linux-kernel - Re: [PATCH v2] erofs: add sysfs node to drop internal caches

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Message-ID: <0b56f59e-b973-4ac2-b234-b362af8adedc@linux.alibaba.com>
Date: Tue, 12 Nov 2024 22:50:58 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Chunhai Guo <guochunhai@...o.com>, xiang@...nel.org
Cc: chao@...nel.org, huyue2@...lpad.com, jefflexu@...ux.alibaba.com,
 dhavale@...gle.com, linux-erofs@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] erofs: add sysfs node to drop internal caches



On 2024/11/12 19:40, Chunhai Guo wrote:
> Add a sysfs node to drop compression-related caches, currently used to
> drop in-memory pclusters and compressed folios.
> 
> Signed-off-by: Chunhai Guo <guochunhai@...o.com>
> ---
> v1: https://lore.kernel.org/linux-erofs/fabdfe9f-9293-45c2-8cf2-3d86c248ab4c@linux.alibaba.com
> change since v1:
>   - Change subject as suggested by Gao Xiang.
>   - Use different bits to indicate different meanings in the sysfs node.
> ---
>   Documentation/ABI/testing/sysfs-fs-erofs | 11 +++++++++++
>   fs/erofs/internal.h                      |  2 ++
>   fs/erofs/sysfs.c                         | 15 +++++++++++++++
>   fs/erofs/zdata.c                         |  1 -
>   4 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
> index 284224d1b56f..44d863cd07b5 100644
> --- a/Documentation/ABI/testing/sysfs-fs-erofs
> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
> @@ -16,3 +16,14 @@ 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@...o.com>
> +Description:	Writing to this will drop compression-related caches,
> +		currently used to drop in-memory pclusters and
> +		compressed folios:

		cached compressed folios:

> +
> +		- 1 : drop in-memory compressed folios

		- 1 : invalidate cached compressed folios

> +		- 2 : drop in-memory pclusters
> +		- 3 : drop in-memory pclusters and compressed folios

		- 3 : drop in-memory pclusters and cached compressed folios

> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 3905d991c49b..0328e6b98c1b 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -450,6 +450,8 @@ static inline void erofs_pagepool_add(struct page **pagepool, struct page *page)
>   void erofs_release_pages(struct page **pagepool);
>   
>   #ifdef CONFIG_EROFS_FS_ZIP
> +#define MNGD_MAPPING(sbi)	((sbi)->managed_cache->i_mapping)
> +
>   extern atomic_long_t erofs_global_shrink_cnt;
>   void erofs_shrinker_register(struct super_block *sb);
>   void erofs_shrinker_unregister(struct super_block *sb);
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index 63cffd0fd261..01d509e43827 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 +166,18 @@ 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 || t > 3)
> +			return -EINVAL;> +
> +		if (t & 1)
> +			invalidate_mapping_pages(MNGD_MAPPING(sbi), 0, -1);
> +		if (t & 2)
> +			z_erofs_shrink_scan(sbi, ~0UL);

Please switch the order to

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

		if (t & 1)
			invalidate_mapping_pages(MNGD_MAPPING(sbi), 0, -1);

So that all cached folios could be disconnected first.

Thanks,
Gao Xiang