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Close race in zfs_zget(). We have to increase usecount first and then

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check for VI_DOOMED flag. Before this change vnode could be reclaimed
between checking for the flag and increasing usecount.

MFC after:	3 days
This commit is contained in:
pjd 2009-09-24 15:49:15 +00:00
parent 9485b3f20f
commit 534a0875d3
1 changed files with 20 additions and 10 deletions
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30
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_znode.c
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@ -890,17 +890,25 @@ again:
if (zp->z_unlinked) {
err = ENOENT;
} else {
if ((vp = ZTOV(zp)) != NULL) {
VI_LOCK(vp);
if ((vp->v_iflag & VI_DOOMED) != 0) {
VI_UNLOCK(vp);
vp = NULL;
} else
VI_UNLOCK(vp);
}
if (vp != NULL)
VN_HOLD(vp);
int dying = 0;
vp = ZTOV(zp);
if (vp == NULL)
dying = 1;
else {
VN_HOLD(vp);
if ((vp->v_iflag & VI_DOOMED) != 0) {
dying = 1;
/*
* Don't VN_RELE() vnode here, because
* it can call vn_lock() which creates
* LOR between vnode lock and znode
* lock. We will VN_RELE() the vnode
* after droping znode lock.
*/
}
}
if (dying) {
if (first) {
ZFS_LOG(1, "dying znode detected (zp=%p)", zp);
first = 0;
@ -912,6 +920,8 @@ again:
dmu_buf_rele(db, NULL);
mutex_exit(&zp->z_lock);
ZFS_OBJ_HOLD_EXIT(zfsvfs, obj_num);
if (vp != NULL)
VN_RELE(vp);
tsleep(zp, 0, "zcollide", 1);
goto again;
}