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Commit 073cd781 authored by Chris Wilson's avatar Chris Wilson
Browse files

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: 66df1014 ("drm/i915: Keep a small stash of preallocated WC pages")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103109


Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180121173143.17090-1-chris@chris-wilson.co.uk
parent 861023e0

drivers/gpu/drm/i915/i915_gem_gtt.c

+25 −7
Original line number Original line Diff line number Diff line
@@ -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)

static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp)

{

{

	struct pagevec *pvec = &vm->free_pages;

	struct pagevec *pvec = &vm->free_pages;

	struct pagevec stash;





	if (I915_SELFTEST_ONLY(should_fail(&vm->fault_attr, 1)))

	if (I915_SELFTEST_ONLY(should_fail(&vm->fault_attr, 1)))

		i915_gem_shrink_all(vm->i915);

		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))

	if (likely(pvec->nr))

		return pvec->pages[--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 {

	do {

		struct page *page;

		struct page *page;
@@ -403,15 +412,24 @@ static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp) 
		if (unlikely(!page))

		if (unlikely(!page))

			break;

			break;





		pvec->pages[pvec->nr++] = page;

		stash.pages[stash.nr++] = page;

	} while (pagevec_space(pvec));

	} while (stash.nr < pagevec_space(pvec));





	if (unlikely(!pvec->nr))

	if (stash.nr) {

		return NULL;

		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;

		}





	return pvec->pages[--pvec->nr];

		pagevec_release(&stash);

	}



	return likely(pvec->nr) ? pvec->pages[--pvec->nr] : NULL;

}

}





static void vm_free_pages_release(struct i915_address_space *vm,

static void vm_free_pages_release(struct i915_address_space *vm,