.28s%s", name, "-%d");
  718         err = bdi_register(bdi, NULL, tmp, atomic_long_inc_return(&bdi_seq));
  719         if (err) {
  720                 bdi_destroy(bdi);
  721                 return err;
  722         }
  723 
  724         return 0;
  725 }
  726 EXPORT_SYMBOL(bdi_setup_and_register);
  727 
  728 static wait_queue_head_t congestion_wqh[2] = {
  729                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
  730                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
  731         };
  732 static atomic_t nr_bdi_congested[2];
  733 
  734 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
  735 {
  736         enum bdi_state bit;
  737         wait_queue_head_t *wqh = &congestion_wqh[sync];
  738 
  739         bit = sync ? BDI_sync_congested : BDI_async_congested;
  740         if (test_and_clear_bit(bit, &bdi->state))
  741                 atomic_dec(&nr_bdi_congested[sync]);
  742         smp_mb__after_clear_bit();
  743         if (waitqueue_active(wqh))
  744                 wake_up(wqh);
  745 }
  746 EXPORT_SYMBOL(clear_bdi_congested);
  747 
  748 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
  749 {
  750         enum bdi_state bit;
  751 
  752         bit = sync ? BDI_sync_congested : BDI_async_congested;
  753         if (!test_and_set_bit(bit, &bdi->state))
  754                 atomic_inc(&nr_bdi_congested[sync]);
  755 }
  756 EXPORT_SYMBOL(set_bdi_congested);
  757 
  758 /**
  759  * congestion_wait - wait for a backing_dev to become uncongested
  760  * @sync: SYNC or ASYNC IO
  761  * @timeout: timeout in jiffies
  762  *
  763  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
  764  * write congestion.  If no backing_devs are congested then just wait for the
  765  * next write to be completed.
  766  */
  767 long congestion_wait(int sync, long timeout)
  768 {
  769         long ret;
  770         unsigned long start = jiffies;
  771         DEFINE_WAIT(wait);
  772         wait_queue_head_t *wqh = &congestion_wqh[sync];
  773 
  774         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
  775         ret = io_schedule_timeout(timeout);
  776         finish_wait(wqh, &wait);
  777 
  778         trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
  779                                         jiffies_to_usecs(jiffies - start));
  780 
  781         return ret;
  782 }
  783 EXPORT_SYMBOL(congestion_wait);
  784 
  785 /**
  786  * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
  787  * @zone: A zone to check if it is heavily congested
  788  * @sync: SYNC or ASYNC IO
  789  * @timeout: timeout in jiffies
  790  *
  791  * In the event of a congested backing_dev (any backing_dev) and the given
  792  * @zone has experienced recent congestion, this waits for up to @timeout
  793  * jiffies for either a BDI to exit congestion of the given @sync queue
  794  * or a write to complete.
  795  *
  796  * In the absence of zone congestion, cond_resched() is called to yield
  797  * the processor if necessary but otherwise does not sleep.
  798  *
  799  * The return value is 0 if the sleep is for the full timeout. Otherwise,
  800  * it is the number of jiffies that were still remaining when the function
  801  * returned. return_value == timeout implies the function did not sleep.
  802  */
  803 long wait_iff_congested(struct zone *zone, int sync, long timeout)
  804 {
  805         long ret;
  806         unsigned long start = jiffies;
  807         DEFINE_WAIT(wait);
  808         wait_queue_head_t *wqh = &congestion_wqh[sync];
  809 
  810         /*
  811          * If there is no congestion, or heavy congestion is not being
  812          * encountered in the current zone, yield if necessary instead
  813          * of sleeping on the congestion queue
  814          */
  815         if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
  816                         !zone_is_reclaim_congested(zone)) {
  817                 cond_resched();
  818 
  819                 /* In case we scheduled, work out time remaining */
  820                 ret = timeout - (jiffies - start);
  821                 if (ret < 0)
  822                         ret = 0;
  823 
  824                 goto out;
  825         }
  826 
  827         /* Sleep until uncongested or a write happens */
  828         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
  829         ret = io_schedule_timeout(timeout);
  830         finish_wait(wqh, &wait);
  831 
  832 out:
  833         trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
  834                                         jiffies_to_usecs(jiffies - start));
  835 
  836         return ret;
  837 }
  838 EXPORT_SYMBOL(wait_iff_congested);
  839 
  840 int pdflush_proc_obsolete(struct ctl_table *table, int write,
  841                         void __user *buffer, size_t *lenp, loff_t *ppos)
  842 {
  843         char kbuf[] = "\n";
  844 
  845         if (*ppos) {
  846                 *lenp = 0;
  847                 return 0;
  848         }
  849 
  850         if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
  851                 return -EFAULT;
  852         printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
  853                         table->procname);
  854 
  855         *lenp = 2;
  856         *ppos += *lenp;
  857         return 2;
  858 }
Cache object: 2aa4e402b01fc7157cbab93c7337fcd1
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FreeBSD/Linux Kernel Cross Reference sys/mm/backing-dev.c

FreeBSD/Linux Kernel Cross Reference
sys/mm/backing-dev.c
