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Revision 809b1e4945774c9ec5619a8f4e2189b7b3833c0c authored by Hannes Reinecke on 21 January 2021, 17:50:56 UTC, committed by Mike Snitzer on 21 January 2021, 20:06:45 UTC 
dm: avoid filesystem lookup in dm_get_dev_t()
 
This reverts commit
644bda6f3460 ("dm table: fall back to getting device using name_to_dev_t()")

dm_get_dev_t() is just used to convert an arbitrary 'path' string
into a dev_t. It doesn't presume that the device is present; that
check will be done later, as the only caller is dm_get_device(),
which does a dm_get_table_device() later on, which will properly
open the device.

So if the path string already _is_ in major:minor representation
we can convert it directly, avoiding a recursion into the filesystem
to lookup the block device.

This avoids a hang in multipath_message() when the filesystem is
inaccessible.

Fixes: 644bda6f3460 ("dm table: fall back to getting device using name_to_dev_t()")
Cc: stable@vger.kernel.org
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
1 parent 004b8ae
Raw File
up.c 
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Uniprocessor-only support functions.  The counterpart to kernel/smp.c
 */

#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/smp.h>
#include <linux/hypervisor.h>

int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
				int wait)
{
	unsigned long flags;

	if (cpu != 0)
		return -ENXIO;

	local_irq_save(flags);
	func(info);
	local_irq_restore(flags);

	return 0;
}
EXPORT_SYMBOL(smp_call_function_single);

int smp_call_function_single_async(int cpu, call_single_data_t *csd)
{
	unsigned long flags;

	local_irq_save(flags);
	csd->func(csd->info);
	local_irq_restore(flags);
	return 0;
}
EXPORT_SYMBOL(smp_call_function_single_async);

void on_each_cpu(smp_call_func_t func, void *info, int wait)
{
	unsigned long flags;

	local_irq_save(flags);
	func(info);
	local_irq_restore(flags);
}
EXPORT_SYMBOL(on_each_cpu);

/*
 * Note we still need to test the mask even for UP
 * because we actually can get an empty mask from
 * code that on SMP might call us without the local
 * CPU in the mask.
 */
void on_each_cpu_mask(const struct cpumask *mask,
		      smp_call_func_t func, void *info, bool wait)
{
	unsigned long flags;

	if (cpumask_test_cpu(0, mask)) {
		local_irq_save(flags);
		func(info);
		local_irq_restore(flags);
	}
}
EXPORT_SYMBOL(on_each_cpu_mask);

/*
 * Preemption is disabled here to make sure the cond_func is called under the
 * same condtions in UP and SMP.
 */
void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
			   void *info, bool wait, const struct cpumask *mask)
{
	unsigned long flags;

	preempt_disable();
	if (cond_func(0, info)) {
		local_irq_save(flags);
		func(info);
		local_irq_restore(flags);
	}
	preempt_enable();
}
EXPORT_SYMBOL(on_each_cpu_cond_mask);

void on_each_cpu_cond(smp_cond_func_t cond_func, smp_call_func_t func,
		      void *info, bool wait)
{
	on_each_cpu_cond_mask(cond_func, func, info, wait, NULL);
}
EXPORT_SYMBOL(on_each_cpu_cond);

int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys)
{
	int ret;

	if (cpu != 0)
		return -ENXIO;

	if (phys)
		hypervisor_pin_vcpu(0);
	ret = func(par);
	if (phys)
		hypervisor_pin_vcpu(-1);

	return ret;
}
EXPORT_SYMBOL_GPL(smp_call_on_cpu);
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