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Date:      Sun, 18 Aug 2019 18:40:12 +0000 (UTC)
From:      Mateusz Guzik <mjg@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r351193 - head/sys/kern
Message-ID:  <201908181840.x7IIeCAL055888@repo.freebsd.org>
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Author: mjg
Date: Sun Aug 18 18:40:12 2019
New Revision: 351193
URL: https://svnweb.freebsd.org/changeset/base/351193

Log:
  vfs: stop always overwriting ->mnt_stat in VFS_STATFS
  
  The struct is already populated on each mount (and remount). Fields are either
  constant or not used by filesystem in the first place.
  
  Some infrequently used functions use it to avoid having to allocate a new buffer
  and are left alone.
  
  The current code results in an avoidable copying single-threaded and significant
  cache line bouncing multithreaded
  
  While here deduplicate initial filling of the struct.
  
  Reviewed by:	kib
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D21317

Modified:
  head/sys/kern/vfs_mount.c
  head/sys/kern/vfs_syscalls.c

Modified: head/sys/kern/vfs_mount.c
==============================================================================
--- head/sys/kern/vfs_mount.c	Sun Aug 18 17:12:06 2019	(r351192)
+++ head/sys/kern/vfs_mount.c	Sun Aug 18 18:40:12 2019	(r351193)
@@ -1831,12 +1831,15 @@ vfs_copyopt(struct vfsoptlist *opts, const char *name,
 int
 __vfs_statfs(struct mount *mp, struct statfs *sbp)
 {
-	int error;
 
-	error = mp->mnt_op->vfs_statfs(mp, &mp->mnt_stat);
-	if (sbp != &mp->mnt_stat)
-		*sbp = mp->mnt_stat;
-	return (error);
+	/*
+	 * Set these in case the underlying filesystem fails to do so.
+	 */
+	sbp->f_version = STATFS_VERSION;
+	sbp->f_namemax = NAME_MAX;
+	sbp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
+
+	return (mp->mnt_op->vfs_statfs(mp, sbp));
 }
 
 void

Modified: head/sys/kern/vfs_syscalls.c
==============================================================================
--- head/sys/kern/vfs_syscalls.c	Sun Aug 18 17:12:06 2019	(r351192)
+++ head/sys/kern/vfs_syscalls.c	Sun Aug 18 18:40:12 2019	(r351193)
@@ -248,7 +248,6 @@ statfs_scale_blocks(struct statfs *sf, long max_size)
 static int
 kern_do_statfs(struct thread *td, struct mount *mp, struct statfs *buf)
 {
-	struct statfs *sp;
 	int error;
 
 	if (mp == NULL)
@@ -262,17 +261,9 @@ kern_do_statfs(struct thread *td, struct mount *mp, st
 	if (error != 0)
 		goto out;
 #endif
-	/*
-	 * Set these in case the underlying filesystem fails to do so.
-	 */
-	sp = &mp->mnt_stat;
-	sp->f_version = STATFS_VERSION;
-	sp->f_namemax = NAME_MAX;
-	sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
-	error = VFS_STATFS(mp, sp);
+	error = VFS_STATFS(mp, buf);
 	if (error != 0)
 		goto out;
-	*buf = *sp;
 	if (priv_check(td, PRIV_VFS_GENERATION)) {
 		buf->f_fsid.val[0] = buf->f_fsid.val[1] = 0;
 		prison_enforce_statfs(td->td_ucred, mp, buf);
@@ -476,13 +467,6 @@ restart:
 		if (sfsp != NULL && count < maxcount) {
 			sp = &mp->mnt_stat;
 			/*
-			 * Set these in case the underlying filesystem
-			 * fails to do so.
-			 */
-			sp->f_version = STATFS_VERSION;
-			sp->f_namemax = NAME_MAX;
-			sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
-			/*
 			 * If MNT_NOWAIT is specified, do not refresh
 			 * the fsstat cache.
 			 */
@@ -4545,7 +4529,6 @@ sys_fhstatfs(struct thread *td, struct fhstatfs_args *
 int
 kern_fhstatfs(struct thread *td, fhandle_t fh, struct statfs *buf)
 {
-	struct statfs *sp;
 	struct mount *mp;
 	struct vnode *vp;
 	int error;
@@ -4569,16 +4552,7 @@ kern_fhstatfs(struct thread *td, fhandle_t fh, struct 
 	if (error != 0)
 		goto out;
 #endif
-	/*
-	 * Set these in case the underlying filesystem fails to do so.
-	 */
-	sp = &mp->mnt_stat;
-	sp->f_version = STATFS_VERSION;
-	sp->f_namemax = NAME_MAX;
-	sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
-	error = VFS_STATFS(mp, sp);
-	if (error == 0)
-		*buf = *sp;
+	error = VFS_STATFS(mp, buf);
 out:
 	vfs_unbusy(mp);
 	return (error);

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