A change to KPI of vm_pager_get_pages() and underlying VOP_GETPAGES().

o With new KPI consumers can request contiguous ranges of pages, and
  unlike before, all pages will be kept busied on return, like it was
  done before with the 'reqpage' only. Now the reqpage goes away. With
  new interface it is easier to implement code protected from race
  conditions.

  Such arrayed requests for now should be preceeded by a call to
  vm_pager_haspage() to make sure that request is possible. This
  could be improved later, making vm_pager_haspage() obsolete.

  Strenghtening the promises on the business of the array of pages
  allows us to remove such hacks as swp_pager_free_nrpage() and
  vm_pager_free_nonreq().

o New KPI accepts two integer pointers that may optionally point at
  values for read ahead and read behind, that a pager may do, if it
  can. These pages are completely owned by pager, and not controlled
  by the caller.

  This shifts the UFS-specific readahead logic from vm_fault.c, which
  should be file system agnostic, into vnode_pager.c. It also removes
  one VOP_BMAP() request per hard fault.

Discussed with:	kib, alc, jeff, scottl
Sponsored by:	Nginx, Inc.
Sponsored by:	Netflix

4 files changed, 46 insertions, 65 deletions

diff --git a/sys/fs/fuse/fuse_vnops.c b/sys/fs/fuse/fuse_vnops.c
index 12b9778..5031864 100644
--- a/sys/fs/fuse/fuse_vnops.c
+++ b/sys/fs/fuse/fuse_vnops.c
@@ -1753,6 +1753,10 @@ fuse_vnop_getpages(struct vop_getpages_args *ap)
 	cred = curthread->td_ucred;	/* XXX */
 	pages = ap->a_m;
 	count = ap->a_count;
+	if (ap->a_rbehind)
+		*ap->a_rbehind = 0;
+	if (ap->a_rahead)
+		*ap->a_rahead = 0;
 
 	if (!fsess_opt_mmap(vnode_mount(vp))) {
 		FS_DEBUG("called on non-cacheable vnode??\n");
@@ -1761,26 +1765,21 @@ fuse_vnop_getpages(struct vop_getpages_args *ap)
 	npages = btoc(count);
 
 	/*
-	 * If the requested page is partially valid, just return it and
-	 * allow the pager to zero-out the blanks.  Partially valid pages
-	 * can only occur at the file EOF.
+	 * If the last page is partially valid, just return it and allow
+	 * the pager to zero-out the blanks.  Partially valid pages can
+	 * only occur at the file EOF.
+	 *
+	 * XXXGL: is that true for FUSE, which is a local filesystem,
+	 * but still somewhat disconnected from the kernel?
 	 */
-
 	VM_OBJECT_WLOCK(vp->v_object);
-	fuse_vm_page_lock_queues();
-	if (pages[ap->a_reqpage]->valid != 0) {
-		for (i = 0; i < npages; ++i) {
-			if (i != ap->a_reqpage) {
-				fuse_vm_page_lock(pages[i]);
-				vm_page_free(pages[i]);
-				fuse_vm_page_unlock(pages[i]);
-			}
+	if (pages[npages - 1]->valid != 0) {
+		if (--npages == 0) {
+			VM_OBJECT_WUNLOCK(vp->v_object);
+			return (VM_PAGER_OK);
 		}
-		fuse_vm_page_unlock_queues();
-		VM_OBJECT_WUNLOCK(vp->v_object);
-		return 0;
-	}
-	fuse_vm_page_unlock_queues();
+		count = npages << PAGE_SHIFT;
+        }
 	VM_OBJECT_WUNLOCK(vp->v_object);
 
 	/*
@@ -1811,17 +1810,6 @@ fuse_vnop_getpages(struct vop_getpages_args *ap)
 
 	if (error && (uio.uio_resid == count)) {
 		FS_DEBUG("error %d\n", error);
-		VM_OBJECT_WLOCK(vp->v_object);
-		fuse_vm_page_lock_queues();
-		for (i = 0; i < npages; ++i) {
-			if (i != ap->a_reqpage) {
-				fuse_vm_page_lock(pages[i]);
-				vm_page_free(pages[i]);
-				fuse_vm_page_unlock(pages[i]);
-			}
-		}
-		fuse_vm_page_unlock_queues();
-		VM_OBJECT_WUNLOCK(vp->v_object);
 		return VM_PAGER_ERROR;
 	}
 	/*
@@ -1862,8 +1850,6 @@ fuse_vnop_getpages(struct vop_getpages_args *ap)
 			 */
 			;
 		}
-		if (i != ap->a_reqpage)
-			vm_page_readahead_finish(m);
 	}
 	fuse_vm_page_unlock_queues();
 	VM_OBJECT_WUNLOCK(vp->v_object);
diff --git a/sys/fs/nfsclient/nfs_clbio.c b/sys/fs/nfsclient/nfs_clbio.c
index 53ba7ef..56478680 100644
--- a/sys/fs/nfsclient/nfs_clbio.c
+++ b/sys/fs/nfsclient/nfs_clbio.c
@@ -101,6 +101,10 @@ ncl_getpages(struct vop_getpages_args *ap)
 	nmp = VFSTONFS(vp->v_mount);
 	pages = ap->a_m;
 	count = ap->a_count;
+	if (ap->a_rbehind)
+		*ap->a_rbehind = 0;
+	if (ap->a_rahead)
+		*ap->a_rahead = 0;
 
 	if ((object = vp->v_object) == NULL) {
 		ncl_printf("nfs_getpages: called with non-merged cache vnode??\n");
@@ -132,12 +136,18 @@ ncl_getpages(struct vop_getpages_args *ap)
 	 * If the requested page is partially valid, just return it and
 	 * allow the pager to zero-out the blanks.  Partially valid pages
 	 * can only occur at the file EOF.
+	 *
+	 * XXXGL: is that true for NFS, where short read can occur???
 	 */
-	if (pages[ap->a_reqpage]->valid != 0) {
-		vm_pager_free_nonreq(object, pages, ap->a_reqpage, npages,
-		    FALSE);
-		return (VM_PAGER_OK);
+	VM_OBJECT_WLOCK(object);
+	if (pages[npages - 1]->valid != 0) {
+		if (--npages == 0) {
+			VM_OBJECT_WUNLOCK(object);
+			return (VM_PAGER_OK);
+		}
+		count = npages << PAGE_SHIFT;
 	}
+	VM_OBJECT_WUNLOCK(object);
 
