[PATCH 1/2] vfs: add lock owner argument to flush operation

[Miklos Szeredi]

Pass the POSIX lock owner ID to the flush operation.

This is useful for filesystems which don't want to store any locking
state in inode->i_flock but want to handle locking/unlocking POSIX
locks internally.  FUSE is one such filesystem but I think it possible
that some network filesystems would need this also.

Also add a flag to indicate that a POSIX locking request was generated
by close(), so filesystems using the above feature won't send an extra
locking request in this case.

f_op->flush() is only called from filp_close().  Since the added
argument may safely be ignored by filesystems the API/ABI remains
backward compatible.  Only a compile time warning is generated if the
signature of the flush method is old.  The next patch fixes up all the
in-tree uses of flush(), out-of-tree uses can migrate at will.

Signed-off-by: Miklos Szeredi <miklos@xxxxxxxxxx>

Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h	2006-04-09 11:17:01.000000000 +0200
+++ linux/include/linux/fs.h	2006-04-09 11:18:58.000000000 +0200
@@ -679,6 +679,7 @@ extern spinlock_t files_lock;
 #define FL_FLOCK	2
 #define FL_ACCESS	8	/* not trying to lock, just looking */
 #define FL_LEASE	32	/* lease held on this file */
+#define FL_CLOSE	64	/* unlock on close */
 #define FL_SLEEP	128	/* A blocking lock */
 
 /*
@@ -1025,7 +1026,7 @@ struct file_operations {
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
 	int (*open) (struct inode *, struct file *);
-	int (*flush) (struct file *);
+	int (*flush) (struct file *, fl_owner_t id);
 	int (*release) (struct inode *, struct file *);
 	int (*fsync) (struct file *, struct dentry *, int datasync);
 	int (*aio_fsync) (struct kiocb *, int datasync);
Index: linux/fs/locks.c
===================================================================
--- linux.orig/fs/locks.c	2006-04-09 11:17:58.000000000 +0200
+++ linux/fs/locks.c	2006-04-09 11:18:58.000000000 +0200
@@ -1902,7 +1902,7 @@ void locks_remove_posix(struct file *fil
 		return;
 
 	lock.fl_type = F_UNLCK;
-	lock.fl_flags = FL_POSIX;
+	lock.fl_flags = FL_POSIX | FL_CLOSE;
 	lock.fl_start = 0;
 	lock.fl_end = OFFSET_MAX;
 	lock.fl_owner = owner;
Index: linux/fs/open.c
===================================================================
--- linux.orig/fs/open.c	2006-04-09 11:17:01.000000000 +0200
+++ linux/fs/open.c	2006-04-09 11:18:58.000000000 +0200
@@ -1137,7 +1137,7 @@ int filp_close(struct file *filp, fl_own
 	}
 
 	if (filp->f_op && filp->f_op->flush)
-		retval = filp->f_op->flush(filp);
+		retval = filp->f_op->flush(filp, id);
 
 	dnotify_flush(filp, id);
 	locks_remove_posix(filp, id);
-
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