Konstantin Belousov 140dedb81c The r241025 fixed the case when a binary, executed from nullfs mount, ... was still possible to open for write from the lower filesystem. There is a symmetric situation where the binary could already has file descriptors opened for write, but it can be executed from the nullfs overlay. Handle the issue by passing one v_writecount reference to the lower vnode if nullfs vnode has non-zero v_writecount. Note that only one write reference can be donated, since nullfs only keeps one use reference on the lower vnode. Always use the lower vnode v_writecount for the checks. Introduce the VOP_GET_WRITECOUNT to read v_writecount, which is currently always bypassed to the lower vnode, and VOP_ADD_WRITECOUNT to manipulate the v_writecount value, which manages a single bypass reference to the lower vnode. Caling the VOPs instead of directly accessing v_writecount provide the fix described in the previous paragraph. Tested by: pho MFC after: 3 weeks		2012-11-02 13:56:36 +00:00
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ffs	Fix problem with geom_label(4) not recognizing UFS labels on filesystems	2012-10-30 21:32:10 +00:00
ufs	The r241025 fixed the case when a binary, executed from nullfs mount,	2012-11-02 13:56:36 +00:00