releases/2.6.38.8/ext4-use-schedule_timeout_interruptible-for-waiting-in.patch

   1 From 4ed5c033c11b33149d993734a6a8de1016e8f03f Mon Sep 17 00:00:00 2001
   2 From: Lukas Czerner <lczerner@redhat.com>
   3 Date: Fri, 20 May 2011 13:49:04 -0400
   4 Subject: ext4: Use schedule_timeout_interruptible() for waiting in
   5  lazyinit thread
   6
   7 From: Lukas Czerner <lczerner@redhat.com>
   8
   9 commit 4ed5c033c11b33149d993734a6a8de1016e8f03f upstream.
  10
  11 In order to make lazyinit eat approx. 10% of io bandwidth at max, we
  12 are sleeping between zeroing each single inode table. For that purpose
  13 we are using timer which wakes up thread when it expires. It is set
  14 via add_timer() and this may cause troubles in the case that thread
  15 has been woken up earlier and in next iteration we call add_timer() on
  16 still running timer hence hitting BUG_ON in add_timer(). We could fix
  17 that by using mod_timer() instead however we can use
  18 schedule_timeout_interruptible() for waiting and hence simplifying
  19 things a lot.
  20
  21 This commit exchange the old "waiting mechanism" with simple
  22 schedule_timeout_interruptible(), setting the time to sleep. Hence we
  23 do not longer need li_wait_daemon waiting queue and others, so get rid
  24 of it.
  25
  26 Addresses-Red-Hat-Bugzilla: #699708
  27
  28 Signed-off-by: Lukas Czerner <lczerner@redhat.com>
  29 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  30 Reviewed-by: Eric Sandeen <sandeen@redhat.com>
  31 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  32
  33 ---
  34  fs/ext4/ext4.h  |    4 ----
  35  fs/ext4/super.c |   31 ++++++-------------------------
  36  2 files changed, 6 insertions(+), 29 deletions(-)
  37
  38 --- a/fs/ext4/ext4.h
  39 +++ b/fs/ext4/ext4.h
  40 @@ -1590,12 +1590,8 @@ void ext4_get_group_no_and_offset(struct
  41   */
  42  struct ext4_lazy_init {
  43         unsigned long           li_state;
  44 -
  45 -       wait_queue_head_t       li_wait_daemon;
  46         wait_queue_head_t       li_wait_task;
  47 -       struct timer_list       li_timer;
  48         struct task_struct      *li_task;
  49 -
  50         struct list_head        li_request_list;
  51         struct mutex            li_list_mtx;
  52  };
  53 --- a/fs/ext4/super.c
  54 +++ b/fs/ext4/super.c
  55 @@ -2645,12 +2645,6 @@ static void print_daily_error_info(unsig
  56         mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
  57  }
  58
  59 -static void ext4_lazyinode_timeout(unsigned long data)
  60 -{
  61 -       struct task_struct *p = (struct task_struct *)data;
  62 -       wake_up_process(p);
  63 -}
  64 -
  65  /* Find next suitable group and run ext4_init_inode_table */
  66  static int ext4_run_li_request(struct ext4_li_request *elr)
  67  {
  68 @@ -2698,7 +2692,7 @@ static int ext4_run_li_request(struct ex
  69
  70  /*
  71   * Remove lr_request from the list_request and free the
  72 - * request tructure. Should be called with li_list_mtx held
  73 + * request structure. Should be called with li_list_mtx held
  74   */
  75  static void ext4_remove_li_request(struct ext4_li_request *elr)
  76  {
  77 @@ -2744,14 +2738,10 @@ static int ext4_lazyinit_thread(void *ar
  78         struct ext4_lazy_init *eli = (struct ext4_lazy_init *)arg;
  79         struct list_head *pos, *n;
  80         struct ext4_li_request *elr;
  81 -       unsigned long next_wakeup;
  82 -       DEFINE_WAIT(wait);
  83 +       unsigned long next_wakeup, cur;
  84
  85         BUG_ON(NULL == eli);
  86
  87 -       eli->li_timer.data = (unsigned long)current;
  88 -       eli->li_timer.function = ext4_lazyinode_timeout;
  89 -
  90         eli->li_task = current;
  91         wake_up(&eli->li_wait_task);
  92
  93 @@ -2785,19 +2775,15 @@ cont_thread:
  94                 if (freezing(current))
  95                         refrigerator();
  96
  97 -               if ((time_after_eq(jiffies, next_wakeup)) ||
  98 +               cur = jiffies;
  99 +               if ((time_after_eq(cur, next_wakeup)) ||
 100                     (MAX_JIFFY_OFFSET == next_wakeup)) {
 101                         cond_resched();
 102                         continue;
 103                 }
 104
 105 -               eli->li_timer.expires = next_wakeup;
 106 -               add_timer(&eli->li_timer);
 107 -               prepare_to_wait(&eli->li_wait_daemon, &wait,
 108 -                               TASK_INTERRUPTIBLE);
 109 -               if (time_before(jiffies, next_wakeup))
 110 -                       schedule();
 111 -               finish_wait(&eli->li_wait_daemon, &wait);
 112 +               schedule_timeout_interruptible(next_wakeup - cur);
 113 +
 114                 if (kthread_should_stop()) {
 115                         ext4_clear_request_list();
 116                         goto exit_thread;
 117 @@ -2821,12 +2807,10 @@ exit_thread:
 118                 goto cont_thread;
 119         }
 120         mutex_unlock(&eli->li_list_mtx);
 121 -       del_timer_sync(&ext4_li_info->li_timer);
 122         eli->li_task = NULL;
 123         wake_up(&eli->li_wait_task);
 124
 125         kfree(ext4_li_info);
 126 -       ext4_lazyinit_task = NULL;
 127         ext4_li_info = NULL;
 128         mutex_unlock(&ext4_li_mtx);
 129
 130 @@ -2854,7 +2838,6 @@ static int ext4_run_lazyinit_thread(void
 131         if (IS_ERR(ext4_lazyinit_task)) {
 132                 int err = PTR_ERR(ext4_lazyinit_task);
 133                 ext4_clear_request_list();
 134 -               del_timer_sync(&ext4_li_info->li_timer);
 135                 kfree(ext4_li_info);
 136                 ext4_li_info = NULL;
 137                 printk(KERN_CRIT "EXT4: error %d creating inode table "
 138 @@ -2903,9 +2886,7 @@ static int ext4_li_info_new(void)
 139         INIT_LIST_HEAD(&eli->li_request_list);
 140         mutex_init(&eli->li_list_mtx);
 141
 142 -       init_waitqueue_head(&eli->li_wait_daemon);
 143         init_waitqueue_head(&eli->li_wait_task);
 144 -       init_timer(&eli->li_timer);
 145         eli->li_state |= EXT4_LAZYINIT_QUIT;
 146
 147         ext4_li_info = eli;