[autofs4 patch] Use /proc/mounts instead of /etc/mtab

[autofs4 patch] Use /proc/mounts instead of /etc/mtab

[Jeff Moyer]

Hi, Ian, list,

Here is a patch to consult /proc/mounts instead of /etc/mtab when
deciding if a path has already been mounted.  The problem with using
/etc/mtab, as you know, is that it sometimes does not get updated.  We
know that /proc/mounts will always be right, so why not use it?

The patch will determine if /proc/mounts is available at run-time, and
so will continue to work in the event that proc isn't available.

Comments welcome.

-Jeff

diff --git a/daemon/automount.c b/daemon/automount.c
index c09eaf6..766c472 100644
--- a/daemon/automount.c
+++ b/daemon/automount.c
@@ -333,7 +333,7 @@ static int umount_multi(const char *path
 
 	debug("umount_multi: path=%s incl=%d\n", path, incl);
 
-	mntlist = get_mnt_list(_PATH_MOUNTED, path, incl);
+	mntlist = get_mnt_list(path_mounted, path, incl);
 
 	if (!mntlist) {
 		warn("umount_multi: no mounts found under %s", path);
@@ -445,7 +445,7 @@ static int mount_autofs(char *path)
 	struct stat st;
 	int len;
 
-	if ((ap.state != ST_INIT) || is_mounted(_PATH_MOUNTED, path)) {
+	if ((ap.state != ST_INIT) || is_mounted(path_mounted, path)) {
 		/* This can happen if an autofs process is already running*/
 		error("mount_autofs: already mounted");
 		return -1;
@@ -1844,6 +1844,16 @@ int handle_mounts(char *path)
 	return 0;
 }
 
+void init_path_mounted(void)
+{
+	struct stat st;
+
+	if (stat(PROC_MOUNTS, &st) == 0)
+		path_mounted = PROC_MOUNTS;
+	else
+		path_mounted = _PATH_MOUNTED;
+}
+
 int main(int argc, char *argv[])
 {
 	char *path, *map, *mapfmt;
@@ -1928,6 +1938,8 @@ int main(int argc, char *argv[])
 	if (!dumpmap)
 		become_daemon();
 
+	init_path_mounted();
+
 	path = argv[0];
 	map = argv[1];
 	mapargv = (const char **) &argv[2];
diff --git a/daemon/spawn.c b/daemon/spawn.c
index 53887f9..b7e1511 100644
--- a/daemon/spawn.c
+++ b/daemon/spawn.c
@@ -119,7 +119,7 @@ void discard_pending(int sig)
  */
 int signal_children(int sig)
 {
-	struct mnt_list *mnts = get_mnt_list(_PATH_MOUNTED, "/", 0);
+	struct mnt_list *mnts = get_mnt_list(path_mounted, "/", 0);
 	struct mnt_list *next;
 	pid_t pgrp = getpgrp();
 	int ret = -1;
diff --git a/include/automount.h b/include/automount.h
index 14ec07b..c5f4707 100644
--- a/include/automount.h
+++ b/include/automount.h
@@ -40,6 +40,7 @@ #endif
 #define AUTOFS_SUPER_MAGIC 0x00000187L
 
 #define DEFAULT_TIMEOUT (5*60)			/* 5 minutes */
+#define PROC_MOUNTS	"/proc/mounts"
 #define AUTOFS_LOCK	"/var/lock/autofs"	/* To serialize access to mount */
 #define MOUNTED_LOCK	_PATH_MOUNTED "~"	/* mounts' lock file */
 #define MTAB_NOTUPDATED 0x1000			/* mtab succeded but not updated */
@@ -121,6 +122,7 @@ struct autofs_point {
 };
 
 extern struct autofs_point ap; 
+const char *path_mounted;
 
 /* Standard function used by daemon or modules */
 
diff --git a/lib/cache.c b/lib/cache.c
index 0f71fe2..c774dc0 100644
--- a/lib/cache.c
+++ b/lib/cache.c
@@ -268,7 +268,7 @@ int cache_delete(const char *root, const
 	if (!path)
 		return CHE_FAIL;
 
