Hi,
while playing with suspend to ram I found a strange behavior with usb
key.
This can be easily reproduced by doing :
- plug a usb key
- start to read the usb key : "cat /dev/sdx > /dev/null"
- go to suspend : "echo mem > /sys/power/state"
- while in suspend, unplug and replug the usb key (simulate usb power
loss for computer that keep power)
- exit suspend
- there is read error on the usb key
Because the power was cut during s2ram, the usb stack reset the device
<1>.
When new data transfer are done, we got a UNIT_ATTENTION from the
device <2> and IO error are returned to user space application.
After some investigation it seems some (all on the 3 I tested) usb key
report as removable, and scsi layer abort the transfer in case of
UNIT_ATTENTION <3>.
The usb storage driver call scsi_report_bus_reset after device reset,
but because of commit dfcf7775 <4>, we don't ignore unit attention if
"sshdr.asc == 0x28 && sshdr.ascq == 0x00" ("Not-ready to ready").
If dfcf7775 is reverted there is no more Buffer I/O error.
Is that possible to find a way to restore the behavior before dfcf7775
commit (no Buffer I/O error after device reset) after a suspend to ram ?
Matthieu CASTET
PS : the same error happen if sg_reset -b /dev/sdx is used on the
device.
<1>
[ 117.070255] usb 2-1.4: reset high-speed USB device number 3 using
ehci-pci [...]
[ 117.543922] Restarting tasks ... done.
[ 117.548390] video LNXVIDEO:01: Restoring backlight state
<2>
[ 117.549179] sd 6:0:0:0: [sdb] Media Changed
[ 117.549184] sd 6:0:0:0: [sdb]
[ 117.549187] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 117.549189] sd 6:0:0:0: [sdb]
[ 117.549191] Sense Key : Unit Attention [current]
[ 117.549195] Info fld=0x0
[ 117.549197] sd 6:0:0:0: [sdb]
[ 117.549201] Add. Sense: Not ready to ready change, medium may have
changed [ 117.549203] sd 6:0:0:0: [sdb] CDB:
[ 117.549205] Read(10): 28 00 00 02 c9 00 00 00 f0 00
[ 117.549212] end_request: I/O error, dev sdb, sector 182528
[ 117.549218] Buffer I/O error on device sdb1, logical block 22560
[ 117.549225] Buffer I/O error on device sdb1, logical block 22561
[ 117.549228] Buffer I/O error on device sdb1, logical block 22562
[ 117.549231] Buffer I/O error on device sdb1, logical block 22563
[ 117.549233] Buffer I/O error on device sdb1, logical block 22564
[ 117.549235] Buffer I/O error on device sdb1, logical block 22565
[ 117.549238] Buffer I/O error on device sdb1, logical block 22566
[ 117.549240] Buffer I/O error on device sdb1, logical block 22567
[ 117.549243] Buffer I/O error on device sdb1, logical block 22568
[ 117.549245] Buffer I/O error on device sdb1, logical block 22569
[ 117.809462] sd 6:0:0:0: [sdb] No Caching mode page found
[ 117.809470] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[ 117.812696] sd 6:0:0:0: [sdb] No Caching mode page found
[ 117.812703] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[ 117.813688] sdb: sdb1
<3>
case UNIT_ATTENTION:
if (cmd->device->removable) {
/* Detected disc change. Set a bit
* and quietly refuse further access.
*/
cmd->device->changed = 1;
description = "Media Changed";
action = ACTION_FAIL;
} else {
/* Must have been a power glitch, or a
* bus reset. Could not have been a
* media change, so we just retry the
* command and see what happens.
*/
action = ACTION_RETRY;
}
<4>
commit dfcf7775815504d13a1d273073810058caf84b9d
Author: TARUISI Hiroaki <taruishi.hiroak@xxxxxxxxxxxxxx>
Date: Thu Aug 11 20:25:20 2011 +0900
[SCSI] Fix out of spec CD-ROM problem with media change
Some CD-ROMs fail to report a media change correctly. The specific
one for this patch simply fails to respond to commands, then gives a
UNIT ATTENTION after being reset which returns ASC/ASCQ 28/00. This
is out of spec behaviour, but add a check in the eat CC/UA on reset
path to catch this case so the CD-ROM will function somewhat properly.
[jejb: fixed up white space and accepted without signoff]
Signed-off-by: James Bottomley <JBottomley@xxxxxxxxxxxxx>
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index a4b9cdb..dc6131e 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -293,8 +293,16 @@ static int scsi_check_sense(struct scsi_cmnd *scmd)
* so that we can deal with it there.
*/
if (scmd->device->expecting_cc_ua) {
- scmd->device->expecting_cc_ua = 0;
- return NEEDS_RETRY;
+ /*
+ * Because some device does not queue unit
+ * attentions correctly, we carefully check
+ * additional sense code and qualifier so as
+ * not to squash media change unit attention.
+ */
+ if (sshdr.asc != 0x28 || sshdr.ascq != 0x00) {
+ scmd->device->expecting_cc_ua = 0;
+ return NEEDS_RETRY;
+ }
}
/*
* if the device is in the process of becoming ready, we
--
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