Re: rpc.mountd high cpu usage

[Sander Klein <roedie@roedie.nl>]

Hi,

Thank you very much for this patch. I've added the ZFS magic and tested 
it on my nfs-utils-1.2.8 package and it looks like it fixes my issue.

Is there any chance this patch will be accepted upstream with the 
ZFS_SUPER_MAGIC as shown below?

Greets,

Sander

 From e4f5b38c87ef8d713c6d0a3169afaf1acc7e22c6 Mon Sep 17 00:00:00 2001
 From: Karel Zak <kzak@redhat.com>
Date: Mon, 6 Jan 2014 12:03:01 +0100
Subject: [PATCH] mountd: optimize libblkid usage

  * use get_uuid_blkdev() only first time for the path (it means
    that uuid_by_path() is called with type==0)

  * don't use libblkid for btrfs, network or pseudo filesystems

Note that the patch defines the fs type ID rather than include
<linux/magic.h> as this file seems incomplete and libc specific).

Signed-off-by: Karel Zak <kzak@redhat.com>
---
  utils/mountd/cache.c | 38 +++++++++++++++++++++++++++++++++++---
  1 file changed, 35 insertions(+), 3 deletions(-)

Index: nfs-utils-1.2.8/utils/mountd/cache.c
===================================================================
--- nfs-utils-1.2.8.orig/utils/mountd/cache.c	2013-05-02 
14:21:12.000000000 +0200
+++ nfs-utils-1.2.8/utils/mountd/cache.c	2014-01-07 20:46:55.799904557 
+0100
@@ -266,6 +266,27 @@
  	return 1;
  }

+
+/*
+ * Don't ask libblkid for these filesystems. Note that BTRF is ignored, 
because
+ * we generate the identifier from statfs->f_fsid. The rest are network 
or
+ * pseudo filesystems. (See <linux/magic.h> for the basic IDs.)
+ */
+static const long int nonblkid_filesystems[] = {
+	0x2fc12fc1,	/* ZFS_SUPER_MAGIC */
+	0x9123683E,	/* BTRFS_SUPER_MAGIC */
+	0xFF534D42,	/* CIFS_MAGIC_NUMBER */
+	0x1373,		/* DEVFS_SUPER_MAGIC */
+	0x73757245,	/* CODA_SUPER_MAGIC */
+	0x564C,		/* NCP_SUPER_MAGIC */
+	0x6969,		/* NFS_SUPER_MAGIC */
+	0x9FA0,		/* PROC_SUPER_MAGIC */
+	0x62656572,	/* SYSFS_MAGIC */
+	0x517B,		/* SMB_SUPER_MAGIC */
+	0x01021994,	/* TMPFS_SUPER_MAGIC */
+	0		/* last */
+};
+
  static int uuid_by_path(char *path, int type, size_t uuidlen, char 
*uuid)
  {
  	/* get a uuid for the filesystem found at 'path'.
@@ -297,12 +318,24 @@
  	 */
  	struct statfs64 st;
  	char fsid_val[17];
-	const char *blkid_val;
+	const char *blkid_val = NULL;
  	const char *val;
+	int rc;
+
+	rc = statfs64(path, &st);
+
+	if (type == 0 && rc == 0) {
+		const long int *bad;

-	blkid_val = get_uuid_blkdev(path);
+		for (bad = nonblkid_filesystems; *bad; bad++) {
+			if (*bad == st.f_type)
+				break;
+		}
+		if (*bad == 0)
+			blkid_val = get_uuid_blkdev(path);
+	}

-	if (statfs64(path, &st) == 0 &&
+	if (rc == 0 &&
  	    (st.f_fsid.__val[0] || st.f_fsid.__val[1]))
  		snprintf(fsid_val, 17, "%08x%08x",
  			 st.f_fsid.__val[0], st.f_fsid.__val[1]);