Remap reserved posix characters by default (part 3/3)

This is a bigger patch, but its size is mostly due to
a single change for how we check for remapping illegal characters
in file names - a lot of repeated, small changes to
the way callers request converting file names.

The final patch in the series does the following:

1) changes default behavior for cifs to be more intuitive.
Currently we do not map by default to seven reserved characters,
ie those valid in POSIX but not in NTFS/CIFS/SMB3/Windows,
unless a mount option (mapchars) is specified.  Change this
to by default always map and map using the SFM maping
(like the Mac uses) unless the server negotiates the CIFS Unix
Extensions (like Samba does when mounting with the cifs protocol)
when the remapping of the characters is unnecessary.  This should
help SMB3 mounts in particular since Samba will likely be
able to implement this mapping with its new "vfs_fruit" module
as it will be doing for the Mac.
2) if the user specifies the existing "mapchars" mount option then
use the "SFU" (Microsoft Services for Unix, SUA) style mapping of
the seven characters instead.
3) if the user specifies "nomapposix" then disable SFM/MAC style mapping
(so no character remapping would be used unless the user specifies
"mapchars" on mount as well, as above).
4) change all the places in the code that check for the superblock
flag on the mount which is set by mapchars and passed in on all
path based operation and change it to use a small function call
instead to set the mapping type properly (and check for the
mapping type in the cifs unicode functions)

Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 25 insertions, 5 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d8eb6a74b211..24fa08d261fb 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -70,6 +70,7 @@ enum {
 	Opt_forcegid, Opt_noforcegid,
 	Opt_noblocksend, Opt_noautotune,
 	Opt_hard, Opt_soft, Opt_perm, Opt_noperm,
+	Opt_mapposix, Opt_nomapposix,
 	Opt_mapchars, Opt_nomapchars, Opt_sfu,
 	Opt_nosfu, Opt_nodfs, Opt_posixpaths,
 	Opt_noposixpaths, Opt_nounix,
@@ -124,8 +125,10 @@ static const match_table_t cifs_mount_option_tokens = {
 	{ Opt_soft, "soft" },
 	{ Opt_perm, "perm" },
 	{ Opt_noperm, "noperm" },
-	{ Opt_mapchars, "mapchars" },
+	{ Opt_mapchars, "mapchars" }, /* SFU style */
 	{ Opt_nomapchars, "nomapchars" },
+	{ Opt_mapposix, "mapposix" }, /* SFM style */
+	{ Opt_nomapposix, "nomapposix" },
 	{ Opt_sfu, "sfu" },
 	{ Opt_nosfu, "nosfu" },
 	{ Opt_nodfs, "nodfs" },
@@ -1231,6 +1234,14 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 	vol->linux_uid = current_uid();
 	vol->linux_gid = current_gid();
 
+	/*
+	 * default to SFM style remapping of seven reserved characters
+	 * unless user overrides it or we negotiate CIFS POSIX where
+	 * it is unnecessary.  Can not simultaneously use more than one mapping
+	 * since then readdir could list files that open could not open
+	 */
+	vol->remap = true;
+
 	/* default to only allowing write access to owner of the mount */
 	vol->dir_mode = vol->file_mode = S_IRUGO | S_IXUGO | S_IWUSR;
 
@@ -1338,10 +1349,18 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			vol->noperm = 1;
 			break;
 		case Opt_mapchars:
-			vol->remap = 1;
+			vol->sfu_remap = true;
+			vol->remap = false; /* disable SFM mapping */
 			break;
 		case Opt_nomapchars:
-			vol->remap = 0;
+			vol->sfu_remap = false;
+			break;
+		case Opt_mapposix:
+			vol->remap = true;
+			vol->sfu_remap = false; /* disable SFU mapping */
+			break;
+		case Opt_nomapposix:
+			vol->remap = false;
 			break;
 		case Opt_sfu:
 			vol->sfu_emul = 1;
@@ -3197,6 +3216,8 @@ void cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
 	if (pvolume_info->server_ino)
 		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_SERVER_INUM;
 	if (pvolume_info->remap)
+		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_MAP_SFM_CHR;
+	if (pvolume_info->sfu_remap)
 		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_MAP_SPECIAL_CHR;
 	if (pvolume_info->no_xattr)
 		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_XATTR;
@@ -3340,8 +3361,7 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
 	ref_path = check_prefix ? full_path + 1 : volume_info->UNC + 1;
 
 	rc = get_dfs_path(xid, ses, ref_path, cifs_sb->local_nls,
-			  &num_referrals, &referrals,
-			  cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
+			  &num_referrals, &referrals, cifs_remap(cifs_sb));
 
 	if (!rc && num_referrals > 0) {
 		char *fake_devname = NULL;