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 as a precaution on hard drives which do not support the Synchronize Cache command and therefore the cache flushing functionality. 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 a/drivers/scsi/sd.c b/drivers/scsi/sd.c --- a/drivers/scsi/sd.c 2019-03-17 18:22:04.822720851 +0100 +++ b/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;
