From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk, jack@suse.cz, hannes@cmpxchg.org,
mhocko@kernel.org, vdavydov.dev@gmail.com
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org,
Tejun Heo <tj@kernel.org>
Subject: [PATCH 3/5] writeback: Separate out wb_get_lookup() from wb_get_create()
Date: Mon, 26 Aug 2019 09:06:54 -0700 [thread overview]
Message-ID: <20190826160656.870307-4-tj@kernel.org> (raw)
In-Reply-To: <20190826160656.870307-1-tj@kernel.org>
Separate out wb_get_lookup() which doesn't try to create one if there
isn't already one from wb_get_create(). This will be used by later
patches.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
---
include/linux/backing-dev.h | 2 ++
mm/backing-dev.c | 55 +++++++++++++++++++++++++------------
2 files changed, 39 insertions(+), 18 deletions(-)
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 84cdcfbc763f..97967ce06de3 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -230,6 +230,8 @@ static inline int bdi_sched_wait(void *word)
struct bdi_writeback_congested *
wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
void wb_congested_put(struct bdi_writeback_congested *congested);
+struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
+ struct cgroup_subsys_state *memcg_css);
struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
struct cgroup_subsys_state *memcg_css,
gfp_t gfp);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 612aa7c5ddbd..d9daa3e422d0 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -618,13 +618,12 @@ static int cgwb_create(struct backing_dev_info *bdi,
}
/**
- * wb_get_create - get wb for a given memcg, create if necessary
+ * wb_get_lookup - get wb for a given memcg
* @bdi: target bdi
* @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
- * @gfp: allocation mask to use
*
- * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
- * create one. The returned wb has its refcount incremented.
+ * Try to get the wb for @memcg_css on @bdi. The returned wb has its
+ * refcount incremented.
*
* This function uses css_get() on @memcg_css and thus expects its refcnt
* to be positive on invocation. IOW, rcu_read_lock() protection on
@@ -641,6 +640,39 @@ static int cgwb_create(struct backing_dev_info *bdi,
* each lookup. On mismatch, the existing wb is discarded and a new one is
* created.
*/
+struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
+ struct cgroup_subsys_state *memcg_css)
+{
+ struct bdi_writeback *wb;
+
+ if (!memcg_css->parent)
+ return &bdi->wb;
+
+ rcu_read_lock();
+ wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ if (wb) {
+ struct cgroup_subsys_state *blkcg_css;
+
+ /* see whether the blkcg association has changed */
+ blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
+ if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
+ wb = NULL;
+ css_put(blkcg_css);
+ }
+ rcu_read_unlock();
+
+ return wb;
+}
+
+/**
+ * wb_get_create - get wb for a given memcg, create if necessary
+ * @bdi: target bdi
+ * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
+ * @gfp: allocation mask to use
+ *
+ * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
+ * create one. See wb_get_lookup() for more details.
+ */
struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
struct cgroup_subsys_state *memcg_css,
gfp_t gfp)
@@ -653,20 +685,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
return &bdi->wb;
do {
- rcu_read_lock();
- wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
- if (wb) {
- struct cgroup_subsys_state *blkcg_css;
-
- /* see whether the blkcg association has changed */
- blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
- &io_cgrp_subsys);
- if (unlikely(wb->blkcg_css != blkcg_css ||
- !wb_tryget(wb)))
- wb = NULL;
- css_put(blkcg_css);
- }
- rcu_read_unlock();
+ wb = wb_get_lookup(bdi, memcg_css);
} while (!wb && !cgwb_create(bdi, memcg_css, gfp));
return wb;
--
2.17.1
next prev parent reply other threads:[~2019-08-26 16:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 16:06 [PATCHSET v3] writeback, memcg: Implement foreign inode flushing Tejun Heo
2019-08-26 16:06 ` [PATCH 1/5] writeback: Generalize and expose wb_completion Tejun Heo
2019-08-26 16:06 ` [PATCH 2/5] bdi: Add bdi->id Tejun Heo
2019-08-26 16:06 ` Tejun Heo [this message]
2019-08-26 16:06 ` [PATCH 4/5] writeback, memcg: Implement cgroup_writeback_by_id() Tejun Heo
2019-08-26 16:06 ` [PATCH 5/5] writeback, memcg: Implement foreign dirty flushing Tejun Heo
2019-08-27 14:47 ` Jan Kara
2019-08-27 15:23 ` [PATCHSET v3] writeback, memcg: Implement foreign inode flushing Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2019-08-15 19:56 [PATCHSET v2] " Tejun Heo
2019-08-15 19:58 ` [PATCH 3/5] writeback: Separate out wb_get_lookup() from wb_get_create() Tejun Heo
2019-08-16 15:45 ` Jan Kara
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