Re: filesystem transactions API

[Jamie Lokier]

Artem B. Bityuckiy wrote:
> Jamie Lokier wrote:
> >The problem with making them exclusive locks is that you halt the
> >system for the duration of the transaction.  If it's a big transaction
> >such as updating 1000 files for a package update, that blocks a lot of
> >programs for a long time, and it's not necessary.
> 
> Surely we'll anyway block others if we have a kernel-level
> transaction support?  What is the difference in which layer to
> block?

No.  Why would you block?  You can have transactions without blocking
other processes.

When updating, say, the core-utils package (which contains cat),
there's no reason why a program which executes "cat" should have to
block during the update.  It can simply execute the old one until the
new one is committed at the end of the update.

It's analogous to RCU for protecting kernel data structures without
blocking readers.

-- Jamie
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