On Mon, May 11, 2026 at 05:02:06AM -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. > > Note: compaction_alloc_noprof() has the opposite ordering > (post_alloc_hook before prep_compound_page). This is fine because > compaction always passes USER_ADDR_NONE, so folio_zero_user() is > never called there and folio_nr_pages() is never reached inside > post_alloc_hook(). >
We can't really know that this will stay true forever, may as well change the ordering there to prevent a tripping hazard. Possibly you might want to just squash this change with the next patch and add a comment that the ordering is now explicit and required that way to be correct. (possibly patches 4-5-6 should just be one patch, since it's all really the same change, but 4 seems fine by itself). > Signed-off-by: Michael S. Tsirkin <[email protected]> > Assisted-by: Claude:claude-opus-4-6 > Assisted-by: cursor-agent:GPT-5.4-xhigh Reviewed-by: Gregory Price <[email protected]>
