Unverified Commit ae8c5117 authored by Kent Overstreet's avatar Kent Overstreet Committed by Christian Brauner
Browse files

fs: add FS_IOC_GETFSSYSFSPATH 



Add a new ioctl for getting the sysfs name of a filesystem - the path
under /sys/fs.

This is going to let us standardize exporting data from sysfs across
filesystems, e.g. time stats.

The returned path will always be of the form "$FSTYP/$SYSFS_IDENTIFIER",
where the sysfs identifier may be a UUID (for bcachefs) or a device name
(xfs).

Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20240207025624.1019754-6-kent.overstreet@linux.dev


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent e2f7dd6e

fs/ioctl.c

+17 −0
Original line number Diff line number Diff line
@@ -776,6 +776,20 @@ static int ioctl_getfsuuid(struct file *file, void __user *argp) 
	return copy_to_user(argp, &u, sizeof(u)) ? -EFAULT : 0;

}



static int ioctl_get_fs_sysfs_path(struct file *file, void __user *argp)

{

	struct super_block *sb = file_inode(file)->i_sb;



	if (!strlen(sb->s_sysfs_name))

		return -ENOIOCTLCMD;



	struct fs_sysfs_path u = {};



	u.len = scnprintf(u.name, sizeof(u.name), "%s/%s", sb->s_type->name, sb->s_sysfs_name);



	return copy_to_user(argp, &u, sizeof(u)) ? -EFAULT : 0;

}



/*

 * do_vfs_ioctl() is not for drivers and not intended to be EXPORT_SYMBOL()'d.

 * It's just a simple helper for sys_ioctl and compat_sys_ioctl.
@@ -861,6 +875,9 @@ static int do_vfs_ioctl(struct file *filp, unsigned int fd, 
	case FS_IOC_GETFSUUID:

		return ioctl_getfsuuid(filp, argp);



	case FS_IOC_GETFSSYSFSPATH:

		return ioctl_get_fs_sysfs_path(filp, argp);



	default:

		if (S_ISREG(inode->i_mode))

			return file_ioctl(filp, cmd, argp);

include/linux/fs.h

+43 −0
Original line number Diff line number Diff line
@@ -1255,10 +1255,23 @@ struct super_block { 
	struct fsnotify_mark_connector __rcu	*s_fsnotify_marks;

#endif



	/*

	 * q: why are s_id and s_sysfs_name not the same? both are human

	 * readable strings that identify the filesystem

	 * a: s_id is allowed to change at runtime; it's used in log messages,

	 * and we want to when a device starts out as single device (s_id is dev

	 * name) but then a device is hot added and we have to switch to

	 * identifying it by UUID

	 * but s_sysfs_name is a handle for programmatic access, and can't

	 * change at runtime

	 */

	char			s_id[32];	/* Informational name */

	uuid_t			s_uuid;		/* UUID */

	u8			s_uuid_len;	/* Default 16, possibly smaller for weird filesystems */



	/* if set, fs shows up under sysfs at /sys/fs/$FSTYP/s_sysfs_name */

	char			s_sysfs_name[UUID_STRING_LEN + 1];



	unsigned int		s_max_links;



	/*
@@ -2541,6 +2554,36 @@ static inline void super_set_uuid(struct super_block *sb, const u8 *uuid, unsign 
	memcpy(&sb->s_uuid, uuid, len);

}



/* set sb sysfs name based on sb->s_bdev */

static inline void super_set_sysfs_name_bdev(struct super_block *sb)

{

	snprintf(sb->s_sysfs_name, sizeof(sb->s_sysfs_name), "%pg", sb->s_bdev);

}



/* set sb sysfs name based on sb->s_uuid */

static inline void super_set_sysfs_name_uuid(struct super_block *sb)

{

	WARN_ON(sb->s_uuid_len != sizeof(sb->s_uuid));

	snprintf(sb->s_sysfs_name, sizeof(sb->s_sysfs_name), "%pU", sb->s_uuid.b);

}



/* set sb sysfs name based on sb->s_id */

static inline void super_set_sysfs_name_id(struct super_block *sb)

{

	strscpy(sb->s_sysfs_name, sb->s_id, sizeof(sb->s_sysfs_name));

}



/* try to use something standard before you use this */

__printf(2, 3)

static inline void super_set_sysfs_name_generic(struct super_block *sb, const char *fmt, ...)

{

	va_list args;



	va_start(args, fmt);

	vsnprintf(sb->s_sysfs_name, sizeof(sb->s_sysfs_name), fmt, args);

	va_end(args);

}



extern int current_umask(void);



extern void ihold(struct inode * inode);

include/uapi/linux/fs.h

+10 −0
Original line number Diff line number Diff line
@@ -77,6 +77,11 @@ struct fsuuid2 { 
	__u8	uuid[16];

};



struct fs_sysfs_path {

	__u8			len;

	__u8			name[128];

};



/* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */

#define FILE_DEDUPE_RANGE_SAME		0

#define FILE_DEDUPE_RANGE_DIFFERS	1
@@ -230,6 +235,11 @@ struct fsxattr { 
#define FS_IOC_SETFSLABEL		_IOW(0x94, 50, char[FSLABEL_MAX])

/* Returns the external filesystem UUID, the same one blkid returns */

#define FS_IOC_GETFSUUID		_IOR(0x15, 0, struct fsuuid2)

/*

 * Returns the path component under /sys/fs/ that refers to this filesystem;

 * also /sys/kernel/debug/ for filesystems with debugfs exports

 */

#define FS_IOC_GETFSSYSFSPATH		_IOR(0x15, 1, struct fs_sysfs_path)



/*

 * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)