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SubjectDisk failure behavior
Hi,

I am using a back-port of libata from ~ 2.6.20 on a 2.6.9
Red Hat kernel. I have SATA disks (using AHCI) in the
system which are hot-pluggable. The problem I am facing
is that, certain disk failures bring the system into a
weird state. The system tries to reset the disk but fails.
Finally it prints a message "reset failed, giving up."

At this point the port is left in a frozen state and
the interrupts from the port are masked. If now, this disk is
pulled out and a healthy disk is inserted, the new disk's
insertion does not raise any event/notification/interrupt.
In fact, the only way at this point to get the disk to work is
to reboot.

Below is a snippet of the code, I am referring to, from v2.6.20.
File - drivers/ata/libata-eh.c & function-name - ata_eh_recover

/* reset */
if (ehc->i.action & ATA_EH_RESET_MASK) {
ata_eh_freeze_port(ap);

rc = ata_eh_reset(ap, ata_port_nr_vacant(ap), prereset,
softreset, hardreset, postreset);
if (rc) {
ata_port_printk(ap, KERN_ERR,
"reset failed, giving up\n");
goto out;
}

ata_eh_thaw_port(ap);
}

A possible work-around is to thaw the port before going to "out".
That would enable the interrupts again before going to "out".
I understand that would enable future interrupts from the old disk as well,
but I am willing to live with that, if it helps to detect the new device.

/* reset */
if (ehc->i.action & ATA_EH_RESET_MASK) {
ata_eh_freeze_port(ap);

rc = ata_eh_reset(ap, ata_port_nr_vacant(ap), prereset,
softreset, hardreset, postreset);
if (rc) {
ata_port_printk(ap, KERN_ERR,
"reset failed, giving up\n");
+ ata_eh_thaw_port(ap);
goto out;
}

ata_eh_thaw_port(ap);
}

I have tested this successfully. But I would like to ask you if this would
possibly "break" some other functionality ? I am new to the kernel ata stuff
and want to be sure before I use this.

Thanks,
Chaitanya



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