[PATCH] fuse: add number of waiting requests attribute

This patch adds the 'waiting' attribute which indicates how many filesystem
requests are currently waiting to be completed.  A non-zero value without any
filesystem activity indicates a hung or deadlocked filesystem.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 21 insertions, 3 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index de4a0a0bda8a..c72e44b58d09 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -109,18 +109,24 @@ struct fuse_req *fuse_get_request(struct fuse_conn *fc)
         int intr;
         sigset_t oldset;
 
+        atomic_inc(&fc->num_waiting);
         block_sigs(&oldset);
         intr = down_interruptible(&fc->outstanding_sem);
         restore_sigs(&oldset);
-        return intr ? NULL : do_get_request(fc);
+        if (intr) {
+                atomic_dec(&fc->num_waiting);
+                return NULL;
+        }
+        return do_get_request(fc);
 }
 
 static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req)
 {
         spin_lock(&fuse_lock);
-        if (req->preallocated)
+        if (req->preallocated) {
+                atomic_dec(&fc->num_waiting);
                 list_add(&req->list, &fc->unused_list);
-        else
+        } else
                 fuse_request_free(req);
 
         /* If we are in debt decrease that first */
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6ef1e5f5873b..bcb453f68111 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -280,6 +280,9 @@ struct fuse_conn {
         /** Is create not implemented by fs? */
         unsigned no_create : 1;
 
+        /** The number of requests waiting for completion */
+        atomic_t num_waiting;
+
         /** Negotiated minor version */
         unsigned minor;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 514b700c863d..182235923cdd 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -555,7 +555,16 @@ static struct file_system_type fuse_fs_type = {
         .kill_sb        = kill_anon_super,
 };
 
+static ssize_t fuse_conn_waiting_show(struct fuse_conn *fc, char *page)
+{
+        return sprintf(page, "%i\n", atomic_read(&fc->num_waiting));
+}
+
+static struct fuse_conn_attr fuse_conn_waiting =
+        __ATTR(waiting, 0400, fuse_conn_waiting_show, NULL);
+
 static struct attribute *fuse_conn_attrs[] = {
+        &fuse_conn_waiting.attr,
         NULL,
 };