On Tue 17-08-21 22:56:54, Shaoying Xu wrote:
> Ext4 file system has default lazy inode table initialization setup once
> it is mounted. However, it has issue on computing the next schedule time
> that makes the timeout same amount in jiffies but different real time in
> secs if with various HZ values. Therefore, fix by measuring the current
> time in a more granular unit nanoseconds and make the next schedule time
> independent of the HZ value.
>
> Fixes: bfff68738f1c ("ext4: add support for lazy inode table initialization")
> Signed-off-by: Shaoying Xu <shaoyi@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Thanks for the patch. It seems to have fallen through the cracks. It looks
good just some nits: The timeout will be still dependent on the HZ value
because we use jiffie-granular timer. But yes, I guess it is unnecessary
to make the imprecision 10x worse when we know we are likely dealing with
small numbers.
> @@ -3460,14 +3460,13 @@ static int ext4_run_li_request(struct ext4_li_request *elr)
> ret = 1;
>
> if (!ret) {
Please add a comment here so that we don't forget. Like:
/* Use ns-granular time as init can be really fast */
With this feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
> - timeout = jiffies;
> + start_time = ktime_get_real_ns();
> ret = ext4_init_inode_table(sb, group,
> elr->lr_timeout ? 0 : 1);
> trace_ext4_lazy_itable_init(sb, group);
> if (elr->lr_timeout == 0) {
> - timeout = (jiffies - timeout) *
> - EXT4_SB(elr->lr_super)->s_li_wait_mult;
> - elr->lr_timeout = timeout;
> + elr->lr_timeout = nsecs_to_jiffies((ktime_get_real_ns() - start_time) *
> + EXT4_SB(elr->lr_super)->s_li_wait_mult);
> }
> elr->lr_next_sched = jiffies + elr->lr_timeout;
> elr->lr_next_group = group + 1;
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
