Re: [PATCH v10 1/1] proto: add ability to populate a filesystem from a directory

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, May 22, 2025 at 05:10:03PM -0400, Luca Di Maio wrote:
> This patch implements the functionality to populate a newly created XFS
> filesystem directly from an existing directory structure.
> 
> It resuses existing protofile logic, it branches if input is a
> directory.
> 
> The population process steps are as follows:
>   - create the root inode before populating content
>   - recursively process nested directories
>   - handle regular files, directories, symlinks, char devices, block
>     devices, sockets, fifos
>   - preserve attributes (ownership, permissions)
>   - preserve mtime timestamps from source files to maintain file history
>     - use current time for atime/ctime/crtime
>     - possible to specify atime=1 to preserve atime timestamps from
>       source files
>   - preserve extended attributes and fsxattrs for all file types
>   - preserve hardlinks
> 
> At the moment, the implementation for the hardlink tracking is very
> simple, as it involves a linear search.
> from my local testing using larger source directories
> (1.3mln inodes, ~400k hardlinks) the difference was actually
> just a few seconds (given that most of the time is doing i/o).
> We might want to revisit that in the future if this becomes a
> bottleneck.
> 
> This functionality makes it easier to create populated filesystems
> without having to mount them, it's particularly useful for
> reproducible builds.

In addition to all of hch's comments...

