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[PATCH 01/19] dcache: convert dentry_stat.nr_unused to per-cpu counters

To: glommer@xxxxxxxxxxxxx
Subject: [PATCH 01/19] dcache: convert dentry_stat.nr_unused to per-cpu counters
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 28 Nov 2012 10:14:28 +1100
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <1354058086-27937-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1354058086-27937-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

Before we split up the dcache_lru_lock, the unused dentry counter
needs to be made independent of the global dcache_lru_lock. Convert
it to per-cpu counters to do this.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/dcache.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 3a463d0..2fc0daa 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -118,6 +118,7 @@ struct dentry_stat_t dentry_stat = {
 };
 
 static DEFINE_PER_CPU(unsigned int, nr_dentry);
+static DEFINE_PER_CPU(unsigned int, nr_dentry_unused);
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
 static int get_nr_dentry(void)
@@ -129,10 +130,20 @@ static int get_nr_dentry(void)
        return sum < 0 ? 0 : sum;
 }
 
+static int get_nr_dentry_unused(void)
+{
+       int i;
+       int sum = 0;
+       for_each_possible_cpu(i)
+               sum += per_cpu(nr_dentry_unused, i);
+       return sum < 0 ? 0 : sum;
+}
+
 int proc_nr_dentry(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();
        return proc_dointvec(table, write, buffer, lenp, ppos);
 }
 #endif
@@ -312,7 +323,7 @@ static void dentry_lru_add(struct dentry *dentry)
                spin_lock(&dcache_lru_lock);
                list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
                dentry->d_sb->s_nr_dentry_unused++;
-               dentry_stat.nr_unused++;
+               this_cpu_inc(nr_dentry_unused);
                spin_unlock(&dcache_lru_lock);
        }
 }
@@ -322,7 +333,7 @@ static void __dentry_lru_del(struct dentry *dentry)
        list_del_init(&dentry->d_lru);
        dentry->d_flags &= ~DCACHE_SHRINK_LIST;
        dentry->d_sb->s_nr_dentry_unused--;
-       dentry_stat.nr_unused--;
+       this_cpu_dec(nr_dentry_unused);
 }
 
 /*
@@ -360,7 +371,7 @@ static void dentry_lru_move_list(struct dentry *dentry, 
struct list_head *list)
        if (list_empty(&dentry->d_lru)) {
                list_add_tail(&dentry->d_lru, list);
                dentry->d_sb->s_nr_dentry_unused++;
-               dentry_stat.nr_unused++;
+               this_cpu_inc(nr_dentry_unused);
        } else {
                list_move_tail(&dentry->d_lru, list);
        }
-- 
1.7.10

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