btrfs recently had a bug where a direct io partial write resulted in a
hole in the file. Add a new generic test which creates a 2MiB file,
mmaps it, touches the first byte, then does an O_DIRECT write of the
mmapped buffer into a new file. This should result in the mapped pages
being a mix of in and out of page cache and thus a partial write, for
filesystems using iomap and IOMAP_DIO_PARTIAL.
Signed-off-by: Boris Burkov <boris@xxxxxx>
---
.gitignore | 1 +
src/Makefile | 2 +-
src/dio-buf-fault.c | 83 +++++++++++++++++++++++++++++++++++++++++++
tests/generic/708 | 48 +++++++++++++++++++++++++
tests/generic/708.out | 2 ++
5 files changed, 135 insertions(+), 1 deletion(-)
create mode 100644 src/dio-buf-fault.c
create mode 100755 tests/generic/708
create mode 100644 tests/generic/708.out
diff --git a/.gitignore b/.gitignore
index cfff8f85..644290f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -72,6 +72,7 @@ tags
/src/deduperace
/src/detached_mounts_propagation
/src/devzero
+/src/dio-buf-fault
/src/dio-interleaved
/src/dio-invalidate-cache
/src/dirhash_collide
diff --git a/src/Makefile b/src/Makefile
index a574f7bd..24cd4747 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -19,7 +19,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
t_ofd_locks t_mmap_collision mmap-write-concurrent \
t_get_file_time t_create_short_dirs t_create_long_dirs t_enospc \
t_mmap_writev_overlap checkpoint_journal mmap-rw-fault allocstale \
- t_mmap_cow_memory_failure fake-dump-rootino
+ t_mmap_cow_memory_failure fake-dump-rootino dio-buf-fault
LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \
diff --git a/src/dio-buf-fault.c b/src/dio-buf-fault.c
new file mode 100644
index 00000000..36ff6710
--- /dev/null
+++ b/src/dio-buf-fault.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023 Meta Platforms, Inc. All Rights Reserved.
+ */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE /* to get definition of O_DIRECT flag. */
+#endif
+
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+/*
+ * mmap a source file, then do a direct write of that mmapped region to a
+ * destination file.
+ */
+
+int prep_mmap_buffer(char *src_filename, int *fd, void **addr)
+{
+ struct stat st;
+ int ret;
+
+ *fd = open(src_filename, O_RDWR, 0666);
+ if (*fd == -1)
+ err(1, "failed to open %s", src_filename);
+
+ ret = fstat(*fd, &st);
+ if (ret)
+ err(1, "failed to stat %d", *fd);
+
+ *addr = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, *fd, 0);
+ if (*addr == MAP_FAILED)
+ err(1, "failed to mmap %d", *fd);
+
+ return st.st_size;
+}
+
+int do_dio(char *dst_filename, void *buf, size_t sz)
+{
+ int fd;
+ ssize_t ret;
+
+ fd = open(dst_filename, O_CREAT | O_TRUNC | O_WRONLY | O_DIRECT, 0666);
+ if (fd == -1)
+ err(1, "failed to open %s", dst_filename);
+ while (sz) {
+ ret = write(fd, buf, sz);
+ if (ret < 0) {
+ if (errno == -EINTR)
+ continue;
+ else
+ err(1, "failed to write %lu bytes to %d", sz, fd);
+ } else if (ret == 0) {
+ break;
+ }
+ buf += ret;
+ sz -= ret;
+ }
+ return sz;
+}
+
+int main(int argc, char *argv[]) {
+ size_t sz;
+ int fd;
+ void *buf = NULL;
+ char c;
+
+ if (argc != 3)
+ errx(1, "no in and out file name arguments given");
+ sz = prep_mmap_buffer(argv[1], &fd, &buf);
+
+ /* touch the first page of the mapping to bring it into cache */
+ c = ((char *)buf)[0];
+ printf("%u\n", c);
+
+ do_dio(argv[2], buf, sz);
+}
diff --git a/tests/generic/708 b/tests/generic/708
new file mode 100755
index 00000000..ff2e162b
--- /dev/null
+++ b/tests/generic/708
@@ -0,0 +1,48 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2023 Meta Platforms, Inc. All Rights Reserved.
+#
+# FS QA Test 708
+#
+# Test iomap direct_io partial writes.
+#
+# Create a reasonably large file, then run a program which mmaps it,
+# touches the first page, then dio writes it to a second file. This
+# can result in a page fault reading from the mmapped dio write buffer and
+# thus the iompap direct_io partial write codepath.
+#
+. ./common/preamble
+_begin_fstest quick auto
+_fixed_by_kernel_commit XXXX 'btrfs: fix dio continue after short write due to buffer page fault'
+
+# Override the default cleanup function.
+_cleanup()
+{
+ cd /
+ rm -r -f $tmp.*
+ rm -f $TEST_DIR/dio-buf-fault.*
+}
+
+# Import common functions.
+. ./common/filter
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_require_test
+_require_odirect
+_require_test_program dio-buf-fault
+src=$TEST_DIR/dio-buf-fault.src
+dst=$TEST_DIR/dio-buf-fault.dst
+
+echo "Silence is golden"
+
+$XFS_IO_PROG -fc "pwrite -q 0 $((2 * 1024 * 1024))" $src
+sync
+$here/src/dio-buf-fault $src $dst >> $seqres.full || _fail "failed doing the dio copy"
+diff $src $dst
+
+# success, all done
+status=$?
+exit
diff --git a/tests/generic/708.out b/tests/generic/708.out
new file mode 100644
index 00000000..33c478ad
--- /dev/null
+++ b/tests/generic/708.out
@@ -0,0 +1,2 @@
+QA output created by 708
+Silence is golden
--
2.39.1