> Signed-off-by: Luca Di Maio <luca.dimaio1@gmail.com>
> ---
>  man/man8/mkfs.xfs.8.in |  41 ++-
>  mkfs/proto.c           | 765 ++++++++++++++++++++++++++++++++++++++++-
>  mkfs/proto.h           |  18 +-
>  mkfs/xfs_mkfs.c        |  23 +-
>  4 files changed, 821 insertions(+), 26 deletions(-)
> 
> diff --git a/man/man8/mkfs.xfs.8.in b/man/man8/mkfs.xfs.8.in
> index 37e3a88e..bb38c148 100644
> --- a/man/man8/mkfs.xfs.8.in
> +++ b/man/man8/mkfs.xfs.8.in
> @@ -28,7 +28,7 @@ mkfs.xfs \- construct an XFS filesystem
>  .I naming_options
>  ] [
>  .B \-p
> -.I protofile_options
> +.I prototype_options
>  ] [
>  .B \-q
>  ] [
> @@ -977,30 +977,39 @@ option set.
>  .PP
>  .PD 0
>  .TP
> -.BI \-p " protofile_options"
> +.BI \-p " prototype_options"
>  .TP
>  .BI "Section Name: " [proto]
>  .PD
> -These options specify the protofile parameters for populating the filesystem.
> +These options specify the prototype parameters for populating the filesystem.
>  The valid
> -.I protofile_options
> +.I prototype_options
>  are:
>  .RS 1.2i
>  .TP
> -.BI [file=] protofile
> +.BI [file=]
>  The
>  .B file=
>  prefix is not required for this CLI argument for legacy reasons.
>  If specified as a config file directive, the prefix is required.
> -
> +.TP
> +.BI [file=] directory
>  If the optional
>  .PD
> -.I protofile
> -argument is given,
> +.I prototype
> +argument is given, and it's a directory,
>  .B mkfs.xfs
> -uses
> -.I protofile
> -as a prototype file and takes its directions from that file.
> +will populate the root file system with the contents of the given directory.
> +Content, timestamps (atime, mtime), attributes and extended attributes are preserved
> +for all file types.
> +.TP
> +.BI [file=] protofile
> +If the optional
> +.PD
> +.I prototype
> +argument is given, and points to a regular file,
> +.B mkfs.xfs
> +uses it as a prototype file and takes its directions from that file.
>  The blocks and inodes specifiers in the
>  .I protofile
>  are provided for backwards compatibility, but are otherwise unused.
> @@ -1136,8 +1145,16 @@ always terminated with the dollar (
>  .B $
>  ) token.
>  .TP
> +.BI atime= value
> +If set to 1, when we're populating the root filesystem from a directory (
> +.B file=directory
> +option)
> +access times are going to be preserved and are copied from the source files.
> +Set to 0 to set access times to the current time instead.
> +By default, this is set to 0.
> +.TP
>  .BI slashes_are_spaces= value
> -If set to 1, slashes ("/") in the first token of each line of the protofile
> +If set to 1, slashes ("/") in the first token of each line of the prototype file
>  are converted to spaces.
>  This enables the creation of a filesystem containing filenames with spaces.
>  By default, this is set to 0.
> diff --git a/mkfs/proto.c b/mkfs/proto.c
> index 7f56a3d8..0c456248 100644
> --- a/mkfs/proto.c
> +++ b/mkfs/proto.c
> @@ -5,6 +5,10 @@
>   */
> 
>  #include "libxfs.h"
> +#include "xfs_format.h"
> +#include <dirent.h>
> +#include <fcntl.h>
> +#include <sys/resource.h>
>  #include <sys/stat.h>
>  #include <sys/xattr.h>
>  #include <linux/xattr.h>
> @@ -21,6 +25,11 @@ static void rsvfile(xfs_mount_t *mp, xfs_inode_t *ip, long long len);
>  static int newregfile(char **pp, char **fname);
>  static void rtinit(xfs_mount_t *mp);
>  static off_t filesize(int fd);
> +static void populate_from_dir(struct xfs_mount *mp,
> +				struct fsxattr *fsxp, char *source_dir);
> +static void walk_dir(struct xfs_mount *mp, struct xfs_inode *pip,
> +				struct fsxattr *fsxp, char *path_buf);
> +static int preserve_atime;
>  static int slashes_are_spaces;
> 
>  /*
> @@ -54,7 +63,7 @@ getnum(
>  	return i;
>  }
> 
> -char *
> +struct proto_source
>  setup_proto(
>  	char	*fname)
>  {
> @@ -63,8 +72,37 @@ setup_proto(
>  	int		fd;
>  	long		size;
> 
> -	if (!fname)
> -		return dflt;
> +	struct proto_source	result = {0};
> +	struct stat	statbuf;
> +
> +	/*
> +	 * If no prototype path is
> +	 * supplied, use the default protofile
> +	 * which creates only a root
> +	 * directory.
> +	 */
> +	if (!fname) {
> +		result.type = PROTO_SRC_PROTOFILE;
> +		result.data = dflt;
> +		return result;
> +	}
> +
> +	if (stat(fname, &statbuf) < 0) {
> +		fail(_("invalid or unreadable source path"), errno);
> +	}
> +
> +	/*
> +	 * handle directory inputs
> +	 */
> +	if (S_ISDIR(statbuf.st_mode)) {
> +		result.type = PROTO_SRC_DIR;
> +		result.data = fname;
> +		return result;
> +	}
> +
> +	/*
> +	 * else this is a protofile, let's handle traditionally
> +	 */
>  	if ((fd = open(fname, O_RDONLY)) < 0 || (size = filesize(fd)) < 0) {
>  		fprintf(stderr, _("%s: failed to open %s: %s\n"),
>  			progname, fname, strerror(errno));
> @@ -90,7 +128,10 @@ setup_proto(
>  	(void)getnum(getstr(&buf), 0, 0, false);	/* block count */
>  	(void)getnum(getstr(&buf), 0, 0, false);	/* inode count */
>  	close(fd);
> -	return buf;
> +
