libmount: add reference counter to libmnt_table

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

10 files changed, 100 insertions, 50 deletions

diff --git a/libmount/docs/libmount-sections.txt b/libmount/docs/libmount-sections.txt
index 3ebc4aaf2..037877f56 100644
--- a/libmount/docs/libmount-sections.txt
+++ b/libmount/docs/libmount-sections.txt
@@ -289,6 +289,8 @@ libmnt_table
 mnt_free_table
 mnt_new_table
 mnt_reset_table
+mnt_ref_table
+mnt_unref_table
 mnt_new_table_from_dir
 mnt_new_table_from_file
 mnt_table_add_fs
diff --git a/libmount/src/cache.c b/libmount/src/cache.c
index cf5c6d430..92f469456 100644
--- a/libmount/src/cache.c
+++ b/libmount/src/cache.c
@@ -81,7 +81,8 @@ struct libmnt_cache *mnt_new_cache(void)
  * mnt_free_cache:
  * @cache: pointer to struct libmnt_cache instance
  *
- * Deallocates the cache.
+ * Deallocates the cache. This function does not care about reference count. Don't
+ * use this function directly -- it's better to use use mnt_unref_cache().
  */
 void mnt_free_cache(struct libmnt_cache *cache)
 {
diff --git a/libmount/src/context.c b/libmount/src/context.c
index 5d5e8fba8..014f0ee90 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -89,9 +89,7 @@ void mnt_free_context(struct libmnt_context *cxt)
 	free(cxt->fstype_pattern);
 	free(cxt->optstr_pattern);
 
-	if (!(cxt->flags & MNT_FL_EXTERN_FSTAB))
-		mnt_free_table(cxt->fstab);
-
+	mnt_unref_table(cxt->fstab);
 	mnt_unref_cache(cxt->cache);
 
 	mnt_context_clear_loopdev(cxt);
@@ -137,7 +135,7 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	fl = cxt->flags;
 
 	mnt_unref_fs(cxt->fs);
-	mnt_free_table(cxt->mtab);
+	mnt_unref_table(cxt->mtab);
 
 	free(cxt->helper);
 	free(cxt->orig_user);
@@ -163,8 +161,6 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	mnt_context_set_tabfilter(cxt, NULL, NULL);
 
 	/* restore non-resettable flags */
-	cxt->flags |= (fl & MNT_FL_EXTERN_FSTAB);
-	cxt->flags |= (fl & MNT_FL_EXTERN_CACHE);
 	cxt->flags |= (fl & MNT_FL_NOMTAB);
 	cxt->flags |= (fl & MNT_FL_FAKE);
 	cxt->flags |= (fl & MNT_FL_SLOPPY);
@@ -891,7 +887,11 @@ int mnt_context_set_options_pattern(struct libmnt_context *cxt, const char *patt
  *
  * The mount context reads /etc/fstab to the private struct libmnt_table by default.
  * This function allows to overwrite the private fstab with an external
- * instance. Note that the external instance is not deallocated by mnt_free_context().
+ * instance.
+ *
+ * This function modify the @tb reference counter. This function does not set
+ * the cache for the @tb. You have to explicitly call mnt_table_set_cache(tb,
+ * mnt_context_get_cache(cxt));
  *
  * The fstab is used read-only and is not modified, it should be possible to
  * share the fstab between more mount contexts (TODO: test it.)
@@ -906,10 +906,10 @@ int mnt_context_set_fstab(struct libmnt_context *cxt, struct libmnt_table *tb)
 	assert(cxt);
 	if (!cxt)
 		return -EINVAL;
-	if (!(cxt->flags & MNT_FL_EXTERN_FSTAB))
-		mnt_free_table(cxt->fstab);
 
-	set_flag(cxt, MNT_FL_EXTERN_FSTAB, tb != NULL);
+	mnt_ref_table(tb);		/* new */
+	mnt_unref_table(cxt->fstab);	/* old */
+
 	cxt->fstab = tb;
 	return 0;
 }
@@ -936,16 +936,12 @@ int mnt_context_get_fstab(struct libmnt_context *cxt, struct libmnt_table **tb)
 			return -ENOMEM;
 		if (cxt->table_errcb)
 			mnt_table_set_parser_errcb(cxt->fstab, cxt->table_errcb);
-		cxt->flags &= ~MNT_FL_EXTERN_FSTAB;
+		mnt_table_set_cache(cxt->fstab, mnt_context_get_cache(cxt));
 		rc = mnt_table_parse_fstab(cxt->fstab, NULL);
 		if (rc)
 			return rc;
 	}
 
