[lvm-devel] master - Additional MD component checking
David Teigland
teigland at sourceware.org
Fri Jun 7 19:25:25 UTC 2019
Gitweb: https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=db98a6e3629aaf6bf42d0e840273b4328f930c89
Commit: db98a6e3629aaf6bf42d0e840273b4328f930c89
Parent: 24bd35b4ce77a5111ee234f554ca139df4b7dd99
Author: David Teigland <teigland at redhat.com>
AuthorDate: Tue May 21 12:06:34 2019 -0500
Committer: David Teigland <teigland at redhat.com>
CommitterDate: Fri Jun 7 13:27:16 2019 -0500
Additional MD component checking
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".
---
lib/cache/lvmcache.c | 7 +++-
lib/commands/toolcontext.h | 2 +
lib/config/config_settings.h | 25 +++++++++++++-
lib/config/defaults.h | 2 +
lib/device/dev-md.c | 5 ++-
lib/device/dev-type.c | 5 ++-
lib/device/device.h | 1 +
lib/label/label.c | 27 +++++++++++++++
test/shell/lvm-on-md.sh | 75 +++++++++++++++++++++++++++++------------
tools/lvmcmdline.c | 55 ++++++++++++++++++++++++------
10 files changed, 166 insertions(+), 38 deletions(-)
diff --git a/lib/cache/lvmcache.c b/lib/cache/lvmcache.c
index 8a29bf4..b62e5e2 100644
--- a/lib/cache/lvmcache.c
+++ b/lib/cache/lvmcache.c
@@ -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;
}
diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index 0ea2132..7d373ab 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -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.
diff --git a/lib/config/config_settings.h b/lib/config/config_settings.h
index efa86e7..e718dec 100644
--- a/lib/config/config_settings.h
+++ b/lib/config/config_settings.h
@@ -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"
diff --git a/lib/config/defaults.h b/lib/config/defaults.h
index fac5b75..6a0d686 100644
--- a/lib/config/defaults.h
+++ b/lib/config/defaults.h
@@ -318,4 +318,6 @@
#define DEFAULT_IO_MEMORY_SIZE_KB 8192
+#define DEFAULT_MD_COMPONENT_CHECKS "auto"
+
#endif /* _LVM_DEFAULTS_H */
diff --git a/lib/device/dev-md.c b/lib/device/dev-md.c
index 261f3f1..08143b7 100644
--- a/lib/device/dev-md.c
+++ b/lib/device/dev-md.c
@@ -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
diff --git a/lib/device/dev-type.c b/lib/device/dev-type.c
index 73e55ca..4e35220 100644
--- a/lib/device/dev-type.c
+++ b/lib/device/dev-type.c
@@ -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;
}
diff --git a/lib/device/device.h b/lib/device/device.h
index 395405a..30e1e79 100644
--- a/lib/device/device.h
+++ b/lib/device/device.h
@@ -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.
diff --git a/lib/label/label.c b/lib/label/label.c
index 10c1c4c..f6ba2d8 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -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);
diff --git a/test/shell/lvm-on-md.sh b/test/shell/lvm-on-md.sh
index 41649be..22cbee8 100644
--- a/test/shell/lvm-on-md.sh
+++ b/test/shell/lvm-on-md.sh
@@ -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"
diff --git a/tools/lvmcmdline.c b/tools/lvmcmdline.c
index 79de85b..30f54e6 100644
--- a/tools/lvmcmdline.c
+++ b/tools/lvmcmdline.c
@@ -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)
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