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The current logic that avoids setting SYSTEMD_ALIAS and SYSTEMD_WANTS on "change" events is flawed in the default "systemd background job" configuration. For systemd, it's important that device properties don't change spuriously. If an "add" event starts lvm2-pvscan@.service for a device, and a "change" event follows, removing SYSTEMD_ALIAS and SYSTEMD_WANTS from the udev db, information about unit dependencies between the device and the pvscan service can be lost in systemd, in particular if the daemon configuration is reloaded. Steps to reproduce problem: - create a device with an LVM PV - remove device - add device (generates "add" and "change" uevents for the device) (at this point SYSTEMD_ALIAS and SYSTEMD_WANTS are clear in udev db) - systemctl daemon-reload (systemd reloads udev db) - vgchange -a n - remove device => the lvm2-pvscan@.service for the device is still active although the device is gone. - add device again => the PV is not detected, because systemd sees the lvm2-pvscan@.service as active and thus doesn't restart it. The original purpose of this logic was to avoid volumes being scanned over and over again. With systemd background jobs, that isn't necessary, because systemd will not restart the job as long as it's active. Signed-off-by: Martin Wilck <mwilck@suse.com>
137 lines
6.3 KiB
Plaintext
137 lines
6.3 KiB
Plaintext
# Copyright (C) 2012 Red Hat, Inc. All rights reserved.
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#
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# This file is part of LVM2.
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# Udev rules for LVM.
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#
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# Scan all block devices having a PV label for LVM metadata.
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# Store this information in LVMetaD (the LVM metadata daemon) and maintain LVM
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# metadata state for improved performance by avoiding further scans while
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# running subsequent LVM commands or while using lvm2app library.
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# Also, notify LVMetaD about any relevant block device removal.
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#
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# This rule is essential for having the information in LVMetaD up-to-date.
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# It also requires blkid to be called on block devices before so only devices
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# used as LVM PVs are processed (ID_FS_TYPE="LVM2_member" or "LVM1_member").
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SUBSYSTEM!="block", GOTO="lvm_end"
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(LVM_EXEC_RULE)
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ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}=="1", GOTO="lvm_end"
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# If the PV label got lost, inform lvmetad immediately.
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# Detect the lost PV label by comparing previous ID_FS_TYPE value with current one.
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ENV{.ID_FS_TYPE_NEW}="$env{ID_FS_TYPE}"
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IMPORT{db}="ID_FS_TYPE"
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ENV{ID_FS_TYPE}=="LVM2_member|LVM1_member", ENV{.ID_FS_TYPE_NEW}!="LVM2_member|LVM1_member", ENV{LVM_PV_GONE}="1"
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ENV{ID_FS_TYPE}="$env{.ID_FS_TYPE_NEW}"
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ENV{LVM_PV_GONE}=="1", GOTO="lvm_scan"
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# Only process devices already marked as a PV - this requires blkid to be called before.
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ENV{ID_FS_TYPE}!="LVM2_member|LVM1_member", GOTO="lvm_end"
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ENV{DM_MULTIPATH_DEVICE_PATH}=="1", GOTO="lvm_end"
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# Inform lvmetad about any PV that is gone.
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ACTION=="remove", GOTO="lvm_scan"
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# Create /dev/disk/by-id/lvm-pv-uuid-<PV_UUID> symlink for each PV
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ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-id/lvm-pv-uuid-$env{ID_FS_UUID_ENC}"
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# If the PV is a special device listed below, scan only if the device is
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# properly activated. These devices are not usable after an ADD event,
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# but they require an extra setup and they are ready after a CHANGE event.
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# Also support coldplugging with ADD event but only if the device is already
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# properly activated.
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# This logic should be eventually moved to rules where those particular
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# devices are processed primarily (MD and loop).
