On 08/04, Chao Yu wrote:
> On 2020/8/4 1:28, Jaegeuk Kim wrote:
> > It doesn't need to wait for checkpoint being completed triggered by end_io.
> >
> > [ 20.157753] ------------[ cut here ]------------
> > [ 20.158393] do not call blocking ops when !TASK_RUNNING; state=2 set at
> > [<0000000096354225>] prepare_to_wait+0xcd/0x430
> > [ 20.159858] WARNING: CPU: 1 PID: 1152 at kernel/sched/core.c:7142
> > __might_sleep+0x149/0x1a0
> > ...
> > [ 20.176110] __submit_merged_write_cond+0x191/0x310
> > [ 20.176739] f2fs_submit_merged_write+0x18/0x20
> > [ 20.177323] f2fs_wait_on_all_pages+0x269/0x2d0
> > [ 20.177899] ? block_operations+0x980/0x980
> > [ 20.178441] ? __kasan_check_read+0x11/0x20
> > [ 20.178975] ? finish_wait+0x260/0x260
> > [ 20.179488] ? percpu_counter_set+0x147/0x230
> > [ 20.180049] do_checkpoint+0x1757/0x2a50
> > [ 20.180558] f2fs_write_checkpoint+0x840/0xaf0
> > [ 20.181126] f2fs_sync_fs+0x287/0x4a0
> >
> > Reported-by: Eric Biggers <ebigg...@kernel.org>
> > Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
> > ---
> > fs/f2fs/checkpoint.c | 6 +-----
> > fs/f2fs/data.c | 4 ----
> > fs/f2fs/f2fs.h | 1 -
> > fs/f2fs/super.c | 1 -
> > 4 files changed, 1 insertion(+), 11 deletions(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 99c8061da55b9..2bdddc725e677 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -1255,11 +1255,7 @@ static void unblock_operations(struct f2fs_sb_info
> > *sbi)
> > void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
> > {
> > - DEFINE_WAIT(wait);
> > -
> > for (;;) {
> > - prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>
> Wouldn't that case high cpu usage before io end?
This is a critical path to wait for IO completion in checkpoint, which would be
better to wait for it to avoid long latency to continue filesystem operations.
Moreover, I expect io_schedule_timeout() can mitigate such the CPU overhead and
actually we don't need to make there-in context switches as well.
>
> > -
> > if (!get_pages(sbi, type))
> > break;
> > @@ -1271,9 +1267,9 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi,
> > int type)
> > FS_CP_META_IO);
> > else if (type == F2FS_WB_CP_DATA)
> > f2fs_submit_merged_write(sbi, DATA);
> > +
> > io_schedule_timeout(DEFAULT_IO_TIMEOUT);
> > }
> > - finish_wait(&sbi->cp_wait, &wait);
> > }
> > static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control
> > *cpc)
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index c1b676be67b9a..588d2871bbe69 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -383,10 +383,6 @@ static void f2fs_write_end_io(struct bio *bio)
> > clear_cold_data(page);
> > end_page_writeback(page);
> > }
> > - if (!get_pages(sbi, F2FS_WB_CP_DATA) &&
> > - wq_has_sleeper(&sbi->cp_wait))
> > - wake_up(&sbi->cp_wait);
> > -
> > bio_put(bio);
> > }
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 02811ce15059b..a036539363030 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1437,7 +1437,6 @@ struct f2fs_sb_info {
> > struct rw_semaphore cp_rwsem; /* blocking FS operations */
> > struct rw_semaphore node_write; /* locking node writes */
> > struct rw_semaphore node_change; /* locking node change */
> > - wait_queue_head_t cp_wait;
> > unsigned long last_time[MAX_TIME]; /* to store time in jiffies */
> > long interval_time[MAX_TIME]; /* to store thresholds */
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 83bf9a02f83f2..5f4d9abc079d6 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -3540,7 +3540,6 @@ static int f2fs_fill_super(struct super_block *sb,
> > void *data, int silent)
> > init_rwsem(&sbi->cp_rwsem);
> > init_rwsem(&sbi->quota_sem);
> > - init_waitqueue_head(&sbi->cp_wait);
> > init_sb_info(sbi);
> > err = init_percpu_info(sbi);
> >