-	if (is_mounted(_PATH_MOUNTED, path)) {
+	if (is_mounted(path_mounted, path)) {
 		free(path);
 		return CHE_FAIL;
 	}
@@ -439,7 +439,7 @@ int cache_ghost(const char *root, int gh
 				break;
 
 			case LKP_MOUNT:
-				if (!is_mounted(_PATH_MOUNTED, gc.direct_base)) {
+				if (!is_mounted(path_mounted, gc.direct_base)) {
 					debug("cache_ghost: attempting to mount map, "
 					      "key %s",
 					      gc.direct_base);
diff --git a/lib/mounts.c b/lib/mounts.c
index 1e40fc1..1dacf14 100644
--- a/lib/mounts.c
+++ b/lib/mounts.c
@@ -294,7 +294,7 @@ int contained_in_local_fs(const char *pa
 	if (!path || !pathlen || pathlen > PATH_MAX)
 		return 0;
 
-	mnts = get_mnt_list(_PATH_MOUNTED, "/", 1);
+	mnts = get_mnt_list(path_mounted, "/", 1);
 	if (!mnts)
 		return 0;
 
@@ -309,13 +309,15 @@ int contained_in_local_fs(const char *pa
 			rv = statfs(this->path, &fs);
 			if (rv != -1 && fs.f_type == AUTOFS_SUPER_MAGIC)
 				ret = 1;
+			/* What is the below testing?  --JEM */
 			else if (this->fs_name[0] == '/') {
 				if (strlen(this->fs_name) > 1) {
 					if (this->fs_name[1] != '/')
 						ret = 1;
 				} else
 					ret = 1;
-			}
+			} else if (!strncmp(this->fs_name, "rootfs", 6))
+				ret = 1;
 			break;
 		}
 	}
@@ -357,7 +359,7 @@ int allow_owner_mount(const char *path)
 	struct mntent ent;
 	int ret = 0;
 
-	if (getuid() || is_mounted(_PATH_MOUNTED, path))
+	if (getuid() || is_mounted(path_mounted, path))
 		return 0;
 
 	if (find_mntent(_PATH_MNTTAB, path, &ent)) {
diff --git a/modules/mount_autofs.c b/modules/mount_autofs.c
index f0edb0a..08ae5f1 100644
--- a/modules/mount_autofs.c
+++ b/modules/mount_autofs.c
@@ -71,7 +71,7 @@ int mount_mount(const char *root, const 
 	debug(MODPREFIX "fullpath=%s what=%s options=%s",
 		  fullpath, what, options);
 
-	if (is_mounted(_PATH_MOUNTED, fullpath)) {
+	if (is_mounted(path_mounted, fullpath)) {
 		error(MODPREFIX 
 		 "warning: about to mount over %s, continuing", fullpath);
 		return 0;
diff --git a/modules/mount_bind.c b/modules/mount_bind.c
index 20ab7bf..fbf1546 100644
--- a/modules/mount_bind.c
+++ b/modules/mount_bind.c
@@ -121,7 +121,7 @@ int mount_mount(const char *root, const 
 		if (!status)
 			existed = 0;
 
-		if (is_mounted(_PATH_MOUNTED, fullpath)) {
+		if (is_mounted(path_mounted, fullpath)) {
 			error(MODPREFIX 
 			  "warning: %s is already mounted", fullpath);
 			return 0;
diff --git a/modules/mount_ext2.c b/modules/mount_ext2.c
index 38d67bf..b2efb96 100644
--- a/modules/mount_ext2.c
+++ b/modules/mount_ext2.c
@@ -69,7 +69,7 @@ int mount_mount(const char *root, const 
 	if (!status)
 		existed = 0;
 
-	if (is_mounted(_PATH_MOUNTED, fullpath)) {
+	if (is_mounted(path_mounted, fullpath)) {
 		error(MODPREFIX 
 		  "warning: %s is already mounted", fullpath);
 		return 0;
diff --git a/modules/mount_generic.c b/modules/mount_generic.c
index b3179d6..0fe6a3d 100644
--- a/modules/mount_generic.c
+++ b/modules/mount_generic.c
@@ -68,7 +68,7 @@ int mount_mount(const char *root, const 
 	if (!status)
 		existed = 0;
 
