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A free Windows-compatible Operating System - mirrored from GitHub
![]() - MmCreateMdl, MmSizeOfMdl: No Change. - MmBuildMdlForNonPagedPool: Do not use MmGetPfnForProcess, just normal PMMPTE manipulation. - This seems to cause issues in certain scenarios, because in ReactOS, nonpaged pool, a resident and guaranteed resources, does not always have its PDEs mapped! - By calling MmGetPfnForProcess, this wound up in the annals of ReactOS mm code, which lazy-remapped the PDE. We detected this issue specifically in the cache manager, and fixed it there. It should not appear anywhere else. - MmAllocatePagesForMdl, MmAllocatePagesForMdlEx, MmFreePagesFromMdl: - The *Ex function is now implemented. - Allocating pages now uses MiAllocatePagesForMdl, which is based on the older MmAllocPagesSpecifyRange. - The code is cleaner, better commented, and better handles partial MDLs. - Cache flags are still ignored (so the Ex functionality isn't really there). - MmMapLockedPages, MmMapLockedPagesSpecifyCache, MmUnmapLockedPages: - These functions now use System PTEs for the mappings, instead of the hacked-up "MDL Mapping Space". - This frees up 256MB of Kernel Virtual Address Space. - Takes advantage of all System PTE functionality. - Once again, optimizations in the System PTE code will be felt here. - For user-space mappings however, the old code is still kept and used. - MiMapLockedPagesInUserSpace and MiUnMapLockedPagesInUserSpace are now in virtual.c and provide this. - MmProbeAndLockPages, MmUnlockPages: - The pages are actually probed now, in SEH. This did not seem to happen before (did someone misread the function's name?) - Probe for write is only done for write access to user pages (as documented). - We do not probe/check for write access for kernel requests (force Operation to be IoReadAccess). - Proper locking is used now: Address Space lock for user mappings, PFN lock for kernel mappings. - Faulting in pages (to make them available before locking) is now done outside the address space/PFN lock. - You don't want to be holding a spinlock/mutex while doing disk I/O! - For write/modify access, if the PTE is not writable, fail the request since the PTE protection overrides. - However, if the PTE is writable but also copy on write, then we'll fault the page in for write access, which is a legitimate operation for certain user-mode scenarios. - The old version always provided the CopyOnWrite behavior, even for non-CopyOnWrite pages! - Reference and lock every valid page that has a PFN entry (non-I/O Pages). - The older code did not seem to lock pages that had to be faulted in (weren't already valid). - Cleanup the cleanup code (no pun intended). Because we now mark the pages as locked early-on, and because of changes in MmUnlockPages, we can simply use MmUnlockPages in case of error, since it will be able to fully back-out and references/locks that we did. - Previous code attempted to do this on its own, in a pretty inconsistent manner, which would leave page leaks (both in references and lock count). - In MmUnlockPages, not as many changes, but we now: - Still make sure that an I/O Mapping MDL doesn't have valid PFN database pages (non-I/O). - An MDL can cover pages that are both I/O mapped and RAM mapped, so we have to unlock/dereference the latter instead of skipping them as the old code did. - Use the PFN lock when checking pages and unlocking/dereferencing them. - Overall, non-complete MDLs are now marked by having a -1 PFN, and the MDL code has been updated to early-break out of page-scanning loops and/or ignore such pages, which can happen in a sparse MDL. - Implementation has been tested on VMWare and QEMU for a variety of tasks and was found to be reliable and stable. svn path=/trunk/; revision=41707 |
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