libmount: add mnt_table_is_empty(), improve table list usage

Currently you have to use mnt_table_remove_fs() + mnt_free_fs() to
destroy the list in the table. This is complicated in same situations.
This patch allows to use mnt_free_fs() only.

Signed-off-by: Karel Zak <kzak@redhat.com>

6 files changed, 35 insertions, 11 deletions

diff --git a/libmount/docs/libmount-sections.txt b/libmount/docs/libmount-sections.txt
index d5083216..f7004fcd 100644
--- a/libmount/docs/libmount-sections.txt
+++ b/libmount/docs/libmount-sections.txt
@@ -303,6 +303,7 @@ mnt_table_get_nents
 mnt_table_get_root_fs
 mnt_table_get_trailing_comment
 mnt_table_get_userdata
+mnt_table_is_empty
 mnt_table_is_fs_mounted
 mnt_table_last_fs
 mnt_table_next_child_fs
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index 0a4f57a6..e09f472a 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -412,6 +412,7 @@ extern void mnt_free_table(struct libmnt_table *tb);
 
 extern int mnt_reset_table(struct libmnt_table *tb);
 extern int mnt_table_get_nents(struct libmnt_table *tb);
+extern int mnt_table_is_empty(struct libmnt_table *tb);
 
 extern int mnt_table_set_userdata(struct libmnt_table *tb, void *data);
 extern void *mnt_table_get_userdata(struct libmnt_table *tb);
diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index f9870e3c..be140000 100644
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -269,6 +269,7 @@ global:
 	mnt_table_get_intro_comment;
 	mnt_table_get_trailing_comment;
 	mnt_table_get_userdata;
+	mnt_table_is_empty;
 	mnt_table_last_fs;
 	mnt_table_replace_file;
 	mnt_table_set_intro_comment;
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 1ba7d5c4..61b872ed 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -266,7 +266,6 @@ struct libmnt_fs {
  */
 struct libmnt_table {
 	int		fmt;		/* MNT_FMT_* file format */
-	int		nents;		/* number of valid entries */
 	int		comms;		/* enable/disable comment parsing */
 	char		*comm_intro;	/* First comment in file */
 	char		*comm_tail;	/* Last comment in file */
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index 2b258c7d..098bf368 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -92,7 +92,6 @@ int mnt_reset_table(struct libmnt_table *tb)
 		mnt_free_fs(fs);
 	}
 
-	tb->nents = 0;
 	return 0;
 }
 
@@ -123,8 +122,29 @@ void mnt_free_table(struct libmnt_table *tb)
  */
 int mnt_table_get_nents(struct libmnt_table *tb)
 {
+	struct list_head *p;
+	int i = 0;
+
+	assert(tb);
+	if (!tb)
+		return -EINVAL;
+	if (list_empty(&tb->ents))
+		return 0;
+	list_for_each(p, &tb->ents)
+		i++;
+	return i;
+}
+
+/**
+ * mnt_table_is_empty:
+ * @tb: pointer to tab
+ *
+ * Returns: 1 if the table is without filesystems, or 0.
+ */
+int mnt_table_is_empty(struct libmnt_table *tb)
+{
 	assert(tb);
-	return tb ? tb->nents : 0;
+	return tb == NULL || list_empty(&tb->ents) ? 1 : 0;
 }
 
 /**
@@ -372,7 +392,6 @@ int mnt_table_add_fs(struct libmnt_table *tb, struct libmnt_fs *fs)
 
 	DBG(TAB, mnt_debug_h(tb, "add entry: %s %s",
 			mnt_fs_get_source(fs), mnt_fs_get_target(fs)));
-	tb->nents++;
 	return 0;
 }
 
@@ -391,7 +410,6 @@ int mnt_table_remove_fs(struct libmnt_table *tb, struct libmnt_fs *fs)
 	if (!tb || !fs)
 		return -EINVAL;
 	list_del(&fs->ents);
-	tb->nents--;
 	return 0;
 }
 
@@ -792,7 +810,7 @@ struct libmnt_fs *mnt_table_find_srcpath(struct libmnt_table *tb, const char *pa
 {
 	struct libmnt_iter itr;
 	struct libmnt_fs *fs = NULL;
-	int ntags = 0;
+	int ntags = 0, nents;
 	char *cn;
 	const char *p;
 
@@ -818,8 +836,10 @@ struct libmnt_fs *mnt_table_find_srcpath(struct libmnt_table *tb, const char *pa
 
 	DBG(TAB, mnt_debug_h(tb, "lookup canonical SRCPATH: '%s'", cn));
 
+	nents = mnt_table_get_nents(tb);
+
 	/* canonicalized paths in struct libmnt_table */
-	if (ntags < mnt_table_get_nents(tb)) {
+	if (ntags < nents) {
 		mnt_reset_iter(&itr, direction);
 		while(mnt_table_next_fs(tb, &itr, &fs) == 0) {
 			if (mnt_fs_streq_srcpath(fs, cn))
@@ -862,7 +882,7 @@ struct libmnt_fs *mnt_table_find_srcpath(struct libmnt_table *tb, const char *pa
 	}
 
 	/* non-canonicalized paths in struct libmnt_table */
-	if (ntags <= mnt_table_get_nents(tb)) {
+	if (ntags <= nents) {
 		mnt_reset_iter(&itr, direction);
 		while(mnt_table_next_fs(tb, &itr, &fs) == 0) {
 			if (mnt_fs_is_netfs(fs) || mnt_fs_is_pseudofs(fs))
@@ -1210,7 +1230,7 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs)
 	DBG(FS, mnt_debug_h(fstab_fs, "is FS mounted? [target=%s]",
 				mnt_fs_get_target(fstab_fs)));
 
-	if (mnt_fs_is_swaparea(fstab_fs) || mnt_table_get_nents(tb) == 0) {
+	if (mnt_fs_is_swaparea(fstab_fs) || mnt_table_is_empty(tb)) {
 		DBG(FS, mnt_debug_h(fstab_fs, "- ignore (swap or no data)"));
 		return 0;
 	}
diff --git a/sys-utils/swapon.c b/sys-utils/swapon.c
index f1e24337..4b4b7160 100644
--- a/sys-utils/swapon.c
+++ b/sys-utils/swapon.c
@@ -188,12 +188,14 @@ static int display_summary(void)
 	if (!st)
 		return -1;
 
+	if (mnt_table_is_empty(st))
+		return 0;
+
 	itr = mnt_new_iter(MNT_ITER_FORWARD);
 	if (!itr)
 		err(EXIT_FAILURE, _("failed to initialize libmount iterator"));
 
-	if (mnt_table_get_nents(st) > 0)
-		printf(_("%s\t\t\t\tType\t\tSize\tUsed\tPriority\n"), _("Filename"));
+	printf(_("%s\t\t\t\tType\t\tSize\tUsed\tPriority\n"), _("Filename"));
 
 	while (mnt_table_next_fs(st, itr, &fs) == 0) {
 		printf("%-39s\t%s\t%jd\t%jd\t%d\n",