fuse: limit queued background requests
Libfuse basically creates a new thread for each new request. This is fine for
synchronous requests, which are naturally limited. However background
requests (especially writepage) can cause a thread creation storm.
To avoid this, limit the number of background requests available to userspace.
This is done by introducing another queue for background requests, and a
counter for the number of "active" requests, which are currently available for
userspace.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index c5c1ebf..67aaf6e 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -296,6 +296,12 @@
/** Number of requests currently in the background */
unsigned num_background;
+ /** Number of background requests currently queued for userspace */
+ unsigned active_background;
+
+ /** The list of background requests set aside for later queuing */
+ struct list_head bg_queue;
+
/** Pending interrupts */
struct list_head interrupts;