[CIFS] add mount option to send mandatory rather than advisory locks

Some applications/subsystems require mandatory byte range locks
(as is used for Windows/DOS/OS2 etc). Sending advisory (posix style)
byte range lock requests (instead of mandatory byte range locks) can
lead to problems for these applications (which expect that other
clients be prevented from writing to portions of the file which
they have locked and are updating).  This mount option allows
mounting cifs with the new mount option "forcemand" (or
"forcemandatorylock") in order to have the cifs client use mandatory
byte range locks (ie SMB/CIFS/Windows/NTFS style locks) rather than
posix byte range lock requests, even if the server would support
posix byte range lock requests.  This has no effect if the server
does not support the CIFS Unix Extensions (since posix style locks
require support for the CIFS Unix Extensions), but for mounts
to Samba servers this can be helpful for Wine and applications
that require mandatory byte range locks.

Acked-by: Jeff Layton <jlayton@redhat.com>
CC: Alexander Bokovoy <ab@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>

6 files changed, 48 insertions, 16 deletions

diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
index e078b7aea143..3d848f463c44 100644
--- a/fs/cifs/CHANGES
+++ b/fs/cifs/CHANGES
@@ -1,3 +1,9 @@
+Version 1.56
+------------
+Add "forcemandatorylock" mount option to allow user to use mandatory
+rather than posix (advisory) byte range locks, even though server would
+support posix byte range locks.
+
 Version 1.55
 ------------
 Various fixes to make delete of open files behavior more predictable
diff --git a/fs/cifs/README b/fs/cifs/README
index a439dc1739b3..da4515e3be20 100644
--- a/fs/cifs/README
+++ b/fs/cifs/README
@@ -463,9 +463,19 @@ A partial list of the supported mount options follows:
                 with cifs style mandatory byte range locks (and most
                 cifs servers do not yet support requesting advisory
                 byte range locks).
+ forcemandatorylock Even if the server supports posix (advisory) byte range
+                locking, send only mandatory lock requests.  For some
+                (presumably rare) applications, originally coded for
+                DOS/Windows, which require Windows style mandatory byte range
+                locking, they may be able to take advantage of this option,
+                forcing the cifs client to only send mandatory locks
+                even if the cifs server would support posix advisory locks.
+                "forcemand" is accepted as a shorter form of this mount
+                option.
  nodfs          Disable DFS (global name space support) even if the
                 server claims to support it.  This can help work around
-                a problem with parsing of DFS paths with Samba 3.0.24 server.
+                a problem with parsing of DFS paths with Samba server
+                versions 3.0.24 and 3.0.25.
  remount        remount the share (often used to change from ro to rw mounts
                 or vice versa)
  cifsacl        Report mode bits (e.g. on stat) based on the Windows ACL for
diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 877c85409f1f..5edd5cc415aa 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -20,7 +20,7 @@
 
 #define CIFS_MOUNT_NO_PERM      1 /* do not do client vfs_perm check */
 #define CIFS_MOUNT_SET_UID      2 /* set current->euid in create etc. */
-#define CIFS_MOUNT_SERVER_INUM  4 /* inode numbers from uniqueid from server */
+#define CIFS_MOUNT_SERVER_INUM  4 /* inode numbers from uniqueid from server  */
 #define CIFS_MOUNT_DIRECT_IO    8 /* do not write nor read through page cache */
 #define CIFS_MOUNT_NO_XATTR     0x10  /* if set - disable xattr support       */
 #define CIFS_MOUNT_MAP_SPECIAL_CHR 0x20 /* remap illegal chars in filenames   */
@@ -30,7 +30,8 @@
 #define CIFS_MOUNT_CIFS_ACL     0x200 /* send ACL requests to non-POSIX srv   */
 #define CIFS_MOUNT_OVERR_UID    0x400 /* override uid returned from server    */
 #define CIFS_MOUNT_OVERR_GID    0x800 /* override gid returned from server    */
-#define CIFS_MOUNT_DYNPERM      0x1000 /* allow in-memory only mode setting */
+#define CIFS_MOUNT_DYNPERM      0x1000 /* allow in-memory only mode setting   */
+#define CIFS_MOUNT_NOPOSIXBRL   0x2000 /* mandatory not posix byte range lock */
 
 struct cifs_sb_info {
         struct cifsTconInfo *tcon;      /* primary mount */
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 074de0b5064d..fb676076946b 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -101,5 +101,5 @@ extern long cifs_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
 extern const struct export_operations cifs_export_ops;
 #endif /* EXPERIMENTAL */
 
