i915: fix slab_create() related memory leaks

For instance, this issue is triggered with "piglit/bin/fcc-blit-between-clears -auto -fbo":
Direct leak of 836 byte(s) in 1 object(s) allocated from:
    #0 0xb71eb6f2 in malloc (/usr/lib/libasan.so.6+0xb26f2)
    #1 0xaefadc78 in slab_add_new_page ../src/util/slab.c:179
    #2 0xaefadc78 in slab_alloc ../src/util/slab.c:221
    #3 0xaef7d461 in i915_texture_transfer_map ../src/gallium/drivers/i915/i915_resource_texture.c:789
    #4 0xac9e931e in pipe_texture_map ../src/gallium/auxiliary/util/u_inlines.h:555
    #5 0xac9e931e in _mesa_map_renderbuffer ../src/mesa/main/renderbuffer.c:494
    #6 0xad49c5e4 in readpixels_memcpy ../src/mesa/main/readpix.c:260
    #7 0xad49c5e4 in _mesa_readpixels ../src/mesa/main/readpix.c:898
    #8 0xad5d8cfe in st_ReadPixels ../src/mesa/state_tracker/st_cb_readpixels.c:568
    #9 0xad4a0caf in read_pixels ../src/mesa/main/readpix.c:1199
    #10 0xad4a0caf in _mesa_ReadnPixelsARB ../src/mesa/main/readpix.c:1216
    #11 0xad4a155b in _mesa_ReadPixels ../src/mesa/main/readpix.c:1231

or "piglit/bin/fcc-read-to-pbo-after-clear -auto":
Direct leak of 772 byte(s) in 1 object(s) allocated from:
    #0 0xb726b6f2 in malloc (/usr/lib/libasan.so.6+0xb26f2)
    #1 0xaf0adc88 in slab_add_new_page ../src/util/slab.c:179
    #2 0xaf0adc88 in slab_alloc ../src/util/slab.c:221
    #3 0xaf07aad7 in i915_buffer_transfer_map ../src/gallium/drivers/i915/i915_resource_buffer.c:75
    #4 0xad10de74 in pipe_buffer_map_range ../src/gallium/auxiliary/util/u_inlines.h:398
    #5 0xad10de74 in _mesa_bufferobj_map_range ../src/mesa/main/bufferobj.c:499
    #6 0xad5677ce in _mesa_map_pbo_dest ../src/mesa/main/pbo.c:308
    #7 0xad59be3b in _mesa_readpixels ../src/mesa/main/readpix.c:894
    #8 0xad6d8cfe in st_ReadPixels ../src/mesa/state_tracker/st_cb_readpixels.c:568
    #9 0xad5a0caf in read_pixels ../src/mesa/main/readpix.c:1199
    #10 0xad5a0caf in _mesa_ReadnPixelsARB ../src/mesa/main/readpix.c:1216
    #11 0xad5a155b in _mesa_ReadPixels ../src/mesa/main/readpix.c:1231

Fixes: e7a73b7 ("gallium: switch drivers to the slab allocator in src/util")
Signed-off-by: Patrick Lerda <[email protected]>
Reviewed-by: Emma Anholt <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27570>

Author: Patrick Lerda

src/gallium/drivers/i915/i915_context.c

@@ -159,6 +159,9 @@ i915_destroy(struct pipe_context *pipe)
       pipe_resource_reference(&i915->constants[i], NULL);
    }
 
+   slab_destroy(&i915->texture_transfer_pool);
+   slab_destroy(&i915->transfer_pool);
+
    FREE(i915);
 }