From cfdfc17a46d0310b2cbe3e654bd8796bf4c75ba2 Mon Sep 17 00:00:00 2001
From: Paul Lawrence <paullawrence@google.com>
Date: Wed, 15 Nov 2023 14:29:23 -0800
Subject: [PATCH] ANDROID: fuse-bpf: Ignore readaheads unless they go to the
 daemon

readpages will be triggered on the fuse fs in passthrough mode though
system calls like fadvise. If the daemon isn't aware of the file, this
will likely cause a hang.

For the moment, simply ignore fadvise in this situation

Bug: 301201239
Test: fuse_test, atest ScopedStorageDeviceTest both pass
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Change-Id: I524a84aeeb1b1593e51264fcc37f7cfa66757168
---
 fs/fuse/file.c                                | 10 ++++++
 .../selftests/filesystems/fuse/fuse_test.c    | 36 +++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 6608de8bea12..390cddc77ae9 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1026,6 +1026,16 @@ static void fuse_readahead(struct readahead_control *rac)
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	unsigned int i, max_pages, nr_pages = 0;
 
+#ifdef CONFIG_FUSE_BPF
+	/*
+	 * Currently no meaningful readahead is possible with fuse-bpf within
+	 * the kernel, so unless the daemon is aware of this file, ignore this
+	 * call.
+	 */
+	if (!get_fuse_inode(inode)->nodeid)
+		return;
+#endif
+
 	if (fuse_is_bad(inode))
 		return;
 
diff --git a/tools/testing/selftests/filesystems/fuse/fuse_test.c b/tools/testing/selftests/filesystems/fuse/fuse_test.c
index 01730e57dc51..528595a8e82f 100644
--- a/tools/testing/selftests/filesystems/fuse/fuse_test.c
+++ b/tools/testing/selftests/filesystems/fuse/fuse_test.c
@@ -2079,6 +2079,41 @@ out:
 	return result;
 }
 
+static int bpf_test_readahead(const char *mount_dir)
+{
+	const char *file_name = "file";
+
+	int result = TEST_FAILURE;
+	int file_fd = -1;
+	int src_fd = -1;
+	int fuse_dev = -1;
+
+	TEST(file_fd = s_creat(s_path(s(ft_src), s(file_name)), 0777),
+	     file_fd != -1);
+	TESTSYSCALL(fallocate(file_fd, 0, 0, 4096));
+	TESTSYSCALL(close(file_fd));
+	file_fd = -1;
+
+	TEST(src_fd = open(ft_src, O_DIRECTORY | O_RDONLY | O_CLOEXEC),
+	     src_fd != -1);
+	TEST(fuse_dev = open("/dev/fuse", O_RDWR | O_CLOEXEC), fuse_dev != -1);
+	TESTEQUAL(mount_fuse(mount_dir, -1, src_fd, &fuse_dev), 0);
+
+	TEST(file_fd = s_open(s_path(s(mount_dir), s(file_name)), O_RDONLY),
+	     file_fd != -1);
+	TESTSYSCALL(posix_fadvise(file_fd, 0, 4096, POSIX_FADV_WILLNEED));
+	usleep(1000);
+	TESTSYSCALL(close(file_fd));
+	file_fd = -1;
+	result = TEST_SUCCESS;
+out:
+	umount(mount_dir);
+	close(fuse_dev);
+	close(src_fd);
+	close(file_fd);
+	return result;
+}
+
 static void parse_range(const char *ranges, bool *run_test, size_t tests)
 {
 	size_t i;
@@ -2208,6 +2243,7 @@ int main(int argc, char *argv[])
 		MAKE_TEST(flock_test),
 		MAKE_TEST(bpf_test_create_and_remove_bpf),
 		MAKE_TEST(bpf_test_mkdir_and_remove_bpf),
+		MAKE_TEST(bpf_test_readahead),
 	};
 #undef MAKE_TEST