[PATCH v1 22/23] cachefiles: add done command for demand read

[Jeffle Xu]

Once has prepared data and filled the hole, user daemon could notify
cachefiles backend by writing 'done' command to devnode.

With done command, the id originally readed from devnode is transferred
back to cachefiles backend. This id identifies the position of the
completed request inside the idr tree, and thus cachefiles backend could
find the corresponding completed request once gets notified.

Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
---
 fs/cachefiles/daemon.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index ce4cc5617dfc..36d0bcf5fc3f 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -48,6 +48,7 @@ static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
 static int cachefiles_daemon_mode(struct cachefiles_cache *, char *);
 static int cachefiles_daemon_bind(struct cachefiles_cache *, char *);
 static void cachefiles_daemon_unbind(struct cachefiles_cache *);
+static int cachefiles_daemon_done(struct cachefiles_cache *, char *);
 
 static unsigned long cachefiles_open;
 
@@ -91,6 +92,7 @@ static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
 	{ "secctx",	cachefiles_daemon_secctx	},
 	{ "tag",	cachefiles_daemon_tag		},
 	{ "mode",	cachefiles_daemon_mode		},
+	{ "done",	cachefiles_daemon_done		},
 	{ "",		NULL				}
 };
 
@@ -604,6 +606,38 @@ static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
 	return 0;
 }
 
+/*
+ * Request completion
+ * - command: "done <id>"
+ */
+static int cachefiles_daemon_done(struct cachefiles_cache *cache, char *args)
+{
+	unsigned long id;
+	int ret;
+	struct cachefiles_req *req;
+
+	_enter(",%s", args);
+
+	if (!*args) {
+		pr_err("Empty id specified\n");
+		return -EINVAL;
+	}
+
+	ret = kstrtoul(args, 0, &id);
+	if (ret)
+		return ret;
+
+	spin_lock(&cache->reqs_lock);
+	req = idr_remove(&cache->reqs, id);
+	spin_unlock(&cache->reqs_lock);
+	if (!req)
+		return -EINVAL;
+
+	complete(&req->done);
+
+	return 0;
+}
+
 /*
  * Request a node in the cache be culled from the current working directory
  * - command: "cull <name>"
-- 
2.27.0