svn commit: r355211 - in head/sys: cddl/contrib/opensolaris/uts/common/fs/zfs kern sys

[Konstantin Belousov]

Author: kib
Date: Fri Nov 29 14:02:32 2019
New Revision: 355211
URL: https://svnweb.freebsd.org/changeset/base/355211

Log:
  Add a VN_OPEN_INVFS flag.
  
  vn_open_cred() assumes that it is called from the top-level of a VFS
  syscall.  Writers must call bwillwrite() before locking any VFS
  resource to wait for cleanup of dirty buffers.
  
  ZFS getextattr() and setextattr() VOPs do call vn_open_cred(), which
  results in wait for unrelated buffers while owning ZFS vnode lock (and
  ZFS does not use buffer cache).  VN_OPEN_INVFS allows caller to skip
  bwillwrite.
  
  Note that ZFS is still incorrect there, because it starts write on an
  mp and locks a vnode while holding another vnode lock.
  
  Reported by:	Willem Jan Withagen <wjw at digiware.nl>
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
  head/sys/kern/vfs_vnops.c
  head/sys/sys/vnode.h

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Fri Nov 29 13:55:56 2019	(r355210)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Fri Nov 29 14:02:32 2019	(r355211)
@@ -5490,7 +5490,7 @@ vop_getextattr {
 	flags = FREAD;
 	NDINIT_ATVP(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, attrname,
 	    xvp, td);
-	error = vn_open_cred(&nd, &flags, 0, 0, ap->a_cred, NULL);
+	error = vn_open_cred(&nd, &flags, VN_OPEN_INVFS, 0, ap->a_cred, NULL);
 	vp = nd.ni_vp;
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	if (error != 0) {
@@ -5627,7 +5627,8 @@ vop_setextattr {
 	flags = FFLAGS(O_WRONLY | O_CREAT);
 	NDINIT_ATVP(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, attrname,
 	    xvp, td);
-	error = vn_open_cred(&nd, &flags, 0600, 0, ap->a_cred, NULL);
+	error = vn_open_cred(&nd, &flags, 0600, VN_OPEN_INVFS, ap->a_cred,
+	    NULL);
 	vp = nd.ni_vp;
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	if (error != 0) {

Modified: head/sys/kern/vfs_vnops.c
==============================================================================
--- head/sys/kern/vfs_vnops.c	Fri Nov 29 13:55:56 2019	(r355210)
+++ head/sys/kern/vfs_vnops.c	Fri Nov 29 14:02:32 2019	(r355211)
@@ -219,7 +219,8 @@ restart:
 			ndp->ni_cnd.cn_flags |= AUDITVNODE1;
 		if (vn_open_flags & VN_OPEN_NOCAPCHECK)
 			ndp->ni_cnd.cn_flags |= NOCAPCHECK;
-		bwillwrite();
+		if ((vn_open_flags & VN_OPEN_INVFS) == 0)
+			bwillwrite();
 		if ((error = namei(ndp)) != 0)
 			return (error);
 		if (ndp->ni_vp == NULL) {

Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h	Fri Nov 29 13:55:56 2019	(r355210)
+++ head/sys/sys/vnode.h	Fri Nov 29 14:02:32 2019	(r355211)
@@ -579,6 +579,7 @@ typedef void vop_getpages_iodone_t(void *, vm_page_t *
 #define	VN_OPEN_NOAUDIT		0x00000001
 #define	VN_OPEN_NOCAPCHECK	0x00000002
 #define	VN_OPEN_NAMECACHE	0x00000004
+#define	VN_OPEN_INVFS		0x00000008
 
 /*
  * Public vnode manipulation functions.