linux-kernel - Re: [ANNOUNCE] Reiser5: Selective File Migration

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Message-ID: <20201004095922.GC1104@bug>
Date:   Sun, 4 Oct 2020 11:59:23 +0200
From:   Pavel Machek <pavel@....cz>
To:     Metztli Information Technology <jose.r.r@...ztli.com>
Cc:     edward.shishkin@...il.com, reiserfs-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE] Reiser5: Selective File Migration - User Interface

Hi!

> > In particular, using this functionality, user is able to push out
> > "hot" files on any high-performance device (e.g. proxy device) and pin
> > them there.

What permissions are normally required for file migration?

> > COMMENT. After ioctl successful completion the file is not necessarily
> > written to the target device! To make sure of it, call fsync(2) after
> > successful ioctl completion, or open the file with O_SYNC flag before
> > migration.

Ok.

> > COMMENT. File migration is a volume operation (like adding, removing a device to/from 
> > a logical volumes), and all volume operations are serialized. So, any attempt to 
> > migrate a file, while performing other operation on that volume will fail. If some 
> > file migration procedure fails (with EBUSY, or other errors), or was interrupted by 
> > user, then it should be repeated in the current mount session. File migration 
> > procedures interrupted by system crash, hared reset, etc) should be repeated in the 
> > next mount sessions.

Dunno. Returning -EBUSY is kind of "interesting" there. I'd expect kernel to queue
the callers, because userland can't really do that easily.

Best regards,
									Pavel


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