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@xxxxxxxxxxxxxx>
---
v2->v3:
- Add fiemap-fault to .gitignore
- Added a _cleanup() helper
- Just let the output of fiemap-fault go instead of using || _fail
- Added the munmap
- Moved $dst to $TEST_DIR/$seq
.gitignore | 1 +
src/Makefile | 2 +-
src/fiemap-fault.c | 74 +++++++++++++++++++++++++++++++++++++++++++
tests/generic/808 | 48 ++++++++++++++++++++++++++++
tests/generic/808.out | 2 ++
5 files changed, 126 insertions(+), 1 deletion(-)
create mode 100644 src/fiemap-fault.c
create mode 100755 tests/generic/808
create mode 100644 tests/generic/808.out
diff --git a/.gitignore b/.gitignore
index 3b160209..f0fb72bd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -205,6 +205,7 @@ tags
/src/vfs/mount-idmapped
/src/log-writes/replay-log
/src/perf/*.pyc
+/src/filemap-fault
# Symlinked files
/tests/generic/035.out
diff --git a/src/Makefile b/src/Makefile
index e7442487..ab98a06f 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 t_snapshot_deleted_subvolume
+ uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault
EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
btrfs_crc32c_forged_name.py popdir.pl popattr.py \
diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c
new file mode 100644
index 00000000..73260068
--- /dev/null
+++ b/src/fiemap-fault.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Meta Platforms, Inc. All Rights Reserved.
+ */
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/fiemap.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int prep_mmap_buffer(int fd, void **addr)
+{
+ struct stat st;
+ int ret;
+
+ ret = fstat(fd, &st);
+ if (ret)
+ err(1, "failed to stat %d", fd);
+
+ *addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+ if (*addr == MAP_FAILED)
+ err(1, "failed to mmap %d", fd);
+
+ return st.st_size;
+}
+
+int main(int argc, char *argv[])
+{
+ struct fiemap *fiemap;
+ size_t sz, last = 0;
+ void *buf = NULL;
+ int ret, fd;
+
+ if (argc != 2)
+ errx(1, "no in and out file name arguments given");
+
+ fd = open(argv[1], O_RDWR, 0666);
+ if (fd == -1)
+ err(1, "failed to open %s", argv[1]);
+
+ sz = prep_mmap_buffer(fd, &buf);
+
+ fiemap = (struct fiemap *)buf;
+ fiemap->fm_flags = 0;
+ fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) /
+ sizeof(struct fiemap_extent);
+
+ while (last < sz) {
+ int i;
+
+ fiemap->fm_start = last;
+ fiemap->fm_length = sz - last;
+
+ ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
+ if (ret < 0)
+ err(1, "fiemap failed %d", errno);
+ for (i = 0; i < fiemap->fm_mapped_extents; i++)
+ last = fiemap->fm_extents[i].fe_logical +
+ fiemap->fm_extents[i].fe_length;
+ }
+
+ munmap(buf, sz);
+ close(fd);
+ return 0;
+}
diff --git a/tests/generic/808 b/tests/generic/808
new file mode 100755
index 00000000..36015f35
--- /dev/null
+++ b/tests/generic/808
@@ -0,0 +1,48 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2024 Meta Platforms, Inc. All Rights Reserved.
+#
+# FS QA Test 808
+#
+# 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 fiemap
+[ $FSTYP == "btrfs" ] && \
+ _fixed_by_kernel_commit b0ad381fa769 \
+ "btrfs: fix deadlock with fiemap and extent locking"
+
+_cleanup()
+{
+ rm -f $dst
+ cd /
+ rm -r -f $tmp.*
+}
+
+# real QA test starts here
+_supported_fs generic
+_require_test
+_require_odirect
+_require_test_program fiemap-fault
+dst=$TEST_DIR/$seq/fiemap-fault
+
+mkdir -p $TEST_DIR/$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 $dst
+
+# success, all done
+status=$?
+exit
+
diff --git a/tests/generic/808.out b/tests/generic/808.out
new file mode 100644
index 00000000..88253428
--- /dev/null
+++ b/tests/generic/808.out
@@ -0,0 +1,2 @@
+QA output created by 808
+Silence is golden
--
2.43.0
