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List:       fuse-devel
Subject:    Re: [fuse-devel] Big write requests
From:       Csaba Henk <csaba () gluster ! com>
Date:       2009-12-17 7:43:12
Message-ID: slrnhijo63.2k47.csaba-ml () beastie ! creo ! hu
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On 2009-12-13, Didier GARCIN <dg.recrutement31@gmail.com> wrote:
> I've just tested the 2.8.1. And would like to know in which conditions big writes are requested ?
> Must I configure FUSE to privilege the big writes ?
> Or would it be a kernel policy that I can't handle ?

When the kernel was enabled to send over-page sized writes, some fs-es
has went broken as they were not ready to handle this.

Consequently, big writes were made optional (and switched off by
default).

Proto amendment is as follows:

- kernel sends INIT with FUSE_BIG_WRITES set if it's capable of
  multiple page sized writes
- in turn, fuse server replies INIT with FUSE_BIG_WRITES set if it
  wants the kernel to do multiple page sized writes

Cf.
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=v2.6.26-rc2-99-g78bb6c

The high-level library handles this for you; if you use it, just should
pass "-obig_writes" to your fs (or do the equivalent setting in your
code), and big writes will work if kernel can do it.

Csaba


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