autofs-5.0.9 - amd lookup add external mounts tracking functions

From: Ian Kent <raven@themaw.net>

Amd automounts can use what's called a sublink option. Using this

option a single containing mount can be specified and symlinks

that point to directories within the mount created instead of a

mount for every directory.

In some cases this can greatly reduce the number of mounts needed

for a map but complicates automounting when using an "in-place"

automounter such as autofs.

Clearly we can't perform the mount and create symlinks within it

so we must us a mount lookaside directory like amd. Those external

mounts also need to be managed.

This patch adds functions to maintain a list of these mounts (much

like a reference counter) so we know if an external mount is present

and if it's time to umount it.

---

 include/mounts.h |    2 +

 lib/mounts.c     |  132 ++++++++++++++++++++++++++++++++++++++++++++++++++++++

 2 files changed, 134 insertions(+)

diff --git a/include/mounts.h b/include/mounts.h

index c2f92ec..3bef086 100644

--- a/include/mounts.h

+++ b/include/mounts.h

@@ -93,6 +93,8 @@ unsigned int get_kver_major(void);

 unsigned int get_kver_minor(void);

 char *make_options_string(char *path, int kernel_pipefd, const char *extra);

 char *make_mnt_name_string(char *path);

+int ext_mount_add(struct list_head *, const char *);

+int ext_mount_remove(struct list_head *, const char *);

 struct mnt_list *get_mnt_list(const char *table, const char *path, int include);

 struct mnt_list *reverse_mnt_list(struct mnt_list *list);

 void free_mnt_list(struct mnt_list *list);

diff --git a/lib/mounts.c b/lib/mounts.c

index 868dcb1..aea6691 100644

--- a/lib/mounts.c

+++ b/lib/mounts.c

@@ -46,6 +46,17 @@ static const char mnt_name_template[]      = "automount(pid%u)";

 static struct kernel_mod_version kver = {0, 0};

 static const char kver_options_template[]  = "fd=%d,pgrp=%u,minproto=3,maxproto=5";

+#define EXT_MOUNTS_HASH_SIZE    50

+

+struct ext_mount {

+	char *mountpoint;

+	struct list_head mount;

+	struct list_head mounts;

+};

+static struct list_head ext_mounts_hash[EXT_MOUNTS_HASH_SIZE];

+static unsigned int ext_mounts_hash_init_done = 0;

+static pthread_mutex_t ext_mount_hash_mutex = PTHREAD_MUTEX_INITIALIZER;

+

 unsigned int linux_version_code(void)

 {

 	struct utsname my_utsname;

@@ -422,6 +433,127 @@ char *make_mnt_name_string(char *path)

 	return mnt_name;

 }

+static void ext_mounts_hash_init(void)

+{

+	int i;

+	for (i = 0; i < EXT_MOUNTS_HASH_SIZE; i++)

+		INIT_LIST_HEAD(&ext_mounts_hash[i]);

+	ext_mounts_hash_init_done = 1;

+}

+

+static struct ext_mount *ext_mount_lookup(const char *mountpoint)

+{

+	u_int32_t hval = hash(mountpoint, EXT_MOUNTS_HASH_SIZE);

+	struct list_head *p, *head;

+

+	if (!ext_mounts_hash_init_done)

+		ext_mounts_hash_init();

+

+	if (list_empty(&ext_mounts_hash[hval]))

+		return NULL;

+

+	head = &ext_mounts_hash[hval];

+	list_for_each(p, head) {

+		struct ext_mount *this = list_entry(p, struct ext_mount, mount);

+		if (!strcmp(this->mountpoint, mountpoint))

+			return this;

+	}

+	return NULL;

+}

+

+int ext_mount_add(struct list_head *entry, const char *path)

+{

+	struct ext_mount *em;

+	char *auto_dir;

+	u_int32_t hval;

+	int ret = 0;

+

+	/* Not a mount in the external mount directory */

+	auto_dir = conf_amd_get_auto_dir();

+	if (strncmp(path, auto_dir, strlen(auto_dir))) {

+		free(auto_dir);

+		return 0;

+	}

+	free(auto_dir);

+

+	pthread_mutex_lock(&ext_mount_hash_mutex);

+

+	em = ext_mount_lookup(path);

+	if (em) {

+		struct list_head *p, *head;

+		head = &em->mounts;

+		list_for_each(p, head) {

+			if (p == entry)

+				goto done;

+		}

+		list_add_tail(entry, &em->mounts);

+		ret = 1;

+		goto done;

+	}

+

+	em = malloc(sizeof(struct ext_mount));

+	if (!em) {

+		ret = -1;

+		goto done;

+	}

+

+	em->mountpoint = strdup(path);

+	if (!em->mountpoint) {

+		free(em);

+		ret = -1;

+		goto done;

+	}

+	INIT_LIST_HEAD(&em->mount);

+	INIT_LIST_HEAD(&em->mounts);

+

+	hval = hash(path, EXT_MOUNTS_HASH_SIZE);

+	list_add_tail(&em->mount, &ext_mounts_hash[hval]);

+

+	list_add_tail(entry, &em->mounts);

+

+	ret = 1;

+done:

+	pthread_mutex_unlock(&ext_mount_hash_mutex);

+	return ret;

+}

+

+int ext_mount_remove(struct list_head *entry, const char *path)

+{

+	struct ext_mount *em;

+	char *auto_dir;

+	int ret = 0;

+

+	/* Not a mount in the external mount directory */

+	auto_dir = conf_amd_get_auto_dir();

+	if (strncmp(path, auto_dir, strlen(auto_dir))) {

+		free(auto_dir);

+		return 0;

+	}

+	free(auto_dir);

+

+	pthread_mutex_lock(&ext_mount_hash_mutex);

+

+	em = ext_mount_lookup(path);

+	if (!em)

+		goto done;

+

+	list_del_init(entry);

+

+	if (!list_empty(&em->mounts))

+		goto done;

+	else {

+		list_del_init(&em->mount);

+		if (list_empty(&em->mount)) {

+			free(em->mountpoint);

+			free(em);

+		}

+		ret = 1;

+	}

+done:

+	pthread_mutex_unlock(&ext_mount_hash_mutex);

+	return ret;

+}

+

 /*

  * Get list of mounts under path in longest->shortest order

  */