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

[Ian Kent <raven@themaw.net>]

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;
>