> +	result.type = PROTO_SRC_PROTOFILE;
> +	result.data = buf;
> +	return result;
> 
>  out_fail:
>  	if (fd >= 0)
> @@ -379,6 +420,13 @@ writeattr(
>  	int			error;
> 
>  	ret = fgetxattr(fd, attrname, valuebuf, valuelen);
> +	/*
> +	 * in case of filedescriptors with O_PATH, fgetxattr() will
> +	 * fail with EBADF. let's try to fallback to lgetxattr() using input
> +	 * path.
> +	 */
> +	if (ret < 0 && errno == EBADF)
> +		ret = lgetxattr(fname, attrname, valuebuf, valuelen);
>  	if (ret < 0) {
>  		if (errno == EOPNOTSUPP)
>  			return;
> @@ -425,6 +473,13 @@ writeattrs(
>  		fail(_("error allocating xattr name buffer"), errno);
> 
>  	ret = flistxattr(fd, namebuf, XATTR_LIST_MAX);
> +	/*
> +	 * in case of filedescriptors with O_PATH, flistxattr() will
> +	 * fail with EBADF. let's try to fallback to llistxattr() using input
> +	 * path.
> +	 */
> +	if (ret < 0 && errno == EBADF)
> +		ret = llistxattr(fname, namebuf, XATTR_LIST_MAX);
>  	if (ret < 0) {
>  		if (errno == EOPNOTSUPP)
>  			goto out_namebuf;
> @@ -933,11 +988,27 @@ void
>  parse_proto(
>  	xfs_mount_t	*mp,
>  	struct fsxattr	*fsx,
> -	char		**pp,
> -	int		proto_slashes_are_spaces)
> +	struct proto_source	*protosource,
> +	int		proto_slashes_are_spaces,
> +	int		proto_preserve_atime)
>  {
>  	slashes_are_spaces = proto_slashes_are_spaces;
> -	parseproto(mp, NULL, fsx, pp, NULL);
> +	preserve_atime = proto_preserve_atime;
> +
> +	/*
> +	 * in case of a file input, we will use the prototype file logic
> +	 * else we will fallback to populate from dir.
> +	 */
> +	switch(protosource->type) {
> +	case PROTO_SRC_PROTOFILE:
> +		parseproto(mp, NULL, fsx, &protosource->data, NULL);
> +		break;
> +	case PROTO_SRC_DIR:
> +		populate_from_dir(mp, fsx, protosource->data);
> +		break;
> +	case PROTO_SRC_NONE:
> +		fail(_("invalid or unreadable source path"), ENOENT);
> +	}
>  }
> 
>  /* Create a sb-rooted metadata file. */
> @@ -1171,3 +1242,683 @@ filesize(
>  		return -1;
>  	return stb.st_size;
>  }
> +
> +/* Try to allow as many open directories as possible. */
> +static void
> +bump_max_fds(void)
> +{
> +	struct rlimit	rlim = {};
> +	int		ret;
> +
> +	ret = getrlimit(RLIMIT_NOFILE, &rlim);
> +	if (ret)
> +		return;
> +
> +	rlim.rlim_cur = rlim.rlim_max;
> +	ret = setrlimit(RLIMIT_NOFILE, &rlim);
> +	if (ret < 0)
> +		fprintf(stderr, _("%s: could not bump fd limit: [ %d - %s]\n"),
> +				progname, errno, strerror(errno));
> +}
> +
> +static void
> +writefsxattrs(
> +	struct xfs_inode	*ip,
> +	struct fsxattr	*fsxp)
> +{
> +	ip->i_projid = fsxp->fsx_projid;
> +	ip->i_extsize = fsxp->fsx_extsize;
> +	ip->i_diflags = xfs_flags2diflags(ip, fsxp->fsx_xflags);
> +	if (xfs_has_v3inodes(ip->i_mount)) {
> +		ip->i_diflags2 = xfs_flags2diflags2(ip, fsxp->fsx_xflags);
> +		ip->i_cowextsize = fsxp->fsx_cowextsize;
> +	}
> +}
> +
> +static void
> +writetimestamps(
> +	struct xfs_inode	*ip,
> +	struct stat	*statbuf)
> +{
> +	struct timespec64	ts;
> +
> +	/*
> +	 * Copy timestamps from source file to destination inode.
> +	 * Usually reproducible archives will delete or not register
> +	 * atime and ctime, for example:
> +	 *    https://www.gnu.org/software/tar/manual/html_section/Reproducibility.html
> +	 * hence we will only copy mtime, and let ctime/crtime be set to
> +	 * current time.
> +	 * atime will be copied over if atime is true.
> +	 */
> +	ts.tv_sec = statbuf->st_mtim.tv_sec;
> +	ts.tv_nsec = statbuf->st_mtim.tv_nsec;
> +	inode_set_mtime_to_ts(VFS_I(ip), ts);
> +
> +	/*
> +	 * in case of atime option, we will copy the atime
> +	 * timestamp from source.
> +	 */
> +	if (preserve_atime) {
> +		ts.tv_sec = statbuf->st_atim.tv_sec;
> +		ts.tv_nsec = statbuf->st_atim.tv_nsec;
> +		inode_set_atime_to_ts(VFS_I(ip), ts);
> +	}
> +}
> +
> +struct hardlink {
> +	ino_t		src_ino;
> +	xfs_ino_t	dst_ino;
> +};
> +
> +struct hardlinks {
> +	size_t		count;
> +	size_t		size;
> +	struct hardlink	*entries;
> +};
> +
> +/* Growth strategy for hardlink tracking array */
> +#define HARDLINK_DEFAULT_GROWTH_FACTOR	2	/* Double size for small arrays */
> +#define HARDLINK_LARGE_GROWTH_FACTOR	0.25	/* Grow by 25% for large arrays */
> +#define HARDLINK_THRESHOLD		1024	/* Threshold to switch growth strategies */
> +#define HARDLINK_TRACKER_INITIAL_SIZE	4096	/* Initial allocation size */
> +
> +/*
> + * keep track of source inodes that are from hardlinks
> + * so we can retrieve them when needed to setup in
> + * destination.
> + */
> +static struct hardlinks hardlink_tracker = { 0 };
> +
> +static void
> +init_hardlink_tracker(void)
> +{
> +	hardlink_tracker.size = HARDLINK_TRACKER_INITIAL_SIZE;
> +	hardlink_tracker.entries = calloc(
> +			hardlink_tracker.size,
> +			sizeof(struct hardlink));
> +	if (!hardlink_tracker.entries)
> +		fail(_("error allocating hardlinks tracking array"), errno);
> +}
> +
> +static void
> +cleanup_hardlink_tracker(void)
> +{
> +	free(hardlink_tracker.entries);

