On Nov 24, 2021, at 6:45 AM, Lukas Czerner <lczerner@xxxxxxxxxx> wrote:
>
> Implement support for FS_IOC_SETFSLABEL and FS_IOC_GETFSLABEL ioctls.
> Try to use the ioctls if possible even before we open the file system
> since we don't need it. Only fall back to the old method in the case the
> file system is not mounted, is mounted read only in the set label case,
> or the ioctls are not suppported by the kernel.
>
> The new ioctls can also be supported by file system drivers other than
> ext4. As a result tune2fs and e2label will work for those file systems
> as well as long as the file system is mounted. Note that we still truncate
> the label exceeds the supported lenghth on extN file system family, while
> we keep the label intact for others.
>
> Update tune2fs and e2label as well.
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> ---
> lib/ext2fs/ext2fs.h | 1 +
> lib/ext2fs/ismounted.c | 5 +++
> misc/e2label.8.in | 7 ++-
> misc/tune2fs.8.in | 8 +++-
> misc/tune2fs.c | 96 ++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 114 insertions(+), 3 deletions(-)
>
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 0ee0e7d0..68f9c1fe 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -531,6 +531,7 @@ typedef struct ext2_struct_inode_scan *ext2_inode_scan;
> #define EXT2_MF_READONLY 4
> #define EXT2_MF_SWAP 8
> #define EXT2_MF_BUSY 16
> +#define EXT2_MF_EXTFS 32
>
> /*
> * Ext2/linux mode flags. We define them here so that we don't need
> diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
> index aee7d726..c73273b8 100644
> --- a/lib/ext2fs/ismounted.c
> +++ b/lib/ext2fs/ismounted.c
> @@ -207,6 +207,11 @@ is_root:
> close(fd);
> (void) unlink(TEST_FILE);
> }
> +
> + if (!strcmp(mnt->mnt_type, "ext4") ||
> + !strcmp(mnt->mnt_type, "ext3") ||
> + !strcmp(mnt->mnt_type, "ext2"))
IMHO, using "!strcmp(...)" reads like "not matching the string ...", so I prefer
to use "strcmp(...) == 0".
> + *mount_flags |= EXT2_MF_EXTFS;
> retval = 0;
> errout:
> endmntent (f);
> diff --git a/misc/e2label.8.in b/misc/e2label.8.in
> index 1dc96199..fa5294c4 100644
> --- a/misc/e2label.8.in
> +++ b/misc/e2label.8.in
> @@ -33,7 +33,12 @@ Ext2 volume labels can be at most 16 characters long; if
> .I volume-label
> is longer than 16 characters,
> .B e2label
> -will truncate it and print a warning message.
> +will truncate it and print a warning message. For other file systems that
> +support online label manipulation and are mounted
> +.B e2label
> +will work as well, but it will not attempt to truncate the
> +.I volume-label
> +at all.
> .PP
> It is also possible to set the volume label using the
> .B \-L
> diff --git a/misc/tune2fs.8.in b/misc/tune2fs.8.in
> index 1e026e5f..628dcdc0 100644
> --- a/misc/tune2fs.8.in
> +++ b/misc/tune2fs.8.in
> @@ -457,8 +457,12 @@ Ext2 file system labels can be at most 16 characters long; if
> .I volume-label
> is longer than 16 characters,
> .B tune2fs
> -will truncate it and print a warning. The volume label can be used
> -by
> +will truncate it and print a warning. For other file systems that
> +support online label manipulation and are mounted
> +.B tune2fs
> +will work as well, but it will not attempt to truncate the
> +.I volume-label
> +at all. The volume label can be used by
> .BR mount (8),
> .BR fsck (8),
> and
> diff --git a/misc/tune2fs.c b/misc/tune2fs.c
> index 71a8e99b..6c162ba5 100644
> --- a/misc/tune2fs.c
