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Subject[PATCH 14/15] writeback: convert bdi_lock to a spinlock
Date
We don't sleep under this lock anymore, so make it a spinlock instead.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 10 +++++-----
include/linux/backing-dev.h | 2 +-
mm/backing-dev.c | 36 ++++++++++++++++++------------------
mm/page-writeback.c | 8 ++++----
4 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index d646e02..e15a3fa 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -216,9 +216,9 @@ static void bdi_start_work(struct backing_dev_info *bdi, struct bdi_work *work)
* it gets created and wakes up, we'll run this work.
*/
if (unlikely(list_empty_careful(&bdi->wb_list))) {
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
bdi_add_default_flusher_task(bdi);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
} else
bdi_sched_work(bdi, work);
}
@@ -518,7 +518,7 @@ void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc)
LIST_HEAD(list);

restart:
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);

list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
struct bdi_work *work;
@@ -537,7 +537,7 @@ restart:
if (!must_wait)
continue;

- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
wbc->bdi = bdi;
generic_sync_bdi_inodes(sb, wbc);
goto restart;
@@ -549,7 +549,7 @@ restart:
__bdi_start_work(bdi, work);
}

- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

/*
* If this is for WB_SYNC_ALL, wait for pending work to complete
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index ef7d904..6815f8b 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -111,7 +111,7 @@ void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
void bdi_add_flusher_task(struct backing_dev_info *bdi);
int bdi_has_dirty_io(struct backing_dev_info *bdi);

-extern struct mutex bdi_lock;
+extern spinlock_t bdi_lock;
extern struct list_head bdi_list;

static inline int wb_is_default_task(struct bdi_writeback *wb)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 18d1194..b3e80c5 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -26,7 +26,7 @@ struct backing_dev_info default_backing_dev_info = {
EXPORT_SYMBOL_GPL(default_backing_dev_info);

static struct class *bdi_class;
-DEFINE_MUTEX(bdi_lock);
+DEFINE_SPINLOCK(bdi_lock);
LIST_HEAD(bdi_list);
LIST_HEAD(bdi_pending_list);

@@ -357,9 +357,9 @@ static int bdi_start_fn(void *ptr)
/*
* Add us to the active bdi_list
*/
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_add(&bdi->bdi_list, &bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

bdi_task_init(bdi, wb);

@@ -479,7 +479,7 @@ static int bdi_forker_task(void *ptr)
if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
wb_do_writeback(me);

- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);

/*
* Check if any existing bdi's have dirty data without
@@ -497,7 +497,7 @@ static int bdi_forker_task(void *ptr)
if (list_empty(&bdi_pending_list)) {
unsigned long wait;

- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
wait = msecs_to_jiffies(dirty_writeback_interval * 10);
schedule_timeout(wait);
try_to_freeze();
@@ -513,7 +513,7 @@ static int bdi_forker_task(void *ptr)
bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
bdi_list);
list_del_init(&bdi->bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

wb = bdi_new_wb(bdi);
if (!wb)
@@ -536,9 +536,9 @@ readd_flush:
* a chance to flush other bdi's to free
* memory.
*/
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_add_tail(&bdi->bdi_list, &bdi_pending_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

bdi_flush_io(bdi);
}
@@ -580,10 +580,10 @@ static void bdi_add_one_flusher_task(struct backing_dev_info *bdi,

static int flusher_add_helper_block(struct backing_dev_info *bdi)
{
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
wait_on_bit_lock(&bdi->state, BDI_pending, bdi_sched_wait,
TASK_UNINTERRUPTIBLE);
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
return 0;
}

@@ -611,9 +611,9 @@ void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
*/
void bdi_add_flusher_task(struct backing_dev_info *bdi)
{
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
bdi_add_one_flusher_task(bdi, flusher_add_helper_block);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
}
EXPORT_SYMBOL(bdi_add_flusher_task);

@@ -635,9 +635,9 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
goto exit;
}

- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_add_tail(&bdi->bdi_list, &bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

bdi->dev = dev;

@@ -661,9 +661,9 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
bdi_put_wb(bdi, wb);
ret = -ENOMEM;
remove_err:
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_del(&bdi->bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
goto exit;
}
}
@@ -700,9 +700,9 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
/*
* Make sure nobody finds us on the bdi_list anymore
*/
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_del(&bdi->bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

/*
* Finally, kill the kernel threads. We don't need to be RCU
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 91c8615..b5f7110 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -314,7 +314,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
{
int ret = 0;

- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
if (min_ratio > bdi->max_ratio) {
ret = -EINVAL;
} else {
@@ -326,7 +326,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
ret = -EINVAL;
}
}
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

return ret;
}
@@ -338,14 +338,14 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
if (max_ratio > 100)
return -EINVAL;

- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
if (bdi->min_ratio > max_ratio) {
ret = -EINVAL;
} else {
bdi->max_ratio = max_ratio;
bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
}
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);

return ret;
}
--
1.6.3.rc0.1.gf800


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