scripts/gdb: replace flags (MS_xyz -> SB_xyz)

Since commit 1751e8a6cb ("Rename superblock flags (MS_xyz ->
SB_xyz)"), scripts/gdb should be updated to replace MS_xyz with SB_xyz.

This change didn't directly affect the running operation of scripts/gdb
until commit e262e32d6b "vfs: Suppress MS_* flag defs within the
kernel unless explicitly enabled" removed the definitions used by
constants.py.

Update constants.py.in to utilise the new internal flags, matching the
implementation at fs/proc_namespace.c::show_sb_opts.

Note to stable, e262e32d6b landed in v5.0-rc1 (which was just
released), so we'll want this picked back to 5.0 stable once this patch
hits mainline (akpm just picked it up).  Without this, debugging a
kernel a kernel via GDB+QEMU is broken in the 5.0 release.

[kieran.bingham@ideasonboard.com: add fixes tag, reword commit message]
Link: http://lkml.kernel.org/r/20190305103014.25847-1-kieran.bingham@ideasonboard.com
Fixes: e262e32d6b "vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled"
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: Dan Robertson <danlrobertson89@gmail.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/constants.py.in

@@ -37,12 +37,12 @@
 import gdb
 
 /* linux/fs.h */
-LX_VALUE(MS_RDONLY)
-LX_VALUE(MS_SYNCHRONOUS)
-LX_VALUE(MS_MANDLOCK)
-LX_VALUE(MS_DIRSYNC)
-LX_VALUE(MS_NOATIME)
-LX_VALUE(MS_NODIRATIME)
+LX_VALUE(SB_RDONLY)
+LX_VALUE(SB_SYNCHRONOUS)
+LX_VALUE(SB_MANDLOCK)
+LX_VALUE(SB_DIRSYNC)
+LX_VALUE(SB_NOATIME)
+LX_VALUE(SB_NODIRATIME)
 
 /* linux/mount.h */
 LX_VALUE(MNT_NOSUID)

scripts/gdb/linux/proc.py

@@ -114,11 +114,11 @@ def info_opts(lst, opt):
     return opts
 
 
-FS_INFO = {constants.LX_MS_SYNCHRONOUS: ",sync",
-           constants.LX_MS_MANDLOCK: ",mand",
-           constants.LX_MS_DIRSYNC: ",dirsync",
-           constants.LX_MS_NOATIME: ",noatime",
-           constants.LX_MS_NODIRATIME: ",nodiratime"}
+FS_INFO = {constants.LX_SB_SYNCHRONOUS: ",sync",
+           constants.LX_SB_MANDLOCK: ",mand",
+           constants.LX_SB_DIRSYNC: ",dirsync",
+           constants.LX_SB_NOATIME: ",noatime",
+           constants.LX_SB_NODIRATIME: ",nodiratime"}
 
 MNT_INFO = {constants.LX_MNT_NOSUID: ",nosuid",
             constants.LX_MNT_NODEV: ",nodev",
@@ -184,7 +184,7 @@ values of that process namespace"""
             fstype = superblock['s_type']['name'].string()
             s_flags = int(superblock['s_flags'])
             m_flags = int(vfs['mnt']['mnt_flags'])
-            rd = "ro" if (s_flags & constants.LX_MS_RDONLY) else "rw"
+            rd = "ro" if (s_flags & constants.LX_SB_RDONLY) else "rw"
 
             gdb.write(
                 "{} {} {} {}{}{} 0 0\n"