Revert "[fuse] fix deadlock between fuse_put_super() and request_end()"
Miklos Szeredi [Wed, 26 Apr 2006 08:48:55 +0000 (10:48 +0200)]
This reverts 73ce8355c243a434524a34c05cc417dd0467996e commit.

It was wrong, because it didn't take into account the requirement,
that iput() for background requests must be performed synchronously
with ->put_super(), otherwise active inodes may remain after unmount.

The right solution is to keep the sbput_sem and perform iput() within
the locked region, but move fput() outside sbput_sem.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>

fs/fuse/dev.c
fs/fuse/fuse_i.h
fs/fuse/inode.c

index cc750c6..4967bd4 100644 (file)
@@ -128,14 +128,20 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
        }
 }
 
-void fuse_remove_background(struct fuse_conn *fc, struct fuse_req *req)
+void fuse_release_background(struct fuse_conn *fc, struct fuse_req *req)
 {
-       list_del_init(&req->bg_entry);
+       iput(req->inode);
+       iput(req->inode2);
+       if (req->file)
+               fput(req->file);
+       spin_lock(&fc->lock);
+       list_del(&req->bg_entry);
        if (fc->num_background == FUSE_MAX_BACKGROUND) {
                fc->blocked = 0;
                wake_up_all(&fc->blocked_waitq);
        }
        fc->num_background--;
+       spin_unlock(&fc->lock);
 }
 
 /*
@@ -165,27 +171,17 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
                wake_up(&req->waitq);
                fuse_put_request(fc, req);
        } else {
-               struct inode *inode = req->inode;
-               struct inode *inode2 = req->inode2;
-               struct file *file = req->file;
                void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
                req->end = NULL;
-               req->inode = NULL;
-               req->inode2 = NULL;
-               req->file = NULL;
-               if (!list_empty(&req->bg_entry))
-                       fuse_remove_background(fc, req);
                spin_unlock(&fc->lock);
-
+               down_read(&fc->sbput_sem);
+               if (fc->mounted)
+                       fuse_release_background(fc, req);
+               up_read(&fc->sbput_sem);
                if (end)
                        end(fc, req);
                else
                        fuse_put_request(fc, req);
-
-               if (file)
-                       fput(file);
-               iput(inode);
-               iput(inode2);
        }
 }
 
index 59661c4..0474202 100644 (file)
@@ -258,9 +258,15 @@ struct fuse_conn {
        /** waitq for blocked connection */
        wait_queue_head_t blocked_waitq;
 
+       /** RW semaphore for exclusion with fuse_put_super() */
+       struct rw_semaphore sbput_sem;
+
        /** The next unique request id */
        u64 reqctr;
 
+       /** Mount is active */
+       unsigned mounted;
+
        /** Connection established, cleared on umount, connection
            abort and device release */
        unsigned connected;
@@ -471,11 +477,11 @@ void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req);
 void request_send_background(struct fuse_conn *fc, struct fuse_req *req);
 
 /**
- * Remove request from the the background list
+ * Release inodes and file associated with background request
  */
-void fuse_remove_background(struct fuse_conn *fc, struct fuse_req *req);
+void fuse_release_background(struct fuse_conn *fc, struct fuse_req *req);
 
-/** Abort all requests */
+/* Abort all requests */
 void fuse_abort_conn(struct fuse_conn *fc);
 
 /**
index 43a6fc0..fd34037 100644 (file)
@@ -204,26 +204,17 @@ static void fuse_put_super(struct super_block *sb)
 {
        struct fuse_conn *fc = get_fuse_conn_super(sb);
 
+       down_write(&fc->sbput_sem);
+       while (!list_empty(&fc->background))
+               fuse_release_background(fc,
+                                       list_entry(fc->background.next,
+                                                  struct fuse_req, bg_entry));
+
        spin_lock(&fc->lock);
+       fc->mounted = 0;
        fc->connected = 0;
-       while (!list_empty(&fc->background)) {
-               struct fuse_req *req = list_entry(fc->background.next,
-                                                 struct fuse_req, bg_entry);
-               struct inode *inode = req->inode;
-               struct inode *inode2 = req->inode2;
-
-               /* File would hold a reference to vfsmount */
-               BUG_ON(req->file);
-               req->inode = NULL;
-               req->inode2 = NULL;
-               fuse_remove_background(fc, req);
-
-               spin_unlock(&fc->lock);
-               iput(inode);
-               iput(inode2);
-               spin_lock(&fc->lock);
-       }
        spin_unlock(&fc->lock);
+       up_write(&fc->sbput_sem);
        /* Flush all readers on this fs */
        kill_fasync(&fc->fasync, SIGIO, POLL_IN);
        wake_up_all(&fc->waitq);
@@ -395,6 +386,7 @@ static struct fuse_conn *new_conn(void)
                INIT_LIST_HEAD(&fc->processing);
                INIT_LIST_HEAD(&fc->io);
                INIT_LIST_HEAD(&fc->background);
+               init_rwsem(&fc->sbput_sem);
                kobj_set_kset_s(fc, connections_subsys);
                kobject_init(&fc->kobj);
                atomic_set(&fc->num_waiting, 0);
@@ -549,6 +541,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
                goto err_free_req;
 
        sb->s_root = root_dentry;
+       fc->mounted = 1;
        fc->connected = 1;
        kobject_get(&fc->kobj);
        file->private_data = fc;