[PATCH] fstests: add a regression test for fiemap into an mmap range

[Josef Bacik <josef@toxicpanda.com>]

Btrfs had a deadlock that you could trigger by mmap'ing a large file and
using that as the buffer for fiemap.  This test adds a c program to do
this, and the fstest creates a large enough file and then runs the
reproducer on the file.  Without the fix btrfs deadlocks, with the fix
we pass fine.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 src/Makefile          |  2 +-
 tests/generic/740     | 41 +++++++++++++++++++++++++++++++++++++++++
 tests/generic/740.out |  2 ++
 3 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 tests/generic/740
 create mode 100644 tests/generic/740.out

diff --git a/src/Makefile b/src/Makefile
index d79015ce..916f6755 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
 	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \
 	detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \
-	uuid_ioctl
+	uuid_ioctl fiemap-fault
 
 EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
 	      btrfs_crc32c_forged_name.py popdir.pl popattr.py \
diff --git a/tests/generic/740 b/tests/generic/740
new file mode 100644
index 00000000..46ec5820
--- /dev/null
+++ b/tests/generic/740
@@ -0,0 +1,41 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2023 Meta Platforms, Inc.  All Rights Reserved.
+#
+# FS QA Test 708
+#
+# Test fiemap into an mmaped buffer of the same file
+#
+# Create a reasonably large file, then run a program which mmaps it and uses
+# that as a buffer for an fiemap call.  This is a regression test for btrfs
+# where we used to hold a lock for the duration of the fiemap call which would
+# result in a deadlock if we page faulted.
+#
+. ./common/preamble
+_begin_fstest quick auto
+[ $FSTYP == "btrfs" ] && \
+	_fixed_by_kernel_commit xxxxxxxxxxxx \
+		"btrfs: fix deadlock with fiemap and extent locking"
+
+# real QA test starts here
+_supported_fs generic
+_require_test
+_require_odirect
+_require_test_program fiemap-fault
+dst=$TEST_DIR/fiemap-fault-$seq
+
+echo "Silence is golden"
+
+for i in $(seq 0 2 1000)
+do
+	$XFS_IO_PROG -d -f -c "pwrite -q $((i * 4096)) 4096" $dst
+done
+
+$here/src/fiemap-fault $dst > /dev/null || _fail "failed doing fiemap"
+
+rm -f $dst
+
+# success, all done
+status=$?
+exit
+
diff --git a/tests/generic/740.out b/tests/generic/740.out
new file mode 100644
index 00000000..3f841e60
--- /dev/null
+++ b/tests/generic/740.out
@@ -0,0 +1,2 @@
+QA output created by 740
+Silence is golden
-- 
2.43.0