[PATCH V4 6/7] loop: use xarray to store workers

Ming Lei
2021-08-06T08:04:24Z

css->id is unique in io controller wide, so replace rbtree with xarray
for querying/storing 'blkcg_css' by using css->id as key, then code is
simplified a lot.

Acked-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/block/loop.c | 45 ++++++++++++++++++++++----------------------
drivers/block/loop.h | 3 ++-
2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c322d6468ee7..f77fa9e5eb49 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -971,7 +971,6 @@ static void loop_config_discard(struct loop_device *lo)
}

struct loop_worker {
- struct rb_node rb_node;
struct work_struct work;
struct list_head cmd_list;
struct list_head idle_list;
@@ -998,6 +997,10 @@ static struct cgroup_subsys_state *loop_rq_blkcg_css(struct loop_cmd *cmd)
return &blkcg->css;
return NULL;
}
+static int loop_blkcg_css_id(struct cgroup_subsys_state *css)
+{
+ return css->id;
+}
#else
static inline int queue_on_root_worker(struct cgroup_subsys_state *css)
{
@@ -1007,6 +1010,10 @@ static struct cgroup_subsys_state *loop_rq_blkcg_css(struct loop_cmd *cmd)
{
return NULL;
}
+static int loop_blkcg_css_id(struct cgroup_subsys_state *css)
+{
+ return 0;
+}
#endif

static struct cgroup_subsys_state *loop_rq_get_memcg_css(
@@ -1019,35 +1026,23 @@ static struct cgroup_subsys_state *loop_rq_get_memcg_css(

static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
{
- struct rb_node **node = &(lo->worker_tree.rb_node), *parent = NULL;
- struct loop_worker *cur_worker, *worker = NULL;
+ struct loop_worker *worker = NULL;
struct work_struct *work;
struct list_head *cmd_list;
struct cgroup_subsys_state *blkcg_css = loop_rq_blkcg_css(cmd);
+ gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;

spin_lock(&lo->lo_work_lock);

if (queue_on_root_worker(blkcg_css))
goto queue_work;

- node = &lo->worker_tree.rb_node;
-
- while (*node) {
- parent = *node;
- cur_worker = container_of(*node, struct loop_worker, rb_node);
- if (cur_worker->blkcg_css == blkcg_css) {
- worker = cur_worker;
- break;
- } else if ((long)cur_worker->blkcg_css < (long)blkcg_css) {
- node = &(*node)->rb_left;
- } else {
- node = &(*node)->rb_right;
- }
- }
+ /* css->id is unique in each cgroup subsystem */
+ worker = xa_load(&lo->workers, loop_blkcg_css_id(blkcg_css));
if (worker)
goto queue_work;

- worker = kzalloc(sizeof(struct loop_worker), GFP_NOWAIT | __GFP_NOWARN);
+ worker = kzalloc(sizeof(*worker), gfp);
/*
* In the event we cannot allocate a worker, just queue on the
* rootcg worker and issue the I/O as the rootcg
@@ -1061,8 +1056,13 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
INIT_LIST_HEAD(&worker->cmd_list);
INIT_LIST_HEAD(&worker->idle_list);
worker->lo = lo;
- rb_link_node(&worker->rb_node, parent, node);
- rb_insert_color(&worker->rb_node, &lo->worker_tree);
+
+ if (xa_err(xa_store(&lo->workers, loop_blkcg_css_id(blkcg_css),
+ worker, gfp))) {
+ kfree(worker);
+ worker = NULL;
+ }
+
queue_work:
if (worker) {
/*
@@ -1218,7 +1218,7 @@ static void __loop_free_idle_workers(struct loop_device *lo, bool force)
LOOP_IDLE_WORKER_TIMEOUT))
break;
list_del(&worker->idle_list);
- rb_erase(&worker->rb_node, &lo->worker_tree);
+ xa_erase(&lo->workers, loop_blkcg_css_id(worker->blkcg_css));
css_put(worker->blkcg_css);
kfree(worker);
}
@@ -1314,7 +1314,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
INIT_WORK(&lo->rootcg_work, loop_rootcg_workfn);
INIT_LIST_HEAD(&lo->rootcg_cmd_list);
INIT_LIST_HEAD(&lo->idle_worker_list);
- lo->worker_tree = RB_ROOT;
+ xa_init(&lo->workers);
INIT_DELAYED_WORK(&lo->idle_work, loop_free_idle_workers);
lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
lo->lo_device = bdev;
@@ -1416,6 +1416,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
destroy_workqueue(lo->workqueue);
__loop_free_idle_workers(lo, true);
cancel_delayed_work_sync(&lo->idle_work);
+ xa_destroy(&lo->workers);

spin_lock_irq(&lo->lo_lock);
lo->lo_backing_file = NULL;
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index 9df889af1bcf..cab34da1e1bb 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -14,6 +14,7 @@
#include <linux/blk-mq.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
+#include <linux/xarray.h>
#include <uapi/linux/loop.h>

/* Possible states of device */
@@ -59,7 +60,7 @@ struct loop_device {
struct work_struct rootcg_work;
struct list_head rootcg_cmd_list;
struct list_head idle_worker_list;
- struct rb_root worker_tree;
+ struct xarray workers;
struct delayed_work idle_work;
bool use_dio;
bool sysfs_inited;
--
2.31.1