autofs: add ignore mount option

Add an autofs file system mount option that can be used to provide a
generic indicator to applications that the mount entry should be ignored
when displaying mount information.

In other OSes that provide autofs and that provide a mount list to user
space based on the kernel mount list a no-op mount option ("ignore" is
the one use on the most common OS) is allowed so that autofs file system
users can optionally use it.

The idea is that it be used by user space programs to exclude autofs
mounts from consideration when reading the mounts list.

Prior to the change to link /etc/mtab to /proc/self/mounts all I needed
to do to achieve this was to use mount(2) and not update the mtab but
now that no longer works.

I know the symlinking happened a long time ago and I considered doing
this then but, at the time I couldn't remember the commonly used option
name and thought persuading the various utility maintainers would be too
hard.

But now I have a RHEL request to do this for compatibility for a widely
used product so I want to go ahead with it and try and enlist the help
of some utility package maintainers.

Clearly, without the option nothing can be done so it's at least a
start.

Link: http://lkml.kernel.org/r/154725123970.11260.6113771566924907275.stgit@pluto-themaw-net
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/autofs/autofs_i.h b/fs/autofs/autofs_i.h
index 3e59f0ed777bff66542a32cda86e2f90b1a821ef..b735f2b1e462073bf0125f62e93b41c61e900b94 100644 (file)
--- a/fs/autofs/autofs_i.h
+++ b/fs/autofs/autofs_i.h
@@ -105,6 +105,7 @@ struct autofs_wait_queue {
 
 #define AUTOFS_SBI_CATATONIC   0x0001
 #define AUTOFS_SBI_STRICTEXPIRE 0x0002
+#define AUTOFS_SBI_IGNORE      0x0004
 
 struct autofs_sb_info {
        u32 magic;

diff --git a/fs/autofs/inode.c b/fs/autofs/inode.c
index 078992eee299d0861236518643ee164f838e1e2a..8647ecaa89fc6e441a6a8fac335c014b7892d3c7 100644 (file)
--- a/fs/autofs/inode.c
+++ b/fs/autofs/inode.c
@@ -89,6 +89,8 @@ static int autofs_show_options(struct seq_file *m, struct dentry *root)
                seq_printf(m, ",indirect");
        if (sbi->flags & AUTOFS_SBI_STRICTEXPIRE)
                seq_printf(m, ",strictexpire");
+       if (sbi->flags & AUTOFS_SBI_IGNORE)
+               seq_printf(m, ",ignore");
 #ifdef CONFIG_CHECKPOINT_RESTORE
        if (sbi->pipe)
                seq_printf(m, ",pipe_ino=%ld", file_inode(sbi->pipe)->i_ino);
@@ -111,7 +113,8 @@ static const struct super_operations autofs_sops = {
 };
 
 enum {Opt_err, Opt_fd, Opt_uid, Opt_gid, Opt_pgrp, Opt_minproto, Opt_maxproto,
-       Opt_indirect, Opt_direct, Opt_offset, Opt_strictexpire};
+       Opt_indirect, Opt_direct, Opt_offset, Opt_strictexpire,
+       Opt_ignore};
 
 static const match_table_t tokens = {
        {Opt_fd, "fd=%u"},
@@ -124,6 +127,7 @@ static const match_table_t tokens = {
        {Opt_direct, "direct"},
        {Opt_offset, "offset"},
        {Opt_strictexpire, "strictexpire"},
+       {Opt_ignore, "ignore"},
        {Opt_err, NULL}
 };
 
@@ -206,6 +210,9 @@ static int parse_options(char *options,
                case Opt_strictexpire:
                        sbi->flags |= AUTOFS_SBI_STRICTEXPIRE;
                        break;
+               case Opt_ignore:
+                       sbi->flags |= AUTOFS_SBI_IGNORE;
+                       break;
                default:
                        return 1;
                }

diff --git a/include/uapi/linux/auto_fs.h b/include/uapi/linux/auto_fs.h
index 082119630b49c2575512f7c7a876b4feff67c10b..1f7925afad2dc976634bb047e835ecf9c5e3e630 100644 (file)
--- a/include/uapi/linux/auto_fs.h
+++ b/include/uapi/linux/auto_fs.h
@@ -23,7 +23,7 @@
 #define AUTOFS_MIN_PROTO_VERSION       3
 #define AUTOFS_MAX_PROTO_VERSION       5
 
-#define AUTOFS_PROTO_SUBVERSION                4
+#define AUTOFS_PROTO_SUBVERSION                5
 
 /*
  * The wait_queue_token (autofs_wqt_t) is part of a structure which is passed