The existing mremap() logic has grown organically over a very long period of time, resulting in code that is in many parts, very difficult to follow and full of subtleties and sources of confusion. In addition, it is difficult to thread state through the operation correctly, as function arguments have expanded, some parameters are expected to be temporarily altered during the operation, others are intended to remain static and some can be overridden. This series completely refactors the mremap implementation, sensibly separating functions, adding comments to explain the more subtle aspects of the implementation and making use of small structs to thread state through everything. The reason for doing so is to lay the groundwork for planned future changes to the mremap logic, changes which require the ability to easily pass around state. Additionally, it would be unhelpful to add yet more logic to code that is already difficult to follow without first refactoring it like this. The first patch in this series additionally fixes a bug when a VMA with start address zero is partially remapped. Tested on real hardware under heavy workload and all self tests are passing. Lorenzo Stoakes (7): mm/mremap: correctly handle partial mremap() of VMA starting at 0 mm/mremap: refactor mremap() system call implementation mm/mremap: introduce and use vma_remap_struct threaded state mm/mremap: initial refactor of move_vma() mm/mremap: complete refactor of move_vma() mm/mremap: refactor move_page_tables(), abstracting state mm/mremap: thread state through move page table operation mm/internal.h | 49 +- mm/mmap.c | 5 +- mm/mremap.c | 1440 +++++++++++++++++++++++++++++++++---------------- 3 files changed, 1033 insertions(+), 461 deletions(-) -- 2.48.1
