[PATCH v6 12/22] erofs: add cookie context helper functions

[Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>]

Introduce "struct erofs_fscache" for managing cookie for backinig file,
and helper functions for initializing and cleaning up this context
structure.

Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
 fs/erofs/fscache.c  | 61 +++++++++++++++++++++++++++++++++++++++++++++
 fs/erofs/internal.h | 14 +++++++++++
 2 files changed, 75 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 08cf570a0810..73235fd43bf6 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -7,6 +7,67 @@
 
 static struct fscache_volume *volume;
 
+static int erofs_fscache_init_cookie(struct erofs_fscache *ctx, char *path)
+{
+	struct fscache_cookie *cookie;
+
+	cookie = fscache_acquire_cookie(volume, FSCACHE_ADV_WANT_CACHE_SIZE,
+					path, strlen(path),
+					NULL, 0, 0);
+	if (!cookie)
+		return -EINVAL;
+
+	fscache_use_cookie(cookie, false);
+	ctx->cookie = cookie;
+	return 0;
+}
+
+static inline void erofs_fscache_cleanup_cookie(struct erofs_fscache *ctx)
+{
+	struct fscache_cookie *cookie = ctx->cookie;
+
+	fscache_unuse_cookie(cookie, NULL, NULL);
+	fscache_relinquish_cookie(cookie, false);
+	ctx->cookie = NULL;
+}
+
+/*
+ * erofs_fscache_get - create an fscache context for blob file
+ * @sb:		superblock
+ * @path:	name of blob file
+ *
+ * Return: fscache context on success, ERR_PTR() on failure.
+ */
+struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path)
+{
+	struct erofs_fscache *ctx;
+	int ret;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	ret = erofs_fscache_init_cookie(ctx, path);
+	if (ret) {
+		erofs_err(sb, "failed to init cookie");
+		goto err;
+	}
+
+	return ctx;
+err:
+	kfree(ctx);
+	return ERR_PTR(ret);
+}
+
+void erofs_fscache_put(struct erofs_fscache *ctx)
+{
+	if (!ctx)
+		return;
+
+	erofs_fscache_cleanup_cookie(ctx);
+	kfree(ctx);
+}
+
 int __init erofs_init_fscache(void)
 {
 	volume = fscache_acquire_volume("erofs", NULL, NULL, 0);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 45b8b0dd8a27..d4f2b43cedae 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -96,6 +96,10 @@ 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
@@ -620,9 +624,19 @@ static inline int z_erofs_load_lzma_config(struct super_block *sb,
 #ifdef CONFIG_EROFS_FS_ONDEMAND
 int erofs_init_fscache(void);
 void erofs_exit_fscache(void);
+
+struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path);
+void erofs_fscache_put(struct erofs_fscache *ctx);
 #else
 static inline int erofs_init_fscache(void) { return 0; }
 static inline void erofs_exit_fscache(void) {}
+
+static inline struct erofs_fscache *erofs_fscache_get(struct super_block *sb,
+						      char *path)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+static inline void erofs_fscache_put(struct erofs_fscache *ctx) {}
 #endif
 
 #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
-- 
2.27.0