-	if (is_mounted(_PATH_MOUNTED, fullpath)) {
+	if (is_mounted(path_mounted, fullpath)) {
 		error(MODPREFIX "warning: %s is already mounted", fullpath);
 		return 0;
 	}
diff --git a/modules/mount_nfs.c b/modules/mount_nfs.c
index 3f9de50..c0546b9 100644
--- a/modules/mount_nfs.c
+++ b/modules/mount_nfs.c
@@ -596,7 +596,7 @@ #endif
 	if (!status)
 		existed = 0;
 
-	if (is_mounted(_PATH_MOUNTED, fullpath)) {
+	if (is_mounted(path_mounted, fullpath)) {
 		error(MODPREFIX 
 		      "warning: %s is already mounted", fullpath);
 		return 0;

Re: [autofs4 patch] Use /proc/mounts instead of /etc/mtab

[Ian Kent]

On Wed, 2006-11-08 at 22:03 -0500, Jeff Moyer wrote:
> Hi, Ian, list,
> 
> Here is a patch to consult /proc/mounts instead of /etc/mtab when
> deciding if a path has already been mounted.  The problem with using
> /etc/mtab, as you know, is that it sometimes does not get updated.  We
> know that /proc/mounts will always be right, so why not use it?

Good for v4 but keep in mind that in v5 /proc/mounts can have a lot of
entries compared to /etc/mtab. The cost of doing this can be quite high.
mount(8) must play well with mtab for v5.

