Date:   Sun, 26 Jun 2022 12:43:56 +0800
From:   Zorro Lang <zlang@...hat.com>
To:     Jeremy Bongio <bongiojp@...il.com>
Cc:     Ted Tso <tytso@....edu>, fstests@...r.kernel.org,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4/056: add a check to make sure ext4 uuid ioctls
 get/set during fsstress.

On Sat, Jun 25, 2022 at 01:53:21AM -0700, Jeremy Bongio wrote:
> Adds a utility to get/set uuid through ext4 ioctl. Executes the ioctls while
> running fsstress. These ioctls are used by tune2fs to safely change the uuid
> without racing other filesystem modifications.
> 
> Signed-off-by: Jeremy Bongio <bongiojp@...il.com>
> ---

Hi Jeremy,

Thanks for the patch, some picky review points as below:

>  src/Makefile       |   4 +-
>  src/global.h       |   2 +
>  src/uuid_ioctl.c   | 106 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/ext4/056     |  59 +++++++++++++++++++++++++
>  tests/ext4/056.out |   1 +
>  5 files changed, 170 insertions(+), 2 deletions(-)
>  create mode 100644 src/uuid_ioctl.c
>  create mode 100755 tests/ext4/056
>  create mode 100644 tests/ext4/056.out
> 
> diff --git a/src/Makefile b/src/Makefile
> index 111ce1d9..e33e04de 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -31,14 +31,14 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
>  	dio-invalidate-cache stat_test t_encrypted_d_revalidate \
>  	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
> +	detached_mounts_propagation ext4_resize uuid_ioctl
>  
>  EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
>  	      btrfs_crc32c_forged_name.py
>  
>  SUBDIRS = log-writes perf
>  
> -LLDLIBS = $(LIBHANDLE) $(LIBACL) -lpthread -lrt
> +LLDLIBS = $(LIBHANDLE) $(LIBACL) -lpthread -lrt -luuid
>  
>  ifeq ($(HAVE_XLOG_ASSIGN_LSN), true)
>  LINUX_TARGETS += loggen
> diff --git a/src/global.h b/src/global.h
> index b4407099..747d95f8 100644
> --- a/src/global.h
> +++ b/src/global.h
> @@ -184,4 +184,6 @@ roundup_64(unsigned long long x, unsigned int y)
>  	return rounddown_64(x + y - 1, y);
>  }
>  
> +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
> +
>  #endif /* GLOBAL_H */
> diff --git a/src/uuid_ioctl.c b/src/uuid_ioctl.c
> new file mode 100644
> index 00000000..51480689
> --- /dev/null
> +++ b/src/uuid_ioctl.c
> @@ -0,0 +1,106 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Test program which uses the raw ext4 set_fsuuid ioctl directly.
> + * SYNOPSIS:
> + *   $0 COMMAND MOUNT_POINT [UUID]
> + *
> + * COMMAND must be either "get" or "set".
> + * The UUID must be a 16 octet represented as 32 hexadecimal digits in canonical
> + * textual representation, e.g. output from `uuidgen`.
> + *
> + */
> +
> +#include <stdio.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +#include <unistd.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/ioctl.h>
> +#include <uuid/uuid.h>
> +#include <linux/fs.h>
> +#include "global.h"
> +
> +struct fsuuid {
> +        size_t len;
> +        __u8 *b;
> +};
> +
> +#ifndef EXT4_IOC_GETFSUUID
> +#define EXT4_IOC_GETFSUUID      _IOR('f', 44, struct fsuuid)
> +#endif
> +
> +#ifndef EXT4_IOC_SETFSUUID
> +#define EXT4_IOC_SETFSUUID      _IOW('f', 45, struct fsuuid)
> +#endif
> +
> +int main(int argc, char **argv)
> +{
> +	int	error, fd;
> +        struct fsuuid fsuuid;
        ^

Bad indent at here, please check the indent of this program.

