From 073cd7816685ac77c6d8b4d321a5586c9177b76a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sun, 21 Jan 2018 17:31:43 +0000 Subject: [PATCH] drm/i915: Protect WC stash allocation against direct reclaim As we attempt to allocate pages for use in a new WC stash, direct reclaim may run underneath us and fill up the WC stash. We have to be careful then not to overflow the pvec. Fixes: 66df1014efba ("drm/i915: Keep a small stash of preallocated WC pages") Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103109 Signed-off-by: Chris Wilson Cc: Matthew Auld Cc: Joonas Lahtinen Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20180121173143.17090-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem_gtt.c | 32 ++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 26dee5e61e99..be227512430a 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -377,6 +377,7 @@ static gen6_pte_t iris_pte_encode(dma_addr_t addr, static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp) { struct pagevec *pvec = &vm->free_pages; + struct pagevec stash; if (I915_SELFTEST_ONLY(should_fail(&vm->fault_attr, 1))) i915_gem_shrink_all(vm->i915); @@ -395,7 +396,15 @@ static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp) if (likely(pvec->nr)) return pvec->pages[--pvec->nr]; - /* Otherwise batch allocate pages to amoritize cost of set_pages_wc. */ + /* + * Otherwise batch allocate pages to amoritize cost of set_pages_wc. + * + * We have to be careful as page allocation may trigger the shrinker + * (via direct reclaim) which will fill up the WC stash underneath us. + * So we add our WB pages into a temporary pvec on the stack and merge + * them into the WC stash after all the allocations are complete. + */ + pagevec_init(&stash); do { struct page *page; @@ -403,15 +412,24 @@ static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp) if (unlikely(!page)) break; - pvec->pages[pvec->nr++] = page; - } while (pagevec_space(pvec)); + stash.pages[stash.nr++] = page; + } while (stash.nr < pagevec_space(pvec)); - if (unlikely(!pvec->nr)) - return NULL; + if (stash.nr) { + int nr = min_t(int, stash.nr, pagevec_space(pvec)); + struct page **pages = stash.pages + stash.nr - nr; - set_pages_array_wc(pvec->pages, pvec->nr); + if (nr && !set_pages_array_wc(pages, nr)) { + memcpy(pvec->pages + pvec->nr, + pages, sizeof(pages[0]) * nr); + pvec->nr += nr; + stash.nr -= nr; + } + + pagevec_release(&stash); + } - return pvec->pages[--pvec->nr]; + return likely(pvec->nr) ? pvec->pages[--pvec->nr] : NULL; } static void vm_free_pages_release(struct i915_address_space *vm, -- 2.30.2