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drm/i915/gem: Break out some shmem backend utils
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Break out some shmem backend utils for future reuse by the TTM backend:
shmem_alloc_st(), shmem_free_st() and __shmem_writeback() which we can
use to provide a shmem-backed TTM page pool for cached-only TTM
buffer objects.

Main functional change here is that we now compute the page sizes using
the dma segments rather than using the physical page address segments.

v2(Reported-by: kernel test robot <lkp@intel.com>)
    - Make sure we initialise the mapping on the error path in
      shmem_get_pages()

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211018091055.1998191-1-matthew.auld@intel.com
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Thomas Hellström authored and Matthew Auld committed Oct 22, 2021
1 parent ef3e619 commit f05b985
Showing 1 changed file with 106 additions and 75 deletions.
181 changes: 106 additions & 75 deletions drivers/gpu/drm/i915/gem/i915_gem_shmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,46 +25,61 @@ static void check_release_pagevec(struct pagevec *pvec)
cond_resched();
}

static int shmem_get_pages(struct drm_i915_gem_object *obj)
static void shmem_free_st(struct sg_table *st, struct address_space *mapping,
bool dirty, bool backup)
{
struct drm_i915_private *i915 = to_i915(obj->base.dev);
struct intel_memory_region *mem = obj->mm.region;
const unsigned long page_count = obj->base.size / PAGE_SIZE;
struct sgt_iter sgt_iter;
struct pagevec pvec;
struct page *page;

mapping_clear_unevictable(mapping);

pagevec_init(&pvec);
for_each_sgt_page(page, sgt_iter, st) {
if (dirty)
set_page_dirty(page);

if (backup)
mark_page_accessed(page);

if (!pagevec_add(&pvec, page))
check_release_pagevec(&pvec);
}
if (pagevec_count(&pvec))
check_release_pagevec(&pvec);

sg_free_table(st);
kfree(st);
}

static struct sg_table *shmem_alloc_st(struct drm_i915_private *i915,
size_t size, struct intel_memory_region *mr,
struct address_space *mapping,
unsigned int max_segment)
{
const unsigned long page_count = size / PAGE_SIZE;
unsigned long i;
struct address_space *mapping;
struct sg_table *st;
struct scatterlist *sg;
struct sgt_iter sgt_iter;
struct page *page;
unsigned long last_pfn = 0; /* suppress gcc warning */
unsigned int max_segment = i915_sg_segment_size();
unsigned int sg_page_sizes;
gfp_t noreclaim;
int ret;

/*
* Assert that the object is not currently in any GPU domain. As it
* wasn't in the GTT, there shouldn't be any way it could have been in
* a GPU cache
*/
GEM_BUG_ON(obj->read_domains & I915_GEM_GPU_DOMAINS);
GEM_BUG_ON(obj->write_domain & I915_GEM_GPU_DOMAINS);

/*
* If there's no chance of allocating enough pages for the whole
* object, bail early.
*/
if (obj->base.size > resource_size(&mem->region))
return -ENOMEM;
if (size > resource_size(&mr->region))
return ERR_PTR(-ENOMEM);

st = kmalloc(sizeof(*st), GFP_KERNEL);
if (!st)
return -ENOMEM;
return ERR_PTR(-ENOMEM);

rebuild_st:
if (sg_alloc_table(st, page_count, GFP_KERNEL)) {
kfree(st);
return -ENOMEM;
return ERR_PTR(-ENOMEM);
}

/*
Expand All @@ -73,14 +88,12 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
*
* Fail silently without starting the shrinker
*/
mapping = obj->base.filp->f_mapping;
mapping_set_unevictable(mapping);
noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
noreclaim |= __GFP_NORETRY | __GFP_NOWARN;

sg = st->sgl;
st->nents = 0;
sg_page_sizes = 0;
for (i = 0; i < page_count; i++) {
const unsigned int shrink[] = {
I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
Expand Down Expand Up @@ -135,10 +148,9 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
if (!i ||
sg->length >= max_segment ||
page_to_pfn(page) != last_pfn + 1) {
if (i) {
sg_page_sizes |= sg->length;
if (i)
sg = sg_next(sg);
}

st->nents++;
sg_set_page(sg, page, PAGE_SIZE, 0);
} else {
Expand All @@ -149,14 +161,65 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
/* Check that the i965g/gm workaround works. */
GEM_BUG_ON(gfp & __GFP_DMA32 && last_pfn >= 0x00100000UL);
}
if (sg) { /* loop terminated early; short sg table */
sg_page_sizes |= sg->length;
if (sg) /* loop terminated early; short sg table */
sg_mark_end(sg);
}

/* Trim unused sg entries to avoid wasting memory. */
i915_sg_trim(st);

return st;
err_sg:
sg_mark_end(sg);
if (sg != st->sgl) {
shmem_free_st(st, mapping, false, false);
} else {
mapping_clear_unevictable(mapping);
sg_free_table(st);
kfree(st);
}

