From 6a0bdffa0073857870a4ed1b4489762146359eb4 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 20 Jun 2012 16:04:19 -0400 Subject: [PATCH] SCSI & usb-storage: add try_rc_10_first flag Several bug reports have been received recently for USB mass-storage devices that don't handle READ CAPACITY(16) commands properly. They report bogus sizes, in some cases becoming unusable as a result. The bugs were triggered by commit 09b6b51b0b6c1b9bb61815baf205e4d74c89ff04 (SCSI & usb-storage: add flags for VPD pages and REPORT LUNS), which caused usb-storage to stop overriding the SCSI level reported by devices. By default, the sd driver will try READ CAPACITY(16) first for any device whose level is above SCSI_SPC_2. It seems likely that any device large enough to require the use of READ CAPACITY(16) (i.e., 2 TB or more) would be able to handle READ CAPACITY(10) commands properly. Indeed, I don't know of any devices that don't handle READ CAPACITY(10) properly. Therefore this patch (as1559) adds a new flag telling the sd driver to try READ CAPACITY(10) before READ CAPACITY(16), and sets this flag for every USB mass-storage device. If a device really is larger than 2 TB, sd will fall back to READ CAPACITY(16) just as it used to. This fixes Bugzilla #43391. Signed-off-by: Alan Stern Acked-by: Hans de Goede CC: "James E.J. Bottomley" CC: Matthew Dharm Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/sd.c | 2 ++ drivers/usb/storage/scsiglue.c | 6 ++++++ include/scsi/scsi_device.h | 1 + 3 files changed, 9 insertions(+) diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 6f0a4c6..6f72b80 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1899,6 +1899,8 @@ static int sd_try_rc16_first(struct scsi_device *sdp) { if (sdp->host->max_cmd_len < 16) return 0; + if (sdp->try_rc_10_first) + return 0; if (sdp->scsi_level > SCSI_SPC_2) return 1; if (scsi_device_protection(sdp)) diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c index a324a5d..11418da 100644 --- a/drivers/usb/storage/scsiglue.c +++ b/drivers/usb/storage/scsiglue.c @@ -202,6 +202,12 @@ static int slave_configure(struct scsi_device *sdev) if (us->fflags & US_FL_NO_READ_CAPACITY_16) sdev->no_read_capacity_16 = 1; + /* + * Many devices do not respond properly to READ_CAPACITY_16. + * Tell the SCSI layer to try READ_CAPACITY_10 first. + */ + sdev->try_rc_10_first = 1; + /* assume SPC3 or latter devices support sense size > 18 */ if (sdev->scsi_level > SCSI_SPC_2) us->fflags |= US_FL_SANE_SENSE; diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 6efb2e1..ba96988 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -151,6 +151,7 @@ struct scsi_device { SD_LAST_BUGGY_SECTORS */ unsigned no_read_disc_info:1; /* Avoid READ_DISC_INFO cmds */ unsigned no_read_capacity_16:1; /* Avoid READ_CAPACITY_16 cmds */ + unsigned try_rc_10_first:1; /* Try READ_CAPACACITY_10 first */ unsigned is_visible:1; /* is the device visible in sysfs */ DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */ -- 2.7.4