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

[Chunhai Guo]

Add a sysfs node to drop all compression-related caches, including
pclusters and attached compressed pages.

Signed-off-by: Chunhai Guo <guochunhai at 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 at 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;
+		z_erofs_shrink_scan(sbi, ~0UL);
+		return len;
 	}
 	return 0;
 }
-- 
2.34.1