[XFS] add a FMODE flag to make XFS invisible I/O less hacky

XFS has a mode called invisble I/O that doesn't update any of the
timestamps.  It's used for HSM-style applications and exposed through
the nasty open by handle ioctl.

Instead of doing directly assignment of file operations that set an
internal flag for it add a new FMODE_NOCMTIME flag that we can check
in the normal file operations.

(addition of the generic VFS flag has been ACKed by Al as an interims
 solution)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 51bd9370d437..965b9ba3865d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -81,6 +81,14 @@ extern int dir_notify_enable;
 #define FMODE_WRITE_IOCTL       ((__force fmode_t)128)
 #define FMODE_NDELAY_NOW        ((__force fmode_t)256)
 
+/*
+ * Don't update ctime and mtime.
+ *
+ * Currently a special hack for the XFS open_by_handle ioctl, but we'll
+ * hopefully graduate it to a proper O_CMTIME flag supported by open(2) soon.
+ */
+#define FMODE_NOCMTIME          ((__force fmode_t)2048)
+
 #define RW_MASK         1
 #define RWA_MASK        2
 #define READ 0