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writeback: move backing_dev_info->wb_lock and ->worklist into bdi_writeback 

Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear.  For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi.  To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->wb_lock and ->worklist into wb.

* The lock protects bdi->worklist and bdi->wb.dwork scheduling.  While
  moving, rename it to wb->work_lock as wb->wb_lock is confusing.
  Also, move wb->dwork downwards so that it's colocated with the new
  ->work_lock and ->work_list fields.

* bdi_writeback_workfn()		-> wb_workfn()
  bdi_wakeup_thread_delayed(bdi)	-> wb_wakeup_delayed(wb)
  bdi_wakeup_thread(bdi)		-> wb_wakeup(wb)
  bdi_queue_work(bdi, ...)		-> wb_queue_work(wb, ...)
  __bdi_start_writeback(bdi, ...)	-> __wb_start_writeback(wb, ...)
  get_next_work_item(bdi)		-> get_next_work_item(wb)

* bdi_wb_shutdown() is renamed to wb_shutdown() and now takes @wb.
  The function contained parts which belong to the containing bdi
  rather than the wb itself - testing cap_writeback_dirty and
  bdi_remove_from_list() invocation.  Those are moved to
  bdi_unregister().

* bdi_wb_{init|exit}() are renamed to wb_{init|exit}().
  Initializations of the moved bdi->wb_lock and ->work_list are
  relocated from bdi_init() to wb_init().

* As there's still only one bdi_writeback per backing_dev_info, all
  uses of bdi->state are mechanically replaced with bdi->wb.state
  introducing no behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-05-22 17:13:30 -04:00 committed by Jens Axboe
parent de1fff37b2
commit f0054bb1e1
3 changed files with 75 additions and 82 deletions
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86
fs/fs-writeback.c
View File

