From: Miklos Szeredi <mszeredi@redhat.com>
Date: Tue, 10 Sep 2019 15:04:08 +0200
Subject: fuse: simplify 'nofail' request
Git-commit: 40ac7ab2d02176f8a70e37b88e41637ed97b304b
Patch-mainline: v5.4-rc1
References: jsc#SLE-13782

Instead of complex games with a reserved request, just use __GFP_NOFAIL.

Both calers (flush, readdir) guarantee that connection was already
initialized, so no need to wait for fc->initialized.

Also remove unneeded clearing of FR_BACKGROUND flag.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/fuse/dev.c    | 64 ++++----------------------------------------------------
 fs/fuse/file.c   |  2 +-
 fs/fuse/fuse_i.h |  8 +------
 fs/fuse/inode.c  |  1 -
 4 files changed, 6 insertions(+), 69 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e865c6b61652..7833aee97565 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -242,52 +242,6 @@ struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
 }
 EXPORT_SYMBOL_GPL(fuse_get_req_for_background);
 
-/*
- * Return request in fuse_file->reserved_req.  However that may
- * currently be in use.  If that is the case, wait for it to become
- * available.
- */
-static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
-					 struct file *file)
-{
-	struct fuse_req *req = NULL;
-	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
-	struct fuse_file *ff = file->private_data;
-
-	do {
-		wait_event(fc->reserved_req_waitq, ff->reserved_req);
-		spin_lock(&fi->lock);
-		if (ff->reserved_req) {
-			req = ff->reserved_req;
-			ff->reserved_req = NULL;
-			req->stolen_file = get_file(file);
-		}
-		spin_unlock(&fi->lock);
-	} while (!req);
-
-	return req;
-}
-
-/*
- * Put stolen request back into fuse_file->reserved_req
- */
-static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
-{
-	struct file *file = req->stolen_file;
-	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
-	struct fuse_file *ff = file->private_data;
-
-	WARN_ON(req->max_pages);
-	spin_lock(&fi->lock);
-	memset(req, 0, sizeof(*req));
-	fuse_request_init(req, NULL, NULL, 0);
-	BUG_ON(ff->reserved_req);
-	ff->reserved_req = req;
-	wake_up_all(&fc->reserved_req_waitq);
-	spin_unlock(&fi->lock);
-	fput(file);
-}
-
 /*
  * Gets a requests for a file operation, always succeeds
  *
@@ -301,25 +255,18 @@ static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
  * filesystem should not have it's own file open.  If deadlock is
  * intentional, it can still be broken by "aborting" the filesystem.
  */
-struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
-					     struct file *file)
+struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc)
 {
 	struct fuse_req *req;
 
 	atomic_inc(&fc->num_waiting);
-	wait_event(fc->blocked_waitq, fc->initialized);
-	/* Matches smp_wmb() in fuse_set_initialized() */
-	smp_rmb();
-	req = fuse_request_alloc(0);
-	if (!req)
-		req = get_reserved_req(fc, file);
+	req = __fuse_request_alloc(0, GFP_KERNEL | __GFP_NOFAIL);
 
 	req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
 	req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
 	req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
 
 	__set_bit(FR_WAITING, &req->flags);
-	__clear_bit(FR_BACKGROUND, &req->flags);
 	return req;
 }
 
@@ -342,10 +289,7 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
 			fuse_drop_waiting(fc);
 		}
 
-		if (req->stolen_file)
-			put_reserved_req(fc, req);
-		else
-			fuse_request_free(req);
+		fuse_request_free(req);
 	}
 }
 EXPORT_SYMBOL_GPL(fuse_put_request);
@@ -719,7 +663,7 @@ void fuse_force_forget(struct file *file, u64 nodeid)
 
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.nlookup = 1;
-	req = fuse_get_req_nofail_nopages(fc, file);
+	req = fuse_get_req_nofail_nopages(fc);
 	req->in.h.opcode = FUSE_FORGET;
 	req->in.h.nodeid = nodeid;
 	req->in.numargs = 1;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1f90722f0ee8..7d12c1d27132 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -432,7 +432,7 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (err)
 		return err;
 
-	req = fuse_get_req_nofail_nopages(fc, file);
+	req = fuse_get_req_nofail_nopages(fc);
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;
 	inarg.lock_owner = fuse_lock_owner_id(fc, id);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index a89362ee46d9..dd199391d6b9 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -435,8 +435,6 @@ struct fuse_req {
 	/** Request completion callback */
 	void (*end)(struct fuse_conn *, struct fuse_req *);
 
-	/** Request is stolen from fuse_file->reserved_req */
-	struct file *stolen_file;
 };
 
 struct fuse_iqueue {
@@ -580,9 +578,6 @@ struct fuse_conn {
 	/** waitq for blocked connection */
 	wait_queue_head_t blocked_waitq;
 
-	/** waitq for reserved requests */
-	wait_queue_head_t reserved_req_waitq;
-
 	/** Connection established, cleared on umount, connection
 	    abort and device release */
 	unsigned connected;
@@ -927,8 +922,7 @@ void __fuse_get_request(struct fuse_req *req);
 /**
  * Gets a requests for a file operation, always succeeds
  */
-struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
-					     struct file *file);
+struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc);
 
 /**
  * Decrement reference count of a request.  If count goes to zero free
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4eaea0b29965..2b9cc19fedcb 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -617,7 +617,6 @@ void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns)
 	refcount_set(&fc->count, 1);
 	atomic_set(&fc->dev_count, 1);
 	init_waitqueue_head(&fc->blocked_waitq);
-	init_waitqueue_head(&fc->reserved_req_waitq);
 	fuse_iqueue_init(&fc->iq);
 	INIT_LIST_HEAD(&fc->bg_queue);
 	INIT_LIST_HEAD(&fc->entry);