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@xxxxxxxxxxxxxxx> 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@xxxxxxxxxx> > > > Suggested-by: Tomasz Figa <tfiga@xxxxxxxxxx> > > > --- > > > 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
