Prefaulting for i/o buffers

[Pawel Jakub Dawidek]

On Mon, Feb 06, 2012 at 12:12:59AM +0200, Konstantin Belousov wrote:
> http://people.freebsd.org/~kib/misc/vm1.9.patch

--- a/sys/fs/nfsclient/nfs_clbio.c
+++ b/sys/fs/nfsclient/nfs_clbio.c
@@ -820,7 +820,10 @@ do_sync:
 			t_uio->uio_segflg = UIO_SYSSPACE;
 			t_uio->uio_rw = UIO_WRITE;
 			t_uio->uio_td = td;
-			bcopy(uiop->uio_iov->iov_base, t_iov->iov_base, size);
+			error = copyin(uiop->uio_iov->iov_base,
+			    t_iov->iov_base, size);
+			if (error != 0)
+				goto err_free;

Good catch. It makes me wonder if uiop will always point at userland
buffer. What if we eg. AUDIT subsystem writing from within the kernel to
a file stored on NFS file system?

+	if (lock->rl_currdep == TAILQ_FIRST(&lock->rl_waiters) &&
+	    lock->rl_currdep != NULL)
+		lock->rl_currdep = TAILQ_NEXT(lock->rl_currdep, rl_q_link);
+	for (entry = lock->rl_currdep; entry;

Minor style inconsistency. Two lines earlier you compare pointer with
NULL, which is nice, but here you treat pointer as boolean.

+void
+rangelock_unlock(struct rangelock *lock, void *cookie)
+{
+	struct rl_q_entry *entry;
+
+	MPASS(lock != NULL && cookie != NULL);
+
+	entry = cookie;
+	sleepq_lock(lock);
+	rangelock_unlock_locked(lock, entry);
+}

You could drop using addtional 'entry' variable and just pass 'cookie'
directly. Although current code is self-explaining what 'cookie'
actually is, so I kinda like it as-is.

+/*
+ * Add the lock request to the queue of the pending requests for
+ * rangelock.  Sleeps until the request can be granted.

s/request/lock/ ?

@@ -216,6 +218,7 @@ thread_fini(void *mem, int size)
 
 	td = (struct thread *)mem;
 	EVENTHANDLER_INVOKE(thread_fini, td);
+	rlqentry_free(td->td_rlqe);

Not sure if it was intended or not, but td_rlqe can be NULL now, so it
might be worth checking that. It is not a big deal, as uma_zfree() can handle
NULL pointers though.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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