[PATCH v4 14/24] erofs: introduce superblock registration

[Gao Xiang]

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    |  9 +++++++++
 fs/erofs/utils.c    | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 fs/erofs/utils.c

diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
index 481a966caf06..930770be124f 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 47af34f1fe50..2d437bcf140d 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -61,6 +61,10 @@ 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	/* CONFIG_EROFS_FS_ZIP */
 	u32 blocks;
 	u32 meta_blkaddr;
 #ifdef CONFIG_EROFS_FS_XATTR
@@ -400,5 +404,14 @@ 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	/* !CONFIG_EROFS_FS_ZIP */
+
 #endif	/* __EROFS_INTERNAL_H */
 
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 9b040be8c607..c9fe585a38a6 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -354,6 +354,8 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
 	if (unlikely(!sb->s_root))
 		return -ENOMEM;
 
+	erofs_shrinker_register(sb);
+
 	if (!silent)
 		infoln("mounted on %s with opts: %s.", sb->s_id, (char *)data);
 	return 0;
@@ -385,6 +387,12 @@ static void erofs_kill_sb(struct super_block *sb)
 	sb->s_fs_info = NULL;
 }
 
+/* called when ->s_root is non-NULL */
+static void erofs_put_super(struct super_block *sb)
+{
+	erofs_shrinker_unregister(sb);
+}
+
 static struct file_system_type erofs_fs_type = {
 	.owner          = THIS_MODULE,
 	.name           = "erofs",
@@ -496,6 +504,7 @@ static int erofs_remount(struct super_block *sb, int *flags, char *data)
 }
 
 const struct super_operations erofs_sops = {
+	.put_super = erofs_put_super,
 	.alloc_inode = alloc_inode,
 	.free_inode = free_inode,
 	.statfs = erofs_statfs,
diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
new file mode 100644
index 000000000000..791b2df1f761
--- /dev/null
+++ b/fs/erofs/utils.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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	/* !CONFIG_EROFS_FS_ZIP */
+
-- 
2.17.1