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Commit 6a0bdffa0073857870a4ed1b4489762146359eb4

Authored by Alan Stern
Committed by Greg Kroah-Hartman
1 parent 1e2c4e59d2
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

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 <stern@rowland.harvard.edu>
Acked-by: Hans de Goede <hdegoede@redhat.com>
CC: "James E.J. Bottomley" <JBottomley@parallels.com>
CC: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Showing 3 changed files with 9 additions and 0 deletions Side-by-side Diff

... ... @@ -1899,6 +1899,8 @@
1899 1899 {
1900 1900 if (sdp->host->max_cmd_len < 16)
1901 1901 return 0;
  1902 + if (sdp->try_rc_10_first)
  1903 + return 0;
1902 1904 if (sdp->scsi_level > SCSI_SPC_2)
1903 1905 return 1;
1904 1906 if (scsi_device_protection(sdp))
drivers/usb/storage/scsiglue.c
Diff comments   View file @ 6a0bdff
... ... @@ -202,6 +202,12 @@
202 202 if (us->fflags & US_FL_NO_READ_CAPACITY_16)
203 203 sdev->no_read_capacity_16 = 1;
204 204  
  205 + /*
  206 + * Many devices do not respond properly to READ_CAPACITY_16.
  207 + * Tell the SCSI layer to try READ_CAPACITY_10 first.
  208 + */
  209 + sdev->try_rc_10_first = 1;
  210 +
205 211 /* assume SPC3 or latter devices support sense size > 18 */
206 212 if (sdev->scsi_level > SCSI_SPC_2)
207 213 us->fflags |= US_FL_SANE_SENSE;
include/scsi/scsi_device.h
Diff comments   View file @ 6a0bdff
... ... @@ -151,6 +151,7 @@
151 151 SD_LAST_BUGGY_SECTORS */
152 152 unsigned no_read_disc_info:1; /* Avoid READ_DISC_INFO cmds */
153 153 unsigned no_read_capacity_16:1; /* Avoid READ_CAPACITY_16 cmds */
  154 + unsigned try_rc_10_first:1; /* Try READ_CAPACACITY_10 first */
154 155 unsigned is_visible:1; /* is the device visible in sysfs */
155 156  
156 157 DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */