Most modern OSs have the ability to flag certain mounts as ones to

be ignored by default by the df(1) program.  This is used mostly to
avoid stat()-ing entries that do not represent "real" disk mount
points (such as those made by an automounter such as amd.)  It is
also useful not to have to stat() these entries because it takes
longer to report them that for other file systems, being that these
mount points are served by a user-level file server and resulting in
several context switches.  Worse, if the automounter is down
unexpectedly, a causal df(1) will hang in an interruptible way.

PR:		kern/9764
Submitted by:	Erez Zadok <ezk@cs.columbia.edu>

5 files changed, 21 insertions, 11 deletions

diff --git a/bin/df/df.1 b/bin/df/df.1
index 9c875dc..eb97ccc 100644
--- a/bin/df/df.1
+++ b/bin/df/df.1
@@ -40,7 +40,7 @@
 .Nd display free disk space
 .Sh SYNOPSIS
 .Nm df
-.Op Fl ikn
+.Op Fl aikn
 .Op Fl t Ar type
 .Op Ar file | Ar filesystem ...
 .Sh DESCRIPTION
@@ -59,6 +59,9 @@ option below).
 .Pp
 The following options are available:
 .Bl -tag -width Ds
+.It Fl a
+Show all mount points, including those that were mounted with the MNT_IGNORE
+flag.
 .It Fl i
 Include statistics on the number of free inodes.
 .It Fl k
diff --git a/bin/df/df.c b/bin/df/df.c
index b402efd..ebe9d84 100644
--- a/bin/df/df.c
+++ b/bin/df/df.c
@@ -73,7 +73,7 @@ void	  prtstat __P((struct statfs *, int));
 int	  ufs_df __P((char *, int));
 void	  usage __P((void));
 
-int	iflag, nflag;
+int	aflag = 0, iflag, nflag;
 struct	ufs_args mdev;
 
 int
@@ -88,8 +88,11 @@ main(argc, argv)
 	char *mntpt, *mntpath, **vfslist;
 
 	vfslist = NULL;
-	while ((ch = getopt(argc, argv, "iknt:")) != -1)
+	while ((ch = getopt(argc, argv, "aiknt:")) != -1)
 		switch (ch) {
+		case 'a':
+			aflag = 1;
+			break;
 		case 'i':
 			iflag = 1;
 			break;
@@ -130,8 +133,10 @@ main(argc, argv)
 					maxwidth = width;
 			}
 		}
-		for (i = 0; i < mntsize; i++)
-			prtstat(&mntbuf[i], maxwidth);
+		for (i = 0; i < mntsize; i++) {
+			if (aflag || (mntbuf[i].f_flags & MNT_IGNORE) == 0)
+				prtstat(&mntbuf[i], maxwidth);
+		}
 		exit(rv);
 	}
 
@@ -377,6 +382,6 @@ void
 usage()
 {
 	(void)fprintf(stderr,
-	    "usage: df [-ikn] [-t type] [file | filesystem ...]\n");
+	    "usage: df [-aikn] [-t type] [file | filesystem ...]\n");
 	exit(1);
 }
diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index 9e3efbb..c1f21e7 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -289,11 +289,11 @@ update:
 		mp->mnt_kern_flag |= MNTK_WANTRDWR;
 	mp->mnt_flag &=~ (MNT_NOSUID | MNT_NOEXEC | MNT_NODEV |
 	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME |
-	    MNT_NOSYMFOLLOW |
+	    MNT_NOSYMFOLLOW | MNT_IGNORE |
 	    MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
 	mp->mnt_flag |= SCARG(uap, flags) & (MNT_NOSUID | MNT_NOEXEC |
 	    MNT_NODEV | MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_FORCE |
-	    MNT_NOSYMFOLLOW |
+	    MNT_NOSYMFOLLOW | MNT_IGNORE |
 	    MNT_NOATIME | MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
 	/*
 	 * Mount the filesystem.
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 9e3efbb..c1f21e7 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -289,11 +289,11 @@ update:
 		mp->mnt_kern_flag |= MNTK_WANTRDWR;
 	mp->mnt_flag &=~ (MNT_NOSUID | MNT_NOEXEC | MNT_NODEV |
 	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME |
-	    MNT_NOSYMFOLLOW |
+	    MNT_NOSYMFOLLOW | MNT_IGNORE |
 	    MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
 	mp->mnt_flag |= SCARG(uap, flags) & (MNT_NOSUID | MNT_NOEXEC |
 	    MNT_NODEV | MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_FORCE |
-	    MNT_NOSYMFOLLOW |
+	    MNT_NOSYMFOLLOW | MNT_IGNORE |
 	    MNT_NOATIME | MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
 	/*
 	 * Mount the filesystem.
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index ad0ed65..4d6764d 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -149,6 +149,7 @@ struct mount {
 #define	MNT_QUOTA	0x00002000	/* quotas are enabled on filesystem */
 #define	MNT_ROOTFS	0x00004000	/* identifies the root filesystem */
 #define	MNT_USER	0x00008000	/* mounted by a user */
+#define	MNT_IGNORE	0x00800000	/* do not show entry in df */
 
 /*
  * Mask of flags that are visible to statfs()
@@ -162,7 +163,8 @@ struct mount {
 			MNT_DEFEXPORTED	| MNT_EXPORTANON| MNT_EXKERB	| \
 			MNT_LOCAL	| MNT_USER	| MNT_QUOTA	| \
 			MNT_ROOTFS	| MNT_NOATIME	| MNT_NOCLUSTERR| \
-			MNT_NOCLUSTERW	| MNT_SUIDDIR	| MNT_SOFTDEP	 \
+			MNT_NOCLUSTERW	| MNT_SUIDDIR	| MNT_SOFTDEP	| \
+			MNT_IGNORE \
 			/*	| MNT_EXPUBLIC */)
 /*
  * External filesystem command modifier flags.