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SubjectRe: [Ocfs2-devel] [PATCH 01/11] ocfs2_dlmfs: Add capabilities parameter.
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>


Joel Becker wrote:
> Over time, dlmfs has added some features that were not part of the
> initial ABI. Unfortunately, some of these features are not detectable
> via standard usage. For example, Linux's default poll always returns
> POLLIN, so there is no way for a caller of poll(2) to know when dlmfs
> added poll support. Instead, we provide this list of new capabilities.
>
> Capabilities is a read-only attribute. We do it as a module parameter
> so we can discover it whether dlmfs is built in, loaded, or even not
> loaded (via modinfo).
>
> The ABI features are local to this machine's dlmfs mount. This is
> distinct from the locking protocol, which is concerned with inter-node
> interaction.
>
> Signed-off-by: Joel Becker <joel.becker@oracle.com>
> ---
> fs/ocfs2/dlm/dlmfs.c | 36 ++++++++++++++++++++++++++++++++++++
> 1 files changed, 36 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ocfs2/dlm/dlmfs.c b/fs/ocfs2/dlm/dlmfs.c
> index 02bf178..77d0df4 100644
> --- a/fs/ocfs2/dlm/dlmfs.c
> +++ b/fs/ocfs2/dlm/dlmfs.c
> @@ -81,6 +81,42 @@ static const struct dlm_protocol_version user_locking_protocol = {
> .pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
> };
>
> +
> +/*
> + * These are the ABI capabilities of dlmfs.
> + *
> + * Over time, dlmfs has added some features that were not part of the
> + * initial ABI. Unfortunately, some of these features are not detectable
> + * via standard usage. For example, Linux's default poll always returns
> + * POLLIN, so there is no way for a caller of poll(2) to know when dlmfs
> + * added poll support. Instead, we provide this list of new capabilities.
> + *
> + * Capabilities is a read-only attribute. We do it as a module parameter
> + * so we can discover it whether dlmfs is built in, loaded, or even not
> + * loaded.
> + *
> + * The ABI features are local to this machine's dlmfs mount. This is
> + * distinct from the locking protocol, which is concerned with inter-node
> + * interaction.
> + */
> +#define DLMFS_CAPABILITIES ""
> +extern int param_set_dlmfs_capabilities(const char *val,
> + struct kernel_param *kp)
> +{
> + printk(KERN_ERR "%s: readonly parameter\n", kp->name);
> + return -EINVAL;
> +}
> +static int param_get_dlmfs_capabilities(char *buffer,
> + struct kernel_param *kp)
> +{
> + return strlcpy(buffer, DLMFS_CAPABILITIES,
> + strlen(DLMFS_CAPABILITIES) + 1);
> +}
> +module_param_call(capabilities, param_set_dlmfs_capabilities,
> + param_get_dlmfs_capabilities, NULL, 0444);
> +MODULE_PARM_DESC(capabilities, DLMFS_CAPABILITIES);
> +
> +
> /*
> * decodes a set of open flags into a valid lock level and a set of flags.
> * returns < 0 if we have invalid flags
>



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