@ -109,34 +109,33 @@ static inline struct inode *wb_inode(struct list_head *head)
EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
static void bdi_wakeup_thread(struct backing_dev_info *bdi)
static void wb_wakeup(struct bdi_writeback *wb)
{
spin_lock_bh(&bdi->wb_lock);
if (test_bit(WB_registered, &bdi->wb.state))
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
spin_unlock_bh(&bdi->wb_lock);
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
mod_delayed_work(bdi_wq, &wb->dwork, 0);
spin_unlock_bh(&wb->work_lock);
}
static void bdi_queue_work(struct backing_dev_info *bdi,
struct wb_writeback_work *work)
static void wb_queue_work(struct bdi_writeback *wb,
struct wb_writeback_work *work)
{
trace_writeback_queue(bdi, work);
trace_writeback_queue(wb->bdi, work);
spin_lock_bh(&bdi->wb_lock);
if (!test_bit(WB_registered, &bdi->wb.state)) {
spin_lock_bh(&wb->work_lock);
if (!test_bit(WB_registered, &wb->state)) {
if (work->done)
complete(work->done);
goto out_unlock;
}
list_add_tail(&work->list, &bdi->work_list);
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
list_add_tail(&work->list, &wb->work_list);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
out_unlock:
spin_unlock_bh(&bdi->wb_lock);
spin_unlock_bh(&wb->work_lock);
}
static void
__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
bool range_cyclic, enum wb_reason reason)
static void __wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
bool range_cyclic, enum wb_reason reason)
{
struct wb_writeback_work *work;
@ -146,8 +145,8 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
*/
work = kzalloc(sizeof(*work), GFP_ATOMIC);
if (!work) {
trace_writeback_nowork(bdi);
bdi_wakeup_thread(bdi);
trace_writeback_nowork(wb->bdi);
wb_wakeup(wb);
return;
}
@ -156,7 +155,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
work->range_cyclic = range_cyclic;
work->reason = reason;
bdi_queue_work(bdi, work);
wb_queue_work(wb, work);
}
/**
@ -174,7 +173,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
enum wb_reason reason)
{
__bdi_start_writeback(bdi, nr_pages, true, reason);
__wb_start_writeback(&bdi->wb, nr_pages, true, reason);
}
/**
@ -194,7 +193,7 @@ void bdi_start_background_writeback(struct backing_dev_info *bdi)
* writeback as soon as there is no other work to do.
*/
trace_writeback_wake_background(bdi);
bdi_wakeup_thread(bdi);
wb_wakeup(&bdi->wb);
}
/*
@ -898,7 +897,7 @@ static long wb_writeback(struct bdi_writeback *wb,
* after the other works are all done.
*/
if ((work->for_background || work->for_kupdate) &&
!list_empty(&wb->bdi->work_list))
!list_empty(&wb->work_list))
break;
/*
@ -969,18 +968,17 @@ static long wb_writeback(struct bdi_writeback *wb,
/*
* Return the next wb_writeback_work struct that hasn't been processed yet.
*/
static struct wb_writeback_work *
get_next_work_item(struct backing_dev_info *bdi)
static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
{
struct wb_writeback_work *work = NULL;
spin_lock_bh(&bdi->wb_lock);
if (!list_empty(&bdi->work_list)) {
work = list_entry(bdi->work_list.next,
spin_lock_bh(&wb->work_lock);
if (!list_empty(&wb->work_list)) {
work = list_entry(wb->work_list.next,
struct wb_writeback_work, list);
list_del_init(&work->list);
}
spin_unlock_bh(&bdi->wb_lock);
spin_unlock_bh(&wb->work_lock);
return work;
}
@ -1052,14 +1050,13 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
*/
static long wb_do_writeback(struct bdi_writeback *wb)
{
struct backing_dev_info *bdi = wb->bdi;
struct wb_writeback_work *work;
long wrote = 0;
set_bit(WB_writeback_running, &wb->state);
while ((work = get_next_work_item(bdi)) != NULL) {
while ((work = get_next_work_item(wb)) != NULL) {
trace_writeback_exec(bdi, work);
trace_writeback_exec(wb->bdi, work);
wrote += wb_writeback(wb, work);
@ -1087,43 +1084,42 @@ static long wb_do_writeback(struct bdi_writeback *wb)
* Handle writeback of dirty data for the device backed by this bdi. Also
* reschedules periodically and does kupdated style flushing.
*/
void bdi_writeback_workfn(struct work_struct *work)
void wb_workfn(struct work_struct *work)
{
struct bdi_writeback *wb = container_of(to_delayed_work(work),
struct bdi_writeback, dwork);
struct backing_dev_info *bdi = wb->bdi;
long pages_written;
set_worker_desc("flush-%s", dev_name(bdi->dev));
set_worker_desc("flush-%s", dev_name(wb->bdi->dev));
current->flags |= PF_SWAPWRITE;
if (likely(!current_is_workqueue_rescuer() ||
!test_bit(WB_registered, &wb->state))) {
/*
* The normal path. Keep writing back @bdi until its
* The normal path. Keep writing back @wb until its
* work_list is empty. Note that this path is also taken
* if @bdi is shutting down even when we're running off the
* if @wb is shutting down even when we're running off the
* rescuer as work_list needs to be drained.
*/
do {
pages_written = wb_do_writeback(wb);
trace_writeback_pages_written(pages_written);
} while (!list_empty(&bdi->work_list));
} while (!list_empty(&wb->work_list));
} else {
/*
* bdi_wq can't get enough workers and we're running off
* the emergency worker. Don't hog it. Hopefully, 1024 is
* enough for efficient IO.
*/
pages_written = writeback_inodes_wb(&bdi->wb, 1024,
pages_written = writeback_inodes_wb(wb, 1024,
WB_REASON_FORKER_THREAD);
trace_writeback_pages_written(pages_written);
}
if (!list_empty(&bdi->work_list))
if (!list_empty(&wb->work_list))
mod_delayed_work(bdi_wq, &wb->dwork, 0);
else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
bdi_wakeup_thread_delayed(bdi);
wb_wakeup_delayed(wb);
current->flags &= ~PF_SWAPWRITE;
}
@ -1143,7 +1139,7 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
if (!bdi_has_dirty_io(bdi))
continue;
__bdi_start_writeback(bdi, nr_pages, false, reason);
__wb_start_writeback(&bdi->wb, nr_pages, false, reason);
}
rcu_read_unlock();
}
@ -1174,7 +1170,7 @@ static void wakeup_dirtytime_writeback(struct work_struct *w)
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
if (list_empty(&bdi->wb.b_dirty_time))
continue;
bdi_wakeup_thread(bdi);
wb_wakeup(&bdi->wb);
}
rcu_read_unlock();
schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ);
@ -1347,7 +1343,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
trace_writeback_dirty_inode_enqueue(inode);
if (wakeup_bdi)
bdi_wakeup_thread_delayed(bdi);
wb_wakeup_delayed(&bdi->wb);
return;
}
}
@ -1437,7 +1433,7 @@ void writeback_inodes_sb_nr(struct super_block *sb,
if (sb->s_bdi == &noop_backing_dev_info)
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
bdi_queue_work(sb->s_bdi, &work);
wb_queue_work(&sb->s_bdi->wb, &work);
wait_for_completion(&done);
}
EXPORT_SYMBOL(writeback_inodes_sb_nr);
@ -1521,7 +1517,7 @@ void sync_inodes_sb(struct super_block *sb)
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
bdi_queue_work(sb->s_bdi, &work);
wb_queue_work(&sb->s_bdi->wb, &work);
wait_for_completion(&done);
wait_sb_inodes(sb);

