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Additional MD component checking

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If udev info is missing for a device, (which would indicate
if it's an MD component), then do an end-of-device read to
check if a PV is an MD component.  (This is skipped when
using hints since we already know devs in hints are good.)

A new config setting md_component_checks can be used to
disable the additional end-of-device MD checks, or to
always enable end-of-device MD checks.

When both hints and udev info are disabled/unavailable,
the end of PVs will now be scanned by default.  If md
devices with end-of-device superblocks are not being
used, the extra I/O overhead can be avoided by setting
md_component_checks="start".
This commit is contained in:
David Teigland 2019-05-21 12:06:34 -05:00
parent 24bd35b4ce
commit db98a6e362
10 changed files with 166 additions and 38 deletions
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7
lib/cache/lvmcache.c vendored
View File

@ -555,8 +555,11 @@ next:
*/
if (!(info = lvmcache_info_from_pvid(alt->dev->pvid, NULL, 0))) {
/* This shouldn't happen */
log_warn("WARNING: PV %s on duplicate device %s not found in cache.",
/*
* This will happen if a duplicate dev has been dropped already,
* e.g. it was found to be an md component.
*/
log_debug("PVID %s on duplicate device %s not found in cache.",
alt->dev->pvid, dev_name(alt->dev));
goto next;
}

2
lib/commands/toolcontext.h
View File

@ -172,6 +172,7 @@ struct cmd_context {
unsigned pvscan_cache_single:1;
unsigned can_use_one_scan:1;
unsigned is_clvmd:1;
unsigned md_component_detection:1;
unsigned use_full_md_check:1;
unsigned is_activating:1;
unsigned enable_hints:1; /* hints are enabled for cmds in general */
@ -184,6 +185,7 @@ struct cmd_context {
*/
struct dev_filter *filter;
struct dm_list hints;
const char *md_component_checks;
/*
* Configuration.

25
lib/config/config_settings.h
View File

@ -368,7 +368,30 @@ cfg(devices_multipath_component_detection_CFG, "multipath_component_detection",
"Ignore devices that are components of DM multipath devices.\n")
cfg(devices_md_component_detection_CFG, "md_component_detection", devices_CFG_SECTION, 0, CFG_TYPE_BOOL, DEFAULT_MD_COMPONENT_DETECTION, vsn(1, 0, 18), NULL, 0, NULL,
"Ignore devices that are components of software RAID (md) devices.\n")
"Enable detection and exclusion of MD component devices.\n"
"An MD component device is a block device that MD uses as part\n"
"of a software RAID virtual device. When an LVM PV is created\n"
"on an MD device, LVM must only use the top level MD device as\n"
"the PV, and should ignore the underlying component devices.\n"
"In cases where the MD superblock is located at the end of the\n"
"component devices, it is more difficult for LVM to consistently\n"
"identify an MD component, see the md_component_checks setting.\n")
cfg(devices_md_component_checks_CFG, "md_component_checks", devices_CFG_SECTION, CFG_DEFAULT_COMMENTED, CFG_TYPE_STRING, DEFAULT_MD_COMPONENT_CHECKS, vsn(2, 3, 2), NULL, 0, NULL,
"The checks LVM should use to detect MD component devices.\n"
"MD component devices are block devices used by MD software RAID.\n"
"#\n"
"Accepted values:\n"
" auto\n"
" LVM will skip scanning the end of devices when it has other\n"
" indications that the device is not an MD component.\n"
" start\n"
" LVM will only scan the start of devices for MD superblocks.\n"
" This does not incur extra I/O by LVM.\n"
" full\n"
" LVM will scan the start and end of devices for MD superblocks.\n"
" This requires an extra read at the end of devices.\n"
"#\n")
cfg(devices_fw_raid_component_detection_CFG, "fw_raid_component_detection", devices_CFG_SECTION, 0, CFG_TYPE_BOOL, DEFAULT_FW_RAID_COMPONENT_DETECTION, vsn(2, 2, 112), NULL, 0, NULL,
"Ignore devices that are components of firmware RAID devices.\n"

2
lib/config/defaults.h
View File

@ -318,4 +318,6 @@
#define DEFAULT_IO_MEMORY_SIZE_KB 8192
#define DEFAULT_MD_COMPONENT_CHECKS "auto"
#endif /* _LVM_DEFAULTS_H */

