From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Mon, 2 Apr 2012 17:16:21 +0000 (-0700)
Subject: kernel - Add max I/O size cap to vmaxiosize()
X-Git-Tag: v3.4.0rc~1146^2
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/201cd6122f10d34494e93bdd304d21f94f3d0a29

kernel - Add max I/O size cap to vmaxiosize()

* Cap the returned value at MAXPHYS, allowing VCHR devices to set a
  higher max-IO limit (according to DMA limitations) without blowing
  out the pbuf's that the frontend uses to build clustered I/O.
---

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index ec42fe6f2d..ca17cfe1e8 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1366,15 +1366,23 @@ vrecycle(struct vnode *vp)
  *
  * If vp is VCHR or VBLK we dive the device, otherwise we use
  * the vp's mount info.
+ *
+ * The returned value is clamped at MAXPHYS as most callers cannot use
+ * buffers larger than that size.
  */
 int
 vmaxiosize(struct vnode *vp)
 {
-	if (vp->v_type == VBLK || vp->v_type == VCHR) {
-		return(vp->v_rdev->si_iosize_max);
-	} else {
-		return(vp->v_mount->mnt_iosize_max);
-	}
+	int maxiosize;
+
+	if (vp->v_type == VBLK || vp->v_type == VCHR)
+		maxiosize = vp->v_rdev->si_iosize_max;
+	else
+		maxiosize = vp->v_mount->mnt_iosize_max;
+
+	if (maxiosize > MAXPHYS)
+		maxiosize = MAXPHYS;
+	return (maxiosize);
 }
 
 /*