cifs: add SMB3 change notification support

A commonly used SMB3 feature is change notification, allowing an
app to be notified about changes to a directory. The SMB3
Notify request blocks until the server detects a change to that
directory or its contents that matches the completion flags
that were passed in and the "watch_tree" flag (which indicates
whether subdirectories under this directory should be also
included).  See MS-SMB2 2.2.35 for additional detail.

To use this simply pass in the following structure to ioctl:

 struct __attribute__((__packed__)) smb3_notify {
        uint32_t completion_filter;
        bool    watch_tree;
 } __packed;

 using CIFS_IOC_NOTIFY  0x4005cf09
 or equivalently _IOW(CIFS_IOCTL_MAGIC, 9, struct smb3_notify)

SMB3 change notification is supported by all major servers.
The ioctl will block until the server detects a change to that
directory or its subdirectories (if watch_tree is set).

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Acked-by: Paulo Alcantara (SUSE) <pc@cjr.nz>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index e4c935026d5e..4a73e63c4d43 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -169,6 +169,7 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 	unsigned int xid;
 	struct cifsFileInfo *pSMBFile = filep->private_data;
 	struct cifs_tcon *tcon;
+	struct cifs_sb_info *cifs_sb;
 	__u64	ExtAttrBits = 0;
 	__u64   caps;
 
@@ -299,6 +300,21 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 			else
 				rc = 0;
 			break;
+		case CIFS_IOC_NOTIFY:
+			if (!S_ISDIR(inode->i_mode)) {
+				/* Notify can only be done on directories */
+				rc = -EOPNOTSUPP;
+				break;
+			}
+			cifs_sb = CIFS_SB(inode->i_sb);
+			tcon = tlink_tcon(cifs_sb_tlink(cifs_sb));
+			if (tcon && tcon->ses->server->ops->notify) {
+				rc = tcon->ses->server->ops->notify(xid,
+						filep, (void __user *)arg);
+				cifs_dbg(FYI, "ioctl notify rc %d\n", rc);
+			} else
+				rc = -EOPNOTSUPP;
+			break;
 		default:
 			cifs_dbg(FYI, "unsupported ioctl\n");
 			break;