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writeback: implement WB_has_dirty_io wb_state flag

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Currently, wb_has_dirty_io() determines whether a wb (bdi_writeback)
has any dirty inode by testing all three IO lists on each invocation
without actively keeping track.  For cgroup writeback support, a
single bdi will host multiple wb's each of which will host dirty
inodes separately and we'll need to make bdi_has_dirty_io(), which
currently only represents the root wb, aggregate has_dirty_io from all
member wb's, which requires tracking transitions in has_dirty_io state
on each wb.

This patch introduces inode_wb_list_{move|del}_locked() to consolidate
IO list operations leaving queue_io() the only other function which
directly manipulates IO lists (via move_expired_inodes()).  All three
functions are updated to call wb_io_lists_[de]populated() which keep
track of whether the wb has dirty inodes or not and record it using
the new WB_has_dirty_io flag.  inode_wb_list_moved_locked()'s return
value indicates whether the wb had no dirty inodes before.

mark_inode_dirty() is restructured so that the return value of
inode_wb_list_move_locked() can be used for deciding whether to wake
up the wb.

While at it, change {bdi|wb}_has_dirty_io()'s return values to bool.
These functions were returning 0 and 1 before.  Also, add a comment
explaining the synchronization of wb_state flags.

v2: Updated to accommodate b_dirty_time.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-05-22 17:13:45 -04:00 • committed by Jens Axboe
parent 703c270887
commit d6c10f1fc8
4 changed files with 91 additions and 30 deletions
Download patch file Download diff file Expand all files Collapse all files

8
include/linux/backing-dev.h
View file

@ -29,7 +29,7 @@ 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 wb_workfn(struct work_struct *work);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
bool bdi_has_dirty_io(struct backing_dev_info *bdi);
void wb_wakeup_delayed(struct bdi_writeback *wb);
extern spinlock_t bdi_lock;
@ -37,11 +37,9 @@ extern struct list_head bdi_list;
extern struct workqueue_struct *bdi_wq;
static inline int wb_has_dirty_io(struct bdi_writeback *wb)
static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
{
return !list_empty(&wb->b_dirty) ||
!list_empty(&wb->b_io) ||
!list_empty(&wb->b_more_io);
return test_bit(WB_has_dirty_io, &wb->state);
}
static inline void __add_wb_stat(struct bdi_writeback *wb,