> 
> The patch will determine if /proc/mounts is available at run-time, and
> so will continue to work in the event that proc isn't available.
> 
> Comments welcome.
> 
> -Jeff
> 
> diff --git a/daemon/automount.c b/daemon/automount.c
> index c09eaf6..766c472 100644
> --- a/daemon/automount.c
> +++ b/daemon/automount.c
> @@ -333,7 +333,7 @@ static int umount_multi(const char *path
>  
>  	debug("umount_multi: path=%s incl=%d\n", path, incl);
>  
> -	mntlist = get_mnt_list(_PATH_MOUNTED, path, incl);
> +	mntlist = get_mnt_list(path_mounted, path, incl);
>  
>  	if (!mntlist) {
>  		warn("umount_multi: no mounts found under %s", path);
> @@ -445,7 +445,7 @@ static int mount_autofs(char *path)
>  	struct stat st;
>  	int len;
>  
> -	if ((ap.state != ST_INIT) || is_mounted(_PATH_MOUNTED, path)) {
> +	if ((ap.state != ST_INIT) || is_mounted(path_mounted, path)) {
>  		/* This can happen if an autofs process is already running*/
>  		error("mount_autofs: already mounted");
>  		return -1;
> @@ -1844,6 +1844,16 @@ int handle_mounts(char *path)
>  	return 0;
>  }
>  
> +void init_path_mounted(void)
> +{
> +	struct stat st;
> +
> +	if (stat(PROC_MOUNTS, &st) == 0)
> +		path_mounted = PROC_MOUNTS;
> +	else
> +		path_mounted = _PATH_MOUNTED;
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	char *path, *map, *mapfmt;
> @@ -1928,6 +1938,8 @@ int main(int argc, char *argv[])
>  	if (!dumpmap)
>  		become_daemon();
>  
> +	init_path_mounted();
> +
>  	path = argv[0];
>  	map = argv[1];
>  	mapargv = (const char **) &argv[2];
> diff --git a/daemon/spawn.c b/daemon/spawn.c
> index 53887f9..b7e1511 100644
> --- a/daemon/spawn.c
> +++ b/daemon/spawn.c
> @@ -119,7 +119,7 @@ void discard_pending(int sig)
>   */
>  int signal_children(int sig)
>  {
> -	struct mnt_list *mnts = get_mnt_list(_PATH_MOUNTED, "/", 0);
> +	struct mnt_list *mnts = get_mnt_list(path_mounted, "/", 0);
>  	struct mnt_list *next;
>  	pid_t pgrp = getpgrp();
>  	int ret = -1;
> diff --git a/include/automount.h b/include/automount.h
> index 14ec07b..c5f4707 100644
> --- a/include/automount.h
> +++ b/include/automount.h
> @@ -40,6 +40,7 @@ #endif
>  #define AUTOFS_SUPER_MAGIC 0x00000187L
>  
>  #define DEFAULT_TIMEOUT (5*60)			/* 5 minutes */
> +#define PROC_MOUNTS	"/proc/mounts"
>  #define AUTOFS_LOCK	"/var/lock/autofs"	/* To serialize access to mount */
>  #define MOUNTED_LOCK	_PATH_MOUNTED "~"	/* mounts' lock file */
>  #define MTAB_NOTUPDATED 0x1000			/* mtab succeded but not updated */
> @@ -121,6 +122,7 @@ struct autofs_point {
>  };
>  
>  extern struct autofs_point ap; 
> +const char *path_mounted;
>  
>  /* Standard function used by daemon or modules */
>  
> diff --git a/lib/cache.c b/lib/cache.c
> index 0f71fe2..c774dc0 100644
> --- a/lib/cache.c
> +++ b/lib/cache.c
> @@ -268,7 +268,7 @@ int cache_delete(const char *root, const
>  	if (!path)
>  		return CHE_FAIL;
>  
> -	if (is_mounted(_PATH_MOUNTED, path)) {
> +	if (is_mounted(path_mounted, path)) {
>  		free(path);
>  		return CHE_FAIL;
>  	}
> @@ -439,7 +439,7 @@ int cache_ghost(const char *root, int gh
>  				break;
>  
>  			case LKP_MOUNT:
> -				if (!is_mounted(_PATH_MOUNTED, gc.direct_base)) {
> +				if (!is_mounted(path_mounted, gc.direct_base)) {
>  					debug("cache_ghost: attempting to mount map, "
>  					      "key %s",
>  					      gc.direct_base);
> diff --git a/lib/mounts.c b/lib/mounts.c
> index 1e40fc1..1dacf14 100644
> --- a/lib/mounts.c
> +++ b/lib/mounts.c
> @@ -294,7 +294,7 @@ int contained_in_local_fs(const char *pa
>  	if (!path || !pathlen || pathlen > PATH_MAX)
>  		return 0;
>  
> -	mnts = get_mnt_list(_PATH_MOUNTED, "/", 1);
> +	mnts = get_mnt_list(path_mounted, "/", 1);
>  	if (!mnts)
>  		return 0;
>  
> @@ -309,13 +309,15 @@ int contained_in_local_fs(const char *pa
>  			rv = statfs(this->path, &fs);
>  			if (rv != -1 && fs.f_type == AUTOFS_SUPER_MAGIC)
>  				ret = 1;
> +			/* What is the below testing?  --JEM */
>  			else if (this->fs_name[0] == '/') {
>  				if (strlen(this->fs_name) > 1) {
>  					if (this->fs_name[1] != '/')
>  						ret = 1;
>  				} else
>  					ret = 1;
> -			}
> +			} else if (!strncmp(this->fs_name, "rootfs", 6))
> +				ret = 1;
>  			break;
>  		}
>  	}
> @@ -357,7 +359,7 @@ int allow_owner_mount(const char *path)
>  	struct mntent ent;
>  	int ret = 0;
>  
> -	if (getuid() || is_mounted(_PATH_MOUNTED, path))
> +	if (getuid() || is_mounted(path_mounted, path))
>  		return 0;
>  
>  	if (find_mntent(_PATH_MNTTAB, path, &ent)) {
> diff --git a/modules/mount_autofs.c b/modules/mount_autofs.c
> index f0edb0a..08ae5f1 100644
> --- a/modules/mount_autofs.c
> +++ b/modules/mount_autofs.c
> @@ -71,7 +71,7 @@ int mount_mount(const char *root, const 
>  	debug(MODPREFIX "fullpath=%s what=%s options=%s",
>  		  fullpath, what, options);
>  
> -	if (is_mounted(_PATH_MOUNTED, fullpath)) {
> +	if (is_mounted(path_mounted, fullpath)) {
>  		error(MODPREFIX 
>  		 "warning: about to mount over %s, continuing", fullpath);
>  		return 0;
> diff --git a/modules/mount_bind.c b/modules/mount_bind.c
> index 20ab7bf..fbf1546 100644
> --- a/modules/mount_bind.c
> +++ b/modules/mount_bind.c
> @@ -121,7 +121,7 @@ int mount_mount(const char *root, const 
>  		if (!status)
>  			existed = 0;
>  
> -		if (is_mounted(_PATH_MOUNTED, fullpath)) {
> +		if (is_mounted(path_mounted, fullpath)) {
>  			error(MODPREFIX 
>  			  "warning: %s is already mounted", fullpath);
>  			return 0;
> diff --git a/modules/mount_ext2.c b/modules/mount_ext2.c
> index 38d67bf..b2efb96 100644
> --- a/modules/mount_ext2.c
> +++ b/modules/mount_ext2.c
> @@ -69,7 +69,7 @@ int mount_mount(const char *root, const 
>  	if (!status)
>  		existed = 0;
>  
> -	if (is_mounted(_PATH_MOUNTED, fullpath)) {
> +	if (is_mounted(path_mounted, fullpath)) {
>  		error(MODPREFIX 
>  		  "warning: %s is already mounted", fullpath);
>  		return 0;
> diff --git a/modules/mount_generic.c b/modules/mount_generic.c
> index b3179d6..0fe6a3d 100644
> --- a/modules/mount_generic.c
> +++ b/modules/mount_generic.c
> @@ -68,7 +68,7 @@ int mount_mount(const char *root, const 
>  	if (!status)
>  		existed = 0;
>  
> -	if (is_mounted(_PATH_MOUNTED, fullpath)) {
> +	if (is_mounted(path_mounted, fullpath)) {
>  		error(MODPREFIX "warning: %s is already mounted", fullpath);
>  		return 0;
>  	}
> diff --git a/modules/mount_nfs.c b/modules/mount_nfs.c
> index 3f9de50..c0546b9 100644
> --- a/modules/mount_nfs.c
> +++ b/modules/mount_nfs.c
> @@ -596,7 +596,7 @@ #endif
>  	if (!status)
>  		existed = 0;
>  
> -	if (is_mounted(_PATH_MOUNTED, fullpath)) {
> +	if (is_mounted(path_mounted, fullpath)) {
>  		error(MODPREFIX 
>  		      "warning: %s is already mounted", fullpath);
>  		return 0;
> 

