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VFS: remove MNTK_MARKER

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We no longer allow upper filesystems to be unregistered from the base
mount while vfs_notify_upper() or any other upper operation is pending.
New upper mounts can still be registered during this period, but they
will be added at the end of the upper mount tailq.  We therefore no
longer need to allocate marker nodes during vfs_notify_upper() to keep
our place in the iteration.

Reviewed by:	kib, mckusick
Tested by:	pho
Differential Revision:	https://reviews.freebsd.org/D31016
This commit is contained in:
Jason A. Harmening 2021-07-17 21:26:48 -07:00
parent c746ed724d
commit 2bc16e8aaf
2 changed files with 2 additions and 33 deletions
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34
sys/kern/vfs_subr.c
View File

@ -3891,52 +3891,26 @@ vgone(struct vnode *vp)
VI_UNLOCK(vp);
}
static void
notify_lowervp_vfs_dummy(struct mount *mp __unused,
struct vnode *lowervp __unused)
{
}
struct notify_mount {
struct mount mp;
struct mount_upper_node upper;
};
/*
* Notify upper mounts about reclaimed or unlinked vnode.
*/
void
vfs_notify_upper(struct vnode *vp, int event)
{
static struct vfsops vgonel_vfsops = {
.vfs_reclaim_lowervp = notify_lowervp_vfs_dummy,
.vfs_unlink_lowervp = notify_lowervp_vfs_dummy,
};
struct mount *mp;
struct mount_upper_node *ump;
struct notify_mount *mmp;
mp = vp->v_mount;
mp = atomic_load_ptr(&vp->v_mount);
if (mp == NULL)
return;
if (TAILQ_EMPTY(&mp->mnt_notify))
return;
mmp = malloc(sizeof(*mmp), M_TEMP, M_WAITOK | M_ZERO);
mmp->mp.mnt_op = &vgonel_vfsops;
mmp->mp.mnt_kern_flag |= MNTK_MARKER;
mmp->upper.mp = &mmp->mp;
MNT_ILOCK(mp);
mp->mnt_upper_pending++;
KASSERT(mp->mnt_upper_pending > 0,
("%s: mnt_upper_pending %d", __func__, mp->mnt_upper_pending));
for (ump = TAILQ_FIRST(&mp->mnt_notify); ump != NULL;) {
if ((ump->mp->mnt_kern_flag & MNTK_MARKER) != 0) {
ump = TAILQ_NEXT(ump, mnt_upper_link);
continue;
}
TAILQ_INSERT_AFTER(&mp->mnt_notify, ump, &mmp->upper,
mnt_upper_link);
TAILQ_FOREACH(ump, &mp->mnt_notify, mnt_upper_link) {
MNT_IUNLOCK(mp);
switch (event) {
case VFS_NOTIFY_UPPER_RECLAIM:
@ -3950,10 +3924,7 @@ vfs_notify_upper(struct vnode *vp, int event)
break;
}
MNT_ILOCK(mp);
ump = TAILQ_NEXT(&mmp->upper, mnt_upper_link);
TAILQ_REMOVE(&mp->mnt_notify, &mmp->upper, mnt_upper_link);
}
free(mmp, M_TEMP);
mp->mnt_upper_pending--;
if ((mp->mnt_kern_flag & MNTK_UPPER_WAITER) != 0 &&
mp->mnt_upper_pending == 0) {
@ -4391,7 +4362,6 @@ DB_SHOW_COMMAND(mount, db_show_mount)
MNT_KERN_FLAG(MNTK_RECURSE);
MNT_KERN_FLAG(MNTK_UPPER_WAITER);
MNT_KERN_FLAG(MNTK_LOOKUP_EXCL_DOTDOT);
MNT_KERN_FLAG(MNTK_MARKER);
MNT_KERN_FLAG(MNTK_USES_BCACHE);
MNT_KERN_FLAG(MNTK_FPLOOKUP);
MNT_KERN_FLAG(MNTK_TASKQUEUE_WAITER);

1
sys/sys/mount.h
View File

@ -488,7 +488,6 @@ struct mntoptnames {
#define MNTK_RECURSE 0x00000200 /* pending recursive unmount */
#define MNTK_UPPER_WAITER 0x00000400 /* waiting to drain MNTK_UPPER_PENDING */
#define MNTK_LOOKUP_EXCL_DOTDOT 0x00000800
#define MNTK_MARKER 0x00001000
#define MNTK_UNMAPPED_BUFS 0x00002000
#define MNTK_USES_BCACHE 0x00004000 /* FS uses the buffer cache. */
#define MNTK_TEXT_REFS 0x00008000 /* Keep use ref for text */