Zach Brown 36b0df336b scoutfs: add unmount barrier ...

Now that a mount's client is responsible for electing and starting a
server we need to be careful about coordinating unmount.  We can't
let unmounting clients leave the remaining mounted clients without
quorum.

The server carefully tracks who is mounted and who is unmounting while
it is processing farewell requests.  It only sends responses to voting
mounts while quorum remains or once all the voting clients are all
trying to unmount.

We use a field in the quorum blocks to communicate to the final set of
unmounting voters that their farewells have been processed and that they
can finish unmounting without trying to restablish quorum.

The commit introduces and maintains the unmount_barrier field in the
quorum blocks.  It is passed to the server from the election, the
server sends it to the client and writes new versions, and the client
compares what it received with what it sees in quorum blocks.

The commit then has the clients send their unique name to the server
who stores it in persistent mounted client records and compares the
names to the quorum config when deciding which farewell reqeusts
can be responded to.

Now that farewell response processing can block for a very long time it
is moved off into async work so that it doesn't prevent net connections
from being shutdown and re-established.  This also makes it easier to
make global decisions based on the count of pending farewell requests.

Signed-off-by: Zach Brown <zab@versity.com>

2019-04-12 10:54:07 -07:00

kmod

scoutfs: add unmount barrier

2019-04-12 10:54:07 -07:00

Description

No description provided

8 MiB

Languages

C 87%

Shell 9.3%

Roff 2.5%

TeX 0.8%

Makefile 0.4%