On Fri, Dec 13, 2019 at 7:39 AM Phong Tran <tranmanphong@xxxxxxxxx> wrote:
>
> struct ext4_sb_info.system_blks was marked __rcu.
> But access the pointer without using RCU lock and dereference.
> Sparse warning with __rcu notation:
>
> block_validity.c:139:29: warning: incorrect type in argument 1 (different address spaces)
> block_validity.c:139:29: expected struct rb_root const *
> block_validity.c:139:29: got struct rb_root [noderef] <asn:4> *
>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Phong Tran <tranmanphong@xxxxxxxxx>
Thanks Phong! Looks like a real bug fix caught thanks to Sparse. So
let us mark for stable as well?
- Joel
> ---
> fs/ext4/block_validity.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> ---
> change log:
> V2: Add Reviewed-by: Jan Kara <jack@xxxxxxx>
>
> diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
> index d4d4fdfac1a6..1ee04e76bbe0 100644
> --- a/fs/ext4/block_validity.c
> +++ b/fs/ext4/block_validity.c
> @@ -133,10 +133,13 @@ static void debug_print_tree(struct ext4_sb_info *sbi)
> {
> struct rb_node *node;
> struct ext4_system_zone *entry;
> + struct ext4_system_blocks *system_blks;
> int first = 1;
>
> printk(KERN_INFO "System zones: ");
> - node = rb_first(&sbi->system_blks->root);
> + rcu_read_lock();
> + system_blks = rcu_dereference(sbi->system_blks);
> + node = rb_first(&system_blks->root);
> while (node) {
> entry = rb_entry(node, struct ext4_system_zone, node);
> printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ",
> @@ -144,6 +147,7 @@ static void debug_print_tree(struct ext4_sb_info *sbi)
> first = 0;
> node = rb_next(node);
> }
> + rcu_read_unlock();
> printk(KERN_CONT "\n");
> }
>
> --
> 2.20.1
>
