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lockf: ensure atomicity of lockf for open(O_CREAT|O_EXCL|O_EXLOCK)

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or EX_SHLOCK.  Do it by setting a vnode iflag indicating that the locking
exclusive open is in progress, and not allowing F_LOCK request to make
a progress until the first open finishes.

Requested by:	mckusick
Reviewed by:	markj, mckusick
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D28697
This commit is contained in:
Konstantin Belousov 2021-01-30 01:48:55 +02:00
parent 351d06eeb5
commit fa3bd463ce
4 changed files with 38 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
sys/kern/vfs_default.c
View file

@ -423,10 +423,25 @@ int
vop_stdadvlock(struct vop_advlock_args *ap)
{
struct vnode *vp;
struct mount *mp;
struct vattr vattr;
int error;
vp = ap->a_vp;
/*
* Provide atomicity of open(O_CREAT | O_EXCL | O_EXLOCK) for
* local filesystems. See vn_open_cred() for reciprocal part.
*/
mp = vp->v_mount;
if (mp != NULL && (mp->mnt_flag & MNT_LOCAL) != 0 &&
ap->a_op == F_SETLK && (ap->a_flags & F_FIRSTOPEN) == 0) {
VI_LOCK(vp);
while ((vp->v_iflag & VI_FOPENING) != 0)
msleep(vp, VI_MTX(vp), PLOCK, "lockfo", 0);
VI_UNLOCK(vp);
}
if (ap->a_fl->l_whence == SEEK_END) {
/*
* The NFSv4 server must avoid doing a vn_lock() here, since it

23
sys/kern/vfs_vnops.c
View file

@ -228,8 +228,10 @@ vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
struct vattr vat;
struct vattr *vap = &vat;
int fmode, error;
bool first_open;
restart:
first_open = false;
fmode = *flagp;
if ((fmode & (O_CREAT | O_EXCL | O_DIRECTORY)) == (O_CREAT |
O_EXCL | O_DIRECTORY))
@ -275,8 +277,16 @@ vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
#endif
error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
&ndp->ni_cnd, vap);
VOP_VPUT_PAIR(ndp->ni_dvp, error == 0 ? &ndp->ni_vp :
NULL, false);
vp = ndp->ni_vp;
if (error == 0 && (fmode & O_EXCL) != 0 &&
(fmode & (O_EXLOCK | O_SHLOCK)) != 0) {
VI_LOCK(vp);
vp->v_iflag |= VI_FOPENING;
VI_UNLOCK(vp);
first_open = true;
}
VOP_VPUT_PAIR(ndp->ni_dvp, error == 0 ? &vp : NULL,
false);
vn_finished_write(mp);
if (error) {
NDFREE(ndp, NDF_ONLY_PNBUF);
@ -287,7 +297,6 @@ vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
return (error);
}
fmode &= ~O_TRUNC;
vp = ndp->ni_vp;
} else {
if (ndp->ni_dvp == ndp->ni_vp)
vrele(ndp->ni_dvp);
@ -317,6 +326,12 @@ vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
vp = ndp->ni_vp;
}
error = vn_open_vnode(vp, fmode, cred, td, fp);
if (first_open) {
VI_LOCK(vp);
vp->v_iflag &= ~VI_FOPENING;
wakeup(vp);
VI_UNLOCK(vp);
}
if (error)
goto bad;
*flagp = fmode;
@ -352,6 +367,8 @@ vn_open_vnode_advlock(struct vnode *vp, int fmode, struct file *fp)
type = F_FLOCK;
if ((fmode & FNONBLOCK) == 0)
type |= F_WAIT;
if ((fmode & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
type |= F_FIRSTOPEN;
error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, type);
if (error == 0)
fp->f_flag |= FHASLOCK;

1
sys/sys/fcntl.h
View file

@ -287,6 +287,7 @@ typedef __pid_t pid_t;
#define F_POSIX 0x040 /* Use POSIX semantics for lock */
#define F_REMOTE 0x080 /* Lock owner is remote NFS client */
#define F_NOINTR 0x100 /* Ignore signals when waiting */
#define F_FIRSTOPEN 0x200 /* First right to advlock file */
#endif
/*

2
sys/sys/vnode.h
View file

@ -254,6 +254,8 @@ struct xvnode {
#define VI_DOINGINACT 0x0004 /* VOP_INACTIVE is in progress */
#define VI_OWEINACT 0x0008 /* Need to call inactive */
#define VI_DEFINACT 0x0010 /* deferred inactive */
#define VI_FOPENING 0x0020 /* In open, with opening process having the
first right to advlock file */
#define VV_ROOT 0x0001 /* root of its filesystem */
#define VV_ISTTY 0x0002 /* vnode represents a tty */