[DragonFlyBSD - Bug #2863] HAMMER synch tid is zero

[bugtracker-admin at leaf.dragonflybsd.org]

Issue #2863 has been updated by tkusumi.


Also note that the tid value isn't just a number to make hammer snapshots, pfses, etc look nicer via hammer's userspace commands.

It's a core part of mirroring and asof btree, where a larger tid means there was an update to the filesystem's btree that you need to take objects with that tid into account.

It's really a sensitive thing that it needs to be carefully examined.


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Bug #2863: HAMMER synch tid is zero
http://bugs.dragonflybsd.org/issues/2863#change-12778

* Author: shamaz
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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Hello. This appears on DragonFlyBSD 4.2 (and maybe newer) if you try the
following with HAMMER filesystem:

1) Create a new vnode device.
# dd if=/dev/zero of=test.img bs=1m count=15000
# vnconfig -c vn test.img
# disklabel64  -w -r vn4s0 auto
# disklabel64 -e vn4s0
Add a line like "a:      *      0     HAMMER"

2) Create a HAMMER filesystem:
newfs_hammer -f -L TEST /dev/vn4s0a

3) Mount it:
mount /dev/vn4s0a /mnt

4) Try to sync it:
hammer synctid /mnt

You will see zero sync tid (0x0000000000000000). If you try to set some
debug-related sysctls, it will get you no info at all when syncing. Also
hammer pfs-status /mnt will show that sync-end-tid does not increment in
time as it should. I am not sure if it happens with any non-root hammer FS,
or just with those based on vn pseudo disks.

---Files--------------------------------
flusher_tid.patch (492 Bytes)


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