-	/*  never touch an external fstab */
-	if (!(cxt->flags & MNT_FL_EXTERN_FSTAB))
-		mnt_table_set_cache(cxt->fstab, mnt_context_get_cache(cxt));
-
 	if (tb)
 		*tb = cxt->fstab;
 	return 0;
@@ -980,13 +976,12 @@ int mnt_context_get_mtab(struct libmnt_context *cxt, struct libmnt_table **tb)
 					cxt->table_fltrcb,
 					cxt->table_fltrcb_data);
 
+		mnt_table_set_cache(cxt->mtab, mnt_context_get_cache(cxt));
 		rc = mnt_table_parse_mtab(cxt->mtab, cxt->mtab_path);
 		if (rc)
 			return rc;
 	}
 
-	mnt_table_set_cache(cxt->mtab, mnt_context_get_cache(cxt));
-
 	if (tb)
 		*tb = cxt->mtab;
 
@@ -1057,7 +1052,7 @@ int mnt_context_get_table(struct libmnt_context *cxt,
 
 	rc = mnt_table_parse_file(*tb, filename);
 	if (rc) {
-		mnt_free_table(*tb);
+		mnt_unref_table(*tb);
 		return rc;
 	}
 
@@ -1086,6 +1081,11 @@ int mnt_context_set_tables_errcb(struct libmnt_context *cxt,
 	if (!cxt)
 		return -EINVAL;
 
+	if (cxt->mtab)
+		mnt_table_set_parser_errcb(cxt->mtab, cb);
+	if (cxt->fstab)
+		mnt_table_set_parser_errcb(cxt->fstab, cb);
+
 	cxt->table_errcb = cb;
 	return 0;
 }
@@ -1099,8 +1099,9 @@ int mnt_context_set_tables_errcb(struct libmnt_context *cxt,
  * function allows to overwrite the private cache with an external instance.
  * This function increments cache reference counter.
  *
- * If the @cache argument is NULL, then the current private cache instance is
- * reset.
+ * If the @cache argument is NULL, then the current cache instance is reset.
+ * This function apply the cache to fstab and mtab instances (if already
+ * exists).
  *
  * The old cache instance reference counter is de-incremented.
  *
@@ -1115,6 +1116,12 @@ int mnt_context_set_cache(struct libmnt_context *cxt, struct libmnt_cache *cache
 	mnt_unref_cache(cxt->cache);		/* old */
 
 	cxt->cache = cache;
+
+	if (cxt->mtab)
+		mnt_table_set_cache(cxt->mtab, cache);
+	if (cxt->fstab)
+		mnt_table_set_cache(cxt->fstab, cache);
+
 	return 0;
 }
 
@@ -1133,9 +1140,9 @@ struct libmnt_cache *mnt_context_get_cache(struct libmnt_context *cxt)
 		return NULL;
 
 	if (!cxt->cache) {
-		cxt->cache = mnt_new_cache();
-		if (!cxt->cache)
-			return NULL;
+		struct libmnt_cache *cache = mnt_new_cache();
+		mnt_context_set_cache(cxt, cache);
+		mnt_unref_cache(cache);
 	}
 	return cxt->cache;
 }
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index f4efd9804..b95b08bce 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -415,6 +415,9 @@ extern struct libmnt_table *mnt_new_table(void)
 			__ul_attribute__((warn_unused_result));
 extern void mnt_free_table(struct libmnt_table *tb);
 
+extern void mnt_ref_table(struct libmnt_table *table);
+extern void mnt_unref_table(struct libmnt_table *table);
+
 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);
diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index 5a7e0def3..430c58ec6 100644
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -267,6 +267,7 @@ global:
 	mnt_fs_set_comment;
 	mnt_ref_cache;
 	mnt_ref_fs;
+	mnt_ref_table;
 	mnt_table_append_intro_comment;
 	mnt_table_append_trailing_comment;
 	mnt_table_enable_comments;
@@ -284,4 +285,5 @@ global:
 	mnt_table_write_file;
 	mnt_unref_cache;
 	mnt_unref_fs;
+	mnt_unref_table;
 } MOUNT_2.23;
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index bf450a6c1..9e6f4bd28 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -276,6 +276,7 @@ struct libmnt_fs {
 struct libmnt_table {
 	int		fmt;		/* MNT_FMT_* file format */
 	int		nents;		/* number of entries */
+	int		refcount;	/* reference counter */
 	int		comms;		/* enable/disable comment parsing */
 	char		*comm_intro;	/* First comment in file */
 	char		*comm_tail;	/* Last comment in file */
@@ -391,9 +392,6 @@ struct libmnt_context
 #define MNT_FL_FORK		(1 << 12)
 #define MNT_FL_NOSWAPMATCH	(1 << 13)
 