-#define CIFS_VERSION   "1.55"
+#define CIFS_VERSION   "1.5666666"
 #endif                          /* _CIFSFS_H */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d6a3c1c8a6f8..351942042833 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -89,6 +89,7 @@ struct smb_vol {
         bool nullauth:1;   /* attempt to authenticate with null user */
         bool nocase:1;     /* request case insensitive filenames */
         bool nobrl:1;      /* disable sending byte range locks to srv */
+        bool mand_lock:1;  /* send mandatory not posix byte range lock reqs */
         bool seal:1;       /* request transport encryption on share */
         bool nodfs:1;      /* Do not request DFS, even if available */
         bool local_lease:1; /* check leases only on local system, not remote */
@@ -1246,6 +1247,17 @@ cifs_parse_mount_options(char *options, const char *devname,
                         if (vol->file_mode ==
                                 (S_IALLUGO & ~(S_ISUID | S_IXGRP)))
                                 vol->file_mode = S_IALLUGO;
+                } else if (strnicmp(data, "forcemandatorylock", 9) == 0) {
+                        /* will take the shorter form "forcemand" as well */
+                        /* This mount option will force use of mandatory
+                          (DOS/Windows style) byte range locks, instead of
+                          using posix advisory byte range locks, even if the
+                          Unix extensions are available and posix locks would
+                          be supported otherwise. If Unix extensions are not
+                          negotiated this has no effect since mandatory locks
+                          would be used (mandatory locks is all that those
+                          those servers support) */
+                        vol->mand_lock = 1;
                 } else if (strnicmp(data, "setuids", 7) == 0) {
                         vol->setuids = 1;
                 } else if (strnicmp(data, "nosetuids", 9) == 0) {
@@ -2150,6 +2162,8 @@ static void setup_cifs_sb(struct smb_vol *pvolume_info,
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_UNX_EMUL;
         if (pvolume_info->nobrl)
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_BRL;
+        if (pvolume_info->mand_lock)
+                cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NOPOSIXBRL;
         if (pvolume_info->cifs_acl)
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_CIFS_ACL;
         if (pvolume_info->override_uid)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index f0a81e631ae6..babd27a4699a 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -644,10 +644,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
         __u64 length;
         bool wait_flag = false;
         struct cifs_sb_info *cifs_sb;
-        struct cifsTconInfo *pTcon;
+        struct cifsTconInfo *tcon;
         __u16 netfid;
         __u8 lockType = LOCKING_ANDX_LARGE_FILES;
-        bool posix_locking;
+        bool posix_locking = 0;
 
         length = 1 + pfLock->fl_end - pfLock->fl_start;
         rc = -EACCES;
@@ -698,7 +698,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                 cFYI(1, ("Unknown type of lock"));
 
         cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
-        pTcon = cifs_sb->tcon;
+        tcon = cifs_sb->tcon;
 
         if (file->private_data == NULL) {
                 FreeXid(xid);
@@ -706,9 +706,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
         }
         netfid = ((struct cifsFileInfo *)file->private_data)->netfid;
 
-        posix_locking = (cifs_sb->tcon->ses->capabilities & CAP_UNIX) &&
-                        (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(cifs_sb->tcon->fsUnixInfo.Capability));
-
+        if ((tcon->ses->capabilities & CAP_UNIX) &&
+            (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
+            (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL == 0))
+                posix_locking = 1;
         /* BB add code here to normalize offset and length to
         account for negative length which we can not accept over the
         wire */
@@ -719,7 +720,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                                 posix_lock_type = CIFS_RDLCK;
                         else
                                 posix_lock_type = CIFS_WRLCK;
-                        rc = CIFSSMBPosixLock(xid, pTcon, netfid, 1 /* get */,
+                        rc = CIFSSMBPosixLock(xid, tcon, netfid, 1 /* get */,
                                         length, pfLock,
                                         posix_lock_type, wait_flag);
                         FreeXid(xid);
@@ -727,10 +728,10 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                 }
 
                 /* BB we could chain these into one lock request BB */
-                rc = CIFSSMBLock(xid, pTcon, netfid, length, pfLock->fl_start,
+                rc = CIFSSMBLock(xid, tcon, netfid, length, pfLock->fl_start,
                                  0, 1, lockType, 0 /* wait flag */ );
                 if (rc == 0) {
-                        rc = CIFSSMBLock(xid, pTcon, netfid, length,
+                        rc = CIFSSMBLock(xid, tcon, netfid, length,
                                          pfLock->fl_start, 1 /* numUnlock */ ,
                                          0 /* numLock */ , lockType,
                                          0 /* wait flag */ );
@@ -767,7 +768,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                 if (numUnlock == 1)
                         posix_lock_type = CIFS_UNLCK;
 
-                rc = CIFSSMBPosixLock(xid, pTcon, netfid, 0 /* set */,
+                rc = CIFSSMBPosixLock(xid, tcon, netfid, 0 /* set */,
                                       length, pfLock,
                                       posix_lock_type, wait_flag);
         } else {
@@ -775,7 +776,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                         (struct cifsFileInfo *)file->private_data;
 
                 if (numLock) {
-                        rc = CIFSSMBLock(xid, pTcon, netfid, length,
+                        rc = CIFSSMBLock(xid, tcon, netfid, length,
                                         pfLock->fl_start,
                                         0, numLock, lockType, wait_flag);
 
@@ -796,7 +797,7 @@ int cifs_lock(struct file *file, int cmd, struct file_lock *pfLock)
                                 if (pfLock->fl_start <= li->offset &&
                                                 (pfLock->fl_start + length) >=
                                                 (li->offset + li->length)) {
-                                        stored_rc = CIFSSMBLock(xid, pTcon,
+                                        stored_rc = CIFSSMBLock(xid, tcon,
                                                         netfid,
                                                         li->length, li->offset,
                                                         1, 0, li->type, false);