Please zero out hardlink_tracker now that you've freed the array so that
some future user won't accidentally add code that walks off the end of a
dead pointer if they call get_hardlink_dst_inode after
cleanup_hardlink_tracker.

> +}
> +
> +static xfs_ino_t
> +get_hardlink_dst_inode(
> +	xfs_ino_t	i_ino)
> +{
> +	for (size_t i = 0; i < hardlink_tracker.count; i++) {
> +		if (hardlink_tracker.entries[i].src_ino == i_ino) {
> +			return hardlink_tracker.entries[i].dst_ino;
> +		}
> +	}
> +	return 0;
> +}
> +
> +static void
> +track_hardlink_inode(
> +	ino_t		src_ino,
> +	xfs_ino_t	dst_ino)
> +{
> +	if (hardlink_tracker.count >= hardlink_tracker.size) {
> +		/*
> +		 * double for smaller capacity.
> +		 * instead grow by 25% steps for larger capacities.
> +		 */
> +		const size_t old_size = hardlink_tracker.size;
> +		size_t new_size = old_size * HARDLINK_DEFAULT_GROWTH_FACTOR;
> +		if (old_size > HARDLINK_THRESHOLD)
> +			new_size = old_size + (old_size * HARDLINK_LARGE_GROWTH_FACTOR);
> +
> +		struct hardlink *resized_array = reallocarray(
> +			hardlink_tracker.entries,
> +			new_size,
> +			sizeof(struct hardlink));
> +		if (!resized_array)
> +			fail(_("error enlarging hardlinks tracking array"), errno);
> +
> +		memset(&resized_array[old_size], 0,
> +				(new_size - old_size) * sizeof(struct hardlink));
> +
> +		hardlink_tracker.entries = resized_array;
> +		hardlink_tracker.size = new_size;
> +	}
> +
> +	hardlink_tracker.entries[hardlink_tracker.count].src_ino = src_ino;
> +	hardlink_tracker.entries[hardlink_tracker.count].dst_ino = dst_ino;
> +	hardlink_tracker.count++;
> +}
> +
> +/*
> + * this function will first check in our tracker if
> + * the input hardlink has already been stored, if not
> + * report false so create_file() can continue handling
> + * the inode as a regular file type, and later save
> + * the source inode in our buffer for future consumption.
> + */
> +static bool
> +handle_hardlink(
> +	struct xfs_mount	*mp,
> +	struct xfs_inode	*pip,
> +	struct xfs_name	xname,
> +	struct stat	file_stat)
> +{
> +	int		error;
> +	xfs_ino_t		dst_ino;
> +	struct xfs_inode	*ip;
> +	struct xfs_trans	*tp;
> +	struct xfs_parent_args *ppargs = NULL;
> +
> +	tp = getres(mp, 0);
> +	ppargs = newpptr(mp);
> +	dst_ino = get_hardlink_dst_inode(file_stat.st_ino);
> +
> +	/*
> +	 * we didn't find the hardlink inode, this means
> +	 * it's the first time we see it, report error
> +	 * so create_file() can continue handling the inode
> +	 * as a regular file type, and later save
> +	 * the source inode in our buffer for future consumption.
> +	 */
> +	if (dst_ino == 0)
> +		return false;
> +
> +	error = libxfs_iget(mp, NULL, dst_ino, 0, &ip);
> +	if (error)
> +		fail(_("failed to get inode"), error);
> +
> +	/*
> +	 * In case the inode was already in our tracker
> +	 * we need to setup the hardlink and skip file
> +	 * copy.
> +	 */
> +	libxfs_trans_ijoin(tp, pip, 0);
> +	libxfs_trans_ijoin(tp, ip, 0);
> +	newdirent(mp, tp, pip, &xname, ip, ppargs);
> +
> +	/*
> +	 * Increment the link count
> +	 */
> +	libxfs_bumplink(tp, ip);
> +
> +	libxfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
> +
> +	error = -libxfs_trans_commit(tp);
> +	if (error)
> +		fail(_("Error encountered creating file from prototype file"), error);
> +
> +	libxfs_parent_finish(mp, ppargs);
> +	libxfs_irele(ip);
> +
> +	return true;
> +}
> +
> +static void
> +create_file(
> +	struct xfs_mount	*mp,
> +	struct xfs_inode	*pip,
> +	struct fsxattr	*fsxp,
> +	int		mode,
> +	struct cred	creds,
> +	struct xfs_name	xname,
> +	int		flags,
> +	struct stat	file_stat,
> +	xfs_dev_t		rdev,
> +	int		fd,
> +	char		*fname)
> +{
> +
> +	int		error;
> +	struct xfs_inode	*ip;
> +	struct xfs_trans	*tp;
> +	struct xfs_parent_args *ppargs = NULL;
> +
> +	/*
> +	 * if handle_hardlink() returns true it means the hardlink has
> +	 * been correctly found and set, so we don't need to
> +	 * do anything else.
> +	 */
> +	if (file_stat.st_nlink > 1 && handle_hardlink(mp, pip, xname, file_stat)) {
> +		close(fd);
> +		return;
> +	}
> +	/*
> +	 * if instead we have an error it means the hardlink
> +	 * was not registered, so we proceed to treat it like
> +	 * a regular file, and save it to our tracker later.
> +	 */
> +	tp = getres(mp, 0);
> +	ppargs = newpptr(mp);
> +
> +	error = creatproto(&tp, pip, mode, rdev, &creds, fsxp, &ip);
> +	if (error)
> +		fail(_("Inode allocation failed"), error);
> +
> +	libxfs_trans_ijoin(tp, pip, 0);
> +	newdirent(mp, tp, pip, &xname, ip, ppargs);
> +
> +	/*
> +	 * copy over timestamps
> +	 */
> +	writetimestamps(ip, &file_stat);
> +
> +	libxfs_trans_log_inode(tp, ip, flags);
> +
> +	error = -libxfs_trans_commit(tp);
> +	if (error)
> +		fail(_("Error encountered creating file from prototype file"), error);
> +
> +	libxfs_parent_finish(mp, ppargs);
> +
> +	/*
> +	 * copy over file content, attributes,
> +	 * extended attributes and timestamps
> +	 */
> +	if (fd >= 0) {
> +		writefile(ip, fname, fd);
> +		writeattrs(ip, fname, fd);
> +		close(fd);
> +	}
> +	/*
> +	 * we do fsxattr also for file types where we don't have
> +	 * an fd, for example FIFOs
> +	 */
> +	writefsxattrs(ip, fsxp);
> +
> +	/*
> +	 * if we're here it means this is the first time we're
> +	 * encountering an hardlink, so we need to store it
> +	 */
> +	if (file_stat.st_nlink > 1)
> +		track_hardlink_inode(file_stat.st_ino, ip->i_ino);
> +
> +	libxfs_irele(ip);
> +}
> +
> +static void
> +handle_direntry(
> +	struct xfs_mount	*mp,
> +	struct xfs_inode	*pip,
> +	struct fsxattr	*fsxp,
> +	char		*path_buf,
> +	struct dirent	*entry)
> +{
> +	char		link_target[XFS_SYMLINK_MAXLEN];
> +	int		error;
> +	int 		fd = -1;
> +	int 		flags;
> +	int 		majdev;
> +	int 		mindev;
> +	int 		mode;

