c8a95a285d
by myself. It solves a serious vm_map corruption problem that can occur with the buffer cache when block sizes > 64K are used. This code has been heavily tested in -stable but only tested somewhat on -current. An MFC will occur in a few days. My additions include the vm_map_simplify_entry() and minor buffer cache boundry case fix. Make the buffer cache use a system map for buffer cache KVM rather then a normal map. Ensure that VM objects are not allocated for system maps. There were cases where a buffer map could wind up with a backing VM object -- normally harmless, but this could also result in the buffer cache blocking in places where it assumes no blocking will occur, possibly resulting in corrupted maps. Fix a minor boundry case in the buffer cache size limit is reached that could result in non-optimal code. Add vm_map_simplify_entry() calls to prevent 'creeping proliferation' of vm_map_entry's in the buffer cache's vm_map. Previously only a simple linear optimization was made. (The buffer vm_map typically has only a handful of vm_map_entry's. This stabilizes it at that level permanently). PR: 20609 Submitted by: (Tor Egge) tegge |
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