On Fri, May 08, 2020 at 05:18:56PM -0700, Bart Van Assche wrote:
> On 2020-05-08 16:32, Bart Van Assche wrote:
> > On 2020-05-04 19:09, Ming Lei wrote:
> >> @@ -310,19 +313,30 @@ static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
> >> /**
> >> * blk_mq_all_tag_busy_iter - iterate over all started requests in a tag map
> >> * @tags: Tag map to iterate over.
> >> - * @fn: Pointer to the function that will be called for each started
> >> - * request. @fn will be called as follows: @fn(rq, @priv,
> >> - * reserved) where rq is a pointer to a request. 'reserved'
> >> - * indicates whether or not @rq is a reserved request. Return
> >> - * true to continue iterating tags, false to stop.
> >> + * @fn: Pointer to the function that will be called for each request
> >> + * when .busy_rq_fn(rq) returns true. @fn will be called as
> >> + * follows: @fn(rq, @priv, reserved) where rq is a pointer to a
> >> + * request. 'reserved' indicates whether or not @rq is a reserved
> >> + * request. Return true to continue iterating tags, false to stop.
> >> + * @busy_rq_fn: Pointer to the function that will be called for each request,
> >> + * @busy_rq_fn's type is same with @fn. Only when @busy_rq_fn(rq,
> >> + * @priv, reserved) returns true, @fn will be called on this rq.
> >> * @priv: Will be passed as second argument to @fn.
> >> */
> >> -static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
> >> - busy_tag_iter_fn *fn, void *priv)
> >> +void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
> >> + busy_tag_iter_fn *fn, busy_rq_iter_fn *busy_rq_fn,
> >> + void *priv)
> >> {
> >
> > The name 'busy_rq_fn' is not ideal because it is named after one
> > specific use case, namely checking whether or not a request is busy (has
> > already been started). How about using the name 'pred_fn' ('pred' from
> > predicate because it controls whether the other function is called)?
> > Since only the context that passes 'fn' can know what data structure
> > 'priv' points to and since 'busy_rq_fn' is passed from another context,
> > can 'busy_rq_fn' even know what data 'priv' points at? Has it been
> > considered not to pass the 'priv' argument to 'busy_rq_fn'?
>
> Thinking further about this, another possible approach is not to modify
> blk_mq_all_tag_busy_iter() at all and to introduce a new function that
> iterates over all requests instead of only over busy requests. I think
> that approach will result in easier to read code than patch 5/11 because
> each of these request iteration functions will only accept a single
> callback function pointer. Additionally, that approach will make the
> following function superfluous (from patch 7/11):
>
> +static bool blk_mq_inflight_rq(struct request *rq, void *data,
> + bool reserved)
> +{
> + return rq->tag >= 0;
> +}
Fine, then we can save one callback, how about the following way?
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 586c9d6e904a..5e9c743d887b 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -257,6 +257,7 @@ struct bt_tags_iter_data {
busy_tag_iter_fn *fn;
void *data;
bool reserved;
+ bool iterate_all;
};
static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
@@ -274,8 +275,10 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
* test and set the bit before assining ->rqs[].
*/
rq = tags->rqs[bitnr];
- if (rq && blk_mq_request_started(rq))
- return iter_data->fn(rq, iter_data->data, reserved);
+ if (rq) {
+ if (iter_data->iterate_all || blk_mq_request_started(rq))
+ return iter_data->fn(rq, iter_data->data, reserved);
+ }
return true;
}
@@ -294,13 +297,15 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
* bitmap_tags member of struct blk_mq_tags.
*/
static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
- busy_tag_iter_fn *fn, void *data, bool reserved)
+ busy_tag_iter_fn *fn, void *data, bool reserved,
+ bool iterate_all)
{
struct bt_tags_iter_data iter_data = {
.tags = tags,
.fn = fn,
.data = data,
.reserved = reserved,
+ .iterate_all = iterate_all,
};
if (tags->rqs)
@@ -321,8 +326,30 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
busy_tag_iter_fn *fn, void *priv)
{
if (tags->nr_reserved_tags)
- bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
- bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
+ bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true,
+ false);
+ bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false, false);
+}
+
+/**
+ * blk_mq_all_tag_iter - iterate over all requests in a tag map
+ * @tags: Tag map to iterate over.
+ * @fn: Pointer to the function that will be called for each
+ * request. @fn will be called as follows: @fn(rq, @priv,
+ * reserved) where rq is a pointer to a request. 'reserved'
+ * indicates whether or not @rq is a reserved request. Return
+ * true to continue iterating tags, false to stop.
+ * @priv: Will be passed as second argument to @fn.
+ *
+ * It is the caller's responsility to check rq's state in @fn.
+ */
+void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+ void *priv)
+{
+ if (tags->nr_reserved_tags)
+ bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true,
+ true);
+ bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false, true);
}
/**
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 2b8321efb682..d19546e8246b 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -34,6 +34,8 @@ extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
void *priv);
+void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+ void *priv);
static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt,
struct blk_mq_hw_ctx *hctx)
thanks,
Ming