Nit: space ^ before tab; and all the variable names should be lined up
to the same column...

> +	struct stat	file_stat;
> +	struct xfs_name	xname;
> +	struct xfs_inode	*ip;
> +	struct xfs_trans	*tp;
> +	struct xfs_parent_args *ppargs = NULL;
> +
> +	/*
> +	 * save original path length so we can
> +	 * restore the original value at the end
> +	 * of the function
> +	 */
> +	size_t path_save_len = strlen(path_buf);
> +	size_t path_len = path_save_len;
> +	size_t entry_len = strlen(entry->d_name);
> +
> +	/*
> +	 * ensure the constructed path is within PATH_MAX limits
> +	 */
> +	size_t remaining = PATH_MAX - path_len;
> +	size_t written = snprintf(path_buf + path_len, remaining, "/%s",
> +			entry->d_name);

...and you can do things like:

	size_t			written =
		snprintf(...);

if the columns go far enough to the right that you can't fit them all on
one line.

> +	if (written >= remaining) {
> +		fail(_("path name too long"), ENAMETOOLONG);
> +	}
> +
> +	if (lstat(path_buf, &file_stat) < 0) {
> +		fprintf(stderr, _("%s: cannot stat '%s': %s (errno=%d)\n"),
> +				progname, path_buf, strerror(errno), errno);
> +		exit(1);
> +	}
> +
> +	/*
> +	 * avoid opening FIFOs as they're blocking
> +	 */
> +	int open_flags = O_NOFOLLOW | O_RDONLY | O_NOATIME;
> +	/*
> +	 * symlinks and sockets will need to be opened with O_PATH to work,
> +	 * so we handle this special case.
> +	 */
> +	if (S_ISSOCK(file_stat.st_mode) ||
> +			S_ISLNK(file_stat.st_mode) ||
> +			S_ISFIFO(file_stat.st_mode))

Line these up, please:

	if (S_ISSOCK(...) ||
	    S_ISLNK(...) ||
	    S_ISFIFO(...))

> +		open_flags = O_NOFOLLOW | O_PATH;
> +	if ((fd = open(path_buf, open_flags)) < 0) {


	fd = open(...);
	if (fd < 0) {

> +		fprintf(stderr, _("%s: cannot open %s: %s\n"), progname, path_buf,
> +			strerror(errno));
> +		exit(1);
> +	}
> +
> +	struct cred creds = {
> +		.cr_uid = file_stat.st_uid,
> +		.cr_gid = file_stat.st_gid,
> +	};
> +
> +	xname.name = (unsigned char *)entry->d_name;
> +	xname.len = entry_len;
> +	xname.type = 0;
> +	mode = file_stat.st_mode;
> +	flags = XFS_ILOG_CORE;
> +
> +	switch (file_stat.st_mode & S_IFMT) {
> +	case S_IFDIR:
> +		tp = getres(mp, 0);
> +		ppargs = newpptr(mp);
> +
> +		error = creatproto(&tp, pip, mode, 0, &creds, fsxp, &ip);
> +		if (error)
> +			fail(_("Inode allocation failed"), error);
> +
> +		libxfs_trans_ijoin(tp, pip, 0);
> +
> +		xname.type = XFS_DIR3_FT_DIR;
> +		newdirent(mp, tp, pip, &xname, ip, ppargs);
> +
> +		libxfs_bumplink(tp, pip);
> +		libxfs_trans_log_inode(tp, pip, XFS_ILOG_CORE);
> +		newdirectory(mp, tp, ip, pip);
> +
> +		/*
> +		 * copy over timestamps
> +		 */
> +		writetimestamps(ip, &file_stat);
> +
> +		libxfs_trans_log_inode(tp, ip, flags);
> +
> +		error = -libxfs_trans_commit(tp);
> +		if (error)
> +			fail(_("Directory inode allocation failed."), error);
> +
> +		libxfs_parent_finish(mp, ppargs);
> +		tp = NULL;
> +
> +		/*
> +		 * copy over attributes
> +		 */
> +		writeattrs(ip, entry->d_name, fd);
> +		writefsxattrs(ip, fsxp);
> +		close(fd);
> +
> +		walk_dir(mp, ip, fsxp, path_buf);
> +
> +		libxfs_irele(ip);

Yeah, each of these cases ought to be broken out into smaller function
that each take care of a single child file type.  Not sure why some of
these cases call create_file() and others don't?

