Re: [PATCH 2/2] xfs_db: add an ls command

Dave Chinner
2020-10-28T21:48:33Z

On Mon, Oct 26, 2020 at 04:32:41PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Add to xfs_db the ability to list a directory.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> db/namei.c | 380 ++++++++++++++++++++++++++++++++++++++++++++++
> libxfs/libxfs_api_defs.h | 1
> man/man8/xfs_db.8 | 14 ++
> 3 files changed, 395 insertions(+)
>
>
> diff --git a/db/namei.c b/db/namei.c
> index 3c9889d62338..b2c036e6777a 100644
> --- a/db/namei.c
> +++ b/db/namei.c
> @@ -221,8 +221,388 @@ static const cmdinfo_t path_cmd = {
> .help = path_help,
> };
>
> +/* List a directory's entries. */
> +
> +static const char *filetype_strings[XFS_DIR3_FT_MAX] = {
> + [XFS_DIR3_FT_UNKNOWN] = N_("unknown"),
> + [XFS_DIR3_FT_REG_FILE] = N_("regular"),
> + [XFS_DIR3_FT_DIR] = N_("directory"),
> + [XFS_DIR3_FT_CHRDEV] = N_("chardev"),
> + [XFS_DIR3_FT_BLKDEV] = N_("blkdev"),
> + [XFS_DIR3_FT_FIFO] = N_("fifo"),
> + [XFS_DIR3_FT_SOCK] = N_("socket"),
> + [XFS_DIR3_FT_SYMLINK] = N_("symlink"),
> + [XFS_DIR3_FT_WHT] = N_("whiteout"),
> +};

What does N_() do that is different to _()?

> +static const char *
> +get_dstr(
> + struct xfs_mount *mp,
> + uint8_t filetype)
> +{
> + if (!xfs_sb_version_hasftype(&mp->m_sb))
> + return filetype_strings[XFS_DIR3_FT_UNKNOWN];
> +
> + if (filetype >= XFS_DIR3_FT_MAX)
> + return filetype_strings[XFS_DIR3_FT_UNKNOWN];
> +
> + return filetype_strings[filetype];
> +}
> +
> +static void
> +dir_emit(
> + struct xfs_mount *mp,
> + char *name,
> + ssize_t namelen,
> + xfs_ino_t ino,
> + uint8_t dtype)
> +{
> + char *display_name;
> + struct xfs_name xname = { .name = name };
> + const char *dstr = get_dstr(mp, dtype);
> + xfs_dahash_t hash;
> + bool good;
> +
> + if (namelen < 0) {
> + /* Negative length means that name is null-terminated. */
> + display_name = name;
> + xname.len = strlen(name);
> + good = true;
> + } else {
> + /*
> + * Otherwise, name came from a directory entry, so we have to
> + * copy the string to a buffer so that we can add the null
> + * terminator.
> + */
> + display_name = malloc(namelen + 1);
> + memcpy(display_name, name, namelen);
> + display_name[namelen] = 0;
> + xname.len = namelen;
> + good = libxfs_dir2_namecheck(name, namelen);
> + }
> + hash = libxfs_dir2_hashname(mp, &xname);
> +
> + dbprintf("%-18llu %-14s 0x%08llx %3d %s", ino, dstr, hash, xname.len,
> + display_name);
> + if (!good)
> + dbprintf(_(" (corrupt)"));
> + dbprintf("\n");

Can we get this to emit the directory offset of the entry as well?
Also, can this be done as a single dbprintf call like this?

dbprintf(%-18llu %-14s 0x%08llx %3d %s %s\n",
ino, dstr, hash, xname.len, display_name,
good ? _("(good)") : _("(corrupt)"));

(there will be lots of output on big directories....)

