1 files changed, 377 insertions, 0 deletions

diff --git a/libmount/src/tab_diff.c b/libmount/src/tab_diff.c
new file mode 100644
index 0000000..81694bc
--- /dev/null
+++ b/libmount/src/tab_diff.c
@@ -0,0 +1,377 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * This file is part of libmount from util-linux project.
+ *
+ * Copyright (C) 2011-2018 Karel Zak <kzak@redhat.com>
+ *
+ * libmount is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ */
+
+/**
+ * SECTION: tabdiff
+ * @title: Compare changes in mount tables
+ * @short_description: compare changes in the list of the mounted filesystems
+ */
+#include "mountP.h"
+
+struct tabdiff_entry {
+	int	oper;			/* MNT_TABDIFF_* flags; */
+
+	struct libmnt_fs *old_fs;	/* pointer to the old FS */
+	struct libmnt_fs *new_fs;	/* pointer to the new FS */
+
+	struct list_head changes;
+};
+
+struct libmnt_tabdiff {
+	int nchanges;			/* number of changes */
+
+	struct list_head changes;	/* list with modified entries */
+	struct list_head unused;	/* list with unused entries */
+};
+
+/**
+ * mnt_new_tabdiff:
+ *
+ * Allocates a new table diff struct.
+ *
+ * Returns: new diff handler or NULL.
+ */
+struct libmnt_tabdiff *mnt_new_tabdiff(void)
+{
+	struct libmnt_tabdiff *df = calloc(1, sizeof(*df));
+
+	if (!df)
+		return NULL;
+
+	DBG(DIFF, ul_debugobj(df, "alloc"));
+
+	INIT_LIST_HEAD(&df->changes);
+	INIT_LIST_HEAD(&df->unused);
+	return df;
+}
+
+static void free_tabdiff_entry(struct tabdiff_entry *de)
+{
+	if (!de)
+		return;
+	list_del(&de->changes);
+	mnt_unref_fs(de->new_fs);
+	mnt_unref_fs(de->old_fs);
+	free(de);
+}
+
+/**
+ * mnt_free_tabdiff:
+ * @df: tab diff
+ *
+ * Deallocates tab diff struct and all entries.
+ */
+void mnt_free_tabdiff(struct libmnt_tabdiff *df)
+{
+	if (!df)
+		return;
+
+	DBG(DIFF, ul_debugobj(df, "free"));
+
+	while (!list_empty(&df->changes)) {
+		struct tabdiff_entry *de = list_entry(df->changes.next,
+			                  struct tabdiff_entry, changes);
+		free_tabdiff_entry(de);
+	}
+
+	free(df);
+}
+
+/**
+ * mnt_tabdiff_next_change:
+ * @df: tabdiff pointer
+ * @itr: iterator
+ * @old_fs: returns the old entry or NULL if new entry added
+ * @new_fs: returns the new entry or NULL if old entry removed
+ * @oper: MNT_TABDIFF_{MOVE,UMOUNT,REMOUNT,MOUNT} flags
+ *
+ * The options @old_fs, @new_fs and @oper are optional.
+ *
+ * Returns: 0 on success, negative number in case of error or 1 at the end of list.