5
lib/device/dev-md.c
View File

@ -110,14 +110,17 @@ static int _udev_dev_is_md_component(struct device *dev)
if (!(ext = dev_ext_get(dev)))
return_0;
if (!(value = udev_device_get_property_value((struct udev_device *)ext->handle, DEV_EXT_UDEV_BLKID_TYPE)))
if (!(value = udev_device_get_property_value((struct udev_device *)ext->handle, DEV_EXT_UDEV_BLKID_TYPE))) {
dev->flags |= DEV_UDEV_INFO_MISSING;
return 0;
}
return !strcmp(value, DEV_EXT_UDEV_BLKID_TYPE_SW_RAID);
}
#else
static int _udev_dev_is_md_component(struct device *dev)
{
dev->flags |= DEV_UDEV_INFO_MISSING;
return 0;
}
#endif

5
lib/device/dev-type.c
View File

@ -1170,8 +1170,10 @@ int udev_dev_is_md_component(struct device *dev)
const char *value;
int ret = 0;
if (!obtain_device_list_from_udev())
if (!obtain_device_list_from_udev()) {
dev->flags |= DEV_UDEV_INFO_MISSING;
return 0;
}
if (!(udev_device = _udev_get_dev(dev)))
return 0;
@ -1198,6 +1200,7 @@ int udev_dev_is_mpath_component(struct device *dev)
int udev_dev_is_md_component(struct device *dev)
{
dev->flags |= DEV_UDEV_INFO_MISSING;
return 0;
}

1
lib/device/device.h
View File

@ -37,6 +37,7 @@
#define DEV_BCACHE_WRITE 0x00008000 /* bcache_fd is open with RDWR */
#define DEV_SCAN_FOUND_LABEL 0x00010000 /* label scan read dev and found label */
#define DEV_IS_MD_COMPONENT 0x00020000 /* device is an md component */
#define DEV_UDEV_INFO_MISSING 0x00040000 /* we have no udev info for this device */
/*
* Support for external device info.

27
lib/label/label.c
View File

@ -1022,6 +1022,33 @@ int label_scan(struct cmd_context *cmd)
}
}
/*
* Stronger exclusion of md components that might have been
* misidentified as PVs due to having an end-of-device md superblock.
* If we're not using hints, and are not already doing a full md check
* on devs being scanned, then if udev info is missing for a PV, scan
* the end of the PV to verify it's not an md component. The full
* dev_is_md_component call will do new reads at the end of the dev.
*/
if (cmd->md_component_detection && !cmd->use_full_md_check && !using_hints &&
!strcmp(cmd->md_component_checks, "auto")) {
int once = 0;
dm_list_iterate_items(devl, &scan_devs) {
if (!(devl->dev->flags & DEV_SCAN_FOUND_LABEL))
continue;
if (!(devl->dev->flags & DEV_UDEV_INFO_MISSING))
continue;
if (!once++)
log_debug_devs("Scanning end of PVs with no udev info for MD components");
if (dev_is_md_component(devl->dev, NULL, 1)) {
log_debug_devs("Drop PV from MD component %s", dev_name(devl->dev));
devl->dev->flags &= ~DEV_SCAN_FOUND_LABEL;
lvmcache_del_dev(devl->dev);
}
}
}
dm_list_iterate_items_safe(devl, devl2, &all_devs) {
dm_list_del(&devl->list);
free(devl);