> +		break;
> +	case S_IFLNK:
> +		/*
> +		 * if handle_hardlink() returns true it means the hardlink has
> +		 * been correctly found and set, so we don't need to
> +		 * do anything else.
> +		 */
> +		if (file_stat.st_nlink > 1 &&
> +				handle_hardlink(mp, pip, xname, file_stat)) {
> +			close(fd);
> +			break;
> +		}
> +		/*
> +		 * if instead we have false it means the hardlink
> +		 * was not registered, so we proceed to treat it like
> +		 * a regular symlink, and save it to our tracker later.
> +		 */
> +		ssize_t len = readlink(path_buf, link_target, XFS_SYMLINK_MAXLEN - 1);
> +		if (len < 0)
> +			fail(_("could not resolve symlink"), errno);
> +		if (len >= PATH_MAX -1)
> +			fail(_("symlink target too long"), ENAMETOOLONG);
> +		link_target[len] = '\0';

Link targets don't require null terminators, they have explicit lengths.

> +
> +		tp = getres(mp, XFS_B_TO_FSB(mp, len));
> +		ppargs = newpptr(mp);
> +
> +		error = creatproto(&tp, pip, mode, 0, &creds, fsxp, &ip);
> +		if (error)
> +			fail(_("Inode allocation failed"), error);
> +
> +		writesymlink(tp, ip, link_target, len);
> +		libxfs_trans_ijoin(tp, pip, 0);
> +
> +		xname.type = XFS_DIR3_FT_SYMLINK;
> +		newdirent(mp, tp, pip, &xname, ip, ppargs);
> +
> +		/*
> +		 * copy over timestamps
> +		 */
> +		writetimestamps(ip, &file_stat);
> +
> +		libxfs_trans_log_inode(tp, ip, flags);
> +
> +		error = -libxfs_trans_commit(tp);
> +		if (error)
> +			fail(_("Error encountered creating file from prototype file"),
> +			     error);
> +
> +		libxfs_parent_finish(mp, ppargs);
> +
> +		/*
> +		 * copy over attributes
> +		 *
> +		 * being a symlink we opened the filedescriptor with O_PATH
> +		 * this will make flistxattr() and fgetxattr() fail wil EBADF,
> +		 * so we  will need to fallback to llistxattr() and lgetxattr(),
> +		 * this will need the full path to the original file, not just the
> +		 * entry name.
> +		 */
> +		writeattrs(ip, path_buf, fd);
> +		writefsxattrs(ip, fsxp);
> +		close(fd);
> +
> +		/*
> +		 * if we're here it means this is the first time we're
> +		 * encountering an hardlink, so we need to store it
> +		 */
> +		if (file_stat.st_nlink > 1)
> +			track_hardlink_inode(file_stat.st_ino, ip->i_ino);
> +
> +		libxfs_irele(ip);
> +		break;
> +	case S_IFREG:
> +		xname.type = XFS_DIR3_FT_REG_FILE;
> +		create_file(mp, pip, fsxp, mode, creds, xname, flags, file_stat,
> +			    0, fd, entry->d_name);
> +		break;
> +	case S_IFCHR:
> +		flags |= XFS_ILOG_DEV;
> +		xname.type = XFS_DIR3_FT_CHRDEV;
> +		majdev = major(file_stat.st_rdev);
> +		mindev = minor(file_stat.st_rdev);
> +		create_file(mp, pip, fsxp, mode, creds, xname, flags, file_stat,
> +			    IRIX_MKDEV(majdev, mindev), fd, entry->d_name);
> +		break;
> +	case S_IFBLK:
> +		flags |= XFS_ILOG_DEV;
> +		xname.type = XFS_DIR3_FT_BLKDEV;
> +		majdev = major(file_stat.st_rdev);
> +		mindev = minor(file_stat.st_rdev);
> +		create_file(mp, pip, fsxp, mode, creds, xname, flags, file_stat,
> +			    IRIX_MKDEV(majdev, mindev), fd, entry->d_name);
> +		break;
> +	case S_IFIFO:
> +		/*
> +		 * being a fifo we opened the filedescriptor with O_PATH
> +		 * this will make flistxattr() and fgetxattr() fail wil EBADF,
> +		 * so we  will need to fallback to llistxattr() and lgetxattr(),
> +		 * this will need the full path to the original file, not just the
> +		 * entry name.
> +		 */
> +		create_file(mp, pip, fsxp, mode, creds, xname, flags, file_stat,
> +			    0, fd, path_buf);
> +		break;
> +	case S_IFSOCK:
> +		/*
> +		 * being a socket we opened the filedescriptor with O_PATH
> +		 * this will make flistxattr() and fgetxattr() fail wil EBADF,
> +		 * so we  will need to fallback to llistxattr() and lgetxattr(),
> +		 * this will need the full path to the original file, not just the
> +		 * entry name.
> +		 */
> +		create_file(mp, pip, fsxp, mode, creds, xname, flags, file_stat,
> +			    0, fd, path_buf);

These two (FIFO/SOCK) need to set xname.type too.  Maybe that ought to
be refactored out of parseproto since there's already a
libxfs_mode_to_ftype function for that?