Re: [autofs4 patch] Use /proc/mounts instead of /etc/mtab

[Jeff Moyer]

==> On Thu, 09 Nov 2006 11:17:09 +0800, Ian Kent <raven@themaw.net> said:

Ian> On Wed, 2006-11-08 at 22:03 -0500, Jeff Moyer wrote: > Hi, Ian,
Ian> list,
Ian> > 
Ian> > Here is a patch to consult /proc/mounts instead of /etc/mtab
Ian> when > deciding if a path has already been mounted.  The problem
Ian> with using > /etc/mtab, as you know, is that it sometimes does
Ian> not get updated.  We > know that /proc/mounts will always be
Ian> right, so why not use it?

Ian> Good for v4 but keep in mind that in v5 /proc/mounts can have a
Ian> lot of entries compared to /etc/mtab. The cost of doing this can
Ian> be quite high.  mount(8) must play well with mtab for v5.

It's not just mount(8), but also the caller's responsibility.  You
have to be sure to check for the mtab not updated return value, and
issue another mount call to try to update it.

-Jeff

Re: [autofs4 patch] Use /proc/mounts instead of /etc/mtab

[Ian Kent]

On Wed, 2006-11-08 at 22:25 -0500, Jeff Moyer wrote:
> ==> On Thu, 09 Nov 2006 11:17:09 +0800, Ian Kent <raven@themaw.net> said:
> 
> Ian> On Wed, 2006-11-08 at 22:03 -0500, Jeff Moyer wrote: > Hi, Ian,
> Ian> list,
> Ian> > 
> Ian> > Here is a patch to consult /proc/mounts instead of /etc/mtab
> Ian> when > deciding if a path has already been mounted.  The problem
> Ian> with using > /etc/mtab, as you know, is that it sometimes does
> Ian> not get updated.  We > know that /proc/mounts will always be
> Ian> right, so why not use it?
> 
> Ian> Good for v4 but keep in mind that in v5 /proc/mounts can have a
> Ian> lot of entries compared to /etc/mtab. The cost of doing this can
> Ian> be quite high.  mount(8) must play well with mtab for v5.
> 
> It's not just mount(8), but also the caller's responsibility.  You
> have to be sure to check for the mtab not updated return value, and
> issue another mount call to try to update it.

Ya .. been there before.
I'll need to check that.

Ian