Re: [PATCH] generic: test fsync against a removed directory

On Thu, Apr 09, 2026 at 04:22:27PM +0100, [email protected] wrote:
> From: Filipe Manana <[email protected]>
> 
> Test that if we fsync a directory that became empty after removing it
> and we have a power failure, we are able to mount the filesystem and the
> directory does not exists anymore.
> 
> This exercises a bug found in btrfs which is fixed by the following patch:
> 
>   btrfs: fix missing last_unlink_trans update when removing a directory
> 

Reviewed-by: Boris Burkov <[email protected]>

> Signed-off-by: Filipe Manana <[email protected]>
> ---
>  src/unlink-fsync.c    | 39 ++++++++++++++++++------
>  tests/generic/792     | 69 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/792.out | 10 +++++++
>  3 files changed, 109 insertions(+), 9 deletions(-)
>  create mode 100755 tests/generic/792
>  create mode 100644 tests/generic/792.out
> 
> diff --git a/src/unlink-fsync.c b/src/unlink-fsync.c
> index ce008c6b..364f9226 100644
> --- a/src/unlink-fsync.c
> +++ b/src/unlink-fsync.c
> @@ -4,10 +4,12 @@
>   */
>  
>  /*
> - * Utility to open an existing file, unlink it while holding an open fd on it
> - * and then fsync the file before closing the fd.
> + * Utility to open an existing file or directory, unlink or rmdir it while
> + * holding an open fd on it and then fsync it before closing the fd.
>   */
>  
> +#include <sys/types.h>
> +#include <sys/stat.h>
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <unistd.h>
> @@ -15,24 +17,43 @@
>  
>  int main(int argc, char *argv[])
>  {
> +	struct stat path_stat;
>  	int fd;
>  	int ret;
>  
>  	if (argc != 2) {
> -		fprintf(stderr, "Use: %s <file path>\n", argv[0]);
> +		fprintf(stderr, "Use: %s <file or dir path>\n", argv[0]);
>  		return 1;
>  	}
>  
> -	fd = open(argv[1], O_WRONLY, 0666);
> +	ret = stat(argv[1], &path_stat);
> +	if (ret == -1) {
> +		perror("stat failed");
> +		exit(1);
> +	}
> +
> +	if (S_ISDIR(path_stat.st_mode))
> +		fd = open(argv[1], O_RDONLY | O_DIRECTORY);
> +	else
> +		fd = open(argv[1], O_WRONLY, 0666);
> +
>  	if (fd == -1) {
> -		perror("failed to open file");
> +		perror("failed to open file/dir");
>  		exit(1);
>  	}
>  
> -	ret = unlink(argv[1]);
> -	if (ret == -1) {
> -		perror("unlink failed");
> -		exit(2);
> +	if (S_ISDIR(path_stat.st_mode)) {
> +		ret = rmdir(argv[1]);
> +		if (ret == -1) {
> +			perror("rmdir failed");
> +			exit(2);
> +		}
> +	} else {
> +		ret = unlink(argv[1]);
> +		if (ret == -1) {
> +			perror("unlink failed");
> +			exit(2);
> +		}
>  	}
>  
>  	ret = fsync(fd);
> diff --git a/tests/generic/792 b/tests/generic/792
> new file mode 100755
> index 00000000..892ca2d8
> --- /dev/null
> +++ b/tests/generic/792
> @@ -0,0 +1,69 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2026 SUSE S.A.  All Rights Reserved.
> +#
> +# FS QA Test 792
> +#
> +# Test that if we fsync a directory that became empty after removing it and we
> +# have a power failure, we are able to mount the filesystem and the directory
> +# does not exists anymore.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick log
> +
> +_cleanup()
> +{
> +	_cleanup_flakey
> +	cd /
> +	rm -r -f $tmp.*
> +}
> +
> +. ./common/filter
> +. ./common/dmflakey
> +
> +_require_scratch
> +_require_test_program unlink-fsync
> +_require_dm_target flakey
> +
> +_fixed_by_fs_commit btrfs xxxxxxxxxxxx \
> +	"btrfs: fix missing last_unlink_trans update when removing a directory"
> +
> +_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed"
> +_require_metadata_journaling $SCRATCH_DEV
> +_init_flakey
> +_scratch_mount
> +
> +# Create our first directory and define its permissions (we will later change
> +# them).
> +mkdir $SCRATCH_MNT/dir1
> +chmod a+rwx $SCRATCH_MNT/dir1
> +
> +# Created another directory inside that first directoy and then another one at
> +# the top level.
> +mkdir $SCRATCH_MNT/dir1/dir2
> +mkdir $SCRATCH_MNT/dir3
> +
> +# Persist everything done so far.
> +_scratch_sync
> +
> +# Do some change to the first directory, like change its permissions, fsync it.
> +chmod o-rwx $SCRATCH_MNT/dir1
> +$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/dir1
> +
> +# Now move the second directory from dir1 to dir3, so that dir1 becomes empty.
> +mv $SCRATCH_MNT/dir1/dir2 $SCRATCH_MNT/dir3/
> +
> +# Now open an fd for dir1, rmdir it and fsync it before closing the fd.
> +$here/src/unlink-fsync $SCRATCH_MNT/dir1
> +
> +# Simulate a power failure and replay the log/journal.
> +# The mount should succeed, dir1 must not exist anymore and dir2 must now be
> +# inside dir3.
> +_flakey_drop_and_remount
> +
> +echo -e "Filesystem content after power failure:\n"
> +# Exclude 'lost+found' dir from ext4 and last line if it's blank (due to removal
> +# of 'lost+found').
> +ls -R $SCRATCH_MNT/ | grep -v 'lost+found' | sed -e '${/^$/d;}' | _filter_scratch
> +
> +_exit 0
> diff --git a/tests/generic/792.out b/tests/generic/792.out
> new file mode 100644
> index 00000000..f806258c
> --- /dev/null
> +++ b/tests/generic/792.out
> @@ -0,0 +1,10 @@
> +QA output created by 792
> +Filesystem content after power failure:
> +
> +SCRATCH_MNT/:
> +dir3
> +
> +SCRATCH_MNT/dir3:
> +dir2
> +
> +SCRATCH_MNT/dir3/dir2:
> -- 
> 2.47.2
>