drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)
When converting to folios the cleanup path of shmem_get_pages() was
missed. When a DMA remap fails and the max segment size is greater than
PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
size. The cleanup code isn't properly using the folio apis and as a
result isn't handling compound pages correctly.
Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
Signed-off-by: Brian Geffon <bgeffon@google.com>
Suggested-by: Tomasz Figa <tfiga@google.com>
---
drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index fe69f2c8527d..02ddab5bf5c0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
struct folio *last = NULL;
struct page *page;
- mapping_clear_unevictable(mapping);
-
folio_batch_init(&fbatch);
for_each_sgt_page(page, sgt_iter, st) {
struct folio *folio = page_folio(page);
@@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
return 0;
err_sg:
sg_mark_end(sg);
+ mapping_clear_unevictable(mapping);
if (sg != st->sgl) {
shmem_sg_free_table(st, mapping, false, false);
} else {
- mapping_clear_unevictable(mapping);
sg_free_table(st);
}
@@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
struct address_space *mapping = obj->base.filp->f_mapping;
unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
struct sg_table *st;
- struct sgt_iter sgt_iter;
- struct page *page;
int ret;
/*
@@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
* for PAGE_SIZE chunks instead may be helpful.
*/
if (max_segment > PAGE_SIZE) {
- for_each_sgt_page(page, sgt_iter, st)
- put_page(page);
- sg_free_table(st);
+ /* Leave the mapping unevictable while we retry */
+ shmem_sg_free_table(st, mapping, false, false);
kfree(st);
max_segment = PAGE_SIZE;
@@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
return 0;
err_pages:
+ mapping_clear_unevictable(mapping);
shmem_sg_free_table(st, mapping, false, false);
/*
* shmemfs first checks if there is enough memory to allocate the page
@@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
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);
shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
kfree(pages);
--
2.48.0.rc2.279.g1de40edade-googOn Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> When converting to folios the cleanup path of shmem_get_pages() was
> missed. When a DMA remap fails and the max segment size is greater than
> PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> size. The cleanup code isn't properly using the folio apis and as a
> result isn't handling compound pages correctly.
>
> Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> Signed-off-by: Brian Geffon <bgeffon@google.com>
> Suggested-by: Tomasz Figa <tfiga@google.com>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index fe69f2c8527d..02ddab5bf5c0 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> struct folio *last = NULL;
> struct page *page;
>
> - mapping_clear_unevictable(mapping);
> -
The assymmetry here between the alloc vs. free is a bit annoying.
Maybe we can just keep this here?
Or if avoiding the ping-pong actually mattes in the gtt prepare
error case, then maybe we should rename this guy into
__shmem_sg_free_table() without the mapping_clear_unevictable()
and wrap it in a higher level shmem_sg_free_table() that does
everything?
> folio_batch_init(&fbatch);
> for_each_sgt_page(page, sgt_iter, st) {
> struct folio *folio = page_folio(page);
> @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> return 0;
> err_sg:
> sg_mark_end(sg);
> + mapping_clear_unevictable(mapping);
> if (sg != st->sgl) {
> shmem_sg_free_table(st, mapping, false, false);
> } else {
> - mapping_clear_unevictable(mapping);
> sg_free_table(st);
> }
>
> @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> struct address_space *mapping = obj->base.filp->f_mapping;
> unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> struct sg_table *st;
> - struct sgt_iter sgt_iter;
> - struct page *page;
> int ret;
>
> /*
> @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> * for PAGE_SIZE chunks instead may be helpful.
