From: Baokun Li 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: 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: Baokun Li --- fs/ext4/super.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 87205660c5d0..5c2e931d8a53 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5599,35 +5599,35 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) */ if (!(ctx->spec & EXT4_SPEC_mb_optimize_scan)) { if (sbi->s_groups_count >= MB_DEFAULT_LINEAR_SCAN_THRESHOLD) set_opt2(sb, MB_OPTIMIZE_SCAN); else 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)", err); goto failed_mount5; } /* * We can only set up the journal commit callback once * mballoc is initialized */ if (sbi->s_journal) 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, "unable to initialize " "flex_bg meta info!"); err = -ENOMEM; goto failed_mount6; } @@ -5699,18 +5699,18 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) ext4_quotas_off(sb, EXT4_MAXQUOTAS); failed_mount8: __maybe_unused ext4_release_orphan_info(sb); failed_mount7: ext4_unregister_li_request(sb); 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: dput(sb->s_root); sb->s_root = NULL; failed_mount4: ext4_msg(sb, KERN_ERR, "mount failed"); if (EXT4_SB(sb)->rsv_conversion_wq) -- 2.39.2