linux-kernel - [PATCH v3 2/5] fs/dcache: Report negative dentry number in dentry-state

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Message-Id: <1501266880-26288-3-git-send-email-longman@redhat.com>
Date:   Fri, 28 Jul 2017 14:34:37 -0400
From:   Waiman Long <longman@...hat.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Larry Woodman <lwoodman@...hat.com>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v3 2/5] fs/dcache: Report negative dentry number in dentry-state

The number of negative dentries currently in the system is now reported
in the /proc/sys/fs/dentry-state file.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 fs/dcache.c            | 16 +++++++++++++++-
 include/linux/dcache.h |  7 ++++---
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index ab10b96..fb7e041 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -135,6 +135,7 @@ struct dentry_stat_t dentry_stat = {
  */
 #define NEG_DENTRY_BATCH	(1 << 8)
 static long neg_dentry_percpu_limit __read_mostly;
+static long neg_dentry_nfree_init __read_mostly; /* Free pool initial value */
 static struct {
 	raw_spinlock_t nfree_lock;
 	long nfree;			/* Negative dentry free pool */
@@ -176,11 +177,23 @@ static long get_nr_dentry_unused(void)
 	return sum < 0 ? 0 : sum;
 }
 
+static long get_nr_dentry_neg(void)
+{
+	int i;
+	long sum = 0;
+
+	for_each_possible_cpu(i)
+		sum += per_cpu(nr_dentry_neg, i);
+	sum += neg_dentry_nfree_init - ndblk.nfree;
+	return sum < 0 ? 0 : sum;
+}
+
 int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
 		   size_t *lenp, loff_t *ppos)
 {
 	dentry_stat.nr_dentry = get_nr_dentry();
 	dentry_stat.nr_unused = get_nr_dentry_unused();
+	dentry_stat.nr_negative = get_nr_dentry_neg();
 	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 }
 #endif
@@ -3739,7 +3752,8 @@ static void __init neg_dentry_init(void)
 	raw_spin_lock_init(&ndblk.nfree_lock);
 
 	/* 20% in global pool & 80% in percpu free */
-	ndblk.nfree = totalram_pages * nr_dentry_page * neg_dentry_pc / 500;
+	ndblk.nfree = neg_dentry_nfree_init
+		    = totalram_pages * nr_dentry_page * neg_dentry_pc / 500;
 	cnt = ndblk.nfree * 4 / num_possible_cpus();
 	if (unlikely(cnt < 2 * NEG_DENTRY_BATCH))
 		cnt = 2 * NEG_DENTRY_BATCH;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 5ffcc46..e42c8fc 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -63,9 +63,10 @@ struct qstr {
 struct dentry_stat_t {
 	long nr_dentry;
 	long nr_unused;
-	long age_limit;          /* age in seconds */
-	long want_pages;         /* pages requested by system */
-	long dummy[2];
+	long age_limit;		/* age in seconds */
+	long want_pages;	/* pages requested by system */
+	long nr_negative;	/* # of negative dentries */
+	long dummy;
 };
 extern struct dentry_stat_t dentry_stat;
 
-- 
1.8.3.1