From e15697fcb4d8cf1145e573f4a2dd9ef37fe7de72 Mon Sep 17 00:00:00 2001
From: chs <chs@NetBSD.org>
Date: Sun, 8 Aug 2010 18:17:11 +0000
Subject: [PATCH] in genfs_getpages(), mark the vnode dirty (ie. add to syncer
 worklist and set VI_WRMAPDIRTY) after we have busied the pages rather than
 before.  this prevents other threads calling genfs_do_putpages() from marking
 the vnode clean again while we're in the process of creating new writable
 mappings, since such threads will wait for the page(s) to become unbusy
 before proceeding. fixes the problem recently reported by hannken@ on
 tech-kern.

---
 sys/miscfs/genfs/genfs_io.c | 58 +++++++++++++++++++++++--------------
 1 file changed, 37 insertions(+), 21 deletions(-)

diff --git a/sys/miscfs/genfs/genfs_io.c b/sys/miscfs/genfs/genfs_io.c
index 1c19894ef2c8..d7348d40dfe9 100644
--- a/sys/miscfs/genfs/genfs_io.c
+++ b/sys/miscfs/genfs/genfs_io.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: genfs_io.c,v 1.37 2010/07/29 10:54:50 hannken Exp $	*/
+/*	$NetBSD: genfs_io.c,v 1.38 2010/08/08 18:17:11 chs Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.37 2010/07/29 10:54:50 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.38 2010/08/08 18:17:11 chs Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -62,11 +62,12 @@ static void genfs_dio_iodone(struct buf *);
 
 static int genfs_do_io(struct vnode *, off_t, vaddr_t, size_t, int, enum uio_rw,
     void (*)(struct buf *));
-static inline void genfs_rel_pages(struct vm_page **, int);
+static void genfs_rel_pages(struct vm_page **, int);
+static void genfs_markdirty(struct vnode *);
 
 int genfs_maxdio = MAXPHYS;
 
-static inline void
+static void
 genfs_rel_pages(struct vm_page **pgs, int npages)
 {
 	int i;
@@ -85,6 +86,21 @@ genfs_rel_pages(struct vm_page **pgs, int npages)
 	mutex_exit(&uvm_pageqlock);
 }
 
+static void
+genfs_markdirty(struct vnode *vp)
+{
+	struct genfs_node * const gp = VTOG(vp);
+
+	KASSERT(mutex_owned(&vp->v_interlock));
+	gp->g_dirtygen++;
+	if ((vp->v_iflag & VI_ONWORKLST) == 0) {
+		vn_syncer_add_to_worklist(vp, filedelay);
+	}
+	if ((vp->v_iflag & (VI_WRMAP|VI_WRMAPDIRTY)) == VI_WRMAP) {
+		vp->v_iflag |= VI_WRMAPDIRTY;
+	}
+}
+
 /*
  * generic VM getpages routine.
  * Return PG_BUSY pages for the given range,
@@ -186,16 +202,6 @@ startover:
 		}
 	}
 
-	if (memwrite) {
-		gp->g_dirtygen++;
-		if ((vp->v_iflag & VI_ONWORKLST) == 0) {
-			vn_syncer_add_to_worklist(vp, filedelay);
-		}
-		if ((vp->v_iflag & (VI_WRMAP|VI_WRMAPDIRTY)) == VI_WRMAP) {
-			vp->v_iflag |= VI_WRMAPDIRTY;
-		}
-	}
-
 	/*
 	 * For PGO_LOCKED requests, just return whatever's in memory.
 	 */
@@ -236,6 +242,9 @@ startover:
 			genfs_node_unlock(vp);
 		}
 		error = (ap->a_m[ap->a_centeridx] == NULL ? EBUSY : 0);
+		if (error == 0 && memwrite) {
+			genfs_markdirty(vp);
+		}
 		goto out_err;
 	}
 	mutex_exit(&uobj->vmobjlock);
@@ -696,6 +705,9 @@ out:
 		}
 	}
 	mutex_exit(&uvm_pageqlock);
+	if (memwrite) {
+		genfs_markdirty(vp);
+	}
 	mutex_exit(&uobj->vmobjlock);
 	if (ap->a_m != NULL) {
 		memcpy(ap->a_m, &pgs[ridx],
@@ -708,7 +720,7 @@ out_err_free:
 out_err:
 	if (has_trans)
 		fstrans_done(vp->v_mount);
-	return (error);
+	return error;
 }
 
 /*
@@ -1467,18 +1479,19 @@ genfs_compat_getpages(void *v)
 	orignpages = *ap->a_count;
 	pgs = ap->a_m;
 
-	if (memwrite && (vp->v_iflag & VI_ONWORKLST) == 0) {
-		vn_syncer_add_to_worklist(vp, filedelay);
-	}
 	if (ap->a_flags & PGO_LOCKED) {
 		uvn_findpages(uobj, origoffset, ap->a_count, ap->a_m,
 		    UFP_NOWAIT|UFP_NOALLOC| (memwrite ? UFP_NORDONLY : 0));
 
-		return (ap->a_m[ap->a_centeridx] == NULL ? EBUSY : 0);
+		error = ap->a_m[ap->a_centeridx] == NULL ? EBUSY : 0;
+		if (error == 0 && memwrite) {
+			genfs_markdirty(vp);
+		}
+		return error;
 	}
 	if (origoffset + (ap->a_centeridx << PAGE_SHIFT) >= vp->v_size) {
 		mutex_exit(&uobj->vmobjlock);
-		return (EINVAL);
+		return EINVAL;
 	}
 	if ((ap->a_flags & PGO_SYNCIO) == 0) {
 		mutex_exit(&uobj->vmobjlock);
@@ -1527,8 +1540,11 @@ genfs_compat_getpages(void *v)
 		uvm_page_unbusy(pgs, npages);
 	}
 	mutex_exit(&uvm_pageqlock);
+	if (error == 0 && memwrite) {
+		genfs_markdirty(vp);
+	}
 	mutex_exit(&uobj->vmobjlock);
-	return (error);
+	return error;
 }
 
 int