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>

diff --git a/fs/locks.c b/fs/locks.c
index ee46584c1a40123e395fd178b200d5ff89100f26..242328e17f32e9961310f5403d3aeba34189ed16 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2028,6 +2028,22 @@ posix_unblock_lock(struct file *filp, struct file_lock *waiter)
 
 EXPORT_SYMBOL(posix_unblock_lock);
 
+/**
+ * vfs_cancel_lock - file byte range unblock lock
+ * @filp: The file to apply the unblock to
+ * @fl: The lock to be unblocked
+ *
+ * Used by lock managers to cancel blocked requests
+ */
+int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
+{
+       if (filp->f_op && filp->f_op->lock)
+               return filp->f_op->lock(filp, F_CANCELLK, fl);
+       return 0;
+}
+
+EXPORT_SYMBOL_GPL(vfs_cancel_lock);
+
 static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
 {
        struct inode *inode = NULL;

diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 996f5611cd59dc73ed9d01b2dec84f0708dcf7d9..40b93265d4bae5240896a2c3eaac75fb2577ca76 100644 (file)
--- 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)
 

diff --git a/include/linux/fs.h b/include/linux/fs.h
index c92d0bdff39f6d5327dbb9e660caeda835788d2a..64b8ae205309eb30c66802c567f0a81bc7190765 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -857,6 +857,7 @@ extern int posix_lock_file_wait(struct file *, struct file_lock *);
 extern int posix_unblock_lock(struct file *, struct file_lock *);
 extern int vfs_test_lock(struct file *, struct file_lock *);
 extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
+extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
 extern int flock_lock_file_wait(struct file *filp, struct file_lock *fl);
 extern int __break_lease(struct inode *inode, unsigned int flags);
 extern void lease_get_mtime(struct inode *, struct timespec *time);