Commit d6c10f1f authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe

writeback: implement WB_has_dirty_io wb_state flag

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: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 703c2708
......@@ -93,6 +93,66 @@ static inline struct inode *wb_inode(struct list_head *head)
EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
static bool wb_io_lists_populated(struct bdi_writeback *wb)
{
if (wb_has_dirty_io(wb)) {
return false;
} else {
set_bit(WB_has_dirty_io, &wb->state);
return true;
}
}
static void wb_io_lists_depopulated(struct bdi_writeback *wb)
{
if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
list_empty(&wb->b_io) && list_empty(&wb->b_more_io))
clear_bit(WB_has_dirty_io, &wb->state);
}
/**
* inode_wb_list_move_locked - move an inode onto a bdi_writeback IO list
* @inode: inode to be moved
* @wb: target bdi_writeback
* @head: one of @wb->b_{dirty|io|more_io}
*
* Move @inode->i_wb_list to @list of @wb and set %WB_has_dirty_io.
* Returns %true if @inode is the first occupant of the !dirty_time IO
* lists; otherwise, %false.
*/
static bool inode_wb_list_move_locked(struct inode *inode,
struct bdi_writeback *wb,
struct list_head *head)
{
assert_spin_locked(&wb->list_lock);
list_move(&inode->i_wb_list, head);
/* dirty_time doesn't count as dirty_io until expiration */
if (head != &wb->b_dirty_time)
return wb_io_lists_populated(wb);
wb_io_lists_depopulated(wb);
return false;
}
/**
* inode_wb_list_del_locked - remove an inode from its bdi_writeback IO list
* @inode: inode to be removed
* @wb: bdi_writeback @inode is being removed from
*
* Remove @inode which may be on one of @wb->b_{dirty|io|more_io} lists and
* clear %WB_has_dirty_io if all are empty afterwards.
*/
static void inode_wb_list_del_locked(struct inode *inode,
struct bdi_writeback *wb)
{
assert_spin_locked(&wb->list_lock);
list_del_init(&inode->i_wb_list);
wb_io_lists_depopulated(wb);
}
static void wb_wakeup(struct bdi_writeback *wb)
{
spin_lock_bh(&wb->work_lock);
......@@ -217,7 +277,7 @@ void inode_wb_list_del(struct inode *inode)
struct bdi_writeback *wb = inode_to_wb(inode);
spin_lock(&wb->list_lock);
list_del_init(&inode->i_wb_list);
inode_wb_list_del_locked(inode, wb);
spin_unlock(&wb->list_lock);
}
......@@ -232,7 +292,6 @@ void inode_wb_list_del(struct inode *inode)
*/
static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
{
assert_spin_locked(&wb->list_lock);
if (!list_empty(&wb->b_dirty)) {
struct inode *tail;
......@@ -240,7 +299,7 @@ static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
if (time_before(inode->dirtied_when, tail->dirtied_when))
inode->dirtied_when = jiffies;
}
list_move(&inode->i_wb_list, &wb->b_dirty);
inode_wb_list_move_locked(inode, wb, &wb->b_dirty);
}
/*
......@@ -248,8 +307,7 @@ static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
*/
static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
{
assert_spin_locked(&wb->list_lock);
list_move(&inode->i_wb_list, &wb->b_more_io);
inode_wb_list_move_locked(inode, wb, &wb->b_more_io);
}
static void inode_sync_complete(struct inode *inode)
......@@ -358,6 +416,8 @@ static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, 0, work);
moved += move_expired_inodes(&wb->b_dirty_time, &wb->b_io,
EXPIRE_DIRTY_ATIME, work);
if (moved)
wb_io_lists_populated(wb);
trace_writeback_queue_io(wb, work, moved);
}
......@@ -483,10 +543,10 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
redirty_tail(inode, wb);
} else if (inode->i_state & I_DIRTY_TIME) {
inode->dirtied_when = jiffies;
list_move(&inode->i_wb_list, &wb->b_dirty_time);
inode_wb_list_move_locked(inode, wb, &wb->b_dirty_time);
} else {
/* The inode is clean. Remove from writeback lists. */
list_del_init(&inode->i_wb_list);
inode_wb_list_del_locked(inode, wb);
}
}
......@@ -628,7 +688,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
* touch it. See comment above for explanation.
*/
if (!(inode->i_state & I_DIRTY_ALL))
list_del_init(&inode->i_wb_list);
inode_wb_list_del_locked(inode, wb);
spin_unlock(&wb->list_lock);
inode_sync_complete(inode);
out:
......@@ -1327,37 +1387,39 @@ void __mark_inode_dirty(struct inode *inode, int flags)
* reposition it (that would break b_dirty time-ordering).
*/
if (!was_dirty) {
struct list_head *dirty_list;
bool wakeup_bdi = false;
bdi = inode_to_bdi(inode);
spin_unlock(&inode->i_lock);
spin_lock(&bdi->wb.list_lock);
if (bdi_cap_writeback_dirty(bdi)) {
WARN(!test_bit(WB_registered, &bdi->wb.state),
"bdi-%s not registered\n", bdi->name);
/*
* If this is the first dirty inode for this
* bdi, we have to wake-up the corresponding
* bdi thread to make sure background
* write-back happens later.
*/
if (!wb_has_dirty_io(&bdi->wb))
wakeup_bdi = true;
}
WARN(bdi_cap_writeback_dirty(bdi) &&
!test_bit(WB_registered, &bdi->wb.state),
"bdi-%s not registered\n", bdi->name);
inode->dirtied_when = jiffies;
if (dirtytime)
inode->dirtied_time_when = jiffies;
if (inode->i_state & (I_DIRTY_INODE | I_DIRTY_PAGES))
list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
dirty_list = &bdi->wb.b_dirty;
else
list_move(&inode->i_wb_list,
&bdi->wb.b_dirty_time);
dirty_list = &bdi->wb.b_dirty_time;
wakeup_bdi = inode_wb_list_move_locked(inode, &bdi->wb,
dirty_list);
spin_unlock(&bdi->wb.list_lock);
trace_writeback_dirty_inode_enqueue(inode);
if (wakeup_bdi)
/*
* If this is the first dirty inode for this bdi,
* we have to wake-up the corresponding bdi thread
* to make sure background write-back happens
* later.
*/
if (bdi_cap_writeback_dirty(bdi) && wakeup_bdi)
wb_wakeup_delayed(&bdi->wb);
return;
}
......
......@@ -21,6 +21,7 @@ struct dentry;
enum wb_state {
WB_registered, /* bdi_register() was done */
WB_writeback_running, /* Writeback is in progress */
WB_has_dirty_io, /* Dirty inodes on ->b_{dirty|io|more_io} */
};
enum wb_congested_state {
......
......@@ -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,
......
......@@ -256,7 +256,7 @@ static int __init default_bdi_init(void)
}
subsys_initcall(default_bdi_init);
int bdi_has_dirty_io(struct backing_dev_info *bdi)
bool bdi_has_dirty_io(struct backing_dev_info *bdi)
{
return wb_has_dirty_io(&bdi->wb);
}
......
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