posix_fallocate: push vnop implementation into the fileop layer

This opens the door for other descriptor types to implement
posix_fallocate(2) as needed.

Reviewed by:	kib, bcr (manpages)
Differential Revision:	https://reviews.freebsd.org/D23042

1 files changed, 59 insertions, 0 deletions

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index f15ea0969b7e..61edb3165e01 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -103,6 +103,7 @@ static fo_kqfilter_t	vn_kqfilter;
 static fo_stat_t	vn_statfile;
 static fo_close_t	vn_closefile;
 static fo_mmap_t	vn_mmap;
+static fo_fallocate_t	vn_fallocate;
 
 struct 	fileops vnops = {
 	.fo_read = vn_io_fault,
@@ -119,6 +120,7 @@ struct 	fileops vnops = {
 	.fo_seek = vn_seek,
 	.fo_fill_kinfo = vn_fill_kinfo,
 	.fo_mmap = vn_mmap,
+	.fo_fallocate = vn_fallocate,
 	.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
 };
 
@@ -3150,3 +3152,60 @@ out:
 	free(dat, M_TEMP);
 	return (error);
 }
+
+static int
+vn_fallocate(struct file *fp, off_t offset, off_t len, struct thread *td)
+{
+	struct mount *mp;
+	struct vnode *vp;
+	off_t olen, ooffset;
+	int error;
+#ifdef AUDIT
+	int audited_vnode1 = 0;
+#endif
+
+	vp = fp->f_vnode;
+	if (vp->v_type != VREG)
+		return (ENODEV);
+
+	/* Allocating blocks may take a long time, so iterate. */
+	for (;;) {
+		olen = len;
+		ooffset = offset;
+
+		bwillwrite();
+		mp = NULL;
+		error = vn_start_write(vp, &mp, V_WAIT | PCATCH);
+		if (error != 0)
+			break;
+		error = vn_lock(vp, LK_EXCLUSIVE);
+		if (error != 0) {
+			vn_finished_write(mp);
+			break;
+		}
+#ifdef AUDIT
+		if (!audited_vnode1) {
+			AUDIT_ARG_VNODE1(vp);
+			audited_vnode1 = 1;
+		}
+#endif
+#ifdef MAC
+		error = mac_vnode_check_write(td->td_ucred, fp->f_cred, vp);
+		if (error == 0)
+#endif
+			error = VOP_ALLOCATE(vp, &offset, &len);
+		VOP_UNLOCK(vp);
+		vn_finished_write(mp);
+
+		if (olen + ooffset != offset + len) {
+			panic("offset + len changed from %jx/%jx to %jx/%jx",
+			    ooffset, olen, offset, len);
+		}
+		if (error != 0 || len == 0)
+			break;
+		KASSERT(olen > len, ("Iteration did not make progress?"));
+		maybe_yield();
+	}
+
+	return (error);
+}