Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752683AbbFDKVA (ORCPT ); Thu, 4 Jun 2015 06:21:00 -0400 Received: from protonic.xs4all.nl ([83.163.252.89]:24186 "EHLO protonic.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751175AbbFDKU2 (ORCPT ); Thu, 4 Jun 2015 06:20:28 -0400 From: David Jander To: Pierre Ossman , Ulf Hansson , Sascha Hauer Cc: Johan Rudholm , Adrian Hunter , Javier Martinez Canillas , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, David Jander Subject: [RFC PATCH 2/2] mmc: core.c: Add comment to clarify special cases of ERASE/TRIM Date: Thu, 4 Jun 2015 12:20:14 +0200 Message-Id: <1433413214-21614-1-git-send-email-david@protonic.nl> X-Mailer: git-send-email 2.1.4 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2744 Lines: 71 Signed-off-by: David Jander --- drivers/mmc/core/core.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 6c9611b..b6aa9ad 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -2109,11 +2109,20 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr, !(card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN)) return -EOPNOTSUPP; + /* + * Sanity check: If we do not erase aligned, whole erase-groups, return + * an error, since we intended a "secure" erase, silently not erasing + * something would be unacceptable. + */ if (arg == MMC_SECURE_ERASE_ARG) { if (from % card->erase_size || nr % card->erase_size) return -EINVAL; } + /* + * Make sure only erase-groups that are fully contained in the erase + * region are erased. Silently ignore the rest. + */ if (arg == MMC_ERASE_ARG) { rem = from % card->erase_size; if (rem) { @@ -2140,6 +2149,14 @@ int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr, /* 'from' and 'to' are inclusive */ to -= 1; + /* + * Special case where only one erase-group fits in the timout budget: + * If the region crosses an erase-group boundary on this particular + * case, we will be trimming more than one erase-group which, does not + * fit in the timeout budget of the controller, so we need to split it + * and call mmc_do_erase() twice if necessary. This special case is + * identified by the card->eg_boundary flag. + */ if ((arg & MMC_TRIM_ARGS) && (card->eg_boundary) && (from % card->erase_size)) { rem = card->erase_size - (from % card->erase_size); @@ -2244,7 +2261,16 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card, if (!qty) return 0; - /* We can only erase one erase group special case */ + /* + * When specifying a sector range to trim, chances are we might cross + * an erase-group boundary even if the amount of sectors is less than + * one erase-group. + * If we can only fit one erase-group in the controller timeout budget, + * we have to care that erase-group boundaries are not crossed by a + * single trim operation. We flag that special case with "eg_boundary". + * In all other cases we can just decrement qty and pretend that we + * always touch (qty + 1) erase-groups as a simple optimization. + */ if (qty == 1) card->eg_boundary = 1; else -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/