generic: test concurrent direct IO writes and fsync using same fd

Test that a program that has 2 threads using the same file descriptor and
concurrently doing direct IO writes and fsync doesn't trigger any crash
or deadlock.

This is motivated by a bug found in btrfs fixed by the following patch:

  "btrfs: fix race between direct IO write and fsync when using same fd"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/.gitignore b/.gitignore
index 94f6b5640a3e93d43762dc2115d79496daec7553..f16173d90104e6fc6dfb41ec315c185acbd7f9e2 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -76,6 +76,7 @@ tags
 /src/dio-buf-fault
 /src/dio-interleaved
 /src/dio-invalidate-cache
+/src/dio-write-fsync-same-fd
 /src/dirhash_collide
 /src/dirperf
 /src/dirstress

diff --git a/src/Makefile b/src/Makefile
index 52299b4c0c5fbf2b91ff9aca7c8dcc0eb775d84b..3097c29ef0a872b642a5dfc3b6a142a06e563957 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -20,7 +20,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
        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 dio-buf-fault rewinddir-test \
-       readdir-while-renames dio-append-buf-fault
+       readdir-while-renames dio-append-buf-fault dio-write-fsync-same-fd
 
 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-write-fsync-same-fd.c b/src/dio-write-fsync-same-fd.c
new file mode 100644 (file)
index 0000000..79472a9
--- /dev/null
+++ b/src/dio-write-fsync-same-fd.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 SUSE Linux Products GmbH.  All Rights Reserved.
+ */
+
+/*
+ * Test two threads working with the same file descriptor, one doing direct IO
+ * writes into the file and the other just doing fsync calls. We want to verify
+ * that there are no crashes or deadlocks.
+ *
+ * This program never finishes, it starts two infinite loops to write and fsync
+ * the file. It's meant to be called with the 'timeout' program from coreutils.
+ */
+
+/* Get the O_DIRECT definition. */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <pthread.h>
+
+static int fd;
+
+static ssize_t do_write(int fd, const void *buf, size_t count, off_t offset)
+{
+        while (count > 0) {
+               ssize_t ret;
+
+               ret = pwrite(fd, buf, count, offset);
+               if (ret < 0) {
+                       if (errno == EINTR)
+                               continue;
+                       return ret;
+               }
+               count -= ret;
+               buf += ret;
+       }
+       return 0;
+}
+
+static void *fsync_loop(void *arg)
+{
+       while (1) {
+               int ret;
+
+               ret = fsync(fd);
+               if (ret != 0) {
+                       perror("Fsync failed");
+                       exit(6);
+               }
+       }
+}
+
+int main(int argc, char *argv[])
+{
+       long pagesize;
+       void *write_buf;
+       pthread_t fsyncer;
+       int ret;
+
+       if (argc != 2) {
+               fprintf(stderr, "Use: %s <file path>\n", argv[0]);
+               return 1;
+       }
+
+       fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC | O_DIRECT, 0666);
+       if (fd == -1) {
+               perror("Failed to open/create file");
+               return 1;
+       }
+
+       pagesize = sysconf(_SC_PAGE_SIZE);
+       if (pagesize == -1) {
+               perror("Failed to get page size");
+               return 2;
+       }
+
+       ret = posix_memalign(&write_buf, pagesize, pagesize);
+       if (ret) {
+               perror("Failed to allocate buffer");
+               return 3;
+       }
+
+       ret = pthread_create(&fsyncer, NULL, fsync_loop, NULL);
+       if (ret != 0) {
+               fprintf(stderr, "Failed to create writer thread: %d\n", ret);
+               return 4;
+       }
+
+       while (1) {
+               ret = do_write(fd, write_buf, pagesize, 0);
+               if (ret != 0) {
+                       perror("Write failed");
+                       exit(5);
+               }
+       }
+
+       return 0;
+}

diff --git a/tests/generic/364 b/tests/generic/364
new file mode 100755 (executable)
index 0000000..3402959
--- /dev/null
+++ b/tests/generic/364
@@ -0,0 +1,31 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2024 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test No. 364
+#
+# Test that a program that has 2 threads using the same file descriptor and
+# concurrently doing direct IO writes and fsync doesn't trigger any crash or
+# deadlock.
+#
+. ./common/preamble
+_begin_fstest auto quick
+
+_require_test
+_require_odirect
+_require_test_program dio-write-fsync-same-fd
+_require_command "$TIMEOUT_PROG" timeout
+
+# Triggers very frequently with kernel config CONFIG_BTRFS_ASSERT=y.
+[ $FSTYP == "btrfs" ] && \
+       _fixed_by_kernel_commit xxxxxxxxxxxx \
+       "btrfs: fix race between direct IO write and fsync when using same fd"
+
+# On error the test program writes messages to stderr, causing a golden output
+# mismatch and making the test fail.
+$TIMEOUT_PROG 10s $here/src/dio-write-fsync-same-fd $TEST_DIR/dio-write-fsync-same-fd
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit

diff --git a/tests/generic/364.out b/tests/generic/364.out
new file mode 100644 (file)
index 0000000..6bc54ae
--- /dev/null
+++ b/tests/generic/364.out
@@ -0,0 +1,2 @@
+QA output created by 364
+Silence is golden