> +		break;
> +	default:
> +		break;
> +	}
> +
> +	/*
> +	 * restore path buffer to original length before returning
> +	 * */
> +	path_buf[path_save_len] = '\0';
> +}
> +
> +/*
> + * walk_dir will recursively list files and directories
> + * and populate the mountpoint *mp with them using handle_direntry().
> + */
> +static void
> +walk_dir(
> +	struct xfs_mount	*mp,
> +	struct xfs_inode	*pip,
> +	struct fsxattr	*fsxp,
> +	char		*path_buf)
> +{
> +	DIR		*dir;
> +	struct dirent	*entry;

It's a little strange   ^ that some variable names are aligned to this
column yet others are aligned   ^ to this column; they all should be the
same.

(I wish I could point you at an automatic reformatter but I don't know
of any...)

> +
> +	/*
> +	 * open input directory and iterate over all entries in it.
> +	 * when another directory is found, we will recursively call
> +	 * walk_dir.
> +	 */
> +	if ((dir = opendir(path_buf)) == NULL) {
> +		fprintf(stderr, _("%s: cannot open input dir: %s [%d - %s]\n"),
> +				progname, path_buf, errno, strerror(errno));
> +		exit(1);
> +	}
> +	while ((entry = readdir(dir)) != NULL) {
> +		if (strcmp(entry->d_name, ".") == 0 ||
> +		    strcmp(entry->d_name, "..") == 0)
> +			continue;
> +
> +		handle_direntry(mp, pip, fsxp, path_buf, entry);
> +	}
> +	closedir(dir);
> +}
> +
> +static void
> +populate_from_dir(
> +	struct xfs_mount	*mp,
> +	struct fsxattr	*fsxp,
> +	char		*cur_path)
> +{
> +	int		error;
> +	int 		mode;
> +	int 		fd = -1;

Nit: space ^ here before a tab.