+ */
+int mnt_tabdiff_next_change(struct libmnt_tabdiff *df, struct libmnt_iter *itr,
+		struct libmnt_fs **old_fs, struct libmnt_fs **new_fs, int *oper)
+{
+	int rc = 1;
+	struct tabdiff_entry *de = NULL;
+
+	if (!df || !itr)
+		return -EINVAL;
+
+	if (!itr->head)
+		MNT_ITER_INIT(itr, &df->changes);
+	if (itr->p != itr->head) {
+		MNT_ITER_ITERATE(itr, de, struct tabdiff_entry, changes);
+		rc = 0;
+	}
+
+	if (old_fs)
+		*old_fs = de ? de->old_fs : NULL;
+	if (new_fs)
+		*new_fs = de ? de->new_fs : NULL;
+	if (oper)
+		*oper = de ? de->oper : 0;
+
+	return rc;
+}
+
+static int tabdiff_reset(struct libmnt_tabdiff *df)
+{
+	assert(df);
+
+	DBG(DIFF, ul_debugobj(df, "resetting"));
+
+	/* zeroize all entries and move them to the list of unused
+	 */
+	while (!list_empty(&df->changes)) {
+		struct tabdiff_entry *de = list_entry(df->changes.next,
+			                  struct tabdiff_entry, changes);
+
+		list_del_init(&de->changes);
+		list_add_tail(&de->changes, &df->unused);
+
+		mnt_unref_fs(de->new_fs);
+		mnt_unref_fs(de->old_fs);
+
+		de->new_fs = de->old_fs = NULL;
+		de->oper = 0;
+	}
+
+	df->nchanges = 0;
+	return 0;
+}
+
+static int tabdiff_add_entry(struct libmnt_tabdiff *df, struct libmnt_fs *old,
+			     struct libmnt_fs *new, int oper)
+{
+	struct tabdiff_entry *de;
+
+	assert(df);
+
+	DBG(DIFF, ul_debugobj(df, "add change on %s",
+				mnt_fs_get_target(new ? new : old)));
+
+	if (!list_empty(&df->unused)) {
+		de = list_entry(df->unused.next, struct tabdiff_entry, changes);
+		list_del(&de->changes);
+	} else {
+		de = calloc(1, sizeof(*de));
+		if (!de)
+			return -ENOMEM;
+	}
+
+	INIT_LIST_HEAD(&de->changes);
+
+	mnt_ref_fs(new);
+	mnt_ref_fs(old);
+
+	mnt_unref_fs(de->new_fs);
+	mnt_unref_fs(de->old_fs);
+
+	de->old_fs = old;
+	de->new_fs = new;
+	de->oper = oper;
+
+	list_add_tail(&de->changes, &df->changes);
+	df->nchanges++;
+	return 0;
+}
+
+static struct tabdiff_entry *tabdiff_get_mount(struct libmnt_tabdiff *df,
+					       const char *src,
+					       int id)
+{
+	struct list_head *p;
+
+	assert(df);
+
+	list_for_each(p, &df->changes) {
+		struct tabdiff_entry *de;
+
+		de = list_entry(p, struct tabdiff_entry, changes);
+
+		if (de->oper == MNT_TABDIFF_MOUNT && de->new_fs &&
+		    mnt_fs_get_id(de->new_fs) == id) {
+
+			const char *s = mnt_fs_get_source(de->new_fs);
+
+			if (s == NULL && src == NULL)
+				return de;
+			if (s && src && strcmp(s, src) == 0)
+				return de;
+		}
+	}
+	return NULL;
+}
+
+/**
+ * mnt_diff_tables:
+ * @df: diff handler
+ * @old_tab: old table
+ * @new_tab: new table
+ *
+ * Compares @old_tab and @new_tab, the result is stored in @df and accessible by
+ * mnt_tabdiff_next_change().
+ *
+ * Returns: number of changes, negative number in case of error.
+ */
+int mnt_diff_tables(struct libmnt_tabdiff *df, struct libmnt_table *old_tab,
+		    struct libmnt_table *new_tab)
+{
+	struct libmnt_fs *fs;
+	struct libmnt_iter itr;
+	int no, nn;
+
+	if (!df || !old_tab || !new_tab)
+		return -EINVAL;
+
+	tabdiff_reset(df);
+
+	no = mnt_table_get_nents(old_tab);
+	nn = mnt_table_get_nents(new_tab);
+
+	if (!no && !nn)			/* both tables are empty */
+		return 0;
+
+	DBG(DIFF, ul_debugobj(df, "analyze new (%d entries), "
+				          "old (%d entries)",
+				nn, no));
+
+	mnt_reset_iter(&itr, MNT_ITER_FORWARD);
+
