From: Ken Preslan <kpreslan@redhat.com>
Below is a patch that lets a cluster filesystem (such as GFS) implement
flock across a the cluster.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/locks.c | 40 ++++++++++++++++++++++++++++++++++++++++
25-akpm/include/linux/fs.h | 1 +
2 files changed, 41 insertions(+)
diff -puN fs/locks.c~allow-cluster-wide-flock fs/locks.c
--- 25/fs/locks.c~allow-cluster-wide-flock Mon Aug 30 14:40:54 2004
+++ 25-akpm/fs/locks.c Mon Aug 30 14:40:54 2004
@@ -1318,6 +1318,33 @@ out_unlock:
}
/**
+ * flock_lock_file_wait - Apply a FLOCK-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ *
+ * Add a FLOCK style lock to a file.
+ */
+int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
+{
+ int error;
+ might_sleep();
+ for (;;) {
+ error = flock_lock_file(filp, fl);
+ if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
+ break;
+ error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+ if (!error)
+ continue;
+
+ locks_delete_block(fl);
+ break;
+ }
+ return error;
+}
+
+EXPORT_SYMBOL(flock_lock_file_wait);
+
+/**
* sys_flock: - flock() system call.
* @fd: the file descriptor to lock.
* @cmd: the type of lock to apply.
@@ -1365,6 +1392,13 @@ asmlinkage long sys_flock(unsigned int f
if (error)
goto out_free;
+ if (filp->f_op && filp->f_op->lock) {
+ error = filp->f_op->lock(filp,
+ (can_sleep) ? F_SETLKW : F_SETLK,
+ lock);
+ goto out_free;
+ }
+
for (;;) {
error = flock_lock_file(filp, lock);
if ((error != -EAGAIN) || !can_sleep)
@@ -1732,6 +1766,12 @@ void locks_remove_flock(struct file *fil
if (!inode->i_flock)
return;
+ if (filp->f_op && filp->f_op->lock) {
+ struct file_lock fl = { .fl_flags = FL_FLOCK,
+ .fl_type = F_UNLCK };
+ filp->f_op->lock(filp, F_SETLKW, &fl);
+ }
+
lock_kernel();
before = &inode->i_flock;
diff -puN include/linux/fs.h~allow-cluster-wide-flock include/linux/fs.h
--- 25/include/linux/fs.h~allow-cluster-wide-flock Mon Aug 30 14:40:54 2004
+++ 25-akpm/include/linux/fs.h Mon Aug 30 14:40:54 2004
@@ -697,6 +697,7 @@ extern int posix_lock_file_wait(struct f
extern void posix_block_lock(struct file_lock *, struct file_lock *);
extern void posix_unblock_lock(struct file *, struct file_lock *);
extern int posix_locks_deadlock(struct file_lock *, struct file_lock *);
+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);
extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
_