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/*
* Copyright (C) 2004 Luca Berra
* Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License v.2.1.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "base/memory/zalloc.h"
#include "lib/misc/lib.h"
#include "lib/filters/filter.h"
#include "lib/commands/toolcontext.h"
#ifdef __linux__
#define MSG_SKIPPING "%s: Skipping md component device"
/*
* The purpose of these functions is to ignore md component devices,
* e.g. if /dev/md0 is a raid1 composed of /dev/loop0 and /dev/loop1,
* lvm wants to deal with md0 and ignore loop0 and loop1. md0 should
* pass the filter, and loop0,loop1 should not pass the filter so lvm
* will ignore them.
*
* (This is assuming lvm.conf md_component_detection=1.)
*
* If lvm does *not* ignore the components, then lvm may read lvm
* labels from the component devs and potentially the md dev,
* which can trigger duplicate detection, and/or cause lvm to display
* md components as PVs rather than ignoring them.
*
* If scanning md componenents causes duplicates to be seen, then
* the lvm duplicate resolution will exclude the components.
*
* The lvm md filter has three modes:
*
* 1. look for md superblock at the start of the device
* 2. look for md superblock at the start and end of the device
* 3. use udev to detect components
*
* mode 1 will not detect and exclude components of md devices
* that use superblock version 0.9 or 1.0 which is at the end of the device.
*
* mode 2 will detect these, but mode 2 doubles the i/o done by label
* scan, since there's a read at both the start and end of every device.
*
* mode 3 is used when external_device_info_source="udev". It does
* not require any io from lvm, but this mode is not used by default
* because there have been problems getting reliable info from udev.
*
* lvm uses mode 2 when:
*
* - the command is pvcreate/vgcreate/vgextend, which format new
* devices, and if the user ran these commands on a component
* device of an md device 0.9 or 1.0, then it would cause problems.
* FIXME: this would only really need to scan the end of the
* devices being formatted, not all devices.
*
* - it sees an md device on the system using version 0.9 or 1.0.
* The point of this is just to avoid displaying md components
* from the 'pvs' command.
* FIXME: the cost (double i/o) may not be worth the benefit
* (not showing md components).
*/
/*
* Returns 0 if:
* the device is an md component and it should be ignored.
*
* Returns 1 if:
* the device is not md component and should not be ignored.
*
* The actual md device will pass this filter and should be used,
* it is the md component devices that we are trying to exclude
* that will not pass.
*/
static int _passes_md_filter(struct cmd_context *cmd, struct dev_filter *f __attribute__((unused)), struct device *dev, const char *use_filter_name)
{
int ret;
if (cmd->filter_nodata_only)
return 1;
/*
* When md_component_dectection=0, don't even try to skip md
* components.
*/
if (!md_filtering())
return 1;
ret = dev_is_md_component(dev, NULL, cmd->use_full_md_check);
if (ret == -EAGAIN) {
/* let pass, call again after scan */
dev->flags |= DEV_FILTER_AFTER_SCAN;
log_debug_devs("filter md deferred %s", dev_name(dev));
return 1;
}
if (ret == 0)
return 1;
if (ret == 1) {
log_debug_devs("md filter full %d excluding md component %s", cmd->use_full_md_check, dev_name(dev));
if (dev->ext.src == DEV_EXT_NONE)
log_debug_devs(MSG_SKIPPING, dev_name(dev));
else
log_debug_devs(MSG_SKIPPING " [%s:%p]", dev_name(dev),
dev_ext_name(dev), dev->ext.handle);
return 0;
}
if (ret < 0) {
log_debug_devs("%s: Skipping: error in md component detection",
dev_name(dev));
return 0;
}
return 1;
}
static void _destroy(struct dev_filter *f)
{
if (f->use_count)
log_error(INTERNAL_ERROR "Destroying md filter while in use %u times.", f->use_count);
free(f);
}
struct dev_filter *md_filter_create(struct cmd_context *cmd, struct dev_types *dt)
{
struct dev_filter *f;
if (!(f = zalloc(sizeof(*f)))) {
log_error("md filter allocation failed");
return NULL;
}
f->passes_filter = _passes_md_filter;
f->destroy = _destroy;
f->use_count = 0;
f->private = dt;
f->name = "md";
log_debug_devs("MD filter initialised.");
return f;
}
#else
struct dev_filter *md_filter_create(struct dev_types *dt)
{
return NULL;
}
#endif
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