75
test/shell/lvm-on-md.sh
View File

@ -31,6 +31,10 @@ test -f /proc/mdstat && grep -q raid1 /proc/mdstat || \
aux lvmconf 'devices/md_component_detection = 1'
# This stops lvm from taking advantage of hints which
# will have already excluded md components.
aux lvmconf 'devices/hints = "none"'
# This stops lvm from asking udev if a dev is an md component.
# LVM will ask udev if a dev is an md component, but we don't
# want to rely on that ability in this test.
@ -61,6 +65,10 @@ check lv_field $vg/$lv1 lv_active "active"
pvs "$mddev"
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
sleep 1
vgchange -an $vg
@ -72,12 +80,14 @@ sleep 1
mdadm --stop "$mddev"
aux udev_wait
# with md superblock 1.0 this pvs will report duplicates
# for the two md legs since the md device itself is not
# started
pvs 2>&1 |tee out
cat out
grep "prefers device" out
# The md components should still be detected and excluded.
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
pvs -vvvv
# should not activate from the md legs
not vgchange -ay $vg
@ -104,16 +114,20 @@ not grep "active" out
mdadm --assemble "$mddev" "$dev1" "$dev2"
aux udev_wait
# Now that the md dev is online, pvs can see it and
# ignore the two legs, so there's no duplicate warning
# Now that the md dev is online, pvs can see it
# and check for components even if
# md_component_checks is "start" (which disables
# most default end-of-device scans)
aux lvmconf 'devices/md_component_checks = "start"'
pvs 2>&1 |tee out
cat out
not grep "prefers device" out
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
vgchange -ay $vg 2>&1 |tee out
cat out
not grep "prefers device" out
vgchange -ay $vg
check lv_field $vg/$lv1 lv_active "active"
@ -124,6 +138,9 @@ vgremove -f $vg
aux cleanup_md_dev
# Put this setting back to the default
aux lvmconf 'devices/md_component_checks = "auto"'
# create 2 disk MD raid0 array
# by default using metadata format 1.0 with data at the end of device
# When a raid0 md array is stopped, the components will not look like
@ -149,6 +166,10 @@ check lv_field $vg/$lv1 lv_active "active"
pvs "$mddev"
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
sleep 1
vgchange -an $vg
@ -160,7 +181,14 @@ sleep 1
mdadm --stop "$mddev"
aux udev_wait
pvs 2>&1 |tee pvs.out
# The md components should still be detected and excluded.
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
pvs -vvvv
# should not activate from the md legs
not vgchange -ay $vg
@ -187,16 +215,19 @@ not grep "active" out
mdadm --assemble "$mddev" "$dev1" "$dev2"
aux udev_wait
# Now that the md dev is online, pvs can see it and
# ignore the two legs, so there's no duplicate warning
# Now that the md dev is online, pvs can see it
# and check for components even if
# md_component_checks is "start" (which disables
# most default end-of-device scans)
aux lvmconf 'devices/md_component_checks = "start"'
pvs 2>&1 |tee out
cat out
not grep "prefers device" out
not pvs "$dev1"
not pvs "$dev2"
pvs > out
not grep "$dev1" out
not grep "$dev2" out
vgchange -ay $vg 2>&1 |tee out
cat out
not grep "prefers device" out
check lv_field $vg/$lv1 lv_active "active"

55
tools/lvmcmdline.c
View File

@ -2766,20 +2766,53 @@ static int _init_lvmlockd(struct cmd_context *cmd)
return 1;
}
/*
* md_component_check full: always set use_full_md_check
* which causes filter-md to read the start+end of every
* device on the system (this could be optimized to only
* read the end of PVs.)
*
* md_component_check start: the end of devices will
* not generally be read to check for an md superblock
* (lvm may still scan for end-of-device md superblocks
* if it knows that some exists.)
*
* md_component_check auto: lvm will use some built-in
* heuristics to decide when it should scan the end of
* devices to look for md superblocks, e.g. commands
* like pvcreate that could clobber a component, or if
* udev info is not available and hints are not available.
*/
static void _init_md_checks(struct cmd_context *cmd)
{
/*
* use_full_md_check can also be set later.
* These commands are chosen to always perform
* a full md component check because they initialize
* a new device that could be an md component,
* and they are not run frequently during normal
* operation.
*/
if (!strcmp(cmd->name, "pvcreate") ||
!strcmp(cmd->name, "vgcreate") ||
!strcmp(cmd->name, "vgextend"))
const char *md_check;
cmd->md_component_detection = find_config_tree_bool(cmd, devices_md_component_detection_CFG, NULL);
md_check = find_config_tree_str(cmd, devices_md_component_checks_CFG, NULL);
if (!md_check)
cmd->md_component_checks = "auto";
else if (!strcmp(md_check, "auto") ||
!strcmp(md_check, "start") ||
!strcmp(md_check, "full"))
cmd->md_component_checks = md_check;
else {
log_warn("Ignoring unknown md_component_checks setting, using auto.");
cmd->md_component_checks = "auto";
}
if (!strcmp(cmd->md_component_checks, "full"))
cmd->use_full_md_check = 1;
else if (!strcmp(cmd->md_component_checks, "auto")) {
/* use_full_md_check can also be set later */
if (!strcmp(cmd->name, "pvcreate") ||
!strcmp(cmd->name, "vgcreate") ||
!strcmp(cmd->name, "vgextend"))
cmd->use_full_md_check = 1;
}
log_debug("Using md_component_checks %s use_full_md_check %d",
cmd->md_component_checks, cmd->use_full_md_check);
}
static int _cmd_no_meta_proc(struct cmd_context *cmd)