git: 5e806288f0c7 - stable/14 - unionfs: cache upper/lower mount objects
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Date: Mon, 04 Mar 2024 18:51:48 UTC
The branch stable/14 has been updated by jah:
URL: https://cgit.FreeBSD.org/src/commit/?id=5e806288f0c702e3f35efcf4972a97f0cf7b5676
commit 5e806288f0c702e3f35efcf4972a97f0cf7b5676
Author: Jason A. Harmening <jah@FreeBSD.org>
AuthorDate: 2023-12-22 20:13:35 +0000
Commit: Jason A. Harmening <jah@FreeBSD.org>
CommitDate: 2024-03-04 18:31:49 +0000
unionfs: cache upper/lower mount objects
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
Differential Revision: https://reviews.freebsd.org/D43815
(cherry picked from commit cc3ec9f7597882d36ee487fd436d1b90bed0ebfd)
---
sys/fs/unionfs/union.h | 2 ++
sys/fs/unionfs/union_vfsops.c | 37 ++++++++++++++++++++-----------------
sys/fs/unionfs/union_vnops.c | 4 ++--
3 files changed, 24 insertions(+), 19 deletions(-)
diff --git a/sys/fs/unionfs/union.h b/sys/fs/unionfs/union.h
index cbbb00a68c8a..6c7db47ff209 100644
--- a/sys/fs/unionfs/union.h
+++ b/sys/fs/unionfs/union.h
@@ -53,6 +53,8 @@ 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 */
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
index c717b048c6ab..4dff07eccaba 100644
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -73,7 +73,6 @@ 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;
@@ -305,18 +304,18 @@ 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;
@@ -348,8 +347,8 @@ 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 |
(ump->um_uppermp->mnt_kern_flag & MNTK_SHARED_WRITES);
@@ -403,8 +402,8 @@ 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;
@@ -442,7 +441,11 @@ 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
@@ -482,7 +485,7 @@ 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);
@@ -494,7 +497,7 @@ 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);
@@ -561,10 +564,10 @@ 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));
}
}
diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
index ba20bef199e6..31d30ffb8971 100644
--- a/sys/fs/unionfs/union_vnops.c
+++ b/sys/fs/unionfs/union_vnops.c
@@ -766,7 +766,7 @@ 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:
@@ -837,7 +837,7 @@ 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);