Use helper functions to reduce code duplication in merging vm_entry neighbors

[dougm]

Summary

Use helper functions to reduce code duplication in merging vm_entry neighbors.

[kib]

sys/vm/vm_map.c

1654 ↗

(On Diff #49288)

prev->object.vm_object == NULL

1655 ↗

(On Diff #49288)

No need to indent.

[dougm]

Accept reviewer style suggestions.

[alc]

head/sys/vm/vm_map.c

1648

This function does not by itself prove that two entries are mergeable. Hence, its name is misleading. It's necessary that, for example, the entry is not a submap or in transition. I would like to see those conditions asserted here.

Alternatively, and contradicting my initial comment, giving this function a name like vm_map_simplify_test() would discourage the reuse of this function elsewhere, where the necessary conditions on eflags have not been established.

1651

Now that this code is deindented, this variable is pointless. It's is used once, and computing this value before we know that end == start and the objects match is wasted effort.

1665

vm_map_simplify_deallocate(). Historically, "dispose" functions were simple free operations.

1669–1680

Now that this comment is deindented, the text should be "reflowed".

[dougm]

head/sys/vm/vm_map.c

1648

I'll rename to vm_map_neighbor_test, since 'neighbor' is a term introduced in the comment that describes the 'simplify_entry' function, and 'simplify_test' sounds like we're simplifying some sort of test, which sounds pretty generic.

1665

vm_map_neighbor_deallocate().