From b6758fe7e231c65eaa8f1ea0e1defff53eb890e8 Mon Sep 17 00:00:00 2001
From: markj <markj@FreeBSD.org>
Date: Mon, 29 Apr 2019 13:23:32 +0000
Subject: [PATCH] Stop checking TD_IDLETHREAD() in buffer cache routines.

These predicates are vestigal and cannot be true today.  For example,
idle threads are not allowed to acquire locks.

Also cache curthread in breada().

No functional change intended.

Reviewed by:	kib, mckusick
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D20066
---
 sys/kern/vfs_bio.c | 48 ++++++++++++++++++++--------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 30bc1d957ec..3f5c72919f2 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -2073,8 +2073,11 @@ breada(struct vnode * vp, daddr_t * rablkno, int * rabsize, int cnt,
     struct ucred * cred, int flags, void (*ckhashfunc)(struct buf *))
 {
 	struct buf *rabp;
+	struct thread *td;
 	int i;
 
+	td = curthread;
+
 	for (i = 0; i < cnt; i++, rablkno++, rabsize++) {
 		if (inmem(vp, *rablkno))
 			continue;
@@ -2083,16 +2086,14 @@ breada(struct vnode * vp, daddr_t * rablkno, int * rabsize, int cnt,
 			brelse(rabp);
 			continue;
 		}
-		if (!TD_IS_IDLETHREAD(curthread)) {
 #ifdef RACCT
-			if (racct_enable) {
-				PROC_LOCK(curproc);
-				racct_add_buf(curproc, rabp, 0);
-				PROC_UNLOCK(curproc);
-			}
-#endif /* RACCT */
-			curthread->td_ru.ru_inblock++;
+		if (racct_enable) {
+			PROC_LOCK(curproc);
+			racct_add_buf(curproc, rabp, 0);
+			PROC_UNLOCK(curproc);
 		}
+#endif /* RACCT */
+		td->td_ru.ru_inblock++;
 		rabp->b_flags |= B_ASYNC;
 		rabp->b_flags &= ~B_INVAL;
 		if ((flags & GB_CKHASH) != 0) {
@@ -2148,16 +2149,14 @@ breadn_flags(struct vnode *vp, daddr_t blkno, int size, daddr_t *rablkno,
 	 */
 	readwait = 0;
 	if ((bp->b_flags & B_CACHE) == 0) {
-		if (!TD_IS_IDLETHREAD(td)) {
 #ifdef RACCT
-			if (racct_enable) {
-				PROC_LOCK(td->td_proc);
-				racct_add_buf(td->td_proc, bp, 0);
-				PROC_UNLOCK(td->td_proc);
-			}
-#endif /* RACCT */
-			td->td_ru.ru_inblock++;
+		if (racct_enable) {
+			PROC_LOCK(td->td_proc);
+			racct_add_buf(td->td_proc, bp, 0);
+			PROC_UNLOCK(td->td_proc);
 		}
+#endif /* RACCT */
+		td->td_ru.ru_inblock++;
 		bp->b_iocmd = BIO_READ;
 		bp->b_flags &= ~B_INVAL;
 		if ((flags & GB_CKHASH) != 0) {
@@ -2258,16 +2257,14 @@ bufwrite(struct buf *bp)
 	bp->b_runningbufspace = bp->b_bufsize;
 	space = atomic_fetchadd_long(&runningbufspace, bp->b_runningbufspace);
 
-	if (!TD_IS_IDLETHREAD(curthread)) {
 #ifdef RACCT
-		if (racct_enable) {
-			PROC_LOCK(curproc);
-			racct_add_buf(curproc, bp, 1);
-			PROC_UNLOCK(curproc);
-		}
-#endif /* RACCT */
-		curthread->td_ru.ru_oublock++;
+	if (racct_enable) {
+		PROC_LOCK(curproc);
+		racct_add_buf(curproc, bp, 1);
+		PROC_UNLOCK(curproc);
 	}
+#endif /* RACCT */
+	curthread->td_ru.ru_oublock++;
 	if (oldflags & B_ASYNC)
 		BUF_KERNPROC(bp);
 	bp->b_iooffset = dbtob(bp->b_blkno);
@@ -4019,9 +4016,6 @@ getblkx(struct vnode *vp, daddr_t blkno, int size, int slpflag, int slptimeo,
 		 */
 		if (flags & GB_NOCREAT)
 			return (EEXIST);
-		if (bdomain[bo->bo_domain].bd_freebuffers == 0 &&
-		    TD_IS_IDLETHREAD(curthread))
-			return (EBUSY);
 
 		bsize = vn_isdisk(vp, NULL) ? DEV_BSIZE : bo->bo_bsize;
 		KASSERT(bsize != 0, ("bsize == 0, check bo->bo_bsize"));
-- 
2.45.0