On Mon, Jun 08, 2026 at 04:35:29AM -0400, Michael S. Tsirkin wrote: > Add a _user variant of alloc_contig_frozen_pages that accepts a user_addr > parameter for cache-friendly zeroing of contiguous allocations. > > No functional change; all existing callers continue to pass > USER_ADDR_NONE.
Well, except that you're adding a new function... > > Note for reviewers: non-compound contiguous allocations are Please don't put notes for reviewers in commit messages. > zeroed via kernel_init_pages, same as before this patch. > There is no fault address because these allocations are not > from the page fault path. For compound allocations, user_addr > reaches post_alloc_hook() which calls folio_zero_user() with > the dcache flush on cache-aliasing architectures. Yeah it's exactly this kind of 'just have to know' stuff that makes this user_addr approach unacceptable. We mustn't add more cognitive overhead for already confusing code. Now everybody using these has to figure out what 'user_addr' means and will inevitably get it wrong. This whole approach needs to be rethought. > > Note about Sashiko (sashiko.dev) false positives: sashiko > flags two issues here: (1) user_addr silently ignored for > non-compound allocations, and (2) post_alloc_hook ignores > user_addr. Both are false positives: (1) non-compound > contiguous allocations have no fault address to pass, and > (2) post_alloc_hook does use user_addr when it is not > USER_ADDR_NONE. Please don't put AI hallucinations in commit messages. If you want something to not appear in a commit message, but want reviewers to see it, put it below the '---' in the patch. > > Signed-off-by: Michael S. Tsirkin <[email protected]> This patch is unacceptable for the same reasons given for 7/37. > Assisted-by: Claude:claude-opus-4-6 > --- > include/linux/gfp.h | 6 ++++++ > mm/page_alloc.c | 42 ++++++++++++++++++++++++++++++++---------- > 2 files changed, 38 insertions(+), 10 deletions(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index ee35c5367abc..73109d4e31a4 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -453,6 +453,12 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned > long nr_pages, > #define alloc_contig_frozen_pages(...) \ > alloc_hooks(alloc_contig_frozen_pages_noprof(__VA_ARGS__)) > > +struct page *alloc_contig_frozen_pages_user_noprof(unsigned long nr_pages, > + gfp_t gfp_mask, int nid, nodemask_t *nodemask, > + unsigned long user_addr); > +#define alloc_contig_frozen_pages_user(...) \ > + alloc_hooks(alloc_contig_frozen_pages_user_noprof(__VA_ARGS__)) > + > struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t > gfp_mask, > int nid, nodemask_t *nodemask); > #define alloc_contig_pages(...) \ > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 21b52c879751..6d3f284c607d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6975,13 +6975,15 @@ static void __free_contig_frozen_range(unsigned long > pfn, unsigned long nr_pages > } > > /** > - * alloc_contig_frozen_range() -- tries to allocate given range of frozen > pages > + * __alloc_contig_frozen_range() -- tries to allocate given range of frozen > pages > * @start: start PFN to allocate > * @end: one-past-the-last PFN to allocate > * @alloc_flags: allocation information > * @gfp_mask: GFP mask. Node/zone/placement hints are ignored; only > some > * action and reclaim modifiers are supported. Reclaim modifiers > * control allocation behavior during compaction/migration/reclaim. > + * @user_addr: user virtual address for cache-friendly zeroing, or > + * USER_ADDR_NONE for kernel allocations. Yeah, I really do not want us passing USER_ADDR_NONE for kernel allocations thanks. This is hugely confusing already pretty confusing logic. > * > * The PFN range does not have to be pageblock aligned. The PFN range must > * belong to a single zone. > @@ -6997,8 +6999,9 @@ static void __free_contig_frozen_range(unsigned long > pfn, unsigned long nr_pages > * > * Return: zero on success or negative error code. > */ > -int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end, > - acr_flags_t alloc_flags, gfp_t gfp_mask) > +static int __alloc_contig_frozen_range(unsigned long start, unsigned long > end, > + acr_flags_t alloc_flags, gfp_t gfp_mask, > + unsigned long user_addr) > { > const unsigned int order = ilog2(end - start); > unsigned long outer_start, outer_end; > @@ -7125,7 +7128,7 @@ int alloc_contig_frozen_range_noprof(unsigned long > start, unsigned long end, > struct page *head = pfn_to_page(start); > > check_new_pages(head, order); > - prep_new_page(head, order, gfp_mask, 0, USER_ADDR_NONE); > + prep_new_page(head, order, gfp_mask, 0, user_addr); > } else { > ret = -EINVAL; > WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, > %lu)\n", > @@ -7135,6 +7138,13 @@ int alloc_contig_frozen_range_noprof(unsigned long > start, unsigned long end, > undo_isolate_page_range(start, end); > return ret; > } > + > +int alloc_contig_frozen_range_noprof(unsigned long start, unsigned long end, > + acr_flags_t alloc_flags, gfp_t gfp_mask) > +{ > + return __alloc_contig_frozen_range(start, end, alloc_flags, gfp_mask, > + USER_ADDR_NONE); > +} > EXPORT_SYMBOL(alloc_contig_frozen_range_noprof); > > /** > @@ -7227,14 +7237,16 @@ static bool zone_spans_last_pfn(const struct zone > *zone, > return zone_spans_pfn(zone, last_pfn); > } > > -/** > - * alloc_contig_frozen_pages() -- tries to find and allocate contiguous > range of frozen pages > +/* > + * alloc_contig_frozen_pages_user_noprof() -- allocate contiguous frozen > pages with user address > * @nr_pages: Number of contiguous pages to allocate > * @gfp_mask: GFP mask. Node/zone/placement hints limit the search; > only some > * action and reclaim modifiers are supported. Reclaim modifiers > * control allocation behavior during compaction/migration/reclaim. > * @nid: Target node > * @nodemask: Mask for other possible nodes > + * @user_addr: user virtual address for cache-friendly zeroing, or > + * USER_ADDR_NONE for kernel allocations. > * > * This routine is a wrapper around alloc_contig_frozen_range(). It scans > over > * zones on an applicable zonelist to find a contiguous pfn range which can > then > @@ -7253,8 +7265,9 @@ static bool zone_spans_last_pfn(const struct zone *zone, > * > * Return: pointer to contiguous frozen pages on success, or NULL if not > successful. > */ > -struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > - gfp_t gfp_mask, int nid, nodemask_t *nodemask) > +struct page *alloc_contig_frozen_pages_user_noprof(unsigned long nr_pages, > + gfp_t gfp_mask, int nid, nodemask_t *nodemask, > + unsigned long user_addr) > { > unsigned long ret, pfn, flags; > struct zonelist *zonelist; > @@ -7282,10 +7295,11 @@ struct page > *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > * win the race and cause allocation to fail. > */ > spin_unlock_irqrestore(&zone->lock, flags); > - ret = alloc_contig_frozen_range_noprof(pfn, > + ret = __alloc_contig_frozen_range(pfn, > pfn + nr_pages, > ACR_FLAGS_NONE, > - gfp_mask); > + gfp_mask, > + user_addr); > if (!ret) > return pfn_to_page(pfn); > spin_lock_irqsave(&zone->lock, flags); > @@ -7307,6 +7321,14 @@ struct page *alloc_contig_frozen_pages_noprof(unsigned > long nr_pages, > } > return NULL; > } > +EXPORT_SYMBOL(alloc_contig_frozen_pages_user_noprof); Generally we don't add EXPORT_SYMBOL() for new stuff unless unavoidable. EXPORT_SYMBOL_GPL() is preferred. > + > +struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > + gfp_t gfp_mask, int nid, nodemask_t *nodemask) > +{ > + return alloc_contig_frozen_pages_user_noprof(nr_pages, gfp_mask, nid, > + nodemask, USER_ADDR_NONE); > +} > EXPORT_SYMBOL(alloc_contig_frozen_pages_noprof); > > /** > -- > MST > Thanks, Lorenzo
