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devices: improve handling of duplicate PVs
Example: /dev/loop0 and /dev/loop1 are duplicates, created by copying one backing file to the other. 'identity /dev/loopX' creates an identity mapping for loopX named idmloopX, which adds a duplicate for the named device. The duplicate selection code for lvmetad is incomplete, and lvmetad is disabled for this example. [~]# losetup -f loopfile0 [~]# pvs PV VG Fmt Attr PSize PFree /dev/loop0 foo lvm2 a-- 308.00m 296.00m [~]# losetup -f loopfile1 [~]# pvs Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0 Using duplicate PV /dev/loop1 which is more recent, replacing /dev/loop0 PV VG Fmt Attr PSize PFree /dev/loop1 foo lvm2 a-- 308.00m 308.00m [~]# ./identity /dev/loop0 [~]# pvs Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0 Using duplicate PV /dev/loop1 without holders, replacing /dev/loop0 Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop0 not /dev/loop1 Using duplicate PV /dev/mapper/idmloop0 from subsystem DM, replacing /dev/loop1 PV VG Fmt Attr PSize PFree /dev/mapper/idmloop0 foo lvm2 a-- 308.00m 296.00m [~]# ./identity /dev/loop1 [~]# pvs WARNING: duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV is being used from both devices /dev/loop0 and /dev/loop1 Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0 Using duplicate PV /dev/loop1 which is more recent, replacing /dev/loop0 Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop0 not /dev/loop1 Using duplicate PV /dev/mapper/idmloop0 from subsystem DM, replacing /dev/loop1 Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop1 not /dev/mapper/idmloop0 Using duplicate PV /dev/mapper/idmloop1 which is more recent, replacing /dev/mapper/idmloop0 PV VG Fmt Attr PSize PFree /dev/mapper/idmloop1 foo lvm2 a-- 308.00m 308.00m
This commit is contained in:
David Teigland
parent
6cc37275ce
commit
beb229e1e8
252
lib/cache/lvmcache.c
vendored
252
lib/cache/lvmcache.c
vendored
@ -1529,6 +1529,64 @@ void lvmcache_replace_dev(struct cmd_context *cmd, struct physical_volume *pv,
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pv->dev = dev;
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}
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/*
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* We can see multiple different devices with the
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* same pvid, i.e. duplicates.
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*
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* There may be different reasons for seeing two
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* devices with the same pvid:
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* - multipath showing two paths to the same thing
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* - one device copied to another, e.g. with dd,
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* also referred to as cloned devices.
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* - a "subsystem" taking a device and creating
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* another device of its own that represents the
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* underlying device it is using, e.g. using dm
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* to create an identity mapping of a PV.
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*
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* Given duplicate devices, we have to choose one
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* of them to be the "preferred" dev, i.e. the one
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* that will be referenced in lvmcache, by pv->dev.
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* We can keep the existing dev, that's currently
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* used in lvmcache, or we can replace the existing
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* dev with the new duplicate.
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*
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* Regardless of which device is preferred, we need
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* to print messages explaining which devices were
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* found so that a user can sort out for themselves
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* what has happened if the preferred device is not
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* the one they are interested in.
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*
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* If a user wants to use the non-preferred device,
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* they will need to filter out the device that
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* lvm is preferring.
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*
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* The dev_subsystem calls check if the major number
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* of the dev is part of a subsystem like DM/MD/DRBD.
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* A dev that's part of a subsystem is preferred over a
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* duplicate of that dev that is not part of a
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* subsystem.
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*
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* The has_holders calls check if the device is being
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* used by another, and prefers one that's being used.
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*
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* FIXME: why do we prefer a device without holders
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* over a device with holders? We should understand
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* the reason for that choice.
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*
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* FIXME: there may be other reasons to prefer one
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* device over another:
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*
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* . are there other use/open counts we could check
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* beyond the holders?
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*
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* . check if either is bad/usable and prefer
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* the good one?
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*
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* . prefer the one with smaller minor number?
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* Might avoid disturbing things due to a new
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* transient duplicate?
