[Gluster-devel] how does meta xlator work?

[Anand Avati]

On Wed, Aug 13, 2014 at 8:55 PM, Emmanuel Dreyfus <manu at netbsd.org> wrote:

> Anand Avati <avati at gluster.org> wrote:
>
> > That may / may not work well in practice depending on the number of
> > concurrent apps working on a file.
>
> I am not sure what could make a FS decide that for the same file, one
> file descriptor should use direct I/O and another should not.
>
> Keeping the flag at file descriptor level would require VFS modification
> in the kernel: the filesystem knows nothing about file descriptors, it
> just know vnodes. It could be done, but I expect to meet resistance :-)
>
>
For e.g, glusterfs used to enable directio mode for non-read-only FDs (to
cut overheads) but disable directio for read-only (to leverage readahead).
After big_writes was introduced in Linux FUSE this has changed.

But we should be OK having vnode level switch for now, I think.
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