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Subject[145/146] ext4: Use schedule_timeout_interruptible() for waiting in
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------
lazyinit thread

From: Lukas Czerner <lczerner@redhat.com>

commit 4ed5c033c11b33149d993734a6a8de1016e8f03f upstream.

In order to make lazyinit eat approx. 10% of io bandwidth at max, we
are sleeping between zeroing each single inode table. For that purpose
we are using timer which wakes up thread when it expires. It is set
via add_timer() and this may cause troubles in the case that thread
has been woken up earlier and in next iteration we call add_timer() on
still running timer hence hitting BUG_ON in add_timer(). We could fix
that by using mod_timer() instead however we can use
schedule_timeout_interruptible() for waiting and hence simplifying
things a lot.

This commit exchange the old "waiting mechanism" with simple
schedule_timeout_interruptible(), setting the time to sleep. Hence we
do not longer need li_wait_daemon waiting queue and others, so get rid
of it.

Addresses-Red-Hat-Bugzilla: #699708

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ext4/ext4.h | 4 ----
fs/ext4/super.c | 31 ++++++-------------------------
2 files changed, 6 insertions(+), 29 deletions(-)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1590,12 +1590,8 @@ void ext4_get_group_no_and_offset(struct
*/
struct ext4_lazy_init {
unsigned long li_state;
-
- wait_queue_head_t li_wait_daemon;
wait_queue_head_t li_wait_task;
- struct timer_list li_timer;
struct task_struct *li_task;
-
struct list_head li_request_list;
struct mutex li_list_mtx;
};
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2645,12 +2645,6 @@ static void print_daily_error_info(unsig
mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ); /* Once a day */
}

-static void ext4_lazyinode_timeout(unsigned long data)
-{
- struct task_struct *p = (struct task_struct *)data;
- wake_up_process(p);
-}
-
/* Find next suitable group and run ext4_init_inode_table */
static int ext4_run_li_request(struct ext4_li_request *elr)
{
@@ -2698,7 +2692,7 @@ static int ext4_run_li_request(struct ex

/*
* Remove lr_request from the list_request and free the
- * request tructure. Should be called with li_list_mtx held
+ * request structure. Should be called with li_list_mtx held
*/
static void ext4_remove_li_request(struct ext4_li_request *elr)
{
@@ -2744,14 +2738,10 @@ static int ext4_lazyinit_thread(void *ar
struct ext4_lazy_init *eli = (struct ext4_lazy_init *)arg;
struct list_head *pos, *n;
struct ext4_li_request *elr;
- unsigned long next_wakeup;
- DEFINE_WAIT(wait);
+ unsigned long next_wakeup, cur;

BUG_ON(NULL == eli);

- eli->li_timer.data = (unsigned long)current;
- eli->li_timer.function = ext4_lazyinode_timeout;
-
eli->li_task = current;
wake_up(&eli->li_wait_task);

@@ -2785,19 +2775,15 @@ cont_thread:
if (freezing(current))
refrigerator();

- if ((time_after_eq(jiffies, next_wakeup)) ||
+ cur = jiffies;
+ if ((time_after_eq(cur, next_wakeup)) ||
(MAX_JIFFY_OFFSET == next_wakeup)) {
cond_resched();
continue;
}

- eli->li_timer.expires = next_wakeup;
- add_timer(&eli->li_timer);
- prepare_to_wait(&eli->li_wait_daemon, &wait,
- TASK_INTERRUPTIBLE);
- if (time_before(jiffies, next_wakeup))
- schedule();
- finish_wait(&eli->li_wait_daemon, &wait);
+ schedule_timeout_interruptible(next_wakeup - cur);
+
if (kthread_should_stop()) {
ext4_clear_request_list();
goto exit_thread;
@@ -2821,12 +2807,10 @@ exit_thread:
goto cont_thread;
}
mutex_unlock(&eli->li_list_mtx);
- del_timer_sync(&ext4_li_info->li_timer);
eli->li_task = NULL;
wake_up(&eli->li_wait_task);

kfree(ext4_li_info);
- ext4_lazyinit_task = NULL;
ext4_li_info = NULL;
mutex_unlock(&ext4_li_mtx);

@@ -2854,7 +2838,6 @@ static int ext4_run_lazyinit_thread(void
if (IS_ERR(ext4_lazyinit_task)) {
int err = PTR_ERR(ext4_lazyinit_task);
ext4_clear_request_list();
- del_timer_sync(&ext4_li_info->li_timer);
kfree(ext4_li_info);
ext4_li_info = NULL;
printk(KERN_CRIT "EXT4: error %d creating inode table "
@@ -2903,9 +2886,7 @@ static int ext4_li_info_new(void)
INIT_LIST_HEAD(&eli->li_request_list);
mutex_init(&eli->li_list_mtx);

- init_waitqueue_head(&eli->li_wait_daemon);
init_waitqueue_head(&eli->li_wait_task);
- init_timer(&eli->li_timer);
eli->li_state |= EXT4_LAZYINIT_QUIT;

ext4_li_info = eli;



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