fs: use percpu counter for nr_dentry and nr_dentry_unused

The nr_dentry stat is a globally touched cacheline and atomic operation
twice over the lifetime of a dentry. It is used for the benfit of userspace
only. Turn it into a per-cpu counter and always decrement it in d_free instead
of doing various batching operations to reduce lock hold times in the callers.

Based on an earlier patch from Nick Piggin <npiggin@suse.de>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 99a510cbfbb..8b77ff5c502 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1377,7 +1377,7 @@ static struct ctl_table fs_table[] = {
                 .data           = &dentry_stat,
                 .maxlen         = 6*sizeof(int),
                 .mode           = 0444,
-                .proc_handler   = proc_dointvec,
+                .proc_handler   = proc_nr_dentry,
         },
         {
                 .procname       = "overflowuid",