nfs: introduce mount option '-olocal_lock' to make locks local

NFS clients since 2.6.12 support flock locks by emulating fcntl byte-range
locks. Due to this, some windows applications which seem to use both flock
(share mode lock mapped as flock by Samba) and fcntl locks sequentially on
the same file, can't lock as they falsely assume the file is already locked.
The problem was reported on a setup with windows clients accessing excel files
on a Samba exported share which is originally a NFS mount from a NetApp filer.

Older NFS clients (< 2.6.12) did not see this problem as flock locks were
considered local. To support legacy flock behavior, this patch adds a mount
option "-olocal_lock=" which can take the following values:

   'none'  		- Neither flock locks nor POSIX locks are local
   'flock' 		- flock locks are local
   'posix' 		- fcntl/POSIX locks are local
   'all'		- Both flock locks and POSIX locks are local

Testing:

   - This patch was tested by using -olocal_lock option with different values
     and the NLM calls were noted from the network packet captured.

     'none'  - NLM calls were seen during both flock() and fcntl(), flock lock
   	       was granted, fcntl was denied
     'flock' - no NLM calls for flock(), NLM call was seen for fcntl(),
   	       granted
     'posix' - NLM call was seen for flock() - granted, no NLM call for fcntl()
     'all'   - no NLM calls were seen during both flock() and fcntl()

   - No bugs were seen during NFSv4 locking/unlocking in general and NFSv4
     reboot recovery.

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 32 insertions, 13 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index eb51bd6201da..59cbe1ba0511 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -684,7 +684,8 @@ static ssize_t nfs_file_splice_write(struct pipe_inode_info *pipe,
         return ret;
 }
 
-static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_getlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
         struct inode *inode = filp->f_mapping->host;
         int status = 0;
@@ -699,7 +700,7 @@ static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
         if (nfs_have_delegation(inode, FMODE_READ))
                 goto out_noconflict;
 
-        if (NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)
+        if (is_local)
                 goto out_noconflict;
 
         status = NFS_PROTO(inode)->lock(filp, cmd, fl);
@@ -730,7 +731,8 @@ static int do_vfs_lock(struct file *file, struct file_lock *fl)
         return res;
 }
 
-static int do_unlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
         struct inode *inode = filp->f_mapping->host;
         int status;
@@ -745,15 +747,19 @@ static int do_unlk(struct file *filp, int cmd, struct file_lock *fl)
          *      If we're signalled while cleaning up locks on process exit, we
          *      still need to complete the unlock.
          */
-        /* Use local locking if mounted with "-onolock" */
-        if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
+        /*
+         * Use local locking if mounted with "-onolock" or with appropriate
+         * "-olocal_lock="
+         */
+        if (!is_local)
                 status = NFS_PROTO(inode)->lock(filp, cmd, fl);
         else
                 status = do_vfs_lock(filp, fl);
         return status;
 }
 
-static int do_setlk(struct file *filp, int cmd, struct file_lock *fl)
+static int
+do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
         struct inode *inode = filp->f_mapping->host;
         int status;
@@ -766,8 +772,11 @@ static int do_setlk(struct file *filp, int cmd, struct file_lock *fl)
         if (status != 0)
                 goto out;
 
-        /* Use local locking if mounted with "-onolock" */
-        if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
+        /*
+         * Use local locking if mounted with "-onolock" or with appropriate
+         * "-olocal_lock="
+         */
+        if (!is_local)
                 status = NFS_PROTO(inode)->lock(filp, cmd, fl);
         else
                 status = do_vfs_lock(filp, fl);
@@ -791,6 +800,7 @@ static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
         struct inode *inode = filp->f_mapping->host;
         int ret = -ENOLCK;
+        int is_local = 0;
 
         dprintk("NFS: lock(%s/%s, t=%x, fl=%x, r=%lld:%lld)\n",
                         filp->f_path.dentry->d_parent->d_name.name,
@@ -804,6 +814,9 @@ static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
         if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
                 goto out_err;
 
+        if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FCNTL)
+                is_local = 1;
+
         if (NFS_PROTO(inode)->lock_check_bounds != NULL) {
                 ret = NFS_PROTO(inode)->lock_check_bounds(fl);
                 if (ret < 0)
@@ -811,11 +824,11 @@ static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
         }
 
         if (IS_GETLK(cmd))
-                ret = do_getlk(filp, cmd, fl);
+                ret = do_getlk(filp, cmd, fl, is_local);
         else if (fl->fl_type == F_UNLCK)
-                ret = do_unlk(filp, cmd, fl);
+                ret = do_unlk(filp, cmd, fl, is_local);
         else
-                ret = do_setlk(filp, cmd, fl);
+                ret = do_setlk(filp, cmd, fl, is_local);
 out_err:
         return ret;
 }
@@ -825,6 +838,9 @@ out_err:
  */
 static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
 {
+        struct inode *inode = filp->f_mapping->host;
+        int is_local = 0;
+
         dprintk("NFS: flock(%s/%s, t=%x, fl=%x)\n",
                         filp->f_path.dentry->d_parent->d_name.name,
                         filp->f_path.dentry->d_name.name,
@@ -833,14 +849,17 @@ static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
         if (!(fl->fl_flags & FL_FLOCK))
                 return -ENOLCK;
 
+        if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
+                is_local = 1;
+
         /* We're simulating flock() locks using posix locks on the server */
         fl->fl_owner = (fl_owner_t)filp;
         fl->fl_start = 0;
         fl->fl_end = OFFSET_MAX;
 
         if (fl->fl_type == F_UNLCK)
-                return do_unlk(filp, cmd, fl);
-        return do_setlk(filp, cmd, fl);
+                return do_unlk(filp, cmd, fl, is_local);
+        return do_setlk(filp, cmd, fl, is_local);
 }
 
 /*