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authorTejun Heo <tj@kernel.org>2019-08-26 19:06:53 +0300
committerJens Axboe <axboe@kernel.dk>2019-08-27 18:22:38 +0300
commit34f8fe501f0624de115d087680c84000b5d9abc9 (patch)
tree7c21102bb603a5ac0519fcfded63f9df89c25736 /mm/backing-dev.c
parent5b9cce4c7eb0696558dfd4946074ae1fb9d8f05d (diff)
downloadlinux-34f8fe501f0624de115d087680c84000b5d9abc9.tar.xz
bdi: Add bdi->id
There currently is no way to universally identify and lookup a bdi without holding a reference and pointer to it. This patch adds an non-recycling bdi->id and implements bdi_get_by_id() which looks up bdis by their ids. This will be used by memcg foreign inode flushing. I left bdi_list alone for simplicity and because while rb_tree does support rcu assignment it doesn't seem to guarantee lossless walk when walk is racing aginst tree rebalance operations. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm/backing-dev.c')
-rw-r--r--mm/backing-dev.c65
1 files changed, 63 insertions, 2 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index e8e89158adec..612aa7c5ddbd 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/wait.h>
+#include <linux/rbtree.h>
#include <linux/backing-dev.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
@@ -22,10 +23,12 @@ EXPORT_SYMBOL_GPL(noop_backing_dev_info);
static struct class *bdi_class;
/*
- * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
- * locking.
+ * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
+ * reader side locking.
*/
DEFINE_SPINLOCK(bdi_lock);
+static u64 bdi_id_cursor;
+static struct rb_root bdi_tree = RB_ROOT;
LIST_HEAD(bdi_list);
/* bdi_wq serves all asynchronous writeback tasks */
@@ -859,9 +862,58 @@ struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
}
EXPORT_SYMBOL(bdi_alloc_node);
+static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
+{
+ struct rb_node **p = &bdi_tree.rb_node;
+ struct rb_node *parent = NULL;
+ struct backing_dev_info *bdi;
+
+ lockdep_assert_held(&bdi_lock);
+
+ while (*p) {
+ parent = *p;
+ bdi = rb_entry(parent, struct backing_dev_info, rb_node);
+
+ if (bdi->id > id)
+ p = &(*p)->rb_left;
+ else if (bdi->id < id)
+ p = &(*p)->rb_right;
+ else
+ break;
+ }
+
+ if (parentp)
+ *parentp = parent;
+ return p;
+}
+
+/**
+ * bdi_get_by_id - lookup and get bdi from its id
+ * @id: bdi id to lookup
+ *
+ * Find bdi matching @id and get it. Returns NULL if the matching bdi
+ * doesn't exist or is already unregistered.
+ */
+struct backing_dev_info *bdi_get_by_id(u64 id)
+{
+ struct backing_dev_info *bdi = NULL;
+ struct rb_node **p;
+
+ spin_lock_bh(&bdi_lock);
+ p = bdi_lookup_rb_node(id, NULL);
+ if (*p) {
+ bdi = rb_entry(*p, struct backing_dev_info, rb_node);
+ bdi_get(bdi);
+ }
+ spin_unlock_bh(&bdi_lock);
+
+ return bdi;
+}
+
int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
{
struct device *dev;
+ struct rb_node *parent, **p;
if (bdi->dev) /* The driver needs to use separate queues per device */
return 0;
@@ -877,7 +929,15 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
set_bit(WB_registered, &bdi->wb.state);
spin_lock_bh(&bdi_lock);
+
+ bdi->id = ++bdi_id_cursor;
+
+ p = bdi_lookup_rb_node(bdi->id, &parent);
+ rb_link_node(&bdi->rb_node, parent, p);
+ rb_insert_color(&bdi->rb_node, &bdi_tree);
+
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
+
spin_unlock_bh(&bdi_lock);
trace_writeback_bdi_register(bdi);
@@ -918,6 +978,7 @@ EXPORT_SYMBOL(bdi_register_owner);
static void bdi_remove_from_list(struct backing_dev_info *bdi)
{
spin_lock_bh(&bdi_lock);
+ rb_erase(&bdi->rb_node, &bdi_tree);
list_del_rcu(&bdi->bdi_list);
spin_unlock_bh(&bdi_lock);