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Subject[PATCH 07/11] fs/dcache: Add static key negative_reclaim_enable
Date
Add a static_key negative_reclaim_enable to optimize the default case
where negative dentry directory limit "dentry-dir-max" is not set.

Signed-off-by: Waiman Long <longman@redhat.com>
---
fs/dcache.c | 30 ++++++++++++++++++++++++++++--
kernel/sysctl.c | 3 ++-
2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index c5364c2ed5d8..149c0a6c1a6e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -32,6 +32,7 @@
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
#include <linux/list_lru.h>
+#include <linux/jump_label.h>
#include "internal.h"
#include "mount.h"

@@ -134,11 +135,13 @@ int dcache_dentry_dir_max_sysctl __read_mostly;
EXPORT_SYMBOL_GPL(dcache_dentry_dir_max_sysctl);

static LLIST_HEAD(negative_reclaim_list);
+static DEFINE_STATIC_KEY_FALSE(negative_reclaim_enable);
static void negative_reclaim_check(struct dentry *parent);
static void negative_reclaim_workfn(struct work_struct *work);
static DECLARE_WORK(negative_reclaim_work, negative_reclaim_workfn);

#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+proc_handler proc_dcache_dentry_dir_max;

/*
* Here we resort to our own counters instead of using generic per-cpu counters
@@ -188,6 +191,27 @@ int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
dentry_stat.nr_negative = get_nr_dentry_negative();
return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}
+
+/*
+ * Sysctl proc handler for dcache_dentry_dir_max_sysctl
+ */
+int proc_dcache_dentry_dir_max(struct ctl_table *ctl, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int old = dcache_dentry_dir_max_sysctl;
+ int ret;
+
+ ret = proc_dointvec_minmax(ctl, write, buffer, lenp, ppos);
+
+ if (!write || ret || (dcache_dentry_dir_max_sysctl == old))
+ return ret;
+
+ if (!old && dcache_dentry_dir_max_sysctl)
+ static_branch_enable(&negative_reclaim_enable);
+ else if (old && !dcache_dentry_dir_max_sysctl)
+ static_branch_disable(&negative_reclaim_enable);
+ return 0;
+}
#endif

/*
@@ -876,7 +900,8 @@ void dput(struct dentry *dentry)
if (likely(retain_dentry(dentry))) {
struct dentry *neg_parent = NULL;

- if (d_is_negative(dentry)) {
+ if (static_branch_unlikely(&negative_reclaim_enable) &&
+ d_is_negative(dentry)) {
neg_parent = dentry->d_parent;
rcu_read_lock();
}
@@ -886,7 +911,8 @@ void dput(struct dentry *dentry)
* Negative dentry reclaim check is only done when
* a negative dentry is being put into a LRU list.
*/
- if (neg_parent)
+ if (static_branch_unlikely(&negative_reclaim_enable) &&
+ neg_parent)
negative_reclaim_check(neg_parent);
return;
}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cd0a83ff1029..9a4b0a1376e8 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -119,6 +119,7 @@ extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
extern int sysctl_nr_trim_pages;
#endif
extern int dcache_dentry_dir_max_sysctl;
+extern proc_handler proc_dcache_dentry_dir_max;

/* Constants used for minimum and maximum */
#ifdef CONFIG_LOCKUP_DETECTOR
@@ -1956,7 +1957,7 @@ static struct ctl_table fs_table[] = {
.data = &dcache_dentry_dir_max_sysctl,
.maxlen = sizeof(dcache_dentry_dir_max_sysctl),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
+ .proc_handler = proc_dcache_dentry_dir_max,
.extra1 = &zero,
},
{ }
--
2.18.1
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