[PATCH v4] erofs: free pclusters if no cached folio attached

[Gao Xiang]

Just two extra minor nits...

First, the subject line would be
"erofs: free pclusters if no cached folio is attached"

On 2024/11/11 19:38, Chunhai Guo wrote:
> Once a pcluster is fully decompressed and there are no attached cached
> folios, its corresponding `struct z_erofs_pcluster` will be freed. This
> will significantly reduce the frequency of calls to erofs_shrink_scan()
> and the memory allocated for `struct z_erofs_pcluster`.
> 
> The tables below show approximately a 96% reduction in the calls to
> erofs_shrink_scan() and in the memory allocated for `struct
> z_erofs_pcluster` after applying this patch. The results were obtained
> by performing a test to copy a 4.1GB partition on ARM64 Android devices
> running the 6.6 kernel with an 8-core CPU and 12GB of memory.
> 
> 1. The reduction in calls to erofs_shrink_scan():
> +-----------------+-----------+----------+---------+
> |                 | w/o patch | w/ patch |  diff   |
> +-----------------+-----------+----------+---------+
> | Average (times) |   11390   |   390    | -96.57% |
> +-----------------+-----------+----------+---------+
> 
> 2. The reduction in memory released by erofs_shrink_scan():
> +-----------------+-----------+----------+---------+
> |                 | w/o patch | w/ patch |  diff   |
> +-----------------+-----------+----------+---------+
> | Average (Byte)  | 133612656 | 4434552  | -96.68% |
> +-----------------+-----------+----------+---------+
> 
> Signed-off-by: Chunhai Guo <guochunhai at vivo.com>

...

> -static void z_erofs_put_pcluster(struct z_erofs_pcluster *pcl)
> +static void z_erofs_put_pcluster(struct erofs_sb_info *sbi,
> +		struct z_erofs_pcluster *pcl, bool try_free)
>   {
> +	bool free = false;
> +
>   	if (lockref_put_or_lock(&pcl->lockref))
>   		return;
>   
>   	DBG_BUGON(__lockref_is_dead(&pcl->lockref));
> -	if (pcl->lockref.count == 1)
> -		atomic_long_inc(&erofs_global_shrink_cnt);
> -	--pcl->lockref.count;
> +	if (--pcl->lockref.count == 0) {

Second, EROFS codebase uses `!--pcl->lockref.count`
coding style instead of `== 0` since the old checkpatch.pl
will complain this and I'd like to keep consistentency..

Otherwise it looks good to me, if you send out a
new version, I will apply directly.

Thanks,
Gao Xiang