> */
> if (max_segment > PAGE_SIZE) {
> - for_each_sgt_page(page, sgt_iter, st)
> - put_page(page);
> - sg_free_table(st);
> + /* Leave the mapping unevictable while we retry */
> + shmem_sg_free_table(st, mapping, false, false);
> kfree(st);
>
> max_segment = PAGE_SIZE;
> @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> return 0;
>
> err_pages:
> + mapping_clear_unevictable(mapping);
> shmem_sg_free_table(st, mapping, false, false);
> /*
> * shmemfs first checks if there is enough memory to allocate the page
> @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> 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);
> shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> kfree(pages);
> --
> 2.48.0.rc2.279.g1de40edade-goog
--
Ville Syrjälä
Intel
On Thu, Jan 16, 2025 at 04:24:26PM +0200, Ville Syrjälä wrote:
> On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > When converting to folios the cleanup path of shmem_get_pages() was
> > missed. When a DMA remap fails and the max segment size is greater than
> > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > size. The cleanup code isn't properly using the folio apis and as a
> > result isn't handling compound pages correctly.
> >
> > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > Suggested-by: Tomasz Figa <tfiga@google.com>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > 1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > index fe69f2c8527d..02ddab5bf5c0 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > struct folio *last = NULL;
> > struct page *page;
> >
> > - mapping_clear_unevictable(mapping);
> > -
>
> The assymmetry here between the alloc vs. free is a bit annoying.
> Maybe we can just keep this here?
Hmm, I guess with the current code that avoids the ping-pong
we (at least theoretically) could leak the mapping_set_unevictable()
if both i915_gem_gtt_prepare_pages() fails, and then the the
subsequent shmem_sg_alloc_table() retry fails early enough.
So looks to me like the ping-pong would be the only 100% correct
approach.
>
> Or if avoiding the ping-pong actually mattes in the gtt prepare
> error case, then maybe we should rename this guy into
> __shmem_sg_free_table() without the mapping_clear_unevictable()
> and wrap it in a higher level shmem_sg_free_table() that does
> everything?
>
> > folio_batch_init(&fbatch);
> > for_each_sgt_page(page, sgt_iter, st) {
> > struct folio *folio = page_folio(page);
> > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > return 0;
> > err_sg:
> > sg_mark_end(sg);
> > + mapping_clear_unevictable(mapping);
> > if (sg != st->sgl) {
> > shmem_sg_free_table(st, mapping, false, false);
> > } else {
> > - mapping_clear_unevictable(mapping);
> > sg_free_table(st);
> > }
> >
> > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > struct address_space *mapping = obj->base.filp->f_mapping;
> > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > struct sg_table *st;
> > - struct sgt_iter sgt_iter;
> > - struct page *page;
> > int ret;
> >
> > /*
> > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > * for PAGE_SIZE chunks instead may be helpful.
> > */
> > if (max_segment > PAGE_SIZE) {
> > - for_each_sgt_page(page, sgt_iter, st)
> > - put_page(page);
> > - sg_free_table(st);
> > + /* Leave the mapping unevictable while we retry */
> > + shmem_sg_free_table(st, mapping, false, false);
> > kfree(st);
> >
> > max_segment = PAGE_SIZE;
> > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > return 0;
> >
> > err_pages:
> > + mapping_clear_unevictable(mapping);
> > shmem_sg_free_table(st, mapping, false, false);
> > /*
> > * shmemfs first checks if there is enough memory to allocate the page
> > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > 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);
> > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > kfree(pages);
> > --
> > 2.48.0.rc2.279.g1de40edade-goog
>
> --
> Ville Syrjälä
> Intel
--
Ville Syrjälä
Intel
On Thu, Jan 16, 2025 at 9:24 AM Ville Syrjälä
<ville.syrjala@linux.intel.com> wrote:
>
> On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > When converting to folios the cleanup path of shmem_get_pages() was
> > missed. When a DMA remap fails and the max segment size is greater than
> > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > size. The cleanup code isn't properly using the folio apis and as a
> > result isn't handling compound pages correctly.
> >
> > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > Suggested-by: Tomasz Figa <tfiga@google.com>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > 1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > index fe69f2c8527d..02ddab5bf5c0 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > struct folio *last = NULL;
> > struct page *page;
> >
> > - mapping_clear_unevictable(mapping);
> > -
>
> The assymmetry here between the alloc vs. free is a bit annoying.
> Maybe we can just keep this here?
