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

[Gao Xiang]

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 <guochun...@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" <guochun...@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