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. 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