My thought on this was that freeing the sg table is orthogonal to
making the mapping evictable, and shmem_sg_free_table() can be
simplified to not even take the mapping as a parameter.
>
> Or if avoiding the ping-pong actually mattes in the gtt prepare
> error case, then maybe we should rename this guy into
> __shmem_sg_free_table() without the mapping_clear_unevictable()
> and wrap it in a higher level shmem_sg_free_table() that does
> everything?
>
> > folio_batch_init(&fbatch);
> > for_each_sgt_page(page, sgt_iter, st) {
> > struct folio *folio = page_folio(page);
> > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > return 0;
> > err_sg:
> > sg_mark_end(sg);
> > + mapping_clear_unevictable(mapping);
> > if (sg != st->sgl) {
> > shmem_sg_free_table(st, mapping, false, false);
> > } else {
> > - mapping_clear_unevictable(mapping);
> > sg_free_table(st);
> > }
> >
> > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > struct address_space *mapping = obj->base.filp->f_mapping;
> > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > struct sg_table *st;
> > - struct sgt_iter sgt_iter;
> > - struct page *page;
> > int ret;
> >
> > /*
> > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > * for PAGE_SIZE chunks instead may be helpful.
> > */
> > if (max_segment > PAGE_SIZE) {
> > - for_each_sgt_page(page, sgt_iter, st)
> > - put_page(page);
> > - sg_free_table(st);
> > + /* Leave the mapping unevictable while we retry */
> > + shmem_sg_free_table(st, mapping, false, false);
> > kfree(st);
> >
> > max_segment = PAGE_SIZE;
> > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > return 0;
> >
> > err_pages:
> > + mapping_clear_unevictable(mapping);
> > shmem_sg_free_table(st, mapping, false, false);
> > /*
> > * shmemfs first checks if there is enough memory to allocate the page
> > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > 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);
> > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > kfree(pages);
> > --
> > 2.48.0.rc2.279.g1de40edade-goog
>
> --
> Ville Syrjälä
> Intel
On Thu, Jan 16, 2025 at 04:24:26PM +0200, Ville Syrjälä wrote:
> On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > When converting to folios the cleanup path of shmem_get_pages() was
> > missed. When a DMA remap fails and the max segment size is greater than
> > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > size. The cleanup code isn't properly using the folio apis and as a
> > result isn't handling compound pages correctly.
> >
> > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > Suggested-by: Tomasz Figa <tfiga@google.com>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > 1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > index fe69f2c8527d..02ddab5bf5c0 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > struct folio *last = NULL;
> > struct page *page;
> >
> > - mapping_clear_unevictable(mapping);
> > -
>
> The assymmetry here between the alloc vs. free is a bit annoying.
> Maybe we can just keep this here?
Actually, I guess it's a bit more than just annoying since
shmem_sg_free_table() is actually used from outside i915_gem_shmem.c
as well.
>
> Or if avoiding the ping-pong actually mattes in the gtt prepare
> error case, then maybe we should rename this guy into
> __shmem_sg_free_table() without the mapping_clear_unevictable()
> and wrap it in a higher level shmem_sg_free_table() that does
> everything?
>
> > folio_batch_init(&fbatch);
> > for_each_sgt_page(page, sgt_iter, st) {
> > struct folio *folio = page_folio(page);
> > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > return 0;
> > err_sg:
> > sg_mark_end(sg);
> > + mapping_clear_unevictable(mapping);
> > if (sg != st->sgl) {
> > shmem_sg_free_table(st, mapping, false, false);
> > } else {
> > - mapping_clear_unevictable(mapping);
> > sg_free_table(st);
> > }
> >
> > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > struct address_space *mapping = obj->base.filp->f_mapping;
> > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > struct sg_table *st;
> > - struct sgt_iter sgt_iter;
> > - struct page *page;
> > int ret;
> >
> > /*
> > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > * for PAGE_SIZE chunks instead may be helpful.
