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Message-Id: <20171206004159.3755-35-willy@infradead.org>
Date: Tue, 5 Dec 2017 16:41:20 -0800
From: Matthew Wilcox <willy@...radead.org>
To: unlisted-recipients:; (no To-header on input)
Cc: Matthew Wilcox <mawilcox@...rosoft.com>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
Jens Axboe <axboe@...nel.dk>,
Rehas Sachdeva <aquannie@...il.com>, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-nilfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 34/73] mm: Convert cgroup writeback to XArray
From: Matthew Wilcox <mawilcox@...rosoft.com>
This is a fairly naive conversion, leaving in place the GFP_ATOMIC
allocation. By switching the locking around, we could use GFP_KERNEL
and probably simplify the error handling.
Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
include/linux/backing-dev-defs.h | 2 +-
include/linux/backing-dev.h | 2 +-
mm/backing-dev.c | 28 ++++++++++++++++------------
3 files changed, 18 insertions(+), 14 deletions(-)
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index bfe86b54f6c1..074a54aad33c 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -187,7 +187,7 @@ struct backing_dev_info {
struct bdi_writeback wb; /* the root writeback info for this bdi */
struct list_head wb_list; /* list of all wbs */
#ifdef CONFIG_CGROUP_WRITEBACK
- struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
+ struct xarray cgwb_xa; /* radix tree of active cgroup wbs */
struct rb_root cgwb_congested_tree; /* their congested states */
#else
struct bdi_writeback_congested *wb_congested;
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 9038f6c1eeda..50f666d23527 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -271,7 +271,7 @@ static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi
if (!memcg_css->parent)
return &bdi->wb;
- wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ wb = xa_load(&bdi->cgwb_xa, memcg_css->id);
/*
* %current's blkcg equals the effective blkcg of its memcg. No
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 84b2dc76f140..7aa2d893f929 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -417,8 +417,8 @@ static void wb_exit(struct bdi_writeback *wb)
#include <linux/memcontrol.h>
/*
- * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
- * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
+ * cgwb_lock protects bdi->cgwb_xa, bdi->cgwb_congested_tree,
+ * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_xa is also RCU
* protected.
*/
static DEFINE_SPINLOCK(cgwb_lock);
@@ -539,7 +539,7 @@ static void cgwb_kill(struct bdi_writeback *wb)
{
lockdep_assert_held(&cgwb_lock);
- WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
+ WARN_ON(xa_erase(&wb->bdi->cgwb_xa, wb->memcg_css->id) != wb);
list_del(&wb->memcg_node);
list_del(&wb->blkcg_node);
percpu_ref_kill(&wb->refcnt);
@@ -571,7 +571,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
/* look up again under lock and discard on blkcg mismatch */
spin_lock_irqsave(&cgwb_lock, flags);
- wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ wb = xa_load(&bdi->cgwb_xa, memcg_css->id);
if (wb && wb->blkcg_css != blkcg_css) {
cgwb_kill(wb);
wb = NULL;
@@ -615,13 +615,18 @@ static int cgwb_create(struct backing_dev_info *bdi,
if (test_bit(WB_registered, &bdi->wb.state) &&
blkcg_cgwb_list->next && memcg_cgwb_list->next) {
/* we might have raced another instance of this function */
- ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
- if (!ret) {
+ void *curr = xa_cmpxchg(&bdi->cgwb_xa, memcg_css->id, NULL,
+ wb, GFP_ATOMIC);
+ if (!curr) {
list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
list_add(&wb->memcg_node, memcg_cgwb_list);
list_add(&wb->blkcg_node, blkcg_cgwb_list);
css_get(memcg_css);
css_get(blkcg_css);
+ } else if (IS_ERR(curr)) {
+ ret = PTR_ERR(curr);
+ } else {
+ ret = -EEXIST;
}
}
spin_unlock_irqrestore(&cgwb_lock, flags);
@@ -682,7 +687,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
do {
rcu_read_lock();
- wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+ wb = xa_load(&bdi->cgwb_xa, memcg_css->id);
if (wb) {
struct cgroup_subsys_state *blkcg_css;
@@ -704,7 +709,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
{
int ret;
- INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
+ xa_init(&bdi->cgwb_xa);
bdi->cgwb_congested_tree = RB_ROOT;
ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
@@ -717,15 +722,14 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
{
- struct radix_tree_iter iter;
- void **slot;
+ XA_STATE(xas, &bdi->cgwb_xa, 0);
struct bdi_writeback *wb;
WARN_ON(test_bit(WB_registered, &bdi->wb.state));
spin_lock_irq(&cgwb_lock);
- radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
- cgwb_kill(*slot);
+ xas_for_each(&xas, wb, ULONG_MAX)
+ cgwb_kill(wb);
while (!list_empty(&bdi->wb_list)) {
wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
--
2.15.0
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