[PATCH v1 18/23] cachefiles: use idr tree managing pending demand read

[Jeffle Xu <jefflexu@linux.alibaba.com>]

This is in prep for implementing .demand_read() callback for cachefiles.

In the following patch, .demand_read() callback is responsible for
notifying user daemon the requested file range (hole) to read. Then
.demand_read() callback will get blocked until user daemon has prepared
data and filled the hole.

This patch introduces an idr tree to manage all these pending
demand-read IO.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
 fs/cachefiles/daemon.c   | 3 +++
 fs/cachefiles/internal.h | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index 892a9bdba53f..01496fa8c263 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -118,6 +118,8 @@ static int cachefiles_daemon_open(struct inode *inode, struct file *file)
 	INIT_LIST_HEAD(&cache->volumes);
 	INIT_LIST_HEAD(&cache->object_list);
 	spin_lock_init(&cache->object_list_lock);
+	idr_init(&cache->reqs);
+	spin_lock_init(&cache->reqs_lock);
 
 	/* set default caching limits
 	 * - limit at 1% free space and/or free files
@@ -152,6 +154,7 @@ static int cachefiles_daemon_release(struct inode *inode, struct file *file)
 	cachefiles_daemon_unbind(cache);
 
 	/* clean up the control file interface */
+	idr_destroy(&cache->reqs);
 	cache->cachefilesd = NULL;
 	file->private_data = NULL;
 	cachefiles_open = 0;
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index a8e6500889d7..af8ac8107f77 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -15,6 +15,7 @@
 #include <linux/fscache-cache.h>
 #include <linux/cred.h>
 #include <linux/security.h>
+#include <linux/idr.h>
 
 #define CACHEFILES_DIO_BLOCK_SIZE 4096
 
@@ -102,6 +103,9 @@ struct cachefiles_cache {
 	char				*rootdirname;	/* name of cache root directory */
 	char				*secctx;	/* LSM security context */
 	char				*tag;		/* cache binding tag */
+
+	struct idr			reqs;
+	spinlock_t			reqs_lock;
 };
 
 #include <trace/events/cachefiles.h>
-- 
2.27.0