[Linux-cachefs] [PATCH v1 19/23] cachefiles: implement .demand_read() for demand read

[Jeffle Xu]

Implement .demand_read() callback for cachefiels backend.

.demand_read() callback is responsible for notifying user daemon the
pending request to process, and will get blocked until user daemon has
prepared data and filled the hole.

Signed-off-by: Jeffle Xu <jeffl...@linux.alibaba.com>
---
 fs/cachefiles/internal.h | 12 +++++++++
 fs/cachefiles/io.c       | 56 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index af8ac8107f77..eeb6ad7dcd49 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -61,6 +61,18 @@ struct cachefiles_object {
 #define CACHEFILES_OBJECT_USING_TMPFILE        0               /* Have an 
unlinked tmpfile */
 };
 
+struct cachefiles_req_in {
+       uint64_t id;
+       uint64_t off;
+       uint64_t len;
+       char path[NAME_MAX];
+};
+
+struct cachefiles_req {
+       struct completion done;
+       struct cachefiles_req_in req_in;
+};
+
 /*
  * Cache files cache definition
  */
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 60b1eac2ce78..376603e5ed99 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -539,12 +539,68 @@ static void cachefiles_end_operation(struct 
netfs_cache_resources *cres)
        fscache_end_cookie_access(fscache_cres_cookie(cres), 
fscache_access_io_end);
 }
 
+static struct cachefiles_req *cachefiles_alloc_req(struct cachefiles_object 
*object,
+                                                  loff_t start_pos,
+                                                  size_t len)
+{
+       struct cachefiles_req *req;
+       struct cachefiles_req_in *req_in;
+
+       req = kzalloc(sizeof(*req), GFP_KERNEL);
+       if (!req)
+               return NULL;
+
+       req_in = &req->req_in;
+
+       req_in->off = start_pos;
+       req_in->len = len;
+       strncpy(req_in->path, object->d_name, sizeof(req_in->path));
+
+       init_completion(&req->done);
+
+       return req;
+}
+
+int cachefiles_demand_read(struct netfs_cache_resources *cres,
+                          loff_t start_pos, size_t len)
+{
+       struct cachefiles_object *object;
+       struct cachefiles_cache *cache;
+       struct cachefiles_req *req;
+       int ret;
+
+       object = cachefiles_cres_object(cres);
+       cache = object->volume->cache;
+
+       req = cachefiles_alloc_req(object, start_pos, len);
+       if (!req)
+               return -ENOMEM;
+
+       spin_lock(&cache->reqs_lock);
+       ret = idr_alloc(&cache->reqs, req, 0, 0, GFP_KERNEL);
+       if (ret >= 0)
+               req->req_in.id = ret;
+       spin_unlock(&cache->reqs_lock);
+       if (ret < 0) {
+               kfree(req);
+               return -ENOMEM;
+       }
+
+       wake_up_all(&cache->daemon_pollwq);
+
+       wait_for_completion(&req->done);
+       kfree(req);
+
+       return 0;
+}
+
 static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
        .end_operation          = cachefiles_end_operation,
        .read                   = cachefiles_read,
        .write                  = cachefiles_write,
        .prepare_read           = cachefiles_prepare_read,
        .prepare_write          = cachefiles_prepare_write,
+       .demand_read            = cachefiles_demand_read,
 };
 
 /*
-- 
2.27.0

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