Re: [PATCH v16 3/7] drm/ttm: Use fault-injection to test error paths

[Christian König <christian.koenig@xxxxxxx>]

Am 30.01.25 um 11:13 schrieb Thomas Hellström:
> Use fault-injection to test partial TTM swapout and interrupted swapin.
> Return -EINTR for swapin to test the callers ability to handle and
> restart the swapin, and on swapout perform a partial swapout to test that
> the swapin and release_shrunken functionality.
>
> v8:
> - Use the core fault-injection system.
> v9:
> - Fix compliation failure for !CONFIG_FAULT_INJECTION
>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@xxxxxxx>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx> #v7

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

> ---
>   drivers/gpu/drm/ttm/ttm_pool.c | 25 ++++++++++++++++++++++++-
>   1 file changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index ffb7abf52bab..83b10706ba89 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -48,6 +48,13 @@
>   
>   #include "ttm_module.h"
>   
> +#ifdef CONFIG_FAULT_INJECTION
> +#include <linux/fault-inject.h>
> +static DECLARE_FAULT_ATTR(backup_fault_inject);
> +#else
> +#define should_fail(...) false
> +#endif
> +
>   /**
>    * struct ttm_pool_dma - Helper object for coherent DMA mappings
>    *
> @@ -514,6 +521,12 @@ static int ttm_pool_restore_commit(struct ttm_pool_tt_restore *restore,
>   		if (ttm_backup_page_ptr_is_handle(p)) {
>   			unsigned long handle = ttm_backup_page_ptr_to_handle(p);
>   
> +			if (IS_ENABLED(CONFIG_FAULT_INJECTION) && ctx->interruptible &&
> +			    should_fail(&backup_fault_inject, 1)) {
> +				ret = -EINTR;
> +				break;
> +			}
> +
>   			if (handle == 0) {
>   				restore->restored_pages++;
>   				continue;
> @@ -1007,7 +1020,13 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *tt,
>   
>   	alloc_gfp = GFP_KERNEL | __GFP_HIGH | __GFP_NOWARN | __GFP_RETRY_MAYFAIL;
>   
> -	for (i = 0; i < tt->num_pages; ++i) {
> +	num_pages = tt->num_pages;
> +
> +	/* Pretend doing fault injection by shrinking only half of the pages. */
> +	if (IS_ENABLED(CONFIG_FAULT_INJECTION) && should_fail(&backup_fault_inject, 1))
> +		num_pages = DIV_ROUND_UP(num_pages, 2);
> +
> +	for (i = 0; i < num_pages; ++i) {
>   		s64 shandle;
>   
>   		page = tt->pages[i];
> @@ -1293,6 +1312,10 @@ int ttm_pool_mgr_init(unsigned long num_pages)
>   			    &ttm_pool_debugfs_globals_fops);
>   	debugfs_create_file("page_pool_shrink", 0400, ttm_debugfs_root, NULL,
>   			    &ttm_pool_debugfs_shrink_fops);
> +#ifdef CONFIG_FAULT_INJECTION
> +	fault_create_debugfs_attr("backup_fault_inject", ttm_debugfs_root,
> +				  &backup_fault_inject);
> +#endif
>   #endif
>   
>   	mm_shrinker = shrinker_alloc(0, "drm-ttm_pool");