From: Karel Zak <kzak@redhat.com>
Date: Wed, 15 Jul 2026 10:46:06 +0000 (+0200)
Subject: libmount: add VFS test to test_mount_context
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=41fdfa32f86e51f16d928612c54ae8493e45930c;p=thirdparty%2Futil-linux.git

libmount: add VFS test to test_mount_context

Add --vfs test that exercises the pluggable VFS I/O operations with
three sub-options:

  --table <file>   parse a mount table through VFS fopen
  --cache <dev>    probe device via cache (udev, then blkid)
  --blkid <dev>    probe device directly via libblkid VFS

The test sets up VFS callbacks that wrap standard syscalls and report
call counts, verifying that I/O is routed through the pluggable layer.

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

diff --git a/libmount/src/context.c b/libmount/src/context.c
index 782ecd96a..098bed02a 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -3602,6 +3602,8 @@ struct libmnt_ns *mnt_context_switch_target_ns(struct libmnt_context *cxt)
 
 #ifdef TEST_PROGRAM
 
+#include <blkid.h>
+
 static int test_search_helper(struct libmnt_test *ts __attribute__((unused)),
 			      int argc, char *argv[])
 {
@@ -3631,6 +3633,70 @@ static int test_search_helper(struct libmnt_test *ts __attribute__((unused)),
 
 static struct libmnt_lock *lock;
 
+static unsigned int test_vfs_opens;
+static unsigned int test_vfs_closes;
+static unsigned int test_vfs_reads;
+static unsigned int test_vfs_writes;
+static unsigned int test_vfs_lseeks;
+
+static ssize_t test_vfs_read(int fd, void *buf, size_t count)
+{
+	test_vfs_reads++;
+	return read(fd, buf, count);
+}
+
+static ssize_t test_vfs_write(int fd, const void *buf, size_t count)
+{
+	test_vfs_writes++;
+	return write(fd, buf, count);
+}
+
+static int test_vfs_open(const char *pathname, int flags, mode_t mode)
+{
+	test_vfs_opens++;
+	return open(pathname, flags, mode);
+}
+
+static int test_vfs_close(int fd)
+{
+	test_vfs_closes++;
+	return close(fd);
+}
+
+static off_t test_vfs_lseek(int fd, off_t offset, int whence)
+{
+	test_vfs_lseeks++;
+	return lseek(fd, offset, whence);
+}
+
+static FILE *test_vfs_fopen(const char *pathname, const char *mode)
+{
+	fprintf(stderr, "VFS: fopen(\"%s\", \"%s\")\n", pathname, mode);
+	return fopen(pathname, mode);
+}
+
+static void test_vfs_dump_stats(void)
+{
+	fprintf(stderr, "VFS calls: open=%u close=%u read=%u write=%u lseek=%u\n",
+			test_vfs_opens, test_vfs_closes,
+			test_vfs_reads, test_vfs_writes, test_vfs_lseeks);
+}
+
+static int test_set_vfs(struct libmnt_context *cxt)
+{
+	struct ul_vfs_ops ops = {
+		.size      = sizeof(ops),
+		.vfs_read  = test_vfs_read,
+		.vfs_write = test_vfs_write,
+		.vfs_open  = test_vfs_open,
+		.vfs_close = test_vfs_close,
+		.vfs_lseek = test_vfs_lseek,
+		.vfs_fopen = test_vfs_fopen,
+	};
+
+	return mnt_context_set_vfs(cxt, &ops);
+}
+
 static void lock_fallback(void)
 {
 	if (lock)
@@ -3876,6 +3942,101 @@ static int test_mountall(struct libmnt_test *ts __attribute__((unused)),
 
 
 
+static int test_vfs(struct libmnt_test *ts __attribute__((unused)),
+		    int argc, char *argv[])
+{
+	int idx = 1, rc = 0;
+	struct libmnt_context *cxt;
+	struct libmnt_table *tb = NULL;
+
+	cxt = mnt_new_context();
+	if (!cxt)
+		return -ENOMEM;
+
+	test_set_vfs(cxt);
+
+	if (idx < argc && !strcmp(argv[idx], "--table")) {
+		idx++;
+		if (idx >= argc) {
+			rc = -EINVAL;
+			goto done;
+		}
+		rc = mnt_context_get_table(cxt, argv[idx++], &tb);
+		if (rc) {
+			warn("failed to parse table");
+			goto done;
+		}
+		printf("table: parsed %d entries\n",
+				mnt_table_get_nents(tb));
+		mnt_unref_table(tb);
+	}
+
+	if (idx < argc && !strcmp(argv[idx], "--cache")) {
+		struct libmnt_cache *cache;
+		char *type;
+
+		idx++;
+		if (idx >= argc) {
+			rc = -EINVAL;
+			goto done;
+		}
+		cache = mnt_context_get_cache(cxt);
+		if (!cache) {
+			warnx("no cache");
+			rc = -ENOMEM;
+			goto done;
+		}
+		rc = mnt_cache_read_tags(cache, argv[idx]);
+		if (rc < 0) {
+			warn("failed to read tags for %s", argv[idx]);
+			goto done;
+		}
+		type = mnt_get_fstype(argv[idx], NULL, cache);
+		printf("cache: %s type=%s\n", argv[idx], type ? type : "unknown");
+		idx++;
+	}
+
+	if (idx < argc && !strcmp(argv[idx], "--blkid")) {
+		blkid_probe pr;
+		const char *data;
+
+		idx++;
+		if (idx >= argc) {
+			rc = -EINVAL;
+			goto done;
+		}
+		pr = blkid_new_probe();
+		if (!pr) {
+			rc = -ENOMEM;
+			goto done;
+		}
+		blkid_probe_set_vfs(pr, cxt->vfs);
+		if (blkid_probe_open_device(pr, argv[idx], 0)) {
+			warn("failed to open %s", argv[idx]);
+			blkid_free_probe(pr);
+			rc = -errno;
+			goto done;
+		}
+		blkid_probe_enable_superblocks(pr, 1);
+		blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_TYPE);
+
+		rc = blkid_do_safeprobe(pr);
+		if (!rc && !blkid_probe_lookup_value(pr, "TYPE", &data, NULL))
+			printf("blkid: %s type=%s\n", argv[idx], data);
+		else
+			printf("blkid: %s type=unknown\n", argv[idx]);
+
+		blkid_free_probe(pr);
+		idx++;
+		rc = 0;
+	}
+
+done:
+	test_vfs_dump_stats();
+	mnt_free_context(cxt);
+	return rc;
+}
+
 int main(int argc, char *argv[])
 {
 	struct libmnt_test tss[] = {
@@ -3885,6 +4046,7 @@ int main(int argc, char *argv[])
 	{ "--flags", test_flags,   "[-o <opts>] <spec>" },
 	{ "--cxtsync", test_cxtsync, "<fsopts> <cxtopts> <fsopts>" },
 	{ "--search-helper", test_search_helper, "<fstype>" },
+	{ "--vfs", test_vfs, "[--table <file>] [--cache <dev>] [--blkid <dev>]" },
 	{ NULL }};
 
 	umask(S_IWGRP|S_IWOTH);	/* to be compatible with mount(8) */