smb3: add support for stat of WSL reparse points for special file types

This is needed so when mounting to Windows we do not
misinterpret various special files created by Linux (WSL) as symlinks.
An earlier patch addressed readdir.  This patch fixes stat (getattr).

With this patch:
  File: /mnt1/char
  Size: 0          Blocks: 0          IO Block: 16384  character special file
Device: 34h/52d Inode: 844424930132069  Links: 1     Device type: 0,0
Access: (0755/crwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 17:46:51.839458900 -0500
Modify: 2020-10-21 17:46:51.839458900 -0500
Change: 2020-10-21 18:30:39.797358800 -0500
 Birth: -
  File: /mnt1/fifo
  Size: 0          Blocks: 0          IO Block: 16384  fifo
Device: 34h/52d Inode: 1125899906842722  Links: 1
Access: (0755/prwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 16:21:37.259249700 -0500
Modify: 2020-10-21 16:21:37.259249700 -0500
Change: 2020-10-21 18:30:39.797358800 -0500
 Birth: -
  File: /mnt1/block
  Size: 0          Blocks: 0          IO Block: 16384  block special file
Device: 34h/52d Inode: 844424930132068  Links: 1     Device type: 0,0
Access: (0755/brwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 17:10:47.913103200 -0500
Modify: 2020-10-21 17:10:47.913103200 -0500
Change: 2020-10-21 18:30:39.796725500 -0500
 Birth: -

without the patch all show up incorrectly as symlinks with annoying "operation not supported error also returned"
  File: /mnt1/charstat: cannot read symbolic link '/mnt1/char': Operation not supported

  Size: 0          Blocks: 0          IO Block: 16384  symbolic link
Device: 34h/52d Inode: 844424930132069  Links: 1
Access: (0000/l---------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 17:46:51.839458900 -0500
Modify: 2020-10-21 17:46:51.839458900 -0500
Change: 2020-10-21 18:30:39.797358800 -0500
 Birth: -
  File: /mnt1/fifostat: cannot read symbolic link '/mnt1/fifo': Operation not supported

  Size: 0          Blocks: 0          IO Block: 16384  symbolic link
Device: 34h/52d Inode: 1125899906842722  Links: 1
Access: (0000/l---------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 16:21:37.259249700 -0500
Modify: 2020-10-21 16:21:37.259249700 -0500
Change: 2020-10-21 18:30:39.797358800 -0500
 Birth: -
  File: /mnt1/blockstat: cannot read symbolic link '/mnt1/block': Operation not supported

  Size: 0          Blocks: 0          IO Block: 16384  symbolic link
Device: 34h/52d Inode: 844424930132068  Links: 1
Access: (0000/l---------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2020-10-21 17:10:47.913103200 -0500
Modify: 2020-10-21 17:10:47.913103200 -0500
Change: 2020-10-21 18:30:39.796725500 -0500

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

1 files changed, 36 insertions, 8 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index daec31be8571..9ee5f304592f 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -656,7 +656,7 @@ smb311_posix_info_to_fattr(struct cifs_fattr *fattr, struct smb311_posix_qinfo *
 static void
 cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 		       struct super_block *sb, bool adjust_tz,
-		       bool symlink)
+		       bool symlink, u32 reparse_tag)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
@@ -684,8 +684,22 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
 	fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
-
-	if (symlink) {
+	if (reparse_tag == IO_REPARSE_TAG_LX_SYMLINK) {
+		fattr->cf_mode |= S_IFLNK | cifs_sb->mnt_file_mode;
+		fattr->cf_dtype = DT_LNK;
+	} else if (reparse_tag == IO_REPARSE_TAG_LX_FIFO) {
+		fattr->cf_mode |= S_IFIFO | cifs_sb->mnt_file_mode;
+		fattr->cf_dtype = DT_FIFO;
+	} else if (reparse_tag == IO_REPARSE_TAG_AF_UNIX) {
+		fattr->cf_mode |= S_IFSOCK | cifs_sb->mnt_file_mode;
+		fattr->cf_dtype = DT_SOCK;
+	} else if (reparse_tag == IO_REPARSE_TAG_LX_CHR) {
+		fattr->cf_mode |= S_IFCHR | cifs_sb->mnt_file_mode;
+		fattr->cf_dtype = DT_CHR;
+	} else if (reparse_tag == IO_REPARSE_TAG_LX_BLK) {
+		fattr->cf_mode |= S_IFBLK | cifs_sb->mnt_file_mode;
+		fattr->cf_dtype = DT_BLK;
+	} else if (symlink) { /* TODO add more reparse tag checks */
 		fattr->cf_mode = S_IFLNK;
 		fattr->cf_dtype = DT_LNK;
 	} else if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
@@ -740,8 +754,9 @@ cifs_get_file_info(struct file *filp)
 	rc = server->ops->query_file_info(xid, tcon, &cfile->fid, &find_data);
 	switch (rc) {
 	case 0:
+		/* TODO: add support to query reparse tag */
 		cifs_all_info_to_fattr(&fattr, &find_data, inode->i_sb, false,
-				       false);
+				       false, 0 /* no reparse tag */);
 		break;
 	case -EREMOTE:
 		cifs_create_dfs_fattr(&fattr, inode->i_sb);
@@ -910,12 +925,13 @@ cifs_get_inode_info(struct inode **inode,
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
 	bool adjust_tz = false;
 	struct cifs_fattr fattr = {0};
-	bool symlink = false;
+	bool is_reparse_point = false;
 	FILE_ALL_INFO *data = in_data;
 	FILE_ALL_INFO *tmp_data = NULL;
 	void *smb1_backup_rsp_buf = NULL;
 	int rc = 0;
 	int tmprc = 0;
+	__u32 reparse_tag = 0;
 
 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
@@ -938,8 +954,8 @@ cifs_get_inode_info(struct inode **inode,
 			goto out;
 		}
 		rc = server->ops->query_path_info(xid, tcon, cifs_sb,
-						  full_path, tmp_data,
-						  &adjust_tz, &symlink);
+						 full_path, tmp_data,
+						 &adjust_tz, &is_reparse_point);
 		data = tmp_data;
 	}
 
@@ -949,7 +965,19 @@ cifs_get_inode_info(struct inode **inode,
 
 	switch (rc) {
 	case 0:
-		cifs_all_info_to_fattr(&fattr, data, sb, adjust_tz, symlink);
+		/*
+		 * If the file is a reparse point, it is more complicated
+		 * since we have to check if its reparse tag matches a known
+		 * special file type e.g. symlink or fifo or char etc.
+		 */
+		if ((le32_to_cpu(data->Attributes) & ATTR_REPARSE) &&
+		    server->ops->query_reparse_tag) {
+			rc = server->ops->query_reparse_tag(xid, tcon, cifs_sb,
+						full_path, &reparse_tag);
+			cifs_dbg(FYI, "reparse tag 0x%x\n", reparse_tag);
+		}
+		cifs_all_info_to_fattr(&fattr, data, sb, adjust_tz,
+				       is_reparse_point, reparse_tag);
 		break;
 	case -EREMOTE:
 		/* DFS link, no metadata available on this server */