-#define MNT_FL_EXTERN_FSTAB	(1 << 16)	/* cxt->fstab is not private */
-#define MNT_FL_EXTERN_CACHE	(1 << 17)	/* cxt->cache is not private */
-
 #define MNT_FL_MOUNTDATA	(1 << 20)
 #define MNT_FL_TAB_APPLIED	(1 << 21)	/* mtab/fstab merged to cxt->fs */
 #define MNT_FL_MOUNTFLAGS_MERGED (1 << 22)	/* MS_* flags was read from optstr */
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index a2ad604f7..b1078cf81 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -66,7 +66,7 @@ struct libmnt_table *mnt_new_table(void)
 		return NULL;
 
 	DBG(TAB, mnt_debug_h(tb, "alloc"));
-
+	tb->refcount = 1;
 	INIT_LIST_HEAD(&tb->ents);
 	return tb;
 }
@@ -98,10 +98,46 @@ int mnt_reset_table(struct libmnt_table *tb)
 }
 
 /**
+ * mnt_ref_table:
+ * @tb: table pointer
+ *
+ * Increments reference counter.
+ */
+void mnt_ref_table(struct libmnt_table *tb)
+{
+	if (tb) {
+		tb->refcount++;
+		/*DBG(FS, mnt_debug_h(tb, "ref=%d", tb->refcount));*/
+	}
+}
+
+/**
+ * mnt_unref_table:
+ * @tb: table pointer
+ *
+ * De-increments reference counter, on zero the FS is automatically
+ * deallocated by mnt_free_table().
+ */
+void mnt_unref_table(struct libmnt_table *tb)
+{
+	if (tb) {
+		tb->refcount--;
+		/*DBG(FS, mnt_debug_h(tb, "unref=%d", tb->refcount));*/
+		if (tb->refcount <= 0)
+			mnt_free_table(tb);
+	}
+}
+
+
+/**
  * mnt_free_table:
  * @tb: tab pointer
  *
- * Deallocates tab struct and all entries.
+ * Deallocates the table. This function does not care about reference count. Don't
+ * use this function directly -- it's better to use use mnt_unref_table().
+ *
+ * The table entries (filesystems) are unrefrenced by mnt_reset_table() and
+ * cache by mnt_unref_cache().
  */
 void mnt_free_table(struct libmnt_table *tb)
 {
@@ -109,9 +145,11 @@ void mnt_free_table(struct libmnt_table *tb)
 		return;
 
 	mnt_reset_table(tb);
-	mnt_unref_cache(tb->cache);
 
+	WARN_REFCOUNT(TAB, tb, tb->refcount);
 	DBG(TAB, mnt_debug_h(tb, "free"));
+
+	mnt_unref_cache(tb->cache);
 	free(tb->comm_intro);
 	free(tb->comm_tail);
 	free(tb);
@@ -551,7 +589,6 @@ int mnt_table_next_child_fs(struct libmnt_table *tb, struct libmnt_iter *itr,
  *		const char *dir = mnt_fs_get_target(fs);
  *		printf("mount point: %s\n", dir);
  *	}
- *	mnt_free_table(fi);
  *   </programlisting>
  * </informalexample>
  *
@@ -1370,7 +1407,7 @@ struct libmnt_table *create_table(const char *file, int comments)
 	return tb;
 err:
 	fprintf(stderr, "%s: parsing failed\n", file);
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return NULL;
 }
 
