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 /DOMgWab 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jan 16, 2026 at 01:57:21PM +0530, Dev Jain wrote: > The recently added file folio unmap batching support forgets to update > pte_install_uffd_wp_if_needed(), which still updates a single pte. > We end up jumping to the end of the folio in page_vma_mapped_walk(), thus > setting the uffd-wp marker only on a single pte in the batch. Fix this by > passing nr_pages into the function, and set the uffd-wp marker on all ptes. > > Note that, since the nr_pages passed to this function is always derived by > some sort of batching, it is guaranteed that the set of old ptevals of the > batch have uffd-wp bit on all ptes or no ptes, therefore it is safe to derive > the value of the local variable "arm_uffd_pte" from only the particular > pteval passed to this function, but apply the result on all ptes of the batch. > > Use set_pte_at() in a loop to set the markers - we cannot use set_ptes() > as that will increment the PFN, but we don't have any PFN to update here. > > The userspace visible effect of the bug is inaccuracy observed by workloads > relying on uffd-wp regions to install their own pages. > > Fixes: 8798e255b5ec ("mm: rmap: support batched unmapping for file large folios") Hmm this patch isn't upstream yet, so wouldn't this patch be better as a comment replying to the series so it can be respun? You only do a fixes tag for either upstream things that obviously have to stay in place or perhaps things in mm-stable immediately prior to merge window that can't be adjusted. > Signed-off-by: Dev Jain Let's replace this with a comment on the series at [0] please. [0]: https://lore.kernel.org/linux-mm/cover.1766631066.git.baolin.wang@linux.alibaba.com/ Also the original series really shouldn't go in without signoff from me/David. Thanks, Lorenzo > --- > Patch applies on mm-unstable, commit f8ed52ac0cfb. > > I observed this bug during code inspection, but it turns out that the uffd-wp-mremap > selftest will skip some tests with a bogus complain that "MADV_PAGEOUT didn't work, > is swap enabled?" even when swap is enabled. It first sets the region uffd-wp, > then swaps it out, then checks through pagemap whether it got swapped out. For > file folios, this check makes no sense since the ptes are simply cleared, but in > this particular case, because of uffd-wp preservation, we need to store PTE_MARKER_UFFD_WP, > which is stored as a swap entry, that is why the test works out on a non-buggy kernel. > > include/linux/mm_inline.h | 7 ++++--- > mm/memory.c | 14 +------------- > mm/rmap.c | 2 +- > 3 files changed, 6 insertions(+), 17 deletions(-) > > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h > index fa2d6ba811b5..adec1dcb8793 100644 > --- a/include/linux/mm_inline.h > +++ b/include/linux/mm_inline.h > @@ -568,7 +568,7 @@ static inline pte_marker copy_pte_marker( > */ > static inline bool > pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, > - pte_t *pte, pte_t pteval) > + pte_t *pte, pte_t pteval, unsigned int nr_pages) > { > bool arm_uffd_pte = false; > > @@ -599,8 +599,9 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, > arm_uffd_pte = true; > > if (unlikely(arm_uffd_pte)) { > - set_pte_at(vma->vm_mm, addr, pte, > - make_pte_marker(PTE_MARKER_UFFD_WP)); > + for (int i = 0; i < nr_pages; ++i, ++pte, addr += PAGE_SIZE) > + set_pte_at(vma->vm_mm, addr, pte, > + make_pte_marker(PTE_MARKER_UFFD_WP)); > return true; > } > > diff --git a/mm/memory.c b/mm/memory.c > index 6b22dd72ebc8..35ac86d29e77 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1588,8 +1588,6 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, > unsigned long addr, pte_t *pte, int nr, > struct zap_details *details, pte_t pteval) > { > - bool was_installed = false; > - > if (!uffd_supports_wp_marker()) > return false; > > @@ -1600,17 +1598,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, > if (zap_drop_markers(details)) > return false; > > - for (;;) { > - /* the PFN in the PTE is irrelevant. */ > - if (pte_install_uffd_wp_if_needed(vma, addr, pte, pteval)) > - was_installed = true; > - if (--nr == 0) > - break; > - pte++; > - addr += PAGE_SIZE; > - } > - > - return was_installed; > + return pte_install_uffd_wp_if_needed(vma, addr, pte, pteval, nr); > } > > static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, > diff --git a/mm/rmap.c b/mm/rmap.c > index f13480cb9f2e..d6ca002bf79c 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2171,7 +2171,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > * we may want to replace a none pte with a marker pte if > * it's file-backed, so we don't lose the tracking info. > */ > - pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); > + pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval, nr_pages); > > /* Update high watermark before we lower rss */ > update_hiwater_rss(mm); > -- > 2.34.1 >