> +++ b/misc/tune2fs.c
> @@ -52,6 +52,9 @@ extern int optind;
> #include <sys/types.h>
> #include <libgen.h>
> #include <limits.h>
> +#ifdef HAVE_SYS_IOCTL_H
> +#include <sys/ioctl.h>
> +#endif
>
> #include "ext2fs/ext2_fs.h"
> #include "ext2fs/ext2fs.h"
> @@ -70,6 +73,15 @@ extern int optind;
> #define QOPT_ENABLE (1)
> #define QOPT_DISABLE (-1)
>
> +#ifndef FS_IOC_SETFSLABEL
> +#define FSLABEL_MAX 256
> +#define FS_IOC_SETFSLABEL _IOW(0x94, 50, char[FSLABEL_MAX])
> +#endif
> +
> +#ifndef FS_IOC_GETFSLABEL
> +#define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX])
> +#endif
> +
> extern int ask_yn(const char *string, int def);
>
> const char *program_name = "tune2fs";
> @@ -2997,6 +3009,75 @@ fs_update_journal_user(struct ext2_super_block *sb, __u8 old_uuid[UUID_SIZE])
> return 0;
> }
>
> +/*
> + * Use FS_IOC_SETFSLABEL or FS_IOC_GETFSLABEL to set/get file system label
> + * Return: 0 on success
> + * 1 on error
> + * -1 when the old method should be used
> + */
> +int handle_fslabel(int setlabel) {
> + errcode_t ret;
> + int mnt_flags, fd;
> + char label[FSLABEL_MAX];
> + int maxlen = FSLABEL_MAX - 1;
> + char mntpt[PATH_MAX + 1];
> +
> + ret = ext2fs_check_mount_point(device_name, &mnt_flags,
> + mntpt, sizeof(mntpt));
> + if (ret) {
> + com_err(device_name, ret, _("while checking mount status"));
> + return 1;
> + }
> + if (!(mnt_flags & EXT2_MF_MOUNTED) ||
> + (setlabel && (mnt_flags & EXT2_MF_READONLY)))
> + return -1;
> +
> + if (!mntpt[0]) {
> + fprintf(stderr,_("Unknown mount point for %s\n"), device_name);
> + return 1;
> + }
> +
> + fd = open(mntpt, O_RDONLY);
Opening read-only to change the label is a bit strange? It would be better
to open in write mode, and verify in the kernel that this is the case:
fd = open(mntpt, setlabel ? O_WRONLY : O_RDONLY);
> + if (fd < 0) {
> + com_err(mntpt, errno, _("while opening mount point"));
> + return 1;
> + }
> +
> + /* Get fs label */
> + if (!setlabel) {
> + if (ioctl(fd, FS_IOC_GETFSLABEL, &label)) {
> + close(fd);
> + if (errno == ENOTTY)
> + return -1;
> + com_err(mntpt, errno, _("while trying to get fs label"));
> + return 1;
> + }
> + close(fd);
> + printf("%.*s\n", EXT2_LEN_STR(label));
> + return 0;
> + }
> +
> + /* If it's extN file system, truncate the label to appropriate size */
> + if (mnt_flags & EXT2_MF_EXTFS)
> + maxlen = EXT2_LABEL_LEN;
> + if (strlen(new_label) > maxlen) {
> + fputs(_("Warning: label too long, truncating.\n"),
> + stderr);
> + new_label[maxlen] = '\0';
> + }
> +
> + /* Set fs label */
> + if (ioctl(fd, FS_IOC_SETFSLABEL, new_label)) {
> + close(fd);
> + if (errno == ENOTTY)
> + return -1;
> + com_err(mntpt, errno, _("while trying to set fs label"));
> + return 1;
> + }
> + close(fd);
> + return 0;
> +}
> +
> #ifndef BUILD_AS_LIB
> int main(int argc, char **argv)
> #else
> @@ -3038,6 +3119,21 @@ int tune2fs_main(int argc, char **argv)
> #endif
> io_ptr = unix_io_manager;
>
> + /*
> + * Try the get/set fs label using ioctls before we even attempt
> + * to open the file system.
> + */
> + if (L_flag || print_label) {
> + rc = handle_fslabel(L_flag);
> + if (rc != -1) {
> +#ifndef BUILD_AS_LIB
> + exit(rc);
> +#endif
> + return rc;
> + }
> + rc = 0;
> + }
> +
> retry_open:
> if ((open_flag & EXT2_FLAG_RW) == 0 || f_flag)
> open_flag |= EXT2_FLAG_SKIP_MMP;
> --
> 2.31.1
>
Cheers, Andreas
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