 	/*
 	 * We use only the kva address for the buffer, but this is extremely
@@ -167,8 +177,6 @@ ncl_getpages(struct vop_getpages_args *ap)
 
 	if (error && (uio.uio_resid == count)) {
 		ncl_printf("nfs_getpages: error %d\n", error);
-		vm_pager_free_nonreq(object, pages, ap->a_reqpage, npages,
-		    FALSE);
 		return (VM_PAGER_ERROR);
 	}
 
@@ -212,8 +220,6 @@ ncl_getpages(struct vop_getpages_args *ap)
 			 */
 			;
 		}
-		if (i != ap->a_reqpage)
-			vm_page_readahead_finish(m);
 	}
 	VM_OBJECT_WUNLOCK(object);
 	return (0);
diff --git a/sys/fs/smbfs/smbfs_io.c b/sys/fs/smbfs/smbfs_io.c
index a567ce6..5fe6f11 100644
--- a/sys/fs/smbfs/smbfs_io.c
+++ b/sys/fs/smbfs/smbfs_io.c
@@ -424,7 +424,7 @@ smbfs_getpages(ap)
 #ifdef SMBFS_RWGENERIC
 	return vop_stdgetpages(ap);
 #else
-	int i, error, nextoff, size, toff, npages, count, reqpage;
+	int i, error, nextoff, size, toff, npages, count;
 	struct uio uio;
 	struct iovec iov;
 	vm_offset_t kva;
@@ -436,7 +436,7 @@ smbfs_getpages(ap)
 	struct smbnode *np;
 	struct smb_cred *scred;
 	vm_object_t object;
-	vm_page_t *pages, m;
+	vm_page_t *pages;
 
 	vp = ap->a_vp;
 	if ((object = vp->v_object) == NULL) {
@@ -451,26 +451,25 @@ smbfs_getpages(ap)
 	pages = ap->a_m;
 	count = ap->a_count;
 	npages = btoc(count);
-	reqpage = ap->a_reqpage;
+	if (ap->a_rbehind)
+		*ap->a_rbehind = 0;
+	if (ap->a_rahead)
+		*ap->a_rahead = 0;
 
 	/*
 	 * If the requested page is partially valid, just return it and
 	 * allow the pager to zero-out the blanks.  Partially valid pages
 	 * can only occur at the file EOF.
+	 *
+	 * XXXGL: is that true for SMB filesystem?
 	 */
-	m = pages[reqpage];
-
 	VM_OBJECT_WLOCK(object);
-	if (m->valid != 0) {
-		for (i = 0; i < npages; ++i) {
-			if (i != reqpage) {
-				vm_page_lock(pages[i]);
-				vm_page_free(pages[i]);
-				vm_page_unlock(pages[i]);
-			}
+	if (pages[npages - 1]->valid != 0) {
+		if (--npages == 0) {
+			VM_OBJECT_WUNLOCK(object);
+			return (VM_PAGER_OK);
 		}
-		VM_OBJECT_WUNLOCK(object);
-		return 0;
+		count = npages << PAGE_SHIFT;
 	}
 	VM_OBJECT_WUNLOCK(object);
 
@@ -500,22 +499,14 @@ smbfs_getpages(ap)
 
 	relpbuf(bp, &smbfs_pbuf_freecnt);
 
-	VM_OBJECT_WLOCK(object);
 	if (error && (uio.uio_resid == count)) {
 		printf("smbfs_getpages: error %d\n",error);
-		for (i = 0; i < npages; i++) {
-			if (reqpage != i) {
-				vm_page_lock(pages[i]);
-				vm_page_free(pages[i]);
-				vm_page_unlock(pages[i]);
-			}
-		}
-		VM_OBJECT_WUNLOCK(object);
 		return VM_PAGER_ERROR;
 	}
 
 	size = count - uio.uio_resid;
 
+	VM_OBJECT_WLOCK(object);
 	for (i = 0, toff = 0; i < npages; i++, toff = nextoff) {
 		vm_page_t m;
 		nextoff = toff + PAGE_SIZE;
@@ -544,9 +535,6 @@ smbfs_getpages(ap)
 			 */
 			;
 		}
-
-		if (i != reqpage)
-			vm_page_readahead_finish(m);
 	}
 	VM_OBJECT_WUNLOCK(object);
 	return 0;
diff --git a/sys/fs/tmpfs/tmpfs_subr.c b/sys/fs/tmpfs/tmpfs_subr.c
index fa489b2..fcc8782 100644
--- a/sys/fs/tmpfs/tmpfs_subr.c
+++ b/sys/fs/tmpfs/tmpfs_subr.c
@@ -1370,7 +1370,8 @@ retry:
 					VM_OBJECT_WLOCK(uobj);
 					goto retry;
 				} else if (m->valid != VM_PAGE_BITS_ALL)
-					rv = vm_pager_get_pages(uobj, &m, 1, 0);
+					rv = vm_pager_get_pages(uobj, &m, 1,
+					    NULL, NULL);
 				else
 					/* A cached page was reactivated. */
 					rv = VM_PAGER_OK;