Many obsolete hard drives do not support the Synchronize Cache SCSI command. Such command is generally issued during fsync() calls which at the moment therefore fail with the ILLEGAL_REQUEST sense key. Since this failure is currently treated as critical in the kernel SCSI disk driver, such obsolete hard drives cannot be used anymore: they cannot be formatted, mounted and/or checked using tools such as e2fsprogs. Because there is nothing which can be done if the drive does not support such command, such ILLEGAL_REQUEST should be treated as non-critical so that the underlying operation does not fail and the obsolete hard drive can be used normally. This patch disables the Write Cache feature and therefore the cache flushing functionality, as a precaution on hard drives which do not support the Synchronize Cache command. Fixes bug: https://bugzilla.kernel.org/show_bug.cgi?id=203635 Signed-off-by: Guido Trentalancia <guido@xxxxxxxxxxxxxxxx> --- drivers/scsi/sd.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff -pru linux-5.0.2-orig/drivers/scsi/sd.c linux-5.0.2/drivers/scsi/sd.c --- linux-5.0.2-orig/drivers/scsi/sd.c 2019-03-17 18:22:04.822720851 +0100 +++ linux-5.0.2/drivers/scsi/sd.c 2019-03-20 17:41:44.526957307 +0100 @@ -22,6 +22,10 @@ * - Badari Pulavarty <pbadari@xxxxxxxxxx>, Matthew Wilcox * <willy@xxxxxxxxxx>, Kurt Garloff <garloff@xxxxxxx>: * Support 32k/1M disks. + * - Guido Trentalancia <guido@xxxxxxxxxxxxxxxx> ignore Synchronize + * Cache command failures on hard-drives that do not support it + * and disable the Write Cache functionality on such devices as a + * precaution: this allows to keep using several obsolete drives. * * Logging policy (needs CONFIG_SCSI_LOGGING defined): * - setting up transfer: SCSI_LOG_HLQUEUE levels 1 and 2 @@ -1633,6 +1637,20 @@ static int sd_sync_cache(struct scsi_dis } if (res) { + /* + * sshdr.sense_key == ILLEGAL_REQUEST means this drive + * doesn't support sync. There's not much to do and + * sync shouldn't fail. + */ + if (sshdr->sense_key == ILLEGAL_REQUEST && sshdr->asc == 0x20) { + if (sdkp->WCE) { + sdkp->WCE = 0; + sd_printk(KERN_NOTICE, sdkp, "Drive does not support Synchronize Cache(10) command: disabling write cache.\n"); + sd_set_flush_flag(sdkp); + } + return 0; + } + sd_print_result(sdkp, "Synchronize Cache(10) failed", res); if (driver_byte(res) == DRIVER_SENSE) @@ -2022,6 +2040,17 @@ static int sd_done(struct scsi_cmnd *SCp req->rq_flags |= RQF_QUIET; } break; + case SYNCHRONIZE_CACHE: + if (sshdr.asc == 0x20) { + if (sdkp->WCE) { + sdkp->WCE = 0; + sd_printk(KERN_NOTICE, sdkp, "Drive does not support Synchronize Cache(10) command: disabling write cache.\n"); + sd_set_flush_flag(sdkp); + } + SCpnt->result = 0; + good_bytes = scsi_bufflen(SCpnt); + } + break; } } break;
