locks: add lock cancel command

Lock managers need to be able to cancel pending lock requests.  In the case
where the exported filesystem manages its own locks, it's not sufficient just
to call posix_unblock_lock(); we need to let the filesystem know what's
happening too.

We do this by adding a new fcntl lock command: FL_CANCELLK.  Some day this
might also be made available to userspace applications that could benefit from
an asynchronous locking api.

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 996f5611cd59..40b93265d4ba 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -3,6 +3,10 @@
 
 #include <asm/fcntl.h>
 
+/* Cancel a blocking posix lock; internal use only until we expose an
+ * asynchronous lock api to userspace: */
+#define F_CANCELLK      (F_LINUX_SPECIFIC_BASE+5)
+
 #define F_SETLEASE      (F_LINUX_SPECIFIC_BASE+0)
 #define F_GETLEASE      (F_LINUX_SPECIFIC_BASE+1)