[PATCH v7 10/19] erofs: add fscache context helper functions

[Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>]

Introduce a context structure for managing data blobs, and helper
functions for initializing and cleaning up this context structure.

Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
 fs/erofs/fscache.c  | 46 +++++++++++++++++++++++++++++++++++++++++++++
 fs/erofs/internal.h | 19 +++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 7a6d0239ebb1..67a3c4935245 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -5,6 +5,52 @@
 #include <linux/fscache.h>
 #include "internal.h"
 
+/*
+ * Create an fscache context for data blob.
+ * Return: 0 on success and allocated fscache context is assigned to @fscache,
+ *	   negative error number on failure.
+ */
+int erofs_fscache_register_cookie(struct super_block *sb,
+				  struct erofs_fscache **fscache, char *name)
+{
+	struct fscache_volume *volume = EROFS_SB(sb)->volume;
+	struct erofs_fscache *ctx;
+	struct fscache_cookie *cookie;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	cookie = fscache_acquire_cookie(volume, FSCACHE_ADV_WANT_CACHE_SIZE,
+					name, strlen(name), NULL, 0, 0);
+	if (!cookie) {
+		erofs_err(sb, "failed to get cookie for %s", name);
+		kfree(name);
+		return -EINVAL;
+	}
+
+	fscache_use_cookie(cookie, false);
+	ctx->cookie = cookie;
+
+	*fscache = ctx;
+	return 0;
+}
+
+void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
+{
+	struct erofs_fscache *ctx = *fscache;
+
+	if (!ctx)
+		return;
+
+	fscache_unuse_cookie(ctx->cookie, NULL, NULL);
+	fscache_relinquish_cookie(ctx->cookie, false);
+	ctx->cookie = NULL;
+
+	kfree(ctx);
+	*fscache = NULL;
+}
+
 int erofs_fscache_register_fs(struct super_block *sb)
 {
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 952a2f483f94..c6a3351a4d7d 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -97,6 +97,10 @@ struct erofs_sb_lz4_info {
 	u16 max_pclusterblks;
 };
 
+struct erofs_fscache {
+	struct fscache_cookie *cookie;
+};
+
 struct erofs_sb_info {
 	struct erofs_mount_opts opt;	/* options */
 #ifdef CONFIG_EROFS_FS_ZIP
@@ -626,9 +630,24 @@ static inline int z_erofs_load_lzma_config(struct super_block *sb,
 #ifdef CONFIG_EROFS_FS_ONDEMAND
 int erofs_fscache_register_fs(struct super_block *sb);
 void erofs_fscache_unregister_fs(struct super_block *sb);
+
+int erofs_fscache_register_cookie(struct super_block *sb,
+				  struct erofs_fscache **fscache, char *name);
+void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
 #else
 static inline int erofs_fscache_register_fs(struct super_block *sb) { return 0; }
 static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
+
+static inline int erofs_fscache_register_cookie(struct super_block *sb,
+						struct erofs_fscache **fscache,
+						char *name)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache)
+{
+}
 #endif
 
 #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
-- 
2.27.0