From b1489186cc8391e0c1e342f9fbc3eedf6b944c61 Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Mon, 7 Jun 2021 12:15:24 -0700
Subject: [PATCH] ext4: add check to prevent attempting to resize an fs with
sparse_super2
Git-commit: b1489186cc8391e0c1e342f9fbc3eedf6b944c61
Patch-mainline: v5.14-rc1
References: bsc#1197754
The in-kernel ext4 resize code doesn't support filesystem with the
sparse_super2 feature. It fails with errors like this and doesn't finish
the resize:
EXT4-fs (loop0): resizing filesystem from 16640 to 7864320 blocks
EXT4-fs warning (device loop0): verify_reserved_gdb:760: reserved GDT 2 missing grp 1 (32770)
EXT4-fs warning (device loop0): ext4_resize_fs:2111: error (-22) occurred during file system resize
EXT4-fs (loop0): resized filesystem to 2097152
To reproduce:
mkfs.ext4 -b 4096 -I 256 -J size=32 -E resize=$((256*1024*1024)) -O sparse_super2 ext4.img 65M
truncate -s 30G ext4.img
mount ext4.img /mnt
python3 -c 'import fcntl, os, struct ; fd = os.open("/mnt", os.O_RDONLY | os.O_DIRECTORY) ; fcntl.ioctl(fd, 0x40086610, struct.pack("Q", 30 * 1024 * 1024 * 1024 // 4096), False) ; os.close(fd)'
dmesg | tail
e2fsck ext4.img
The userspace resize2fs tool has a check for this case: it checks if the
filesystem has sparse_super2 set and if the kernel provides
/sys/fs/ext4/features/sparse_super2. However, the former check requires
manually reading and parsing the filesystem superblock.
Detect this case in ext4_resize_begin and error out early with a clear
error message.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/74b8ae78405270211943cd7393e65586c5faeed1.1623093259.git.josh@joshtriplett.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/ext4/resize.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -72,6 +72,10 @@ int ext4_resize_begin(struct super_block
"so online resizing is not allowed");
return -EPERM;
}
+ if (ext4_has_feature_sparse_super2(sb)) {
+ ext4_msg(sb, KERN_ERR, "Online resizing not supported with sparse_super2");
+ return -EOPNOTSUPP;
+ }
if (test_and_set_bit_lock(EXT4_FLAGS_RESIZING,
&EXT4_SB(sb)->s_ext4_flags))