FOLL_LONGTERM on a N_MEMORY_PRIVATE node folio is wrong both ways the GUP longterm path resolves it:
a ZONE_NORMAL folio would be pinned in place a ZONE_MOVABLE folio would be migrated off first A private node folio should do neither - the pin should fail in place. Add folio_longterm_pin_forbidden() (true for any private node folio) and reject such a pin in check_and_migrate_movable_pages_or_folios() before any isolation, so nothing is migrated. The gup-fast path defers a private folio to the slow path via folio_allows_longterm_pin(). Signed-off-by: Gregory Price <[email protected]> --- mm/gup.c | 27 +++++++++++++++++++++++++-- mm/internal.h | 25 +++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 2 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 1d32e9a3dc79c..a7d4de223785c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -547,10 +547,10 @@ static struct folio *try_grab_folio_fast(struct page *page, int refs, /* * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a * right zone, so fail and let the caller fall back to the slow - * path. + * path. Fail for private-node folios here so slow path rejects. */ if (unlikely((flags & FOLL_LONGTERM) && - !folio_is_longterm_pinnable(folio))) { + !folio_allows_longterm_pin(folio))) { folio_put_refs(folio, refs); return NULL; } @@ -2389,12 +2389,35 @@ migrate_longterm_unpinnable_folios(struct list_head *movable_folio_list, return ret; } +/* + * True if any folio sits on a private node whose folios may not be longterm + * pinned. Such folios can neither be pinned nor migrated, so the whole pin + * must fail before migration. Checked before any isolation occurs. + */ +static bool pofs_has_ltpin_forbidden(struct pages_or_folios *pofs) +{ + struct folio *folio; + long i = 0; + + for (folio = pofs_get_folio(pofs, i); folio; + folio = pofs_next_folio(folio, pofs, &i)) { + if (folio_longterm_pin_forbidden(folio)) + return true; + } + return false; +} + static long check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs) { LIST_HEAD(movable_folio_list); unsigned long collected; + if (pofs_has_ltpin_forbidden(pofs)) { + pofs_unpin(pofs); + return -EFAULT; + } + collected = collect_longterm_unpinnable_folios(&movable_folio_list, pofs); if (!collected) diff --git a/mm/internal.h b/mm/internal.h index cb9f4a8342e32..85c460296cea1 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -110,6 +110,31 @@ static inline bool page_is_private_managed(struct page *page) return folio_is_private_managed(page_folio(page)); } +/* + * folio_allows_longterm_pin() - may this folio be long-term GUP-pinned? + * + * checks folio_is_longterm_pinnable() rules plus private node permissions. + * private node permission is checked here to resolve circular header + * dependencies in folio_is_longterm_pinnable. + */ +static inline bool folio_allows_longterm_pin(struct folio *folio) +{ + return folio_is_longterm_pinnable(folio) && + !folio_is_private_node(folio); +} + +/* + * folio_longterm_pin_forbidden() - must a longterm pin of this folio fail + * outright (neither pinned in place nor migrated off the node)? + * + * True for any folio on a private node: such memory can be neither pinned + * nor migrated, so the pin must be rejected with the folio left in place. + */ +static inline bool folio_longterm_pin_forbidden(struct folio *folio) +{ + return folio_is_private_node(folio); +} + /* * Maintains state across a page table move. The operation assumes both source * and destination VMAs already exist and are specified by the user. -- 2.53.0-Meta
