Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753590AbcLGVWz (ORCPT ); Wed, 7 Dec 2016 16:22:55 -0500 Received: from mail-wj0-f194.google.com ([209.85.210.194]:33066 "EHLO mail-wj0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752918AbcLGVWu (ORCPT ); Wed, 7 Dec 2016 16:22:50 -0500 From: Nicolai Stange To: Tejun Heo Cc: Shaun Tancheff , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Nicolai Stange Subject: [PATCH] libata-scsi: disable SCT Write Same for the moment Date: Wed, 7 Dec 2016 22:21:33 +0100 Message-Id: <20161207212133.3463-1-nicstange@gmail.com> X-Mailer: git-send-email 2.10.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2402 Lines: 62 SCT Write Same support had been introduced with commit 7b2030942859 ("libata: Add support for SCT Write Same") Some problems, namely excessive userspace segfaults, had been reported at http://lkml.kernel.org/r/20160908192736.GA4356@gmail.com This lead to commit 0ce1b18c42a5 ("libata: Some drives failing on SCT Write Same") which strived to disable SCT Write Same on !ZAC devices. Due to the way this was done and to the logic in sd_config_write_same(), this didn't work for those devices that have ->max_ws_blocks > SD_MAX_WS10_BLOCKS: for these, ->no_write_same and ->max_write_same_sectors would still be non-zero, but ->ws10 == ->ws16 == 0. This would cause sd_setup_write_same_cmnd() to demultiplex REQ_OP_WRITE_SAME requests to WRITE_SAME, and these in turn aren't supported by libata-scsi: EXT4-fs (dm-1): Delayed block allocation failed for inode 2625094 at logical offset 2032 with max blocks 2 with error 121 EXT4-fs (dm-1): This should not happen!! Data will be lost 121 == EREMOTEIO is what scsi_io_completion() asserts in case of invalid opcodes. Back to the original problem of userspace segfaults: this can be tracked down to ata_format_sct_write_same() overwriting the input page. Sometimes, this page is ZERO_PAGE(0) which ceases to be filled with zeros from that point on. Since ZERO_PAGE(0) is used for userspace .bss mappings, code of the following is doomed: static char *a = NULL; /* .bss */ ... if (a) *a = 'a'; This problem is not solved by disabling SCT Write Same for !ZAC devices only. It can certainly be fixed, but the final release is quite close -- so disable SCT Write Same for all ATA devices rather than introducing some SCT key buffer allocation schemes at this point. Fixes: 7b2030942859 ("libata: Add support for SCT Write Same") Signed-off-by: Nicolai Stange --- drivers/ata/libata-scsi.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 982bcfc..c9abb87 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -1234,6 +1234,7 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev) { sdev->use_10_for_rw = 1; sdev->use_10_for_ms = 1; + sdev->no_write_same = 1; /* Schedule policy is determined by ->qc_defer() callback and * it needs to see every deferred qc. Set dev_blocked to 1 to -- 2.10.2