writeback: remove wb_list
The wb_list member of struct backing_device_info always has exactly one
element. Just use the direct bdi->wb pointer instead and simplify some
code.
Also remove bdi_task_init which is now trivial to prepare for the next
patch.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index d5be169..d67989b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -73,9 +73,9 @@
* If the default thread isn't there, make sure we add it. When
* it gets created and wakes up, we'll run this work.
*/
- if (unlikely(list_empty_careful(&bdi->wb_list)))
+ if (unlikely(!bdi->wb.task)) {
wake_up_process(default_backing_dev_info.wb.task);
- else {
+ } else {
struct bdi_writeback *wb = &bdi->wb;
if (wb->task)
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index e9aec0d..50f1461 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -45,8 +45,6 @@
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
struct bdi_writeback {
- struct list_head list; /* hangs off the bdi */
-
struct backing_dev_info *bdi; /* our parent bdi */
unsigned int nr;
@@ -80,8 +78,7 @@
unsigned int max_ratio, max_prop_frac;
struct bdi_writeback wb; /* default writeback info for this bdi */
- spinlock_t wb_lock; /* protects update side of wb_list */
- struct list_head wb_list; /* the flusher threads hanging off this bdi */
+ spinlock_t wb_lock; /* protects work_list */
struct list_head work_list;
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 123bcef..6c2a09c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -65,28 +65,21 @@
static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
struct backing_dev_info *bdi = m->private;
- struct bdi_writeback *wb;
+ struct bdi_writeback *wb = &bdi->wb;
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long bdi_thresh;
unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
struct inode *inode;
- /*
- * inode lock is enough here, the bdi->wb_list is protected by
- * RCU on the reader side
- */
nr_wb = nr_dirty = nr_io = nr_more_io = 0;
spin_lock(&inode_lock);
- list_for_each_entry(wb, &bdi->wb_list, list) {
- nr_wb++;
- list_for_each_entry(inode, &wb->b_dirty, i_list)
- nr_dirty++;
- list_for_each_entry(inode, &wb->b_io, i_list)
- nr_io++;
- list_for_each_entry(inode, &wb->b_more_io, i_list)
- nr_more_io++;
- }
+ list_for_each_entry(inode, &wb->b_dirty, i_list)
+ nr_dirty++;
+ list_for_each_entry(inode, &wb->b_io, i_list)
+ nr_io++;
+ list_for_each_entry(inode, &wb->b_more_io, i_list)
+ nr_more_io++;
spin_unlock(&inode_lock);
get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
@@ -98,19 +91,16 @@
"BdiDirtyThresh: %8lu kB\n"
"DirtyThresh: %8lu kB\n"
"BackgroundThresh: %8lu kB\n"
- "WritebackThreads: %8lu\n"
"b_dirty: %8lu\n"
"b_io: %8lu\n"
"b_more_io: %8lu\n"
"bdi_list: %8u\n"
- "state: %8lx\n"
- "wb_list: %8u\n",
+ "state: %8lx\n",
(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
K(bdi_thresh), K(dirty_thresh),
- K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
- !list_empty(&bdi->bdi_list), bdi->state,
- !list_empty(&bdi->wb_list));
+ K(background_thresh), nr_dirty, nr_io, nr_more_io,
+ !list_empty(&bdi->bdi_list), bdi->state);
#undef K
return 0;
@@ -270,24 +260,6 @@
INIT_LIST_HEAD(&wb->b_more_io);
}
-static void bdi_task_init(struct backing_dev_info *bdi,
- struct bdi_writeback *wb)
-{
- struct task_struct *tsk = current;
-
- spin_lock(&bdi->wb_lock);
- list_add_tail_rcu(&wb->list, &bdi->wb_list);
- spin_unlock(&bdi->wb_lock);
-
- tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
- set_freezable();
-
- /*
- * Our parent may run at a different priority, just set us to normal
- */
- set_user_nice(tsk, 0);
-}
-
static int bdi_start_fn(void *ptr)
{
struct bdi_writeback *wb = ptr;
@@ -301,7 +273,13 @@
list_add_rcu(&bdi->bdi_list, &bdi_list);
spin_unlock_bh(&bdi_lock);
- bdi_task_init(bdi, wb);
+ current->flags |= PF_FLUSHER | PF_SWAPWRITE;
+ set_freezable();
+
+ /*
+ * Our parent may run at a different priority, just set us to normal
+ */
+ set_user_nice(current, 0);
/*
* Clear pending bit and wakeup anybody waiting to tear us down
@@ -312,12 +290,7 @@
ret = bdi_writeback_task(wb);
- /*
- * Remove us from the list
- */
- spin_lock(&bdi->wb_lock);
- list_del_rcu(&wb->list);
- spin_unlock(&bdi->wb_lock);
+ wb->task = NULL;
/*
* Flush any work that raced with us exiting. No new work
@@ -326,7 +299,6 @@
if (!list_empty(&bdi->work_list))
wb_do_writeback(wb, 1);
- wb->task = NULL;
return ret;
}
@@ -391,7 +363,13 @@
{
struct bdi_writeback *me = ptr;
- bdi_task_init(me->bdi, me);
+ current->flags |= PF_FLUSHER | PF_SWAPWRITE;
+ set_freezable();
+
+ /*
+ * Our parent may run at a different priority, just set us to normal
+ */
+ set_user_nice(current, 0);
for (;;) {
struct backing_dev_info *bdi, *tmp;
@@ -598,8 +576,6 @@
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
{
- struct bdi_writeback *wb;
-
if (!bdi_cap_writeback_dirty(bdi))
return;
@@ -615,14 +591,14 @@
bdi_remove_from_list(bdi);
/*
- * Finally, kill the kernel threads. We don't need to be RCU
+ * Finally, kill the kernel thread. We don't need to be RCU
* safe anymore, since the bdi is gone from visibility. Force
* unfreeze of the thread before calling kthread_stop(), otherwise
* it would never exet if it is currently stuck in the refrigerator.
*/
- list_for_each_entry(wb, &bdi->wb_list, list) {
- thaw_process(wb->task);
- kthread_stop(wb->task);
+ if (bdi->wb.task) {
+ thaw_process(bdi->wb.task);
+ kthread_stop(bdi->wb.task);
}
}
@@ -667,7 +643,6 @@
spin_lock_init(&bdi->wb_lock);
INIT_RCU_HEAD(&bdi->rcu_head);
INIT_LIST_HEAD(&bdi->bdi_list);
- INIT_LIST_HEAD(&bdi->wb_list);
INIT_LIST_HEAD(&bdi->work_list);
bdi_wb_init(&bdi->wb, bdi);