@@ -1400,7 +1437,7 @@ int test_copy_fs(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_unref_fs(fs);
 	rc = 0;
 done:
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -1436,7 +1473,7 @@ int test_parse(struct libmnt_test *ts, int argc, char *argv[])
 	rc = 0;
 done:
 	mnt_free_iter(itr);
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -1478,7 +1515,7 @@ int test_find(struct libmnt_test *ts, int argc, char *argv[], int dr)
 		rc = 0;
 	}
 done:
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -1515,7 +1552,7 @@ int test_find_pair(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_fs_print_debug(fs, stdout);
 	rc = 0;
 done:
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -1542,7 +1579,7 @@ int test_find_mountpoint(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_fs_print_debug(fs, stdout);
 	rc = 0;
 done:
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -1587,8 +1624,8 @@ static int test_is_mounted(struct libmnt_test *ts, int argc, char *argv[])
 
 	rc = 0;
 done:
-	mnt_free_table(tb);
-	mnt_free_table(fstab);
+	mnt_unref_table(tb);
+	mnt_unref_table(fstab);
 	mnt_free_iter(itr);
 	return rc;
 }
diff --git a/libmount/src/tab_diff.c b/libmount/src/tab_diff.c
index 71ef0f419..052278233 100644
--- a/libmount/src/tab_diff.c
+++ b/libmount/src/tab_diff.c
@@ -355,8 +355,8 @@ int test_diff(struct libmnt_test *ts, int argc, char *argv[])
 
 	rc = 0;
 done:
-	mnt_free_table(tb_old);
-	mnt_free_table(tb_new);
+	mnt_unref_table(tb_old);
+	mnt_unref_table(tb_new);
 	mnt_free_tabdiff(diff);
 	mnt_free_iter(itr);
 	return rc;
diff --git a/libmount/src/tab_parse.c b/libmount/src/tab_parse.c
index e31dac8c2..532f0ec04 100644
--- a/libmount/src/tab_parse.c
+++ b/libmount/src/tab_parse.c
@@ -821,7 +821,7 @@ struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt)
 	if (tb) {
 		tb->fmt = fmt;
 		if (mnt_table_parse_file(tb, filename) != 0) {
-			mnt_free_table(tb);
+			mnt_unref_table(tb);
 			tb = NULL;
 		}
 	}
@@ -860,7 +860,7 @@ struct libmnt_table *mnt_new_table_from_dir(const char *dirname)
 		return NULL;
 	tb = mnt_new_table();
 	if (tb && mnt_table_parse_dir(tb, dirname) != 0) {
-		mnt_free_table(tb);
+		mnt_unref_table(tb);
 		tb = NULL;
 	}
 	return tb;
@@ -1103,6 +1103,6 @@ int mnt_table_parse_mtab(struct libmnt_table *tb, const char *filename)
 			mnt_table_merge_user_fs(tb, u_fs);
 	}
 
-	mnt_free_table(u_tb);
+	mnt_unref_table(u_tb);
 	return 0;
 }
diff --git a/libmount/src/tab_update.c b/libmount/src/tab_update.c
index b5c92726f..a508b9903 100644
--- a/libmount/src/tab_update.c
+++ b/libmount/src/tab_update.c
@@ -71,7 +71,7 @@ void mnt_free_update(struct libmnt_update *upd)
 	DBG(UPDATE, mnt_debug_h(upd, "free"));
 
 	mnt_unref_fs(upd->fs);
-	mnt_free_table(upd->mountinfo);
+	mnt_unref_table(upd->mountinfo);
 	free(upd->target);
 	free(upd->filename);
 	free(upd);
@@ -698,7 +698,7 @@ static int update_add_entry(struct libmnt_update *upd, struct libmnt_lock *lc)
 	if (lc)
 		mnt_unlock_file(lc);
 
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -729,7 +729,7 @@ static int update_remove_entry(struct libmnt_update *upd, struct libmnt_lock *lc
 	if (lc)
 		mnt_unlock_file(lc);
 
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -761,7 +761,7 @@ static int update_modify_target(struct libmnt_update *upd, struct libmnt_lock *l
 	if (lc)
 		mnt_unlock_file(lc);
 
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -803,7 +803,7 @@ static int update_modify_options(struct libmnt_update *upd, struct libmnt_lock *
 	if (lc)
 		mnt_unlock_file(lc);
 
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }
 
@@ -968,7 +968,7 @@ static int test_replace(struct libmnt_test *ts, int argc, char *argv[])
 	mnt_unref_fs(fs);
 
 	rc = mnt_table_replace_file(tb, mnt_get_fstab_path());
-	mnt_free_table(tb);
+	mnt_unref_table(tb);
 	return rc;
 }