12
include/linux/backing-dev.h
View File

@ -52,7 +52,6 @@ struct bdi_writeback {
unsigned long state; /* Always use atomic bitops on this */
unsigned long last_old_flush; /* last old data flush */
struct delayed_work dwork; /* work item used for writeback */
struct list_head b_dirty; /* dirty inodes */
struct list_head b_io; /* parked for writeback */
struct list_head b_more_io; /* parked for more writeback */
@ -78,6 +77,10 @@ struct bdi_writeback {
struct fprop_local_percpu completions;
int dirty_exceeded;
spinlock_t work_lock; /* protects work_list & dwork scheduling */
struct list_head work_list;
struct delayed_work dwork; /* work item used for writeback */
};
struct backing_dev_info {
@ -93,9 +96,6 @@ struct backing_dev_info {
unsigned int max_ratio, max_prop_frac;
struct bdi_writeback wb; /* default writeback info for this bdi */
spinlock_t wb_lock; /* protects work_list & wb.dwork scheduling */
struct list_head work_list;
struct device *dev;
@ -121,9 +121,9 @@ int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
enum wb_reason reason);
void bdi_start_background_writeback(struct backing_dev_info *bdi);
void bdi_writeback_workfn(struct work_struct *work);
void wb_workfn(struct work_struct *work);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
void wb_wakeup_delayed(struct bdi_writeback *wb);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;

59
mm/backing-dev.c
View File

@ -261,7 +261,7 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
}
/*
* This function is used when the first inode for this bdi is marked dirty. It
* This function is used when the first inode for this wb is marked dirty. It
* wakes-up the corresponding bdi thread which should then take care of the
* periodic background write-out of dirty inodes. Since the write-out would
* starts only 'dirty_writeback_interval' centisecs from now anyway, we just
@ -274,15 +274,15 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
* We have to be careful not to postpone flush work if it is scheduled for
* earlier. Thus we use queue_delayed_work().
*/
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
void wb_wakeup_delayed(struct bdi_writeback *wb)
{
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
spin_lock_bh(&bdi->wb_lock);
if (test_bit(WB_registered, &bdi->wb.state))
queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
spin_unlock_bh(&bdi->wb_lock);
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
spin_unlock_bh(&wb->work_lock);
}
/*
@ -335,28 +335,24 @@ EXPORT_SYMBOL(bdi_register_dev);
/*
* Remove bdi from the global list and shutdown any threads we have running
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
static void wb_shutdown(struct bdi_writeback *wb)
{
/* Make sure nobody queues further work */
spin_lock_bh(&bdi->wb_lock);
if (!test_and_clear_bit(WB_registered, &bdi->wb.state)) {
spin_unlock_bh(&bdi->wb_lock);
spin_lock_bh(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) {
spin_unlock_bh(&wb->work_lock);
return;
}
spin_unlock_bh(&bdi->wb_lock);
spin_unlock_bh(&wb->work_lock);
/*
* Make sure nobody finds us on the bdi_list anymore
* Drain work list and shutdown the delayed_work. !WB_registered
* tells wb_workfn() that @wb is dying and its work_list needs to
* be drained no matter what.
*/
bdi_remove_from_list(bdi);
/*
* Drain work list and shutdown the delayed_work. At this point,
* @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
* is dying and its work_list needs to be drained no matter what.
*/
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
flush_delayed_work(&bdi->wb.dwork);
mod_delayed_work(bdi_wq, &wb->dwork, 0);
flush_delayed_work(&wb->dwork);
WARN_ON(!list_empty(&wb->work_list));
}
/*
@ -381,7 +377,7 @@ EXPORT_SYMBOL(bdi_unregister);
*/
#define INIT_BW (100 << (20 - PAGE_SHIFT))
static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
{
int i, err;
@ -394,7 +390,6 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
INIT_LIST_HEAD(&wb->b_more_io);
INIT_LIST_HEAD(&wb->b_dirty_time);
spin_lock_init(&wb->list_lock);
INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
wb->bw_time_stamp = jiffies;
wb->balanced_dirty_ratelimit = INIT_BW;
@ -402,6 +397,10 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
wb->write_bandwidth = INIT_BW;
wb->avg_write_bandwidth = INIT_BW;
spin_lock_init(&wb->work_lock);
INIT_LIST_HEAD(&wb->work_list);
INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
if (err)
return err;
@ -419,7 +418,7 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
return 0;
}
static void bdi_wb_exit(struct bdi_writeback *wb)
static void wb_exit(struct bdi_writeback *wb)
{
int i;
@ -440,11 +439,9 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = FPROP_FRAC_BASE;
spin_lock_init(&bdi->wb_lock);
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->work_list);
err = bdi_wb_init(&bdi->wb, bdi);
err = wb_init(&bdi->wb, bdi);
if (err)
return err;
@ -454,9 +451,9 @@ EXPORT_SYMBOL(bdi_init);
void bdi_destroy(struct backing_dev_info *bdi)
{
bdi_wb_shutdown(bdi);
WARN_ON(!list_empty(&bdi->work_list));
/* make sure nobody finds us on the bdi_list anymore */
bdi_remove_from_list(bdi);
wb_shutdown(&bdi->wb);
if (bdi->dev) {
bdi_debug_unregister(bdi);
@ -464,7 +461,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
bdi->dev = NULL;
}
bdi_wb_exit(&bdi->wb);
wb_exit(&bdi->wb);
}
EXPORT_SYMBOL(bdi_destroy);