debugfs, e2fsck: fix s_desc_size handling

The s_desc_size in the superblock specifies the group descriptor
size in bytes, but in various places the EXT4_FEATURE_INCOMPAT_64BIT
flag implies that the descriptor size is EXT2_MIN_DESC_SIZE_64BIT
(64 bytes) instead of checking the actual size.  In other places,
the s_desc_size field is used without checking for INCOMPAT_64BIT.

In the case of ext2fs_group_desc() the s_desc_size was being ignored,
and assumed to be sizeof(struct ext4_group_desc), which would result
in garbage for any but the first group descriptor.  Similarly, in
ext2fs_group_desc_csum() and print_csum() they assumed that the
maximum group descriptor size was sizeof(struct ext4_group_desc).
Fix these functions to use the actual superblock s_desc_size if
INCOMPAT_64BIT.

Conversely, in ext2fs_swap_group_desc2() s_desc_size was used
without checking for INCOMPAT_64BIT being set.

The e2fsprogs behaviour is different than that of the kernel,
which always checks INCOMPAT_64BIT, and only uses s_desc_size to
determine the offset of group descriptors and what range of bytes
to checksum.

Allow specifying the s_desc_size field at mke2fs time with the
"-E desc_size=NNN" option.  Allow a power-of-two s_desc_size
value up to s_blocksize if INCOMPAT_64BIT is specified.  This
is not expected to be used by regular users at this time, so it
is not currently documented in the mke2fs usage or man page.

Add m_desc_size_128, f_desc_size_128, and f_desc_bad test cases to
verify mke2fs and e2fsck handling of larger group descriptor sizes.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

3 files changed, 35 insertions, 0 deletions

diff --git a/tests/f_desc_size_bad/expect.1 b/tests/f_desc_size_bad/expect.1
new file mode 100644
index 00000000..009ee041
--- /dev/null
+++ b/tests/f_desc_size_bad/expect.1
@@ -0,0 +1,11 @@
+ext2fs_check_desc: Block group descriptor size incorrect
+../e2fsck/e2fsck: Group descriptors look bad... trying backup blocks...
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+
+test_filesys: ***** FILE SYSTEM WAS MODIFIED *****
+test_filesys: 11/32 files (0.0% non-contiguous), 801/2048 blocks
+Exit status is 1
diff --git a/tests/f_desc_size_bad/expect.2 b/tests/f_desc_size_bad/expect.2
new file mode 100644
index 00000000..d1429fdc
--- /dev/null
+++ b/tests/f_desc_size_bad/expect.2
@@ -0,0 +1,7 @@
+Pass 1: Checking inodes, blocks, and sizes
+Pass 2: Checking directory structure
+Pass 3: Checking directory connectivity
+Pass 4: Checking reference counts
+Pass 5: Checking group summary information
+test_filesys: 11/32 files (0.0% non-contiguous), 801/2048 blocks
+Exit status is 0
diff --git a/tests/f_desc_size_bad/script b/tests/f_desc_size_bad/script
new file mode 100644
index 00000000..54403286
--- /dev/null
+++ b/tests/f_desc_size_bad/script
@@ -0,0 +1,17 @@
+if ! test -x $DEBUGFS_EXE; then
+        echo "$test_name: $test_description: skipped"
+	return 0
+fi
+
+DESCRIPTION="bad superblock s_desc_size"
+SKIP_GUNZIP=true
+touch $TMPFILE
+$MKE2FS -F -o Linux -O 64bit,extents -N 32 -b 1024 -g 512 -E desc_size=128 $TMPFILE 2048 > $test_name.log 2>&1
+$DEBUGFS -R "ssv desc_size 129" -w $TMPFILE >> $test_name.log 2>&1
+
+E2FSCK_TIME=200704102100
+export E2FSCK_TIME
+
+. $cmd_dir/run_e2fsck
+
+unset E2FSCK_TIME