> +	char		path_buf[PATH_MAX];
> +	struct stat	file_stat;
> +	struct xfs_inode	*ip;
> +	struct xfs_trans	*tp;
> +
> +	/*
> +	 * initialize path_buf cur_path, strip trailing slashes
> +	 * they're automatically added when walking the dir
> +	 */
> +	if (strlen(cur_path) > 1 && cur_path[strlen(cur_path)-1] == '/')
> +		cur_path[strlen(cur_path)-1] = '\0';
> +	if (snprintf(path_buf, PATH_MAX, "%s", cur_path) >= PATH_MAX)
> +		fail(_("path name too long"), ENAMETOOLONG);
> +
> +	if (lstat(path_buf, &file_stat) < 0) {
> +		fprintf(stderr, _("%s: cannot stat '%s': %s (errno=%d)\n"),
> +				progname, path_buf, strerror(errno), errno);
> +		exit(1);
> +	}
> +	if ((fd = open(path_buf, O_NOFOLLOW | O_RDONLY | O_NOATIME)) < 0) {
> +		fprintf(stderr, _("%s: cannot open %s: %s\n"), progname, path_buf,
> +			strerror(errno));
> +		exit(1);
> +	}
> +
> +	/*
> +	 * we first ensure we have the root inode
> +	 */
> +	struct cred creds = {
> +		.cr_uid = file_stat.st_uid,
> +		.cr_gid = file_stat.st_gid,
> +	};
> +	mode = file_stat.st_mode;
> +
> +	tp = getres(mp, 0);
> +
> +	error = creatproto(&tp, NULL, mode | S_IFDIR, 0, &creds, fsxp, &ip);
> +	if (error)
> +		fail(_("Inode allocation failed"), error);
> +
> +	mp->m_sb.sb_rootino = ip->i_ino;
> +	libxfs_log_sb(tp);
> +	newdirectory(mp, tp, ip, ip);
> +	libxfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
> +
> +	error = -libxfs_trans_commit(tp);
> +	if (error)
> +		fail(_("Inode allocation failed"), error);
> +
> +	libxfs_parent_finish(mp, NULL);
> +
> +	/*
> +	 * copy over attributes
> +	 */
> +	writeattrs(ip, path_buf, fd);
> +	writefsxattrs(ip, fsxp);
> +
> +	/*
> +	 * RT initialization.  Do this here to ensure that
> +	 * the RT inodes get placed after the root inode.
> +	 */
> +	error = create_metadir(mp);
> +	if (error)
> +		fail(_("Creation of the metadata directory inode failed"), error);
> +
> +	rtinit(mp);
> +
> +	/*
> +	 * by nature of walk_dir() we could be opening
> +	 * a great number of fds for deeply nested directory
> +	 * trees.
> +	 * try to bump max fds limit.
> +	 */
> +	bump_max_fds();
> +
> +	/*
> +	 * initialize the hardlinks tracker
> +	 */
> +	init_hardlink_tracker();
> +	/*
> +	 * now that we have a root inode, let's
> +	 * walk the input dir and populate the partition
> +	 */
> +	walk_dir(mp, ip, fsxp, path_buf);
> +
> +	/*
> +	 * cleanup hardlinks tracker
> +	 */
> +	cleanup_hardlink_tracker();
> +
> +	/*
> +	 * we free up our root inode
> +	 * only when we finished populating the
> +	 * root filesystem
> +	 */
> +	libxfs_irele(ip);
> +}
> diff --git a/mkfs/proto.h b/mkfs/proto.h
> index be1ceb45..476f7851 100644
> --- a/mkfs/proto.h
> +++ b/mkfs/proto.h
> @@ -6,9 +6,21 @@
>  #ifndef MKFS_PROTO_H_
>  #define MKFS_PROTO_H_
> 
> -char *setup_proto(char *fname);
> -void parse_proto(struct xfs_mount *mp, struct fsxattr *fsx, char **pp,
> -		int proto_slashes_are_spaces);
> +enum proto_source_type {
> +	PROTO_SRC_NONE = 0,
> +	PROTO_SRC_PROTOFILE,
> +	PROTO_SRC_DIR
> +};
> +struct proto_source {
> +	enum	proto_source_type type;
> +	char	*data;
> +};
> +
> +struct proto_source setup_proto(char *fname);
> +void parse_proto(struct xfs_mount *mp, struct fsxattr *fsx,
> +		 struct proto_source *protosource,
> +		 int proto_slashes_are_spaces,
> +		 int proto_preserve_atime);
>  void res_failed(int err);
> 
>  #endif /* MKFS_PROTO_H_ */
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index 3f4455d4..a32c077e 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -121,6 +121,7 @@ enum {
> 
>  enum {
>  	P_FILE = 0,
> +	P_ATIME,
>  	P_SLASHES,
>  	P_MAX_OPTS,
>  };
> @@ -709,6 +710,7 @@ static struct opt_params popts = {
>  	.ini_section = "proto",
>  	.subopts = {
>  		[P_FILE] = "file",
> +		[P_ATIME] = "atime",
>  		[P_SLASHES] = "slashes_are_spaces",
>  		[P_MAX_OPTS] = NULL,
>  	},
> @@ -717,6 +719,12 @@ static struct opt_params popts = {
>  		  .conflicts = { { NULL, LAST_CONFLICT } },
>  		  .defaultval = SUBOPT_NEEDS_VAL,
>  		},
> +		{ .index = P_ATIME,
> +		  .conflicts = { { NULL, LAST_CONFLICT } },
> +		  .minval = 0,
> +		  .maxval = 1,
> +		  .defaultval = 1,
> +		},
>  		{ .index = P_SLASHES,
>  		  .conflicts = { { NULL, LAST_CONFLICT } },
>  		  .minval = 0,
> @@ -1045,6 +1053,7 @@ struct cli_params {
>  	int	lsunit;
>  	int	is_supported;
>  	int	proto_slashes_are_spaces;
> +	int	proto_atime;
>  	int	data_concurrency;
>  	int	log_concurrency;
>  	int	rtvol_concurrency;
> @@ -1170,6 +1179,7 @@ usage( void )
>  /* naming */		[-n size=num,version=2|ci,ftype=0|1,parent=0|1]]\n\
>  /* no-op info only */	[-N]\n\
>  /* prototype file */	[-p fname]\n\
> +/* populate from directory */	[-p dirname,atime=0|1]\n\
>  /* quiet */		[-q]\n\
>  /* realtime subvol */	[-r extsize=num,size=num,rtdev=xxx,rgcount=n,rgsize=n,\n\
>  			    concurrency=num]\n\
> @@ -2067,6 +2077,9 @@ proto_opts_parser(
>  	case P_SLASHES:
>  		cli->proto_slashes_are_spaces = getnum(value, opts, subopt);
>  		break;
> +	case P_ATIME:
> +		cli->proto_atime = getnum(value, opts, subopt);
> +		break;
>  	case P_FILE:
>  		fallthrough;
>  	default:
> @@ -5162,7 +5175,7 @@ main(
>  	int			discard = 1;
>  	int			force_overwrite = 0;
>  	int			quiet = 0;
> -	char			*protostring = NULL;
> +	struct proto_source	protosource;
>  	int			worst_freelist = 0;
> 
>  	struct libxfs_init	xi = {
> @@ -5311,8 +5324,6 @@ main(
>  	 */
>  	cfgfile_parse(&cli);
> 
> -	protostring = setup_proto(cli.protofile);
> -
>  	/*
>  	 * Extract as much of the valid config as we can from the CLI input
>  	 * before opening the libxfs devices.
> @@ -5480,7 +5491,11 @@ main(
>  	/*
>  	 * Allocate the root inode and anything else in the proto file.
>  	 */
> -	parse_proto(mp, &cli.fsx, &protostring, cli.proto_slashes_are_spaces);
> +	protosource = setup_proto(cli.protofile);
> +	parse_proto(mp, &cli.fsx,
> +			&protosource,
> +			cli.proto_slashes_are_spaces,
> +			cli.proto_atime);

I almost wonder if we should just dump all the proto* options into
struct proto_source and pass that into parse_proto (instead of five
separate arguments) but that's a cleanup that can happen later...

--D

> 
>  	/*
>  	 * Protect ourselves against possible stupidity
> --
> 2.49.0
>