> > */
> > if (max_segment > PAGE_SIZE) {
> > - for_each_sgt_page(page, sgt_iter, st)
> > - put_page(page);
> > - sg_free_table(st);
> > + /* Leave the mapping unevictable while we retry */
> > + shmem_sg_free_table(st, mapping, false, false);
> > kfree(st);
> >
> > max_segment = PAGE_SIZE;
> > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > return 0;
> >
> > err_pages:
> > + mapping_clear_unevictable(mapping);
> > shmem_sg_free_table(st, mapping, false, false);
> > /*
> > * shmemfs first checks if there is enough memory to allocate the page
> > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > 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);
> > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > kfree(pages);
> > --
> > 2.48.0.rc2.279.g1de40edade-goog
>
> --
> Ville Syrjälä
> Intel
--
Ville Syrjälä
Intel
On Thu, Jan 16, 2025 at 9:38 AM Ville Syrjälä
<ville.syrjala@linux.intel.com> wrote:
>
> On Thu, Jan 16, 2025 at 04:24:26PM +0200, Ville Syrjälä wrote:
> > On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > > When converting to folios the cleanup path of shmem_get_pages() was
> > > missed. When a DMA remap fails and the max segment size is greater than
> > > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > > size. The cleanup code isn't properly using the folio apis and as a
> > > result isn't handling compound pages correctly.
> > >
> > > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > > Suggested-by: Tomasz Figa <tfiga@google.com>
> > > ---
> > > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > > 1 file changed, 5 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > index fe69f2c8527d..02ddab5bf5c0 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > > struct folio *last = NULL;
> > > struct page *page;
> > >
> > > - mapping_clear_unevictable(mapping);
> > > -
> >
> > The assymmetry here between the alloc vs. free is a bit annoying.
> > Maybe we can just keep this here?
>
> Actually, I guess it's a bit more than just annoying since
> shmem_sg_free_table() is actually used from outside i915_gem_shmem.c
> as well.
You're correct, this was a bad oversight on my part. This patch is
going to require a v2 regardless, how do you feel about just changing
shmem_sg_free_table() to not accept a mapping given that managing the
mapping is really orthogonal to cleaning up the sg table.
>
> >
> > Or if avoiding the ping-pong actually mattes in the gtt prepare
> > error case, then maybe we should rename this guy into
> > __shmem_sg_free_table() without the mapping_clear_unevictable()
> > and wrap it in a higher level shmem_sg_free_table() that does
> > everything?
> >
> > > folio_batch_init(&fbatch);
> > > for_each_sgt_page(page, sgt_iter, st) {
> > > struct folio *folio = page_folio(page);
> > > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > > return 0;
> > > err_sg:
> > > sg_mark_end(sg);
> > > + mapping_clear_unevictable(mapping);
> > > if (sg != st->sgl) {
> > > shmem_sg_free_table(st, mapping, false, false);
> > > } else {
> > > - mapping_clear_unevictable(mapping);
> > > sg_free_table(st);
> > > }
> > >
> > > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > struct address_space *mapping = obj->base.filp->f_mapping;
> > > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > > struct sg_table *st;
> > > - struct sgt_iter sgt_iter;
> > > - struct page *page;
> > > int ret;
> > >
> > > /*
> > > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > * for PAGE_SIZE chunks instead may be helpful.
> > > */
> > > if (max_segment > PAGE_SIZE) {
> > > - for_each_sgt_page(page, sgt_iter, st)
> > > - put_page(page);
> > > - sg_free_table(st);
> > > + /* Leave the mapping unevictable while we retry */
> > > + shmem_sg_free_table(st, mapping, false, false);
> > > kfree(st);
> > >
> > > max_segment = PAGE_SIZE;
> > > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > return 0;
> > >
> > > err_pages:
> > > + mapping_clear_unevictable(mapping);
> > > shmem_sg_free_table(st, mapping, false, false);
> > > /*
> > > * shmemfs first checks if there is enough memory to allocate the page
> > > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > > 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);
> > > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > > kfree(pages);
> > > --
> > > 2.48.0.rc2.279.g1de40edade-goog
> >
> > --
> > Ville Syrjälä
> > Intel
>
> --
> Ville Syrjälä
> Intel
On Thu, Jan 16, 2025 at 9:24 AM Ville Syrjälä
<ville.syrjala@linux.intel.com> wrote:
>
> On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > When converting to folios the cleanup path of shmem_get_pages() was
> > missed. When a DMA remap fails and the max segment size is greater than
> > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > size. The cleanup code isn't properly using the folio apis and as a
> > result isn't handling compound pages correctly.
