[CIFS] improve setlease handling

fcntl(F_SETLEASE) currently is not exported by cifs (nor by local file
systems) so cifs grants leases based on how other local processes have
opened the file not by whether the file is cacheable (oplocked).  This
adds the check to make sure that the file is cacheable on the client
before checking whether we can grant the lease locally
(generic_setlease).  It also adds a mount option for cifs (locallease)
if the user wants to override this and try to grant leases even
if the server did not grant oplock.

Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index c6aad77..76919c2 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -618,6 +618,37 @@ static loff_t cifs_llseek(struct file *file, loff_t offset, int origin)
 	return generic_file_llseek_unlocked(file, offset, origin);
 }
 
+#ifdef CONFIG_CIFS_EXPERIMENTAL
+static int cifs_setlease(struct file *file, long arg, struct file_lock **lease)
+{
+	/* note that this is called by vfs setlease with the BKL held
+	   although I doubt that BKL is needed here in cifs */
+	struct inode *inode = file->f_path.dentry->d_inode;
+
+	if (!(S_ISREG(inode->i_mode)))
+		return -EINVAL;
+
+	/* check if file is oplocked */
+	if (((arg == F_RDLCK) &&
+		(CIFS_I(inode)->clientCanCacheRead)) ||
+	    ((arg == F_WRLCK) &&
+		(CIFS_I(inode)->clientCanCacheAll)))
+		return generic_setlease(file, arg, lease);
+	else if (CIFS_SB(inode->i_sb)->tcon->local_lease &&
+			!CIFS_I(inode)->clientCanCacheRead)
+		/* If the server claims to support oplock on this
+		   file, then we still need to check oplock even
+		   if the local_lease mount option is set, but there
+		   are servers which do not support oplock for which
+		   this mount option may be useful if the user
+		   knows that the file won't be changed on the server
+		   by anyone else */
+		return generic_setlease(file, arg, lease);
+	else
+		return -EAGAIN;
+}
+#endif
+
 struct file_system_type cifs_fs_type = {
 	.owner = THIS_MODULE,
 	.name = "cifs",
@@ -696,6 +727,7 @@ const struct file_operations cifs_file_ops = {
 
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	.dir_notify = cifs_dir_notify,
+	.setlease = cifs_setlease,
 #endif /* CONFIG_CIFS_EXPERIMENTAL */
 };
 
@@ -716,6 +748,7 @@ const struct file_operations cifs_file_direct_ops = {
 	.llseek = cifs_llseek,
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	.dir_notify = cifs_dir_notify,
+	.setlease = cifs_setlease,
 #endif /* CONFIG_CIFS_EXPERIMENTAL */
 };
 const struct file_operations cifs_file_nobrl_ops = {
@@ -736,6 +769,7 @@ const struct file_operations cifs_file_nobrl_ops = {
 
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	.dir_notify = cifs_dir_notify,
+	.setlease = cifs_setlease,
 #endif /* CONFIG_CIFS_EXPERIMENTAL */
 };
 
@@ -755,6 +789,7 @@ const struct file_operations cifs_file_direct_nobrl_ops = {
 	.llseek = cifs_llseek,
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	.dir_notify = cifs_dir_notify,
+	.setlease = cifs_setlease,
 #endif /* CONFIG_CIFS_EXPERIMENTAL */
 };
 
@@ -946,6 +981,12 @@ static int cifs_oplock_thread(void *dummyarg)
 				the call */
 			/* mutex_lock(&inode->i_mutex);*/
 			if (S_ISREG(inode->i_mode)) {
+#ifdef CONFIG_CIFS_EXPERIMENTAL
+				if (CIFS_I(inode)->clientCanCacheAll == 0)
+					break_lease(inode, FMODE_READ);
+				else if (CIFS_I(inode)->clientCanCacheRead == 0)
+					break_lease(inode, FMODE_WRITE);
+#endif
 				rc = filemap_fdatawrite(inode->i_mapping);
 				if (CIFS_I(inode)->clientCanCacheRead == 0) {
 					waitrc = filemap_fdatawait(