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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jul 10, 2026 at 04:53:48PM -0700, Andrew Morton wrote: > On Fri, 10 Jul 2026 03:55:20 -0700 Usama Arif wrote: > > > Since commit 368076f52ebe ("mm/huge_memory: add device-private THP support > > to PMD operations") a PMD may hold a device-private swap entry whenever > > an HMM-based GPU driver migrates an anonymous THP folio to device memory > > via migrate_vma_pages(). > > > > pmd_trans_huge_lock() succeeds for such PMDs (pmd_is_huge() returns true > > for any non-present, non-none huge PMD), so several MM walk callbacks > > that used to assume present THP or migration entry are now reachable with > > a device-private PMD. The results range from a VM_BUG_ON() firing on debug > > kernels, to an oops on a bogus vmemmap dereference, to silently isolating > > an unrelated live folio from LRU in the aliasing case. > > Added, thanks. > Thanks Andrew! > I didn't add these as hotfixes - the Fixes: commit is somewhat old. > Feel free to disagree with this! > > Sashiko went nuts over possible pre-existing issues: > > https://sashiko.dev/#/patchset/20260710105557.1987433-1-usama.arif@linux.dev > The pointed out seems plausible? I am working on some tests to catch more errors via hmm-tests. Balbir