Suppose that a file on NFS has partial last page, and this page was marked dirty. NFS VOP_PAGEOUT() method only marks the the page clean up to the block of the last written byte, leaving other blocks dirty. Also any page which erronously exists in the vnode vm_object past EOF is also left marked as dirty.
With the introduction of the buf-cache coherent pager, each pass of syncer over the object with such page results in creation of B_DELWRI buffer due to VOP_WRITE() call. This buffer is noted on next syncer pass, which has e.g. a visible manifestation of shutdown never finishing vnode sync. Note that before buf-cache coherency commit, a dirty page might left never synced to server if a partial writes occur.
Fix this by clearing dirty bits after EOF. Only blocks of the partial page which are completely after EOF are marked clean, to avoid possible user data loss.