The sg3_utils command
sg_reset --device /dev/sda
invokes an ioctl with SG_SCSI_RESET, an argument of
SG_SCSI_RESET_DEVICE, on a device opened with O_NDELAY.
The call chain is like this:
sd_ioctl [sd.c]
scsi_nonblockable_ioctl [scsi_ioctl.c]
if (ndelay) { [this is true]
if (scsi_host_in_recovery(sdev->host))
return -ENODEV;
}
scsi_reset_provider [scsi_error.c]
shost->tmf_in_progress = 1;
scsi_try_bus_device_reset [scsi_error.c]
hostt->eh_device_reset_handler [LLD]
shost->tmf_in_progress = 1;
if that returns 0, return; otherwise try:
scsi_cmd_blk_ioctl
scsi_ioctl
sdev->host->hostt->ioctl [LLD]
where scsi_host_in_recovery is:
static inline int scsi_host_in_recovery(struct Scsi_Host *shost)
{
return shost->shost_state == SHOST_RECOVERY ||
shost->shost_state == SHOST_CANCEL_RECOVERY ||
shost->shost_state == SHOST_DEL_RECOVERY ||
shost->tmf_in_progress;
}
Problem
=======
If you run sg_reset --device concurrently to multiple
devices on the same host, then some of them will run
into tmf_in_progress and have scsi_nonblockable_ioctl
return -ENODEV. This causes sd_ioctl to send the ioctl
request to the LLD's ioctl function, where it gets
rejected as unsupported with -ENOTTY. sg_reset ends
up displaying:
sg_reset: SG_SCSI_RESET failed: Inappropriate ioctl for device
Any suggestions for how to fix this?
Is the check of scsi_host_in_recovery, which includes
tmf_in_progress, too strong? Most LLDs are not parallel
SCSI where you can just have one TMF on the bus at a
time anymore.
Is returning -ENODEV if the host is in recovery the
wrong code? There might be a device there...it's
just that access is temporarily blocked.
Should sd_ioctl not proceed to scsi_ioctl in so many
cases? Perhaps it should:
* proceed if it gets back -EINVAL (and maybe -ENOTTY)
indicating the ioctl specified was bad
* return if it gets back any other error (e.g., -ENODEV,
-EACCESS, or -EIO)
That would at least result in a more meaningful error.
Also, should scsi_nonblockable_ioctl return -ENOTTY rather
than -ENODEV if cmd is unsupported? There's not really
a no-device problem.
---
Rob Elliott HP Server Storage
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