On Mon, Jun 08, 2026 at 04:36:20AM -0400, Michael S. Tsirkin wrote: > Move prep_compound_page() before post_alloc_hook() in prep_new_page(). > > The next patch adds a folio_zero_user() call to post_alloc_hook(), > which uses folio_nr_pages() to determine how many pages to zero. > Without compound metadata set up first, folio_nr_pages() returns 1 > for higher-order allocations, so only the first page would be zeroed. > > All other operations in post_alloc_hook() (arch_alloc_page, KASAN, > debug, page owner, etc.) use raw page pointers with explicit order > counts and are unaffected by this reordering.
I'd put this justification for why this is safe above the 'next patch' stuff. > > Also reorder compaction_alloc_noprof() for consistency. Compaction > currently passes USER_ADDR_NONE so folio_zero_user() is not called Yeah again, this 'just so' stuff of when or when not an address is passed is concerning. > there, but keeping the same ordering avoids a future tripping hazard. No functional changes or functional changes? If none then say so. > > Reviewed-by: Gregory Price <[email protected]> > Signed-off-by: Michael S. Tsirkin <[email protected]> > Assisted-by: Claude:claude-opus-4-6 > Assisted-by: cursor-agent:GPT-5.4-xhigh > --- > mm/compaction.c | 4 ++-- > mm/page_alloc.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 72684fe81e83..4336e433c99b 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1849,10 +1849,10 @@ static struct folio *compaction_alloc_noprof(struct > folio *src, unsigned long da > set_page_private(&freepage[size], start_order); > } > dst = (struct folio *)freepage; > - post_alloc_hook(&dst->page, order, __GFP_MOVABLE, USER_ADDR_NONE); > - set_page_refcounted(&dst->page); > if (order) > prep_compound_page(&dst->page, order); > + post_alloc_hook(&dst->page, order, __GFP_MOVABLE, USER_ADDR_NONE); > + set_page_refcounted(&dst->page); > cc->nr_freepages -= 1 << order; > cc->nr_migratepages -= 1 << order; > return page_rmappable_folio(&dst->page); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0943ab724032..4676fd49819e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1874,11 +1874,11 @@ static void prep_new_page(struct page *page, unsigned > int order, gfp_t gfp_flags > unsigned int > alloc_flags, > unsigned long user_addr) > { > - post_alloc_hook(page, order, gfp_flags, user_addr); > - > if (order && (gfp_flags & __GFP_COMP)) > prep_compound_page(page, order); > > + post_alloc_hook(page, order, gfp_flags, user_addr); > + > /* > * page is set pfmemalloc when ALLOC_NO_WATERMARKS was necessary to > * allocate the page. The expectation is that the caller is taking > -- > MST > Thanks, Lorenzo
