ext4/033: test EXT4_IOC_RESIZE_FS by calling the ioctl directly

E2fsprogs commits 4ea80d031c7e ("resize2fs: adjust new size of the
file system to allow a successful resize") and 50088b1996cc
("resize2fs: attempt to keep the # of inodes valid by removing the
last bg") will automatically reduce the requested new size of the file
system by up to a single block group to avoid overflowing the 32-bit
inode count.   This interferes with ext4/033's test of kernel commit
4f2f76f75143 ("ext4: Forbid overflowing inode count when # resizing".)

Address this by creating a new test program, ext4_resize which calls
the EXT4_IOC_RESIZE_FS ioctl directly so we can correctly test the
kernel's online resize code.

Reported-by: Eric Whitney <enwlinux@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

4 files changed, 63 insertions, 6 deletions

diff --git a/.gitignore b/.gitignore
index 9e6d2fd596..65b93307b7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -77,6 +77,7 @@ tags
 /src/dirperf
 /src/dirstress
 /src/e4compact
+/src/ext4_resize
 /src/fault
 /src/feature
 /src/fiemap-tester
diff --git a/src/Makefile b/src/Makefile
index 25ab061d51..1737ed0e13 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -31,7 +31,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	dio-invalidate-cache stat_test t_encrypted_d_revalidate \
 	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
 	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
-	detached_mounts_propagation
+	detached_mounts_propagation ext4_resize
 
 EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
 	      btrfs_crc32c_forged_name.py
diff --git a/src/ext4_resize.c b/src/ext4_resize.c
new file mode 100644
index 0000000000..1ac51e6fc6
--- /dev/null
+++ b/src/ext4_resize.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Test program which uses the raw ext4 resize_fs ioctl directly.
+ */
+
+#include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/mount.h>
+
+typedef unsigned long long __u64;
+
+#ifndef EXT4_IOC_RESIZE_FS
+#define EXT4_IOC_RESIZE_FS		_IOW('f', 16, __u64)
+#endif
+
+int main(int argc, char **argv)
+{
+	__u64	new_size;
+	int	error, fd;
+	char	*tmp = NULL;
+
+	if (argc != 3) {
+		fputs("insufficient arguments\n", stderr);
+		return 1;
+	}
+	fd = open(argv[1], O_RDONLY);
+	if (!fd) {
+		perror(argv[1]);
+		return 1;
+	}
+
+	new_size = strtoull(argv[2], &tmp, 10);
+	if ((errno) || (*tmp != '\0')) {
+		fprintf(stderr, "%s: invalid new size\n", argv[0]);
+		return 1;
+	}
+
+	error = ioctl(fd, EXT4_IOC_RESIZE_FS, &new_size);
+	if (error < 0) {
+		perror("EXT4_IOC_RESIZE_FS");
+		return 1;
+	}
+	return 0;
+}
diff --git a/tests/ext4/033 b/tests/ext4/033
index 1bc14c034b..22041a1711 100755
--- a/tests/ext4/033
+++ b/tests/ext4/033
@@ -5,7 +5,8 @@
 # FS QA Test 033
 #
 # Test s_inodes_count overflow for huge filesystems. This bug was fixed
-# by commit "ext4: Forbid overflowing inode count when resizing".
+# by commit 4f2f76f75143 ("ext4: Forbid overflowing inode count when
+# resizing".)
 #
 . ./common/preamble
 _begin_fstest auto ioctl resize
@@ -28,7 +29,9 @@ _supported_fs ext4
 _require_scratch_nocheck
 _require_dmhugedisk
 _require_dumpe2fs
-_require_command "$RESIZE2FS_PROG" resize2fs
+_require_test_program ext4_resize
+
+EXT4_RESIZE=$here/src/ext4_resize
 
 # Figure out whether device is large enough
 devsize=$(blockdev --getsize64 $SCRATCH_DEV)
@@ -68,7 +71,8 @@ $DUMPE2FS_PROG -h $DMHUGEDISK_DEV >> $seqres.full 2>&1
 
 # This should fail, s_inodes_count would just overflow!
 echo "Resizing to inode limit + 1..."
-$RESIZE2FS_PROG $DMHUGEDISK_DEV $((limit_groups*group_blocks)) >> $seqres.full 2>&1
+echo $EXT4_RESIZE $SCRATCH_MNT $((limit_groups*group_blocks)) >> $seqres.full 2>&1
+$EXT4_RESIZE $SCRATCH_MNT $((limit_groups*group_blocks)) >> $seqres.full 2>&1
 if [ $? -eq 0 ]; then
 	echo "Resizing succeeded but it should fail!"
 	exit
@@ -76,7 +80,8 @@ fi
 
 # This should succeed, we are maxing out inodes
 echo "Resizing to max group count..."
-$RESIZE2FS_PROG $DMHUGEDISK_DEV $(((limit_groups-1)*group_blocks)) >> $seqres.full 2>&1
+echo $EXT4_RESIZE $SCRATCH_MNT $(((limit_groups-1)*group_blocks)) >> $seqres.full 2>&1
+$EXT4_RESIZE $SCRATCH_MNT $(((limit_groups-1)*group_blocks)) >> $seqres.full 2>&1
 if [ $? -ne 0 ]; then
 	echo "Resizing failed!"
 	exit
@@ -87,7 +92,8 @@ $DUMPE2FS_PROG -h $DMHUGEDISK_DEV >> $seqres.full 2>&1
 
 # This should fail, s_inodes_count would overflow by quite a bit!
 echo "Resizing to device size..."
-$RESIZE2FS_PROG $DMHUGEDISK_DEV >> $seqres.full 2>&1
+echo $EXT4_RESIZE $SCRATCH_MNT $(((limit_groups + 16)*group_blocks)) >> $seqres.full 2>&1
+$EXT4_RESIZE $SCRATCH_MNT $(((limit_groups + 16)*group_blocks)) >> $seqres.full 2>&1
 if [ $? -eq 0 ]; then
 	echo "Resizing succeeded but it should fail!"
 	exit