+	/* all mounted or umounted */
+	if (!no && nn) {
+		while(mnt_table_next_fs(new_tab, &itr, &fs) == 0)
+			tabdiff_add_entry(df, NULL, fs, MNT_TABDIFF_MOUNT);
+		goto done;
+
+	} else if (no && !nn) {
+		while(mnt_table_next_fs(old_tab, &itr, &fs) == 0)
+			tabdiff_add_entry(df, fs, NULL, MNT_TABDIFF_UMOUNT);
+		goto done;
+	}
+
+	/* search newly mounted or modified */
+	while(mnt_table_next_fs(new_tab, &itr, &fs) == 0) {
+		struct libmnt_fs *o_fs;
+		const char *src = mnt_fs_get_source(fs),
+			   *tgt = mnt_fs_get_target(fs);
+
+		o_fs = mnt_table_find_pair(old_tab, src, tgt, MNT_ITER_FORWARD);
+		if (!o_fs)
+			/* 'fs' is not in the old table -- so newly mounted */
+			tabdiff_add_entry(df, NULL, fs, MNT_TABDIFF_MOUNT);
+		else {
+			/* is modified? */
+			const char *v1 = mnt_fs_get_vfs_options(o_fs),
+				   *v2 = mnt_fs_get_vfs_options(fs),
+				   *f1 = mnt_fs_get_fs_options(o_fs),
+				   *f2 = mnt_fs_get_fs_options(fs);
+
+			if ((v1 && v2 && strcmp(v1, v2) != 0) || (f1 && f2 && strcmp(f1, f2) != 0))
+				tabdiff_add_entry(df, o_fs, fs, MNT_TABDIFF_REMOUNT);
+		}
+	}
+
+	/* search umounted or moved */
+	mnt_reset_iter(&itr, MNT_ITER_FORWARD);
+	while(mnt_table_next_fs(old_tab, &itr, &fs) == 0) {
+		const char *src = mnt_fs_get_source(fs),
+			   *tgt = mnt_fs_get_target(fs);
+
+		if (!mnt_table_find_pair(new_tab, src, tgt, MNT_ITER_FORWARD)) {
+			struct tabdiff_entry *de;
+
+			de = tabdiff_get_mount(df, src,	mnt_fs_get_id(fs));
+			if (de) {
+				mnt_ref_fs(fs);
+				mnt_unref_fs(de->old_fs);
+				de->oper = MNT_TABDIFF_MOVE;
+				de->old_fs = fs;
+			} else
+				tabdiff_add_entry(df, fs, NULL, MNT_TABDIFF_UMOUNT);
+		}
+	}
+done:
+	DBG(DIFF, ul_debugobj(df, "%d changes detected", df->nchanges));
+	return df->nchanges;
+}
+
+#ifdef TEST_PROGRAM
+
+static int test_diff(struct libmnt_test *ts, int argc, char *argv[])
+{
+	struct libmnt_table *tb_old, *tb_new;
+	struct libmnt_tabdiff *diff;
+	struct libmnt_iter *itr;
+	struct libmnt_fs *old, *new;
+	int rc = -1, change;
+
+	tb_old = mnt_new_table_from_file(argv[1]);
+	tb_new = mnt_new_table_from_file(argv[2]);
+	diff = mnt_new_tabdiff();
+	itr = mnt_new_iter(MNT_ITER_FORWARD);
+
+	if (!tb_old || !tb_new || !diff || !itr) {
+		warnx("failed to allocate resources");
+		goto done;
+	}
+
+	rc = mnt_diff_tables(diff, tb_old, tb_new);
+	if (rc < 0)
+		goto done;
+
+	while(mnt_tabdiff_next_change(diff, itr, &old, &new, &change) == 0) {
+
+		printf("%s on %s: ", mnt_fs_get_source(new ? new : old),
+				     mnt_fs_get_target(new ? new : old));
+
+		switch(change) {
+		case MNT_TABDIFF_MOVE:
+			printf("MOVED to %s\n", mnt_fs_get_target(new));
+			break;
+		case MNT_TABDIFF_UMOUNT:
+			printf("UMOUNTED\n");
+			break;
+		case MNT_TABDIFF_REMOUNT:
+			printf("REMOUNTED from '%s' to '%s'\n",
+					mnt_fs_get_options(old),
+					mnt_fs_get_options(new));
+			break;
+		case MNT_TABDIFF_MOUNT:
+			printf("MOUNTED\n");
+			break;
+		default:
+			printf("unknown change!\n");
+		}
+	}
+
+	rc = 0;
+done:
+	mnt_unref_table(tb_old);
+	mnt_unref_table(tb_new);
+	mnt_free_tabdiff(diff);
+	mnt_free_iter(itr);
+	return rc;
+}
+
+int main(int argc, char *argv[])
+{
+	struct libmnt_test tss[] = {
+		{ "--diff", test_diff, "<old> <new> prints change" },
+		{ NULL }
+	};
+
+	return mnt_run_test(tss, argc, argv);
+}
+
+#endif /* TEST_PROGRAM */