Commit 27056451 authored by Baokun Li's avatar Baokun Li Committed by Theodore Ts'o
Browse files

ext4: move ext4_percpu_param_init() before ext4_mb_init() 



When running `kvm-xfstests -c ext4/1k -C 1 generic/383` with the
`DOUBLE_CHECK` macro defined, the following panic is triggered:

==================================================================
EXT4-fs error (device vdc): ext4_validate_block_bitmap:423:
                        comm mount: bg 0: bad block bitmap checksum
BUG: unable to handle page fault for address: ff110000fa2cc000
PGD 3e01067 P4D 3e02067 PUD 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 2386 Comm: mount Tainted: G W
                        6.18.0-gba65a4e7120a-dirty #1152 PREEMPT(none)
RIP: 0010:percpu_counter_add_batch+0x13/0xa0
Call Trace:
 <TASK>
 ext4_mark_group_bitmap_corrupted+0xcb/0xe0
 ext4_validate_block_bitmap+0x2a1/0x2f0
 ext4_read_block_bitmap+0x33/0x50
 mb_group_bb_bitmap_alloc+0x33/0x80
 ext4_mb_add_groupinfo+0x190/0x250
 ext4_mb_init_backend+0x87/0x290
 ext4_mb_init+0x456/0x640
 __ext4_fill_super+0x1072/0x1680
 ext4_fill_super+0xd3/0x280
 get_tree_bdev_flags+0x132/0x1d0
 vfs_get_tree+0x29/0xd0
 vfs_cmd_create+0x59/0xe0
 __do_sys_fsconfig+0x4f6/0x6b0
 do_syscall_64+0x50/0x1f0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================

This issue can be reproduced using the following commands:
        mkfs.ext4 -F -q -b 1024 /dev/sda 5G
        tune2fs -O quota,project /dev/sda
        mount /dev/sda /tmp/test

With DOUBLE_CHECK defined, mb_group_bb_bitmap_alloc() reads
and validates the block bitmap. When the validation fails,
ext4_mark_group_bitmap_corrupted() attempts to update
sbi->s_freeclusters_counter. However, this percpu_counter has not been
initialized yet at this point, which leads to the panic described above.

Fix this by moving the execution of ext4_percpu_param_init() to occur
before ext4_mb_init(), ensuring the per-CPU counters are initialized
before they are used.

Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarZhang Yi <yi.zhang@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20251209133116.731350-1-libaokun@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 382dd788

fs/ext4/super.c

+5 −5
Original line number Diff line number Diff line
@@ -5604,6 +5604,10 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) 
			clear_opt2(sb, MB_OPTIMIZE_SCAN);

	}



	err = ext4_percpu_param_init(sbi);

	if (err)

		goto failed_mount5;



	err = ext4_mb_init(sb);

	if (err) {

		ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
@@ -5619,10 +5623,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) 
		sbi->s_journal->j_commit_callback =

			ext4_journal_commit_callback;



	err = ext4_percpu_param_init(sbi);

	if (err)

		goto failed_mount6;



	if (ext4_has_feature_flex_bg(sb))

		if (!ext4_fill_flex_info(sb)) {

			ext4_msg(sb, KERN_ERR,
@@ -5704,8 +5704,8 @@ failed_mount8: __maybe_unused 
failed_mount6:

	ext4_mb_release(sb);

	ext4_flex_groups_free(sbi);

	ext4_percpu_param_destroy(sbi);

failed_mount5:

	ext4_percpu_param_destroy(sbi);

	ext4_ext_release(sb);

	ext4_release_system_zone(sb);

failed_mount4a: