Re: [PATCH 18/19] ext4: Add example fsinfo information [ver #16]

[Darrick J. Wong]

On Tue, Feb 18, 2020 at 05:07:14PM +0000, David Howells wrote:
> Add the ability to list some ext4 volume timestamps as an example.
> 
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: linux-ext4@xxxxxxxxxxxxxxx
> ---
> 
>  fs/ext4/Makefile            |    1 +
>  fs/ext4/ext4.h              |    9 +++++++++
>  fs/ext4/fsinfo.c            |   40 ++++++++++++++++++++++++++++++++++++++++
>  fs/ext4/super.c             |    1 +
>  include/uapi/linux/fsinfo.h |   16 ++++++++++++++++
>  samples/vfs/test-fsinfo.c   |   35 +++++++++++++++++++++++++++++++++++
>  6 files changed, 102 insertions(+)
>  create mode 100644 fs/ext4/fsinfo.c
> 
> diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
> index 4ccb3c9189d8..71d5b460c7c7 100644
> --- a/fs/ext4/Makefile
> +++ b/fs/ext4/Makefile
> @@ -16,3 +16,4 @@ ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o
>  ext4-inode-test-objs			+= inode-test.o
>  obj-$(CONFIG_EXT4_KUNIT_TESTS)		+= ext4-inode-test.o
>  ext4-$(CONFIG_FS_VERITY)		+= verity.o
> +ext4-$(CONFIG_FSINFO)			+= fsinfo.o
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 9a2ee2428ecc..d81b04227da7 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -42,6 +42,7 @@
>  
>  #include <linux/fscrypt.h>
>  #include <linux/fsverity.h>
> +#include <linux/fsinfo.h>
>  
>  #include <linux/compiler.h>
>  
> @@ -3166,6 +3167,14 @@ extern const struct inode_operations ext4_file_inode_operations;
>  extern const struct file_operations ext4_file_operations;
>  extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin);
>  
> +/* fsinfo.c */
> +#ifdef CONFIG_FSINFO
> +struct fsinfo_attribute;
> +extern const struct fsinfo_attribute ext4_fsinfo_attributes[];
> +#else
> +#define ext4_fsinfo_attributes NULL
> +#endif
> +
>  /* inline.c */
>  extern int ext4_get_max_inline_size(struct inode *inode);
>  extern int ext4_find_inline_data_nolock(struct inode *inode);
> diff --git a/fs/ext4/fsinfo.c b/fs/ext4/fsinfo.c
> new file mode 100644
> index 000000000000..545424c410ff
> --- /dev/null
> +++ b/fs/ext4/fsinfo.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Filesystem information for ext4
> + *
> + * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells@xxxxxxxxxx)
> + */
> +
> +#include <linux/mount.h>
> +#include "ext4.h"
> +
> +static int ext4_fsinfo_get_volume_name(struct path *path, struct fsinfo_context *ctx)
> +{
> +	const struct ext4_sb_info *sbi = EXT4_SB(path->mnt->mnt_sb);
> +	const struct ext4_super_block *es = sbi->s_es;
> +
> +	memcpy(ctx->buffer, es->s_volume_name, sizeof(es->s_volume_name));

Shouldn't this be checking that ctx->buffer is large enough to hold
s_volume_name?

> +	return strlen(ctx->buffer);

s_volume_name is /not/ a null-terminated string if the label is 16
characters long.

> +}
> +
> +static int ext4_fsinfo_get_timestamps(struct path *path, struct fsinfo_context *ctx)
> +{
> +	const struct ext4_sb_info *sbi = EXT4_SB(path->mnt->mnt_sb);
> +	const struct ext4_super_block *es = sbi->s_es;
> +	struct fsinfo_ext4_timestamps *ts = ctx->buffer;
> +
> +#define Z(R,S) R = S | (((u64)S##_hi) << 32)
> +	Z(ts->mkfs_time,	es->s_mkfs_time);
> +	Z(ts->mount_time,	es->s_mtime);
> +	Z(ts->write_time,	es->s_wtime);
> +	Z(ts->last_check_time,	es->s_lastcheck);
> +	Z(ts->first_error_time,	es->s_first_error_time);
> +	Z(ts->last_error_time,	es->s_last_error_time);
> +	return sizeof(*ts);
> +}
> +
> +const struct fsinfo_attribute ext4_fsinfo_attributes[] = {
> +	FSINFO_STRING	(FSINFO_ATTR_VOLUME_NAME,	ext4_fsinfo_get_volume_name),
> +	FSINFO_VSTRUCT	(FSINFO_ATTR_EXT4_TIMESTAMPS,	ext4_fsinfo_get_timestamps),
> +	{}
> +};
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 8434217549b3..e21c3d99747e 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1477,6 +1477,7 @@ static const struct super_operations ext4_sops = {
>  	.freeze_fs	= ext4_freeze,
>  	.unfreeze_fs	= ext4_unfreeze,
>  	.statfs		= ext4_statfs,
> +	.fsinfo_attributes = ext4_fsinfo_attributes,
>  	.remount_fs	= ext4_remount,
>  	.show_options	= ext4_show_options,
>  #ifdef CONFIG_QUOTA
> diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
> index 5467f88ca9b0..da9a6f48ec5b 100644
> --- a/include/uapi/linux/fsinfo.h
> +++ b/include/uapi/linux/fsinfo.h
> @@ -38,6 +38,8 @@
>  #define FSINFO_ATTR_AFS_SERVER_NAME	0x301	/* Name of the Nth server (string) */
>  #define FSINFO_ATTR_AFS_SERVER_ADDRESSES 0x302	/* List of addresses of the Nth server */
>  
> +#define FSINFO_ATTR_EXT4_TIMESTAMPS	0x400	/* Ext4 superblock timestamps */

I guess each filesystem gets ... 256 different attrs, and the third
nibble determines the namespace?

--D

>  /*
>   * Optional fsinfo() parameter structure.
>   *
> @@ -323,4 +325,18 @@ struct fsinfo_afs_server_address {
>  
>  #define FSINFO_ATTR_AFS_SERVER_ADDRESSES__STRUCT struct fsinfo_afs_server_address
>  
> +/*
> + * Information struct for fsinfo(FSINFO_ATTR_EXT4_TIMESTAMPS).
> + */
> +struct fsinfo_ext4_timestamps {
> +	__u64		mkfs_time;
> +	__u64		mount_time;
> +	__u64		write_time;
> +	__u64		last_check_time;
> +	__u64		first_error_time;
> +	__u64		last_error_time;
> +};
> +
> +#define FSINFO_ATTR_EXT4_TIMESTAMPS__STRUCT struct fsinfo_ext4_timestamps
> +
>  #endif /* _UAPI_LINUX_FSINFO_H */
> diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
> index fd425c08b00b..53251ee98d1c 100644
> --- a/samples/vfs/test-fsinfo.c
> +++ b/samples/vfs/test-fsinfo.c
> @@ -359,6 +359,40 @@ static void dump_afs_fsinfo_server_address(void *reply, unsigned int size)
>  	printf("family=%u\n", ss->ss_family);
>  }
>  
> +static char *dump_ext4_time(char *buffer, time_t tim)
> +{
> +	struct tm tm;
> +	int len;
> +
> +	if (tim == 0)
> +		return "-";
> +
> +	if (!localtime_r(&tim, &tm)) {
> +		perror("localtime_r");
> +		exit(1);
> +	}
> +	len = strftime(buffer, 100, "%F %T", &tm);
> +	if (len == 0) {
> +		perror("strftime");
> +		exit(1);
> +	}
> +	return buffer;
> +}
> +
> +static void dump_ext4_fsinfo_timestamps(void *reply, unsigned int size)
> +{
> +	struct fsinfo_ext4_timestamps *r = reply;
> +	char buffer[100];
> +
> +	printf("\n");
> +	printf("\tmkfs    : %s\n", dump_ext4_time(buffer, r->mkfs_time));
> +	printf("\tmount   : %s\n", dump_ext4_time(buffer, r->mount_time));
> +	printf("\twrite   : %s\n", dump_ext4_time(buffer, r->write_time));
> +	printf("\tfsck    : %s\n", dump_ext4_time(buffer, r->last_check_time));
> +	printf("\t1st-err : %s\n", dump_ext4_time(buffer, r->first_error_time));
> +	printf("\tlast-err: %s\n", dump_ext4_time(buffer, r->last_error_time));
> +}
> +
>  static void dump_string(void *reply, unsigned int size)
>  {
>  	char *s = reply, *p;
> @@ -433,6 +467,7 @@ static const struct fsinfo_attribute fsinfo_attributes[] = {
>  	FSINFO_STRING	(FSINFO_ATTR_AFS_CELL_NAME,	afs_cell_name),
>  	FSINFO_STRING	(FSINFO_ATTR_AFS_SERVER_NAME,	afs_server_name),
>  	FSINFO_LIST_N	(FSINFO_ATTR_AFS_SERVER_ADDRESSES, afs_fsinfo_server_address),
> +	FSINFO_VSTRUCT	(FSINFO_ATTR_EXT4_TIMESTAMPS,	ext4_fsinfo_timestamps),
>  	{}
>  };
>  
> 
>