mfsymlinks support for SMB2.1/SMB3. Part 2 query symlink

Adds support on SMB2.1 and SMB3 mounts for emulation of symlinks
via the "Minshall/French" symlink format already used for cifs
mounts when mfsymlinks mount option is used (and also used by Apple).
  http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks
This second patch adds support to query them (recognize them as symlinks
and read them).  Third version of patch makes minor corrections
to error handling.

Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

1 files changed, 69 insertions, 1 deletions

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 1216f4f1c6c9..ce7d4bbf3120 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -28,7 +28,9 @@
 #include "cifsproto.h"
 #include "cifs_debug.h"
 #include "cifs_fs_sb.h"
+#ifdef CONFIG_CIFS_SMB2
 #include "smb2proto.h"
+#endif
 
 /*
  * M-F Symlink Functions - Begin
@@ -401,6 +403,72 @@ cifs_create_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
         return rc;
 }
 
+/*
+ * SMB 2.1/SMB3 Protocol specific functions
+ */
+#ifdef CONFIG_CIFS_SMB2
+int
+smb3_query_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
+                      struct cifs_sb_info *cifs_sb, const unsigned char *path,
+                      char *pbuf, unsigned int *pbytes_read)
+{
+        int rc;
+        struct cifs_fid fid;
+        struct cifs_open_parms oparms;
+        struct cifs_io_parms io_parms;
+        int buf_type = CIFS_NO_BUFFER;
+        __le16 *utf16_path;
+        __u8 oplock = SMB2_OPLOCK_LEVEL_II;
+        struct smb2_file_all_info *pfile_info = NULL;
+
+        oparms.tcon = tcon;
+        oparms.cifs_sb = cifs_sb;
+        oparms.desired_access = GENERIC_READ;
+        oparms.create_options = CREATE_NOT_DIR;
+        if (backup_cred(cifs_sb))
+                oparms.create_options |= CREATE_OPEN_BACKUP_INTENT;
+        oparms.disposition = FILE_OPEN;
+        oparms.fid = &fid;
+        oparms.reconnect = false;
+
+        utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
+        if (utf16_path == NULL)
+                return -ENOMEM;
+
+        pfile_info = kzalloc(sizeof(struct smb2_file_all_info) + PATH_MAX * 2,
+                             GFP_KERNEL);
+
+        if (pfile_info == NULL) {
+                kfree(utf16_path);
+                return  -ENOMEM;
+        }
+
+        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, pfile_info, NULL);
+        if (rc)
+                goto qmf_out_open_fail;
+
+        if (pfile_info->EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
+                /* it's not a symlink */
+                rc = -ENOENT; /* Is there a better rc to return? */
+                goto qmf_out;
+        }
+
+        io_parms.netfid = fid.netfid;
+        io_parms.pid = current->tgid;
+        io_parms.tcon = tcon;
+        io_parms.offset = 0;
+        io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;
+        io_parms.persistent_fid = fid.persistent_fid;
+        io_parms.volatile_fid = fid.volatile_fid;
+        rc = SMB2_read(xid, &io_parms, pbytes_read, &pbuf, &buf_type);
+qmf_out:
+        SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
+qmf_out_open_fail:
+        kfree(utf16_path);
+        kfree(pfile_info);
+        return rc;
+}
+
 int
 smb3_create_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
                        struct cifs_sb_info *cifs_sb, const unsigned char *path,
@@ -461,7 +529,7 @@ smb3_create_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
         kfree(utf16_path);
         return rc;
 }
-
+#endif /* CONFIG_CIFS_SMB2 */
 
 /*
  * M-F Symlink Functions - End