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Add a VN_OPEN_INVFS flag.

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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@digiware.nl>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2019-11-29 14:02:32 +00:00
parent 9698d99230
commit fdc6b10d44
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=355211
3 changed files with 6 additions and 3 deletions
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5
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
View File

@ -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) {

3
sys/kern/vfs_vnops.c
View File

@ -219,7 +219,8 @@ vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
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) {

1
sys/sys/vnode.h
View File

@ -579,6 +579,7 @@ typedef void vop_getpages_iodone_t(void *, vm_page_t *, int, int);
#define VN_OPEN_NOAUDIT 0x00000001
#define VN_OPEN_NOCAPCHECK 0x00000002
#define VN_OPEN_NAMECACHE 0x00000004
#define VN_OPEN_INVFS 0x00000008
/*
* Public vnode manipulation functions.