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*/
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struct lvmcache_info *lvmcache_add(struct labeller *labeller, const char *pvid,
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struct device *dev,
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const char *vgname, const char *vgid,
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@ -1576,54 +1634,156 @@ struct lvmcache_info *lvmcache_add(struct labeller *labeller, const char *pvid,
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lvmcache_del_bas(info);
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} else {
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if (existing->dev != dev) {
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/* Is the existing entry a duplicate pvid e.g. md ? */
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if (dev_subsystem_part_major(dt, existing->dev) &&
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!dev_subsystem_part_major(dt, dev)) {
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log_very_verbose("Ignoring duplicate PV %s on "
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"%s - using %s %s",
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pvid, dev_name(dev),
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dev_subsystem_name(dt, existing->dev),
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dev_name(existing->dev));
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return NULL;
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} else if (dm_is_dm_major(MAJOR(existing->dev->dev)) &&
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!dm_is_dm_major(MAJOR(dev->dev))) {
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log_very_verbose("Ignoring duplicate PV %s on "
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"%s - using dm %s",
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pvid, dev_name(dev),
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dev_name(existing->dev));
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return NULL;
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} else if (!dev_subsystem_part_major(dt, existing->dev) &&
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dev_subsystem_part_major(dt, dev))
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log_very_verbose("Duplicate PV %s on %s - "
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"using %s %s", pvid,
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dev_name(existing->dev),
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dev_subsystem_name(dt, existing->dev),
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dev_name(dev));
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else if (!dm_is_dm_major(MAJOR(existing->dev->dev)) &&
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dm_is_dm_major(MAJOR(dev->dev)))
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log_very_verbose("Duplicate PV %s on %s - "
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"using dm %s", pvid,
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dev_name(existing->dev),
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dev_name(dev));
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/* FIXME If both dm, check dependencies */
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//else if (dm_is_dm_major(MAJOR(existing->dev->dev)) &&
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//dm_is_dm_major(MAJOR(dev->dev)))
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//
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else if (!strcmp(pvid_s, existing->dev->pvid)) {
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log_error("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(existing->dev),
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dev_name(dev));
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strncpy(dev->pvid, pvid_s, sizeof(dev->pvid));
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_found_duplicate_pvs = 1;
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return NULL;
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int old_in_subsystem = 0;
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int new_in_subsystem = 0;
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int old_is_dm = 0;
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int new_is_dm = 0;
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int old_has_holders = 0;
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int new_has_holders = 0;
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/*
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* Here are different devices with the same pvid:
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* duplicates. See comment above.
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*/
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/*
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* This flag tells the process_each_pv code to search
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* the devices list for duplicates, so that devices
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* can be processed together with their duplicates
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* (while processing the VG, rather than reporting
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* pv->dev under the VG, and its duplicate outside
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* the VG context.)
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*/
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_found_duplicate_pvs = 1;
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/*
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* The new dev may not have pvid set.
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* The process_each_pv code needs to have the pvid
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* set in each device to detect that the devices
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* are duplicates.
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*/
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strncpy(dev->pvid, pvid_s, sizeof(dev->pvid));
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/*
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* Now decide if we are going to ignore the new
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* device, or replace the existing/old device in
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* lvmcache with the new one.
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*/
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old_in_subsystem = dev_subsystem_part_major(dt, existing->dev);
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new_in_subsystem = dev_subsystem_part_major(dt, dev);
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old_is_dm = dm_is_dm_major(MAJOR(existing->dev->dev));
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new_is_dm = dm_is_dm_major(MAJOR(dev->dev));
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old_has_holders = dm_device_has_holders(MAJOR(existing->dev->dev), MINOR(existing->dev->dev));
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new_has_holders = dm_device_has_holders(MAJOR(dev->dev), MINOR(dev->dev));
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if (old_has_holders && new_has_holders) {
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/*
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* This is not a selection of old or new, but
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* just a warning to be aware of.
