sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming

So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.

Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.

To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:

	struct wait_queue_head::task_list	=> ::head
	struct wait_queue_entry::task_list	=> ::entry

For example, this code:

	rqw->wait.task_list.next != &wait->task_list

... is was pretty unclear (to me) what it's doing, while now it's written this way:

	rqw->wait.head.next != &wait->entry

... which makes it pretty clear that we are iterating a list until we see the head.

Other examples are:

	list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
	list_for_each_entry(wq, &fence->wait.task_list, task_list) {

... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:

	list_for_each_entry_safe(pos, next, &x->head, entry) {
	list_for_each_entry(wq, &fence->wait.head, entry) {

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 6 insertions, 6 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a083f95e04b1..121aa1dbb192 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -933,7 +933,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode, int fla
 
 	hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
 
-	list_del(&wait->task_list);
+	list_del(&wait->entry);
 	clear_bit_unlock(BLK_MQ_S_TAG_WAITING, &hctx->state);
 	blk_mq_run_hw_queue(hctx, true);
 	return 1;
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 5f3a37c2784c..6a9a0f03a67b 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -520,7 +520,7 @@ static inline bool may_queue(struct rq_wb *rwb, struct rq_wait *rqw,
 	 * in line to be woken up, wait for our turn.
 	 */
 	if (waitqueue_active(&rqw->wait) &&
-	    rqw->wait.task_list.next != &wait->task_list)
+	    rqw->wait.head.next != &wait->entry)
 		return false;
 
 	return atomic_inc_below(&rqw->inflight, get_limit(rwb, rw));
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index b95d6bd714c0..9bf1484365b2 100644
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -385,7 +385,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 
 	for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 		INIT_LIST_HEAD(&khd->rqs[i]);
-		INIT_LIST_HEAD(&khd->domain_wait[i].task_list);
+		INIT_LIST_HEAD(&khd->domain_wait[i].entry);
 		atomic_set(&khd->wait_index[i], 0);
 	}
 
@@ -512,7 +512,7 @@ static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
 {
 	struct blk_mq_hw_ctx *hctx = READ_ONCE(wait->private);
 
-	list_del_init(&wait->task_list);
+	list_del_init(&wait->entry);
 	blk_mq_run_hw_queue(hctx, true);
 	return 1;
 }
@@ -536,7 +536,7 @@ static int kyber_get_domain_token(struct kyber_queue_data *kqd,
 	 * run when one becomes available. Note that this is serialized on
 	 * khd->lock, but we still need to be careful about the waker.
 	 */
-	if (list_empty_careful(&wait->task_list)) {
+	if (list_empty_careful(&wait->entry)) {
 		init_waitqueue_func_entry(wait, kyber_domain_wake);
 		wait->private = hctx;
 		ws = sbq_wait_ptr(domain_tokens,
@@ -736,7 +736,7 @@ static int kyber_##name##_waiting_show(void *data, struct seq_file *m)	\
 	struct kyber_hctx_data *khd = hctx->sched_data;			\
 	wait_queue_entry_t *wait = &khd->domain_wait[domain];		\
 									\
-	seq_printf(m, "%d\n", !list_empty_careful(&wait->task_list));	\
+	seq_printf(m, "%d\n", !list_empty_careful(&wait->entry));	\
 	return 0;							\
 }
 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)