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Date:      Tue, 4 Feb 2020 19:05:59 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r357515 - head/sys/fs/tmpfs
Message-ID:  <202002041905.014J5xZ4040189@repo.freebsd.org>
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Author: kib
Date: Tue Feb  4 19:05:58 2020
New Revision: 357515
URL: https://svnweb.freebsd.org/changeset/base/357515

Log:
  tmpfs: add nomtime mount option,
  
  which disables tracking mtime updates due to writes through the shared
  mapped areas backed by tmpfs files.  This removes periodic scans which
  downgrades rw mapped pages to ro to note the writes.
  
  Suggested by:	mjg
  Reviewed by:	markj
  Tested by:	pho
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  Differential revision:	https://reviews.freebsd.org/D23432

Modified:
  head/sys/fs/tmpfs/tmpfs.h
  head/sys/fs/tmpfs/tmpfs_vfsops.c

Modified: head/sys/fs/tmpfs/tmpfs.h
==============================================================================
--- head/sys/fs/tmpfs/tmpfs.h	Tue Feb  4 19:03:37 2020	(r357514)
+++ head/sys/fs/tmpfs/tmpfs.h	Tue Feb  4 19:05:58 2020	(r357515)
@@ -382,6 +382,8 @@ struct tmpfs_mount {
 	bool			tm_ronly;
 	/* Do not use namecache. */
 	bool			tm_nonc;
+	/* Do not update mtime on writes through mmaped areas. */
+	bool			tm_nomtime;
 };
 #define	TMPFS_LOCK(tm) mtx_lock(&(tm)->tm_allnode_lock)
 #define	TMPFS_UNLOCK(tm) mtx_unlock(&(tm)->tm_allnode_lock)

Modified: head/sys/fs/tmpfs/tmpfs_vfsops.c
==============================================================================
--- head/sys/fs/tmpfs/tmpfs_vfsops.c	Tue Feb  4 19:03:37 2020	(r357514)
+++ head/sys/fs/tmpfs/tmpfs_vfsops.c	Tue Feb  4 19:05:58 2020	(r357515)
@@ -92,20 +92,19 @@ static void	tmpfs_susp_clean(struct mount *);
 
 static const char *tmpfs_opts[] = {
 	"from", "size", "maxfilesize", "inodes", "uid", "gid", "mode", "export",
-	"union", "nonc", NULL
+	"union", "nonc", "nomtime", NULL
 };
 
 static const char *tmpfs_updateopts[] = {
-	"from", "export", "size", NULL
+	"from", "export", "nomtime", "size", NULL
 };
 
 /*
- * Handle updates of time from writes to mmaped regions.  Use
- * MNT_VNODE_FOREACH_ALL instead of MNT_VNODE_FOREACH_LAZY, since
+ * Handle updates of time from writes to mmaped regions, if allowed.
+ * Use MNT_VNODE_FOREACH_ALL instead of MNT_VNODE_FOREACH_LAZY, since
  * unmap of the tmpfs-backed vnode does not call vinactive(), due to
- * vm object type is OBJT_SWAP.
- * If lazy, only handle delayed update of mtime due to the writes to
- * mapped files.
+ * vm object type is OBJT_SWAP.  If lazy, only handle delayed update
+ * of mtime due to the writes to mapped files.
  */
 static void
 tmpfs_update_mtime(struct mount *mp, bool lazy)
@@ -113,6 +112,8 @@ tmpfs_update_mtime(struct mount *mp, bool lazy)
 	struct vnode *vp, *mvp;
 	struct vm_object *obj;
 
+	if (VFS_TO_TMPFS(mp)->tm_nomtime)
+		return;
 	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
 		if (vp->v_type != VREG) {
 			VI_UNLOCK(vp);
@@ -327,7 +328,7 @@ tmpfs_mount(struct mount *mp)
 	struct tmpfs_mount *tmp;
 	struct tmpfs_node *root;
 	int error;
-	bool nonc;
+	bool nomtime, nonc;
 	/* Size counters. */
 	u_quad_t pages;
 	off_t nodes_max, size_max, maxfilesize;
@@ -370,6 +371,8 @@ tmpfs_mount(struct mount *mp)
 			mp->mnt_flag &= ~MNT_RDONLY;
 			MNT_IUNLOCK(mp);
 		}
+		tmp->tm_nomtime = vfs_getopt(mp->mnt_optnew, "nomtime", NULL,
+		    0) == 0;
 		return (0);
 	}
 
@@ -395,6 +398,7 @@ tmpfs_mount(struct mount *mp)
 	if (vfs_getopt_size(mp->mnt_optnew, "maxfilesize", &maxfilesize) != 0)
 		maxfilesize = 0;
 	nonc = vfs_getopt(mp->mnt_optnew, "nonc", NULL, NULL) == 0;
+	nomtime = vfs_getopt(mp->mnt_optnew, "nomtime", NULL, NULL) == 0;
 
 	/* Do not allow mounts if we do not have enough memory to preserve
 	 * the minimum reserved pages. */
@@ -441,6 +445,7 @@ tmpfs_mount(struct mount *mp)
 	new_unrhdr64(&tmp->tm_ino_unr, 2);
 	tmp->tm_ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
 	tmp->tm_nonc = nonc;
+	tmp->tm_nomtime = nomtime;
 
 	/* Allocate the root node. */
 	error = tmpfs_alloc_node(mp, tmp, VDIR, root_uid, root_gid,

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