[Cluster-devel] [PATCH] gfs2(5): add rgrplbv and loccookie info the the manpage

[Benjamin Marzinski]

The only issue with these patches is that they are geared for upstream.
Instead of listing the 3.6 and 4.5 linux kernels, the RHEL man pages
should list the relevant rhel kernels.  I suppose the easiest way to
deal with this would be to patch them in the rhel rpms.

-Ben

On Fri, Apr 15, 2016 at 11:33:43AM -0500, Benjamin Marzinski wrote:
> The gfs2 man page didn't have any information about the rgrplvb and
> loccookie mount options. This patch adds it.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  gfs2/man/gfs2.5 | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/gfs2/man/gfs2.5 b/gfs2/man/gfs2.5
> index 0517944..56d1a00 100644
> --- a/gfs2/man/gfs2.5
> +++ b/gfs2/man/gfs2.5
> @@ -165,6 +165,40 @@ the statfs information on a local basis before it is synced back
>  to the master statfs file, even if the time period has not
>  expired. If the setting of statfs_quantum is 0, then this setting
>  is ignored.
> +.TP
> +\fBrgrplvb\fP
> +This flag tells gfs2 to look for information about a resource group's free
> +space and unlinked inodes in its glock lock value block. This keeps gfs2 from
> +having to read in the resource group data from disk, speeding up allocations in
> +some cases.  This option was added in the 3.6 Linux kernel. Prior to this
> +kernel, no information was saved to the resource group lvb. \fBNote:\fP To
> +safely turn on this option, all nodes mounting the filesystem must be running
> +at least a 3.6 Linux kernel. If any nodes had previously mounted the filesystem
> +using older kernels, the filesystem must be unmounted on all nodes before it
> +can be mounted with this option enabled. This option does not need to be
> +enabled on all nodes using a filesystem.
> +.TP
> +\fBloccookie\fP
> +This flag tells gfs2 to use location based readdir cookies, instead of its
> +usual filename hash readdir cookies.  The filename hash cookies are not
> +guaranteed to be unique, and as the number of files in a directory increases,
> +so does the likelihood of a collision.  NFS requires readdir cookies to be
> +unique, which can cause problems with very large directories (over 100,000
> +files). With this flag set, gfs2 will try to give out location based cookies.
> +Since the cookie is 31 bits, gfs2 will eventually run out of unique cookies,
> +and will fail back to using hash cookies. The maximum number of files that
> +could have unique location cookies assuming perfectly even hashing and names of
> +8 or fewer characters is 1,073,741,824. An average directory should be able to
> +give out well over half a billion location based cookies. This option was added
> +in the 4.5 Linux kernel. Prior to this kernel, gfs2 did not add directory
> +entries in a way that allowed it to use location based readdir cookies.
> +\fBNote:\fP To safely turn on this option, all nodes mounting the filesystem
> +must be running at least a 4.5 Linux kernel. If this option is only enabled on
> +some of the nodes mounting a filesystem, the cookies returned by nodes using
> +this option will not be valid on nodes that are not using this option, and vice
> +versa.  Finally, when first enabling this option on a filesystem that had been
> +previously mounted without it, you must make sure that there are no outstanding
> +cookies being cached by other software, such as NFS.
>  
>  .SH BUGS
>  
> -- 
> 2.1.0