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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
backtracetest.c 
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Simple stack backtrace regression test module
 *
 * (C) Copyright 2008 Intel Corporation
 * Author: Arjan van de Ven <arjan@linux.intel.com>
 */

#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>

static void backtrace_test_normal(void)
{
	pr_info("Testing a backtrace from process context.\n");
	pr_info("The following trace is a kernel self test and not a bug!\n");

	dump_stack();
}

static DECLARE_COMPLETION(backtrace_work);

static void backtrace_test_irq_callback(unsigned long data)
{
	dump_stack();
	complete(&backtrace_work);
}

static DECLARE_TASKLET_OLD(backtrace_tasklet, &backtrace_test_irq_callback);

static void backtrace_test_irq(void)
{
	pr_info("Testing a backtrace from irq context.\n");
	pr_info("The following trace is a kernel self test and not a bug!\n");

	init_completion(&backtrace_work);
	tasklet_schedule(&backtrace_tasklet);
	wait_for_completion(&backtrace_work);
}

#ifdef CONFIG_STACKTRACE
static void backtrace_test_saved(void)
{
	unsigned long entries[8];
	unsigned int nr_entries;

	pr_info("Testing a saved backtrace.\n");
	pr_info("The following trace is a kernel self test and not a bug!\n");

	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
	stack_trace_print(entries, nr_entries, 0);
}
#else
static void backtrace_test_saved(void)
{
	pr_info("Saved backtrace test skipped.\n");
}
#endif

static int backtrace_regression_test(void)
{
	pr_info("====[ backtrace testing ]===========\n");

	backtrace_test_normal();
	backtrace_test_irq();
	backtrace_test_saved();

	pr_info("====[ end of backtrace testing ]====\n");
	return 0;
}

static void exitf(void)
{
}

module_init(backtrace_regression_test);
module_exit(exitf);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
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