From 293c259e5e1719ab20eb7d9976f1daf16a7a779a Mon Sep 17 00:00:00 2001
From: Daniel Rosenberg <drosen@google.com>
Date: Fri, 7 Jul 2023 16:07:09 -0700
Subject: [PATCH] UPSTREAM: ANDROID: fuse-bpf: Add partial flock support

This adds passthrough support for flock on fuse-bpf files. It does not
give any control via a bpf filter. The flock will act as though it was
taken on the lower file.

Bug: 289882899
Test: fuse_test -t32 (flock_test)
Change-Id: Iba0b9630766cedbd3195532c5e929891593cfe30
Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 fs/fuse/backing.c | 14 ++++++++++++++
 fs/fuse/file.c    |  8 +++++++-
 fs/fuse/fuse_i.h  |  1 +
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index aad46ab272f7..8db2a0c87f75 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -1016,6 +1016,20 @@ void *fuse_file_write_iter_finalize(struct fuse_bpf_args *fa,
 	return ERR_PTR(fwio->ret);
 }
 
+int fuse_file_flock_backing(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct fuse_file *ff = file->private_data;
+	struct file *backing_file = ff->backing_file;
+	int error;
+
+	fl->fl_file = backing_file;
+	if (backing_file->f_op->flock)
+		error = backing_file->f_op->flock(backing_file, cmd, fl);
+	else
+		error = locks_lock_file_wait(backing_file, fl);
+	return error;
+}
+
 ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	int ret;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 26dd29c54cfb..781f5fe3ab0e 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2697,12 +2697,18 @@ static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
 {
 	struct inode *inode = file_inode(file);
 	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
 	int err;
 
+#ifdef CONFIG_FUSE_BPF
+	/* TODO - this is simply passthrough, not a proper BPF filter */
+	if (ff->backing_file)
+		return fuse_file_flock_backing(file, cmd, fl);
+#endif
+
 	if (fc->no_flock) {
 		err = locks_lock_file_wait(file, fl);
 	} else {
-		struct fuse_file *ff = file->private_data;
 
 		/* emulate flock with POSIX locks */
 		ff->flock = true;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 7e4a24b2d5f7..05e43ad2215e 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1580,6 +1580,7 @@ int fuse_file_write_iter_backing(struct fuse_bpf_args *fa,
 void *fuse_file_write_iter_finalize(struct fuse_bpf_args *fa,
 		struct kiocb *iocb, struct iov_iter *from);
 
+int fuse_file_flock_backing(struct file *file, int cmd, struct file_lock *fl);
 ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma);
 
 int fuse_file_fallocate_initialize(struct fuse_bpf_args *fa,