> +static int
> +list_sfdir(
> + struct xfs_da_args *args)
> +{
> + struct xfs_inode *dp = args->dp;
> + struct xfs_mount *mp = dp->i_mount;
> + struct xfs_dir2_sf_entry *sfep;
> + struct xfs_dir2_sf_hdr *sfp;
> + xfs_ino_t ino;
> + unsigned int i;
> + uint8_t filetype;
> +
> + sfp = (struct xfs_dir2_sf_hdr *)dp->i_df.if_u1.if_data;
> +
> + /* . and .. entries */
> + dir_emit(args->dp->i_mount, ".", -1, dp->i_ino, XFS_DIR3_FT_DIR);
> +
> + ino = libxfs_dir2_sf_get_parent_ino(sfp);
> + dir_emit(args->dp->i_mount, "..", -1, ino, XFS_DIR3_FT_DIR);
> +
> + /* Walk everything else. */
> + sfep = xfs_dir2_sf_firstentry(sfp);
> + for (i = 0; i < sfp->count; i++) {
> + ino = libxfs_dir2_sf_get_ino(mp, sfp, sfep);
> + filetype = libxfs_dir2_sf_get_ftype(mp, sfep);
> +
> + dir_emit(args->dp->i_mount, (char *)sfep->name, sfep->namelen,
> + ino, filetype);
> + sfep = libxfs_dir2_sf_nextentry(mp, sfp, sfep);
> + }
> +
> + return 0;
> +}

Hmmm - how much of the xfs_readdir() implementation from the kernel
does this duplicate? It doesn't contain the seek cookie stuff, but
otherwise it's almost identical, right?

[....]

> +/* If the io cursor points to a directory, list its contents. */
> +static int
> +ls_cur(
> + char *tag,
> + bool direct)

I find the name "direct" rather confusing here. according to
the help below, it will be true when we want to "list the directory
itself, not it's contents"....

> +{
> + struct xfs_inode *dp;
> + int ret = 0;
> +
> + if (iocur_top->typ != &typtab[TYP_INODE]) {
> + dbprintf(_("current object is not an inode.\n"));
> + return -1;
> + }
> +
> + ret = -libxfs_iget(mp, NULL, iocur_top->ino, 0, &dp);
> + if (ret) {
> + dbprintf(_("failed to iget directory %llu, error %d\n"),
> + (unsigned long long)iocur_top->ino, ret);
> + return -1;
> + }
> +
> + if (S_ISDIR(VFS_I(dp)->i_mode) && !direct) {
> + /* List the contents of a directory. */
> + if (tag)
> + dbprintf(_("%s:\n"), tag);
> +
> + ret = listdir(dp);
> + if (ret) {
> + dbprintf(_("failed to list directory %llu: %s\n"),
> + (unsigned long long)iocur_top->ino,
> + strerror(ret));
> + ret = -1;
> + goto rele;
> + }
> + } else if (direct || !S_ISDIR(VFS_I(dp)->i_mode)) {
> + /* List the directory entry associated with a single file. */
> + char inum[32];
> +
> + if (!tag) {
> + snprintf(inum, sizeof(inum), "<%llu>",
> + (unsigned long long)iocur_top->ino);
> + tag = inum;
> + } else {
> + char *p = strrchr(tag, '/');
> +
> + if (p)
> + tag = p + 1;
> + }
> +
> + dir_emit(mp, tag, -1, iocur_top->ino,
> + libxfs_mode_to_ftype(VFS_I(dp)->i_mode));

I'm not sure what this is supposed to do - we turn the current inode
if it's not a directory into a -directory entry- without actually
know it's name? And we can pass in an inode that isn't a directory
and do the same? This doesn't make a huge amount of sense to me - it
tries to display the inode number as a dirent?

> + } else {
> + dbprintf(_("current inode %llu is not a directory.\n"),
> + (unsigned long long)iocur_top->ino);
> + ret = -1;
> + goto rele;
> + }

I don't think we can get to this else branch. If we don't take the
first branch (dir && !direct), the either we are not a dir or direct
is set. The second branch will then be taken if we are not a dir or
direct is set....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com