> +
> +	if (argc < 3) {
> +		fprintf(stderr, "Invalid arguments\n");
> +		return 1;
> +	}
> +
> +	fd = open(argv[2], O_RDONLY);
> +	if (!fd) {
> +		perror(argv[2]);
> +		return 1;
> +	}
> +
> +	BUILD_BUG_ON(sizeof(uuid_t) % 16);
> +	fsuuid.len = 16;
> +	fsuuid.b = calloc(fsuuid.len, sizeof(__u8));
> +
> +	if (strcmp(argv[1], "get") == 0) {
> +		uuid_t uuid;
> +		char uuid_str[37];
> +
> +		if (ioctl(fd, EXT4_IOC_GETFSUUID, &fsuuid)) {
> +			close(fd);
> +			fprintf(stderr, "%s while trying to get fs uuid\n",
> +				strerror(errno));
> +			return 1;
> +		}
> +
> +		memcpy(&uuid, fsuuid.b, sizeof(uuid));
> +		uuid_unparse(uuid, uuid_str);
> +		printf("%s", uuid_str);
> +	} else if (strcmp(argv[1], "set") == 0) {
> +		if (argc != 4) {
> +			fprintf(stderr, "UUID argument missing.\n");
> +			return 1;
> +		}
> +
> +		if (strlen(argv[3]) != 36) {
> +			fprintf(stderr, "Invalid UUID. The UUID should be in "
> +				"canonical format. Example: "
> +				"8c628557-6987-42b2-ba16-b7cc79ddfb43\n");
> +			return 1;
> +		}
> +
> +		uuid_t uuid;
> +		error = uuid_parse(argv[3], uuid);
> +		if (error < 0) {
> +			fprintf(stderr, "%s: invalid UUID.\n", argv[0]);
> +			return 1;
> +		}
> +
> +		memcpy(fsuuid.b, uuid, sizeof(uuid));
> +		if(ioctl(fd, EXT4_IOC_SETFSUUID, &fsuuid)) {
> +			close(fd);
> +			fprintf(stderr, "%s while trying to set fs uuid\n",
> +				strerror(errno));
> +			return 1;
> +		}
> +	} else {
> +		fprintf(stderr, "Invalid command\n");
> +	}
> +
> +	close(fd);
> +	return 0;
> +}
> diff --git a/tests/ext4/056 b/tests/ext4/056
> new file mode 100755
> index 00000000..46631d46
> --- /dev/null
> +++ b/tests/ext4/056
> @@ -0,0 +1,59 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2000-2005 Silicon Graphics, Inc.  All Rights Reserved.
> +#
> +# Test the set/get UUID ioctl.
> +#
> +
> +. ./common/preamble
> +_begin_fstest auto ioctl resize

Why this case is "resize" related?

> +
> +tmpfile="/tmp/$$."
> +trap "rm -f $tmpfile; exit" 0 1 2 3 15

We have default "trap" when you source ./common/preamble. If you need a custom
cleanup by youself, you can define a new one in this case (refer to other cases
which has their own _cleanup).

> +
> +# Import common functions.
> +. ./common/filter
> +
> +# real QA test starts here
> +_supported_fs ext4
> +_require_scratch
> +_require_test_program uuid_ioctl
> +
> +UUID_IOCTL=$here/src/uuid_ioctl
> +
> +# if the ioctl is not supported by the kernel, then skip test.
> +current_uid=$($UUID_IOCTL get $SCRATCH_MNT)
> +if [[ "$current_uid" = "Inappropriate ioctl for device while trying to set fs uuid" ]]; then
> +  _notrun "UUID ioctls are not supported by kernel."
   ^

It's not fault, but we recommended the tab width is 8, for fstests bash script.

> +fi
> +
> +# Create filesystem and mount
> +_scratch_mkfs_ext4 -O metadata_csum_seed >> $seqres.full 2>&1
                                            ^
Generally we make sure $seqres.full is null (rm -f $seqres.full) or truncated
at first. So an easier way is using "> $seqres.full" at the first place which
trys to write $seqres.full, to clean .full file.

> +_scratch_mount >> $seqres.full
> +
> +# Begin fsstress while modifying UUID
> +fsstress_args=$(_scale_fsstress_args -d $SCRATCH_MNT -p 15 -n 999999)
> +"$FSSTRESS_PROG" $fsstress_args > /dev/null &

Better to use "2>&1" if you don't want this case fails on some weird fsstress
error output. Or ">>$seqres.full 2>&1" if you'd like to know what happened
on fsstress.

Do I miss something? I didn't find any place try to make sure above fsstress
process is killed/end (by using kill and wait).

> +
> +test_uuid_ioctl()
> +{
> +  for n in $(seq 1 20); do
> +    new_uuid=$(uuidgen)

I think uuidgen isn't a tool which is 100% installed on all linux system. So

_require_command $UUIDGEN_PROG uuidgen

> +
> +    echo "Setting UUID to ${new_uuid}" >> $seqres.full 2>&1
> +    $UUID_IOCTL set $SCRATCH_MNT $new_uuid >> $seqres.full 2>&1
> +
> +    current_uuid=$($UUID_IOCTL get $SCRATCH_MNT)
> +    echo "$UUID_IOCTL get $SCARTCH_MNT: $current_uuid" >> $seqres.full 2>&1
> +    if [[ "$current_uuid" != "$new_uuid" ]]; then
> +      echo "UUID does not equal what was sent with the ioctl"
> +      exit

I think break is enough, but exit is fine too.

> +    fi
> +  done
> +}
> +
> +test_uuid_ioctl

I'm wondering why not run the code in test_uuid_ioctl directly. Looks like you
just make them into a function, then run this function once. It doesn't use
local variables, or be called many times, or have many complicated lines. Or
you'd like to package the codes in "for n in $(seq 1 20)" loop?

> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/ext4/056.out b/tests/ext4/056.out
> new file mode 100644
> index 00000000..06f52bb4
> --- /dev/null
> +++ b/tests/ext4/056.out
> @@ -0,0 +1 @@
> +QA output created by 056

Silence is golden ?

Thanks,
Zorro

> -- 
> 2.37.0.rc0.161.g10f37bed90-goog
> 

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