Re: [PATCH] erofs: add sysfs node to drop all compression-related caches

[Gao Xiang <hsiangkao@linux.alibaba.com>]

Hi Chunhai,

On 2024/11/12 17:14, Chunhai Guo wrote:
> Add a sysfs node to drop all compression-related caches, including
> pclusters and attached compressed pages.

subject: erofs: add sysfs node to drop internal caches

Add a sysfs node to drop compression-related caches, currently
used to drop in-memory pclusters and compressed folios.

I don't think it really drops `compressed folios`, also see
my comment below:

> 
> Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
> ---
>   Documentation/ABI/testing/sysfs-fs-erofs |  7 +++++++
>   fs/erofs/sysfs.c                         | 11 +++++++++++
>   2 files changed, 18 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
> index 284224d1b56f..b66a3f6d3fdf 100644
> --- a/Documentation/ABI/testing/sysfs-fs-erofs
> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
> @@ -16,3 +16,10 @@ Description:	Control strategy of sync decompression:
>   		  readahead on atomic contexts only.
>   		- 1 (force on): enable for readpage and readahead.
>   		- 2 (force off): disable for all situations.
> +
> +What:		/sys/fs/erofs/<disk>/drop_caches
> +Date:		November 2024
> +Contact:	"Guo Chunhai" <guochunhai@vivo.com>
> +Description:	Writing 1 to this will cause the erofs to drop all
> +		compression-related caches, including pclusters and attached
> +		compressed pages. Any other value is invalid.
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index 63cffd0fd261..f068f01437d5 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -10,6 +10,7 @@
>   
>   enum {
>   	attr_feature,
> +	attr_drop_caches,
>   	attr_pointer_ui,
>   	attr_pointer_bool,
>   };
> @@ -57,11 +58,13 @@ static struct erofs_attr erofs_attr_##_name = {			\
>   
>   #ifdef CONFIG_EROFS_FS_ZIP
>   EROFS_ATTR_RW_UI(sync_decompress, erofs_mount_opts);
> +EROFS_ATTR_FUNC(drop_caches, 0200);
>   #endif
>   
>   static struct attribute *erofs_attrs[] = {
>   #ifdef CONFIG_EROFS_FS_ZIP
>   	ATTR_LIST(sync_decompress),
> +	ATTR_LIST(drop_caches),
>   #endif
>   	NULL,
>   };
> @@ -163,6 +166,14 @@ static ssize_t erofs_attr_store(struct kobject *kobj, struct attribute *attr,
>   			return -EINVAL;
>   		*(bool *)ptr = !!t;
>   		return len;
> +	case attr_drop_caches:
> +		ret = kstrtoul(skip_spaces(buf), 0, &t);
> +		if (ret)
> +			return ret;
> +		if (t != 1)
> +			return -EINVAL;

		if (t & 2)
			z_erofs_shrink_scan(sbi, ~0UL);

		if (t & 1)
			invalidate_mapping_pages(EROFS_I_SB(inode)->managed_cache->i_mapping, 0, -1);

or you could export MNGD_MAPPING macros again.

Thanks,
Gao Xiang