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# DM device:
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KERNEL!="dm-[0-9]*", GOTO="next"
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ENV{DM_UDEV_PRIMARY_SOURCE_FLAG}=="1", ENV{DM_ACTIVATION}=="1", GOTO="lvm_scan"
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GOTO="lvm_end"
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# MD device:
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LABEL="next"
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KERNEL!="md[0-9]*", GOTO="next"
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IMPORT{db}="LVM_MD_PV_ACTIVATED"
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ACTION=="add", ENV{LVM_MD_PV_ACTIVATED}=="1", GOTO="lvm_scan"
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ACTION=="change", ENV{LVM_MD_PV_ACTIVATED}!="1", TEST=="md/array_state", ENV{LVM_MD_PV_ACTIVATED}="1", GOTO="lvm_scan"
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ACTION=="add", KERNEL=="md[0-9]*p[0-9]*", GOTO="lvm_scan"
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ENV{LVM_MD_PV_ACTIVATED}!="1", ENV{SYSTEMD_READY}="0"
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GOTO="lvm_end"
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# Loop device:
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LABEL="next"
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KERNEL!="loop[0-9]*", GOTO="next"
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ACTION=="add", ENV{LVM_LOOP_PV_ACTIVATED}=="1", GOTO="lvm_scan"
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ACTION=="change", ENV{LVM_LOOP_PV_ACTIVATED}!="1", TEST=="loop/backing_file", ENV{LVM_LOOP_PV_ACTIVATED}="1", GOTO="lvm_scan"
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ENV{LVM_LOOP_PV_ACTIVATED}!="1", ENV{SYSTEMD_READY}="0"
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GOTO="lvm_end"
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# If the PV is not a special device listed above, scan only if necessary.
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# For "direct_pvscan" mode (see below), this means run rules only an ADD events.
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# For "systemd_background" mode, systemd takes care of this by activating
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# the lvm2-pvscan@.service only once.
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LABEL="next"
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ACTION!="(PVSCAN_ACTION)", GOTO="lvm_end"
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LABEL="lvm_scan"
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ENV{SYSTEMD_READY}="1"
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# The method for invoking pvscan is selected at build time with the option
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# --(enable|disable)-udev-systemd-background-jobs to "configure".
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# On modern distributions with recent systemd, it's "systemd_background";
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# on others, "direct_pvscan".
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GOTO="(PVSCAN_RULE)"
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LABEL="systemd_background"
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# The table below summarises the situations in which we reach the LABEL="lvm_scan"
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# in the "systemd_background" case.
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# Marked by X, X* means only if the special dev is properly set up.
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# The artificial ADD is supported for coldplugging. We avoid running the pvscan
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# on artificial CHANGE so there's no unexpected autoactivation when WATCH rule fires.
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# N.B. MD and loop never actually reaches lvm_scan on REMOVE as the PV label is gone
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# within a CHANGE event (these are caught by the "LVM_PV_GONE" rule at the beginning).
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#
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# In this case, we simply set up the dependency between the device and the pvscan
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# job using SYSTEMD_ALIAS (which sets up a simplified device identifier that
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# allows using "BindsTo" in the sytemd unit file) and SYSTEMD_WANTS (which tells
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# systemd to start the pvscan job once the device is ready).
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# We need to set these variables for both "add" and "change" events, otherwise
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# systemd may loose information about the device/unit dependencies.
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#
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# | real ADD | real CHANGE | artificial ADD | artificial CHANGE | REMOVE
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# =============================================================================
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# DM | | X | X* | | X
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# MD | | X | X* | |
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# loop | | X | X* | |
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# other | X | X | X | | X
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ACTION!="remove", ENV{LVM_PV_GONE}=="1", RUN+="(BINDIR)/systemd-run (LVM_EXEC)/lvm pvscan --cache $major:$minor", GOTO="lvm_end"
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ENV{SYSTEMD_ALIAS}="/dev/block/$major:$minor"
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ENV{ID_MODEL}="LVM PV $env{ID_FS_UUID_ENC} on /dev/$name"
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ENV{SYSTEMD_WANTS}+="lvm2-pvscan@$major:$minor.service"
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GOTO="lvm_end"
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LABEL="direct_pvscan"
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# The table below summarises the situations in which we reach the LABEL="lvm_scan"
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# for the "direct_pvscan" case.
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# Marked by X, X* means only if the special dev is properly set up.
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# The artificial ADD is supported for coldplugging. We avoid running the pvscan
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# on artificial CHANGE so there's no unexpected autoactivation when WATCH rule fires.
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#
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# In this case, we need to make sure that pvscan is not invoked spuriously, therefore
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# we invoke it only for "add" events for "other" devices.
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#
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# | real ADD | real CHANGE | artificial ADD | artificial CHANGE | REMOVE
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# =============================================================================
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# DM | | X | X* | | X
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# MD | | X | X* | |
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# loop | | X | X* | |
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# other | X | | X | | X
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RUN+="(LVM_EXEC)/lvm pvscan --background --cache --activate ay --major $major --minor $minor", ENV{LVM_SCANNED}="1"
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LABEL="lvm_end"
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