> >
> > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > Suggested-by: Tomasz Figa <tfiga@google.com>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > 1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > index fe69f2c8527d..02ddab5bf5c0 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > struct folio *last = NULL;
> > struct page *page;
> >
> > - mapping_clear_unevictable(mapping);
> > -
>
> The assymmetry here between the alloc vs. free is a bit annoying.
> Maybe we can just keep this here?
If you want, I think this can also be fixed by something like the
following I believe.
Ultimately we don't want to put page on non-head pages in a compound
page. What do you think? If you like this better I can test and mail a v2.
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index fe69f2c8527d..b79cd396e878 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -239,8 +239,14 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
* for PAGE_SIZE chunks instead may be helpful.
*/
if (max_segment > PAGE_SIZE) {
- for_each_sgt_page(page, sgt_iter, st)
+ struct folio *last = NULL;
+ for_each_sgt_page(page, sgt_iter, st) {
+ struct folio *folio = page_folio(page);
+ if (folio == last)
+ continue;
+ last = folio;
put_page(page);
+ }
sg_free_table(st);
kfree(st);
--
2.48.0.rc2.279.g1de40edade-goog
>
> Or if avoiding the ping-pong actually mattes in the gtt prepare
> error case, then maybe we should rename this guy into
> __shmem_sg_free_table() without the mapping_clear_unevictable()
> and wrap it in a higher level shmem_sg_free_table() that does
> everything?
>
> > folio_batch_init(&fbatch);
> > for_each_sgt_page(page, sgt_iter, st) {
> > struct folio *folio = page_folio(page);
> > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > return 0;
> > err_sg:
> > sg_mark_end(sg);
> > + mapping_clear_unevictable(mapping);
> > if (sg != st->sgl) {
> > shmem_sg_free_table(st, mapping, false, false);
> > } else {
> > - mapping_clear_unevictable(mapping);
> > sg_free_table(st);
> > }
> >
> > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > struct address_space *mapping = obj->base.filp->f_mapping;
> > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > struct sg_table *st;
> > - struct sgt_iter sgt_iter;
> > - struct page *page;
> > int ret;
> >
> > /*
> > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > * for PAGE_SIZE chunks instead may be helpful.
> > */
> > if (max_segment > PAGE_SIZE) {
> > - for_each_sgt_page(page, sgt_iter, st)
> > - put_page(page);
> > - sg_free_table(st);
> > + /* Leave the mapping unevictable while we retry */
> > + shmem_sg_free_table(st, mapping, false, false);
> > kfree(st);
> >
> > max_segment = PAGE_SIZE;
> > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > return 0;
> >
> > err_pages:
> > + mapping_clear_unevictable(mapping);
> > shmem_sg_free_table(st, mapping, false, false);
> > /*
> > * shmemfs first checks if there is enough memory to allocate the page
> > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > 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);
> > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > kfree(pages);
> > --
> > 2.48.0.rc2.279.g1de40edade-goog
>
> --
> Ville Syrjälä
> Intel
On Thu, Jan 16, 2025 at 09:36:42AM -0500, Brian Geffon wrote:
> On Thu, Jan 16, 2025 at 9:24 AM Ville Syrjälä
> <ville.syrjala@linux.intel.com> wrote:
> >
> > On Thu, Jan 16, 2025 at 08:56:36AM -0500, Brian Geffon wrote:
> > > When converting to folios the cleanup path of shmem_get_pages() was
> > > missed. When a DMA remap fails and the max segment size is greater than
> > > PAGE_SIZE it will attempt to retry the remap with a PAGE_SIZEd segment
> > > size. The cleanup code isn't properly using the folio apis and as a
> > > result isn't handling compound pages correctly.