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*/
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log_warn("WARNING: duplicate PV %s is being used from both devices %s and %s",
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pvid_s,
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dev_name(existing->dev),
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dev_name(dev));
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}
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if (old_in_subsystem && !new_in_subsystem) {
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/* Use old, ignore new. */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(existing->dev),
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dev_name(dev));
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log_warn("Using duplicate PV %s from subsystem %s, ignoring %s",
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dev_name(existing->dev),
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dev_subsystem_name(dt, existing->dev),
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dev_name(dev));
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return NULL;
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} else if (!old_in_subsystem && new_in_subsystem) {
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/* Use new, replace old. */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(dev),
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dev_name(existing->dev));
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log_warn("Using duplicate PV %s from subsystem %s, replacing %s",
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dev_name(dev),
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dev_subsystem_name(dt, dev),
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dev_name(existing->dev));
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} else if (old_has_holders && !new_has_holders) {
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/* Use new, replace old. */
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/* FIXME: why choose the one without olders? */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(dev),
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dev_name(existing->dev));
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log_warn("Using duplicate PV %s without holders, replacing %s",
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dev_name(dev),
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dev_name(existing->dev));
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} else if (!old_has_holders && new_has_holders) {
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/* Use old, ignore new. */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(existing->dev),
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dev_name(dev));
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log_warn("Using duplicate PV %s without holders, ignoring %s",
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dev_name(existing->dev),
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dev_name(dev));
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return NULL;
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} else if (old_is_dm && new_is_dm) {
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/* Use new, replace old. */
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/* FIXME: why choose the new instead of the old? */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(dev),
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dev_name(existing->dev));
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log_warn("Using duplicate PV %s which is more recent, replacing %s",
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dev_name(dev),
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dev_name(existing->dev));
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} else if (!strcmp(pvid_s, existing->dev->pvid)) {
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/* No criteria to use for preferring old or new. */
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/* FIXME: why choose the new instead of the old? */
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/* FIXME: a transient duplicate would be a reason
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* to select the old instead of the new. */
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log_warn("Found duplicate PV %s: using %s not %s",
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pvid_s,
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dev_name(dev),
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dev_name(existing->dev));
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log_warn("Using duplicate PV %s which is more recent, replacing %s",
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dev_name(dev),
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dev_name(existing->dev));
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}
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} else {
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/*
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* The new dev is the same as the existing dev.
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*
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* FIXME: Why can't we just return NULL here if the
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* device already exists? Things don't seem to work
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* if we do that for some reason.
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*/
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log_verbose("Found same device %s with same pvid %s",
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dev_name(existing->dev), pvid_s);
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}
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if (strcmp(pvid_s, existing->dev->pvid))
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log_debug_cache("Updating pvid cache to %s (%s) from %s (%s)",
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pvid_s, dev_name(dev),
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existing->dev->pvid, dev_name(existing->dev));
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/* Switch over to new preferred device */
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/*
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* FIXME: when could this ever happen?
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* If this does happen, identify when/why here, and
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* if not, remove this code.
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*/
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if (strcmp(pvid_s, existing->dev->pvid)) {
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log_warn("Replacing dev %s pvid %s with dev %s pvid %s",
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dev_name(existing->dev), existing->dev->pvid,
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dev_name(dev), pvid_s);
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}
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/*
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* Switch over to new preferred device.
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*/
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existing->dev = dev;
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info = existing;
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/* Has labeller changed? */
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17
lib/cache/lvmetad.c
vendored
17
lib/cache/lvmetad.c
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@ -366,10 +366,19 @@ static struct lvmcache_info *_pv_populate_lvmcache(struct cmd_context *cmd,
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while (alt_device) {
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dev_alternate = dev_cache_get_by_devt(alt_device->v.i, cmd->filter);
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if (dev_alternate)
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lvmcache_add(fmt->labeller, (const char *)&pvid, dev_alternate,
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vgname, (const char *)&vgid, 0);
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else
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if (dev_alternate) {
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if ((info = lvmcache_add(fmt->labeller, (const char *)&pvid, dev_alternate,
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vgname, (const char *)&vgid, 0))) {
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/*
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* FIXME: when lvmcache_add returns non-NULL,
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* it means that it has made dev_alternate
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* the preferred device in lvmcache.
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* I think that means it should be followed
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* by the same steps done above?
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*/
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log_warn("lvmcache only partially updated for alternate device %s", dev_name(dev));
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}
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} else
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log_warn("Duplicate of PV %s dev %s exists on unknown device %"PRId64 ":%" PRId64,
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pvid_txt, dev_name(dev), MAJOR(alt_device->v.i), MINOR(alt_device->v.i));
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alt_device = alt_device->next;
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@ -225,6 +225,9 @@ int dev_subsystem_part_major(struct dev_types *dt, struct device *dev)
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const char *dev_subsystem_name(struct dev_types *dt, struct device *dev)
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{
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if (MAJOR(dev->dev) == dt->device_mapper_major)
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return "DM";
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if (MAJOR(dev->dev) == dt->md_major)
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return "MD";
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