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 <[email protected]>
---
v1: 
https://lore.kernel.org/linux-erofs/[email protected]
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" <[email protected]>
+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

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