> > >
> > > Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13487
> > > Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
> > > Signed-off-by: Brian Geffon <bgeffon@google.com>
> > > Suggested-by: Tomasz Figa <tfiga@google.com>
> > > ---
> > > drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 13 +++++--------
> > > 1 file changed, 5 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > index fe69f2c8527d..02ddab5bf5c0 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> > > @@ -37,8 +37,6 @@ void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
> > > struct folio *last = NULL;
> > > struct page *page;
> > >
> > > - mapping_clear_unevictable(mapping);
> > > -
> >
> > The assymmetry here between the alloc vs. free is a bit annoying.
> > Maybe we can just keep this here?
>
> If you want, I think this can also be fixed by something like the
> following I believe.
> Ultimately we don't want to put page on non-head pages in a compound
> page. What do you think? If you like this better I can test and mail a v2.
I think having it all in one place would be nicer, if only to avoid
similar oversights in the future.
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index fe69f2c8527d..b79cd396e878 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> @@ -239,8 +239,14 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> * for PAGE_SIZE chunks instead may be helpful.
> */
> if (max_segment > PAGE_SIZE) {
> - for_each_sgt_page(page, sgt_iter, st)
> + struct folio *last = NULL;
> + for_each_sgt_page(page, sgt_iter, st) {
> + struct folio *folio = page_folio(page);
> + if (folio == last)
> + continue;
> + last = folio;
> put_page(page);
> + }
> sg_free_table(st);
> kfree(st);
>
>
> --
> 2.48.0.rc2.279.g1de40edade-goog
>
>
> >
> > Or if avoiding the ping-pong actually mattes in the gtt prepare
> > error case, then maybe we should rename this guy into
> > __shmem_sg_free_table() without the mapping_clear_unevictable()
> > and wrap it in a higher level shmem_sg_free_table() that does
> > everything?
> >
> > > folio_batch_init(&fbatch);
> > > for_each_sgt_page(page, sgt_iter, st) {
> > > struct folio *folio = page_folio(page);
> > > @@ -180,10 +178,10 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
> > > return 0;
> > > err_sg:
> > > sg_mark_end(sg);
> > > + mapping_clear_unevictable(mapping);
> > > if (sg != st->sgl) {
> > > shmem_sg_free_table(st, mapping, false, false);
> > > } else {
> > > - mapping_clear_unevictable(mapping);
> > > sg_free_table(st);
> > > }
> > >
> > > @@ -209,8 +207,6 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > struct address_space *mapping = obj->base.filp->f_mapping;
> > > unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
> > > struct sg_table *st;
> > > - struct sgt_iter sgt_iter;
> > > - struct page *page;
> > > int ret;
> > >
> > > /*
> > > @@ -239,9 +235,8 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > * for PAGE_SIZE chunks instead may be helpful.
> > > */
> > > if (max_segment > PAGE_SIZE) {
> > > - for_each_sgt_page(page, sgt_iter, st)
> > > - put_page(page);
> > > - sg_free_table(st);
> > > + /* Leave the mapping unevictable while we retry */
> > > + shmem_sg_free_table(st, mapping, false, false);
> > > kfree(st);
> > >
> > > max_segment = PAGE_SIZE;
> > > @@ -265,6 +260,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
> > > return 0;
> > >
> > > err_pages:
> > > + mapping_clear_unevictable(mapping);
> > > shmem_sg_free_table(st, mapping, false, false);
> > > /*
> > > * shmemfs first checks if there is enough memory to allocate the page
> > > @@ -402,6 +398,7 @@ void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_
> > > 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);
> > > shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
> > > obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
> > > kfree(pages);
> > > --
> > > 2.48.0.rc2.279.g1de40edade-goog
> >
> > --
> > Ville Syrjälä
> > Intel
--
Ville Syrjälä
Intel
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