tjh.dev / kernel
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drm/shmem-helper: Add and use pages_pin_count

Add separate pages_pin_count for tracking of whether drm-shmem pages are
moveable or not. With the addition of memory shrinker support to drm-shmem,
the pages_use_count will no longer determine whether pages are hard-pinned
in memory, but whether pages exist and are soft-pinned (and could be swapped
out). The pages_pin_count > 1 will hard-pin pages in memory.

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.d>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250322212608.40511-8-dmitry.osipenko@collabora.com

Dmitry Osipenko d586b535 eab10538

+26 -1
+15 -1
drivers/gpu/drm/drm_gem_shmem_helper.c
··· 177 177 drm_gem_shmem_put_pages_locked(shmem); 178 178 179 179 drm_WARN_ON(obj->dev, shmem->pages_use_count); 180 + drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count)); 180 181 181 182 dma_resv_unlock(shmem->base.resv); 182 183 } ··· 258 257 259 258 drm_WARN_ON(shmem->base.dev, drm_gem_is_imported(&shmem->base)); 260 259 260 + if (refcount_inc_not_zero(&shmem->pages_pin_count)) 261 + return 0; 262 + 261 263 ret = drm_gem_shmem_get_pages_locked(shmem); 264 + if (!ret) 265 + refcount_set(&shmem->pages_pin_count, 1); 262 266 263 267 return ret; 264 268 } ··· 273 267 { 274 268 dma_resv_assert_held(shmem->base.resv); 275 269 276 - drm_gem_shmem_put_pages_locked(shmem); 270 + if (refcount_dec_and_test(&shmem->pages_pin_count)) 271 + drm_gem_shmem_put_pages_locked(shmem); 277 272 } 278 273 EXPORT_SYMBOL(drm_gem_shmem_unpin_locked); 279 274 ··· 294 287 int ret; 295 288 296 289 drm_WARN_ON(obj->dev, drm_gem_is_imported(obj)); 290 + 291 + if (refcount_inc_not_zero(&shmem->pages_pin_count)) 292 + return 0; 297 293 298 294 ret = dma_resv_lock_interruptible(shmem->base.resv, NULL); 299 295 if (ret) ··· 320 310 struct drm_gem_object *obj = &shmem->base; 321 311 322 312 drm_WARN_ON(obj->dev, drm_gem_is_imported(obj)); 313 + 314 + if (refcount_dec_not_one(&shmem->pages_pin_count)) 315 + return; 323 316 324 317 dma_resv_lock(shmem->base.resv, NULL); 325 318 drm_gem_shmem_unpin_locked(shmem); ··· 673 660 if (drm_gem_is_imported(&shmem->base)) 674 661 return; 675 662 663 + drm_printf_indent(p, indent, "pages_pin_count=%u\n", refcount_read(&shmem->pages_pin_count)); 676 664 drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count); 677 665 drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count); 678 666 drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
+11
include/drm/drm_gem_shmem_helper.h
··· 40 40 unsigned int pages_use_count; 41 41 42 42 /** 43 + * @pages_pin_count: 44 + * 45 + * Reference count on the pinned pages table. 46 + * 47 + * Pages are hard-pinned and reside in memory if count 48 + * greater than zero. Otherwise, when count is zero, the pages are 49 + * allowed to be evicted and purged by memory shrinker. 50 + */ 51 + refcount_t pages_pin_count; 52 + 53 + /** 43 54 * @madv: State for madvise 44 55 * 45 56 * 0 is active/inuse.