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unionfs: cache upper/lower mount objects

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Store the upper/lower FS mount objects in unionfs per-mount data and
use these instead of the v_mount field of the upper/lower root
vnodes.  As described in the referenced PR, it is unsafe to access this
field on the unionfs unmount path as ZFS rollback may have obliterated
the v_mount field of the upper or lower root vnode.  Use these stored
objects to slightly simplify other code that needs access to the
upper/lower mount objects as well.

PR:		275870
Reported by:	Karlo Miličević <karlo98.m@gmail.com>
Tested by:	Karlo Miličević <karlo98.m@gmail.com>
Reviewed by:	kib (prior version), olce
MFC after:	2 weeks
Differential Revision: https://reviews.freebsd.org/D43815
This commit is contained in:
Jason A. Harmening 2023-12-22 14:13:35 -06:00
parent 5f7312a0d7
commit cc3ec9f759
3 changed files with 24 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
sys/fs/unionfs/union.h
View file

@ -51,6 +51,8 @@ typedef enum _unionfs_whitemode {
} unionfs_whitemode;
struct unionfs_mount {
struct mount *um_lowermp; /* MNT_REFed lower mount object */
struct mount *um_uppermp; /* MNT_REFed upper mount object */
struct vnode *um_lowervp; /* VREFed once */
struct vnode *um_uppervp; /* VREFed once */
struct vnode *um_rootvp; /* ROOT vnode */

37
sys/fs/unionfs/union_vfsops.c
View file

@ -71,7 +71,6 @@ static struct vfsops unionfs_vfsops;
static int
unionfs_domount(struct mount *mp)
{
struct mount *lowermp, *uppermp;
struct vnode *lowerrootvp;
struct vnode *upperrootvp;
struct unionfs_mount *ump;
@ -303,18 +302,18 @@ unionfs_domount(struct mount *mp)
* reused until that happens. We assume the caller holds a reference
* to lowerrootvp as it is the mount's covered vnode.
*/
lowermp = vfs_register_upper_from_vp(ump->um_lowervp, mp,
ump->um_lowermp = vfs_register_upper_from_vp(ump->um_lowervp, mp,
&ump->um_lower_link);
uppermp = vfs_register_upper_from_vp(ump->um_uppervp, mp,
ump->um_uppermp = vfs_register_upper_from_vp(ump->um_uppervp, mp,
&ump->um_upper_link);
vrele(upperrootvp);
if (lowermp == NULL || uppermp == NULL) {
if (lowermp != NULL)
vfs_unregister_upper(lowermp, &ump->um_lower_link);
if (uppermp != NULL)
vfs_unregister_upper(uppermp, &ump->um_upper_link);
if (ump->um_lowermp == NULL || ump->um_uppermp == NULL) {
if (ump->um_lowermp != NULL)
vfs_unregister_upper(ump->um_lowermp, &ump->um_lower_link);
if (ump->um_uppermp != NULL)
vfs_unregister_upper(ump->um_uppermp, &ump->um_upper_link);
vflush(mp, 1, FORCECLOSE, curthread);
free(ump, M_UNIONFSMNT);
mp->mnt_data = NULL;
@ -346,8 +345,8 @@ unionfs_domount(struct mount *mp)
}
MNT_ILOCK(mp);
if ((lowermp->mnt_flag & MNT_LOCAL) != 0 &&
(uppermp->mnt_flag & MNT_LOCAL) != 0)
if ((ump->um_lowermp->mnt_flag & MNT_LOCAL) != 0 &&
(ump->um_uppermp->mnt_flag & MNT_LOCAL) != 0)
mp->mnt_flag |= MNT_LOCAL;
mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNIONFS;
MNT_IUNLOCK(mp);
@ -400,8 +399,8 @@ unionfs_unmount(struct mount *mp, int mntflags)
vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
VOP_UNLOCK(mp->mnt_vnodecovered);
vfs_unregister_upper(ump->um_lowervp->v_mount, &ump->um_lower_link);
vfs_unregister_upper(ump->um_uppervp->v_mount, &ump->um_upper_link);
vfs_unregister_upper(ump->um_lowermp, &ump->um_lower_link);
vfs_unregister_upper(ump->um_uppermp, &ump->um_upper_link);
free(ump, M_UNIONFSMNT);
mp->mnt_data = NULL;
@ -439,7 +438,11 @@ unionfs_quotactl(struct mount *mp, int cmd, uid_t uid, void *arg,
bool unbusy;
ump = MOUNTTOUNIONFSMOUNT(mp);
uppermp = atomic_load_ptr(&ump->um_uppervp->v_mount);
/*
* Issue a volatile load of um_uppermp here, as the mount may be
* torn down after we call vfs_unbusy().
*/
uppermp = atomic_load_ptr(&ump->um_uppermp);
KASSERT(*mp_busy == true, ("upper mount not busy"));
/*
* See comment in sys_quotactl() for an explanation of why the
@ -479,7 +482,7 @@ unionfs_statfs(struct mount *mp, struct statfs *sbp)
mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO);
error = VFS_STATFS(ump->um_lowervp->v_mount, mstat);
error = VFS_STATFS(ump->um_lowermp, mstat);
if (error) {
free(mstat, M_STATFS);
return (error);
@ -491,7 +494,7 @@ unionfs_statfs(struct mount *mp, struct statfs *sbp)
lbsize = mstat->f_bsize;
error = VFS_STATFS(ump->um_uppervp->v_mount, mstat);
error = VFS_STATFS(ump->um_uppermp, mstat);
if (error) {
free(mstat, M_STATFS);
return (error);
@ -558,10 +561,10 @@ unionfs_extattrctl(struct mount *mp, int cmd, struct vnode *filename_vp,
unp = VTOUNIONFS(filename_vp);
if (unp->un_uppervp != NULLVP) {
return (VFS_EXTATTRCTL(ump->um_uppervp->v_mount, cmd,
return (VFS_EXTATTRCTL(ump->um_uppermp, cmd,
unp->un_uppervp, namespace, attrname));
} else {
return (VFS_EXTATTRCTL(ump->um_lowervp->v_mount, cmd,
return (VFS_EXTATTRCTL(ump->um_lowermp, cmd,
unp->un_lowervp, namespace, attrname));
}
}

4
sys/fs/unionfs/union_vnops.c
View file

@ -764,7 +764,7 @@ unionfs_access(struct vop_access_args *ap)
if (lvp != NULLVP) {
if (accmode & VWRITE) {
if (ump->um_uppervp->v_mount->mnt_flag & MNT_RDONLY) {
if ((ump->um_uppermp->mnt_flag & MNT_RDONLY) != 0) {
switch (ap->a_vp->v_type) {
case VREG:
case VDIR:
@ -835,7 +835,7 @@ unionfs_getattr(struct vop_getattr_args *ap)
error = VOP_GETATTR(lvp, ap->a_vap, ap->a_cred);
if (error == 0 && !(ump->um_uppervp->v_mount->mnt_flag & MNT_RDONLY)) {
if (error == 0 && (ump->um_uppermp->mnt_flag & MNT_RDONLY) == 0) {
/* correct the attr toward shadow file/dir. */
if (ap->a_vp->v_type == VREG || ap->a_vp->v_type == VDIR) {
unionfs_create_uppervattr_core(ump, ap->a_vap, &va, td);