Do not set B_NOCACHE on buffers when releasing them in flushbuflist().

If B_NOCACHE is set the pages of vm backed buffers will be invalidated.
However clean buffers can be backed by dirty VM pages so invalidating them
can lead to data loss.
Add support for flush dirty page in the data invalidation function
of some network file systems.

This fixes data losses during vnode recycling (and other code paths
using invalbuf(*,V_SAVE,*,*)) for data written using an mmaped file.

Collaborative effort by: jhb@,mohans@,peter@,ps@,ups@
Reviewed by:	tegge@
MFC after:	7 days

4 files changed, 20 insertions, 1 deletions

diff --git a/sys/fs/nwfs/nwfs_io.c b/sys/fs/nwfs/nwfs_io.c
index 8fdd18a..84ae3cd 100644
--- a/sys/fs/nwfs/nwfs_io.c
+++ b/sys/fs/nwfs/nwfs_io.c
@@ -611,6 +611,10 @@ nwfs_vinvalbuf(vp, td)
 			return EINTR;
 	}
 	np->n_flag |= NFLUSHINPROG;
+
+	if (vp->v_bufobj.bo_object != NULL)
+		vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
+
 	error = vinvalbuf(vp, V_SAVE, td, PCATCH, 0);
 	while (error) {
 		if (error == ERESTART || error == EINTR) {
diff --git a/sys/fs/smbfs/smbfs_io.c b/sys/fs/smbfs/smbfs_io.c
index 478ed55..7e76a87 100644
--- a/sys/fs/smbfs/smbfs_io.c
+++ b/sys/fs/smbfs/smbfs_io.c
@@ -683,6 +683,10 @@ smbfs_vinvalbuf(struct vnode *vp, struct thread *td)
 			return EINTR;
 	}
 	np->n_flag |= NFLUSHINPROG;
+
+	if (vp->v_bufobj.bo_object != NULL)
+		vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
+
 	error = vinvalbuf(vp, V_SAVE, td, PCATCH, 0);
 	while (error) {
 		if (error == ERESTART || error == EINTR) {
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 50f889f..da6a61b 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1134,7 +1134,7 @@ flushbuflist( struct bufv *bufv, int flags, struct bufobj *bo, int slpflag,
 			return (EAGAIN);	/* XXX: why not loop ? */
 		}
 		bremfree(bp);
-		bp->b_flags |= (B_INVAL | B_NOCACHE | B_RELBUF);
+		bp->b_flags |= (B_INVAL | B_RELBUF);
 		bp->b_flags &= ~B_ASYNC;
 		brelse(bp);
 		BO_LOCK(bo);
diff --git a/sys/nfsclient/nfs_bio.c b/sys/nfsclient/nfs_bio.c
index 19228ac..cac2175 100644
--- a/sys/nfsclient/nfs_bio.c
+++ b/sys/nfsclient/nfs_bio.c
@@ -1312,6 +1312,17 @@ nfs_vinvalbuf(struct vnode *vp, int flags, struct thread *td, int intrflg)
 	/*
 	 * Now, flush as required.
 	 */
+	if ((flags & V_SAVE) && (vp->v_bufobj.bo_object != NULL)) {
+		vm_object_page_clean(vp->v_bufobj.bo_object, 0, 0, OBJPC_SYNC);
+		/*
+		 * If the page clean was interrupted, fail the invalidation.
+		 * Not doing so, we run the risk of losing dirty pages in the 
+		 * vinvalbuf() call below.
+		 */
+		if (intrflg && (error = nfs_sigintr(nmp, NULL, td)))
+			goto out;
+	}
+
 	error = vinvalbuf(vp, flags, td, slpflag, 0);
 	while (error) {
 		if (intrflg && (error = nfs_sigintr(nmp, NULL, td)))