Randy Dunlap wrote:
> Eric Sandeen wrote:
>> Now that the filesystem freeze operation has been elevated
>> to the VFS, and is just an ioctl away, some sort of safety net
>> for unintentionally frozen root filesystems may be in order.
>>
>> The timeout thaw originally proposed did not get merged, but
>> perhaps something like this would be useful in emergencies.
>>
>> For example, freeze /path/to/mountpoint may freeze your
>> root filesystem if you forgot that you had that unmounted.
>>
>> I chose 'j' as the last remaining character other than 'h'
>> which is sort of reserved for help (because help is generated
>> on any unknown character).
>>
>> I've tested this on a non-root fs with multiple (nested) freezers,
>> as well as on a system rendered unresponsive due to a frozen
>> root fs.
>>
>> Thanks,
>> -Eric
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>>
>> Index: linux-2.6/drivers/char/sysrq.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/char/sysrq.c 2009-01-16 13:24:14.688575212 -0600
>> +++ linux-2.6/drivers/char/sysrq.c 2009-01-16 13:26:35.232575643 -0600
>> @@ -346,6 +346,17 @@ static struct sysrq_key_op sysrq_moom_op
>> .enable_mask = SYSRQ_ENABLE_SIGNAL,
>> };
>>
>> +static void sysrq_handle_thaw(int key, struct tty_struct *tty)
>> +{
>> + emergency_thaw_all();
>> +}
>> +static struct sysrq_key_op sysrq_thaw_op = {
>> + .handler = sysrq_handle_thaw,
>> + .help_msg = "Thaw(J)",
>
> Can the help text be less terse, e.g.: "thaw-filesystems(J)" ?
Sure, that's good.
> Not capital-T Thaw because that was used to mean "use sysrq-T" to invoke
> this sysrq.
>
>
>> + .action_msg = "Emergency Thaw of all frozen filesystems",
>> + .enable_mask = SYSRQ_ENABLE_SIGNAL,
>> +};
>> +
>> static void sysrq_handle_kill(int key, struct tty_struct *tty)
>> {
>> send_sig_all(SIGKILL);
>> @@ -396,9 +407,9 @@ static struct sysrq_key_op *sysrq_key_ta
>> &sysrq_moom_op, /* f */
>> /* g: May be registered by ppc for kgdb */
>> NULL, /* g */
>> - NULL, /* h */
>> + NULL, /* h - reserved for help */
>
> Yes, thanks.
:)
>> &sysrq_kill_op, /* i */
>> - NULL, /* j */
>> + &sysrq_thaw_op, /* j */
>> &sysrq_SAK_op, /* k */
>> #ifdef CONFIG_SMP
>> &sysrq_showallcpus_op, /* l */
>> Index: linux-2.6/fs/buffer.c
>> ===================================================================
>> --- linux-2.6.orig/fs/buffer.c 2009-01-16 13:24:15.564575078 -0600
>> +++ linux-2.6/fs/buffer.c 2009-01-16 13:26:35.257575540 -0600
>> @@ -258,6 +258,29 @@ struct super_block *freeze_bdev(struct b
>> }
>> EXPORT_SYMBOL(freeze_bdev);
>>
>> +void do_thaw_all(unsigned long unused)
>> +{
>> + struct super_block *sb;
>> + char b[BDEVNAME_SIZE];
>> +
>> + list_for_each_entry(sb, &super_blocks, s_list) {
>> + while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
>> + printk(KERN_WARNING "Emergency Thaw on %s\n",
>> + bdevname(sb->s_bdev, b));
>> + }
>> + printk(KERN_WARNING "Emergency Thaw complete\n");
>> +}
>> +
>> +/**
>> + * emergency_thaw_all -- forcibly thaw every frozen filesystem
>> + *
>> + * Used for emergency unfreeze of all filesystems via SysRq-z
>
> -j
Oops, was going to be unfreeZe 'til I realized peterz took that already!
-Eric
>> + */
>> +void emergency_thaw_all(void)
>> +{
>> + pdflush_operation(do_thaw_all, 0);
>> +}
>> +
>> /**
>> * thaw_bdev -- unlock filesystem
>> * @bdev: blockdevice to unlock
>
>
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