[PATCH 7/9] man/man2/statmount.2: Document STATMOUNT_{UIDMAP,GIDMAP}

Document the STATMOUNT_{UIDMAP,GIDMAP} flags and the corresponding
fields introduced by them. Most of this is based on the commit message
provided here [1].

Link [1]:
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=37c4a9590e1efcae7749682239fc22a330d2d325>

Signed-off-by: Bhavik Sachdev <[email protected]>
---
 man/man2/statmount.2 | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/man/man2/statmount.2 b/man/man2/statmount.2
index 4dc312ec8..4ae609818 100644
--- a/man/man2/statmount.2
+++ b/man/man2/statmount.2
@@ -56,6 +56,10 @@ .SH SYNOPSIS
 .B "    __u32  opt_array;"
 .B "    __u32  opt_sec_num;"
 .B "    __u32  opt_sec_array;"
+.B "    __u32  mnt_uidmap_num;"
+.B "    __u32  mnt_uidmap;"
+.B "    __u32  mnt_gidmap_num;"
+.B "    __u32  mnt_gidmap;"
 .B "    char   str[];"
 .B };
 .EE
@@ -120,6 +124,8 @@ .SS The mnt_id_req structure
 STATMOUNT_SB_SOURCE	/* Want/got sb_source */
 STATMOUNT_OPT_ARRAY	/* Want/got opt_... */
 STATMOUNT_OPT_SEC_ARRAY	/* Want/got opt_sec... */
+STATMOUNT_MNT_UIDMAP	/* Want/got uidmap... */
+STATMOUNT_MNT_GIDMAP	/* Want/got gidmap... */
 .TE
 .in
 .P
@@ -307,6 +313,33 @@ .SS The returned information
 They can be iterated over the help of
 .IR smbuf.opt_sec_num .
 .TP
+.I smbuf.mnt_uidmap_num
+The number of uid mappings in case of an idmapped mount.
+If STATMOUNT_UIDMAP was not unset and this field is 0, the mount is not an idmapped mount.
+.TP
+.TP
+.I smbuf.mnt_uidmap
+The offset to the location in the
+.I smbuf.str
+buffer that contains uid mappings as string array separated by null bytes.
+They can be iterated over with the help of
+.IR smbuf.mnt_uidmap_num .
+The whole range of uid mappings must be resolvable in the caller's user namespace.
+.TP
+.TP
+.I smbuf.mnt_gidmap_num
+The number of gid mappings in case of an idmapped mount.
+If STATMOUNT_GIDMAP was not unset and this field is 0, the mount is not an idmapped mount.
+.TP
+.TP
+.I smbuf.mnt_gidmap
+The offset to the location in the
+.I smbuf.str
+buffer that contains uid mappings as string array separated by null bytes.
+They can be iterated over with the help of
+.IR smbuf.mnt_gidmap_num .
+The whole range of gid mappings must be resolvable in the caller's user namespace.
+.TP
 .SH RETURN VALUE
 On success, zero is returned.
 On error, \-1 is returned, and
-- 
2.52.0