/*
* shmemfs first checks if there is enough memory to allocate the page
* and reports ENOSPC should there be insufficient, along with the usual
* ENOMEM for a genuine allocation failure.
*
* We use ENOSPC in our driver to mean that we have run out of aperture
* space and so want to translate the error from shmemfs back to our
* usual understanding of ENOMEM.
*/
if (ret == -ENOSPC)
ret = -ENOMEM;

return ERR_PTR(ret);
}

static int shmem_get_pages(struct drm_i915_gem_object *obj)
{
struct drm_i915_private *i915 = to_i915(obj->base.dev);
struct intel_memory_region *mem = obj->mm.region;
struct address_space *mapping = obj->base.filp->f_mapping;
const unsigned long page_count = obj->base.size / PAGE_SIZE;
unsigned int max_segment = i915_sg_segment_size();
struct sg_table *st;
struct sgt_iter sgt_iter;
struct page *page;
int ret;

/*
* Assert that the object is not currently in any GPU domain. As it
* wasn't in the GTT, there shouldn't be any way it could have been in
* a GPU cache
*/
GEM_BUG_ON(obj->read_domains & I915_GEM_GPU_DOMAINS);
GEM_BUG_ON(obj->write_domain & I915_GEM_GPU_DOMAINS);

rebuild_st:
st = shmem_alloc_st(i915, obj->base.size, mem, mapping, max_segment);
if (IS_ERR(st)) {
ret = PTR_ERR(st);
goto err_st;
}

ret = i915_gem_gtt_prepare_pages(obj, st);
if (ret) {
/*
Expand All @@ -168,6 +231,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
for_each_sgt_page(page, sgt_iter, st)
put_page(page);
sg_free_table(st);
kfree(st);

max_segment = PAGE_SIZE;
goto rebuild_st;
Expand All @@ -185,28 +249,12 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
if (i915_gem_object_can_bypass_llc(obj))
obj->cache_dirty = true;

__i915_gem_object_set_pages(obj, st, sg_page_sizes);
__i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));

return 0;

err_sg:
sg_mark_end(sg);
err_pages:
mapping_clear_unevictable(mapping);
if (sg != st->sgl) {
struct pagevec pvec;

pagevec_init(&pvec);
for_each_sgt_page(page, sgt_iter, st) {
if (!pagevec_add(&pvec, page))
check_release_pagevec(&pvec);
}
if (pagevec_count(&pvec))
check_release_pagevec(&pvec);
}
sg_free_table(st);
kfree(st);

shmem_free_st(st, mapping, false, false);
/*
* shmemfs first checks if there is enough memory to allocate the page
* and reports ENOSPC should there be insufficient, along with the usual
Expand All @@ -216,6 +264,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
* space and so want to translate the error from shmemfs back to our
* usual understanding of ENOMEM.
*/
err_st:
if (ret == -ENOSPC)
ret = -ENOMEM;

Expand All @@ -236,10 +285,8 @@ shmem_truncate(struct drm_i915_gem_object *obj)
obj->mm.pages = ERR_PTR(-EFAULT);
}

static void
shmem_writeback(struct drm_i915_gem_object *obj)
static void __shmem_writeback(size_t size, struct address_space *mapping)
{
struct address_space *mapping;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = SWAP_CLUSTER_MAX,
Expand All @@ -255,10 +302,9 @@ shmem_writeback(struct drm_i915_gem_object *obj)
* instead of invoking writeback so they are aged and paged out
* as normal.
*/
mapping = obj->base.filp->f_mapping;

/* Begin writeback on each dirty page */
for (i = 0; i < obj->base.size >> PAGE_SHIFT; i++) {
for (i = 0; i < size >> PAGE_SHIFT; i++) {
struct page *page;

page = find_lock_page(mapping, i);
Expand All @@ -281,6 +327,12 @@ shmem_writeback(struct drm_i915_gem_object *obj)
}
}

static void
shmem_writeback(struct drm_i915_gem_object *obj)
{
__shmem_writeback(obj->base.size, obj->base.filp->f_mapping);
}

void
__i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
struct sg_table *pages,
Expand Down Expand Up @@ -313,37 +365,16 @@ __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,

void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_table *pages)
{
struct sgt_iter sgt_iter;
struct pagevec pvec;
struct page *page;

GEM_WARN_ON(IS_DGFX(to_i915(obj->base.dev)));
__i915_gem_object_release_shmem(obj, pages, true);

i915_gem_gtt_finish_pages(obj, pages);

if (i915_gem_object_needs_bit17_swizzle(obj))
i915_gem_object_save_bit_17_swizzle(obj, pages);

mapping_clear_unevictable(file_inode(obj->base.filp)->i_mapping);

pagevec_init(&pvec);
for_each_sgt_page(page, sgt_iter, pages) {
if (obj->mm.dirty)
set_page_dirty(page);

if (obj->mm.madv == I915_MADV_WILLNEED)
mark_page_accessed(page);

if (!pagevec_add(&pvec, page))
check_release_pagevec(&pvec);
}
if (pagevec_count(&pvec))
check_release_pagevec(&pvec);
shmem_free_st(pages, file_inode(obj->base.filp)->i_mapping,
obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
obj->mm.dirty = false;

sg_free_table(pages);
kfree(pages);
}

static void
Expand Down

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