[PATCH v2 14/24] erofs: introduce superblock registration

[Gao Xiang <gaoxiang25@xxxxxxxxxx>]

In order to introducing shrinker solution for erofs,
let's manage all mounted erofs instances at first.

Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
---
 fs/erofs/Makefile   |  2 +-
 fs/erofs/internal.h | 13 +++++++++++++
 fs/erofs/super.c    |  4 ++++
 fs/erofs/utils.c    | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 fs/erofs/utils.c

diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
index 9ab4ccc9328e..6a63c5998980 100644
--- a/fs/erofs/Makefile
+++ b/fs/erofs/Makefile
@@ -5,7 +5,7 @@ EROFS_VERSION = "1.0"
 ccflags-y += -DEROFS_VERSION=\"$(EROFS_VERSION)\"
 
 obj-$(CONFIG_EROFS_FS) += erofs.o
-erofs-objs := super.o inode.o data.o namei.o dir.o
+erofs-objs := super.o inode.o data.o namei.o dir.o utils.o
 erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
 erofs-$(CONFIG_EROFS_FS_ZIP) += zmap.o
 
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index f0a5fd316e09..87287cd9c146 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -60,6 +60,10 @@ typedef u64 erofs_off_t;
 typedef u32 erofs_blk_t;
 
 struct erofs_sb_info {
+#ifdef CONFIG_EROFS_FS_ZIP
+	/* list for all registered superblocks, mainly for shrinker */
+	struct list_head list;
+#endif
 	u32 blocks;
 	u32 meta_blkaddr;
 #ifdef CONFIG_EROFS_FS_XATTR
@@ -404,5 +408,14 @@ int erofs_namei(struct inode *dir, struct qstr *name,
 /* dir.c */
 extern const struct file_operations erofs_dir_fops;
 
+/* utils.c */
+#ifdef CONFIG_EROFS_FS_ZIP
+void erofs_shrinker_register(struct super_block *sb);
+void erofs_shrinker_unregister(struct super_block *sb);
+#else
+static inline void erofs_shrinker_register(struct super_block *sb) {}
+static inline void erofs_shrinker_unregister(struct super_block *sb) {}
+#endif
+
 #endif
 
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index bb1ae1f416e6..60058d3c50d4 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -374,6 +374,8 @@ static int erofs_read_super(struct super_block *sb,
 	snprintf(sbi->dev_name, PATH_MAX, "%s", dev_name);
 	sbi->dev_name[PATH_MAX - 1] = '\0';
 
+	erofs_shrinker_register(sb);
+
 	if (!silent)
 		infoln("mounted on %s with opts: %s.", dev_name,
 		       (char *)data);
@@ -412,6 +414,8 @@ static void erofs_put_super(struct super_block *sb)
 	infoln("unmounted for %s", sbi->dev_name);
 	__putname(sbi->dev_name);
 
+	erofs_shrinker_unregister(sb);
+
 	kfree(sbi);
 	sb->s_fs_info = NULL;
 }
diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
new file mode 100644
index 000000000000..08c8752895bc
--- /dev/null
+++ b/fs/erofs/utils.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/erofs/utils.c
+ *
+ * Copyright (C) 2018 HUAWEI, Inc.
+ *             http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@xxxxxxxxxx>
+ */
+#include "internal.h"
+
+#ifdef CONFIG_EROFS_FS_ZIP
+/* protects the mounted 'erofs_sb_list' */
+static DEFINE_SPINLOCK(erofs_sb_list_lock);
+static LIST_HEAD(erofs_sb_list);
+
+void erofs_shrinker_register(struct super_block *sb)
+{
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
+
+	spin_lock(&erofs_sb_list_lock);
+	list_add(&sbi->list, &erofs_sb_list);
+	spin_unlock(&erofs_sb_list_lock);
+}
+
+void erofs_shrinker_unregister(struct super_block *sb)
+{
+	spin_lock(&erofs_sb_list_lock);
+	list_del(&EROFS_SB(sb)->list);
+	spin_unlock(&erofs_sb_list_lock);
+}
+#endif
+
-- 
2.17.1