Hi Will,
On Thu, May 13 2010 at 9:39pm -0400,
Will Drewry <wad@xxxxxxxxxxxx> wrote:
> Following on the discussion of booting directly to a device-mapper
> device, two things were made clear:
> 1. The ioctl interface's name and uuid are mandatory for udev to work
> 2. There is a functional gap between the dm(-fs) and dm-ioctl
>
> This change adds one function which is used for binding a given mapped
> device to a name+uuid in the dm-ioctl hash table. In addition, it
> ensures that public functions are available that allow mapped devices
> and tables to be created and associated with shared code paths in
> dm-ioctl:
> - suspend flags and block integrity registration are now exposed
> - dm_table_complete() now prepares a table for use completely
> (builds the btree; sets the type; allocates md pools)
I have done a preliminary review and have some comments inlined below.
> Ideally, this lays the groundwork for any kernel code to create fully
> functional mapped devices, but I'd appreciate feedback on if this
> approach makes sense/is safe, preferred function names, and if it
> integrates with the current direction.
>
> (I can also pair this with the init code patch if it makes sense to show
> consumer code.)
It would certainly help follow-on reviews as we take a closer look. For
the next version of your work I'd recommend sharing all related code in
a series (e.g.: core DM patch 1/2, init patch 2/2).
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 9924ea2..66726d1 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -900,7 +900,7 @@ static int setup_indexes(struct dm_table *t)
> /*
> * Builds the btree to index the map.
> */
> -int dm_table_complete(struct dm_table *t)
> +int dm_table_build_index(struct dm_table *t)
> {
> int r = 0;
> unsigned int leaf_nodes;
> @@ -919,6 +919,48 @@ int dm_table_complete(struct dm_table *t)
> return r;
> }
>
> +
> +/*
> + * Prepares the table for use by building the indices,
> + * setting the type, and allocating mempools.
> + */
> +int dm_table_complete(struct dm_table *t)
> +{
> + int r = 0;
> +
> + r = dm_table_build_index(t);
> + if (r) {
> + DMWARN("unable to build btrees");
> + return r;
> + }
> + r = dm_table_set_type(t);
> + if (r) {
> + DMWARN("unable to set table type");
> + return r;
> + }
> + r = dm_table_alloc_md_mempools(t);
> + if (r)
> + DMWARN("unable to allocate mempools");
> +
> + return r;
> +}
Please have dm_table_set_type() come before dm_table_build_index() to
preserve the existing call sequence. It is better to check the type
related constraints before going on to build the indices.
> +
> +/*
> + * Register the mapped device for blk_integrity support if
> + * the underlying devices support it.
> + */
> +int dm_table_prealloc_integrity(struct dm_table *t, struct mapped_device *md)
> +{
> + struct list_head *devices = dm_table_get_devices(t);
> + struct dm_dev_internal *dd;
> +
> + list_for_each_entry(dd, devices, list)
> + if (bdev_get_integrity(dd->dm_dev.bdev))
> + return blk_integrity_register(dm_disk(md), NULL);
> +
> + return 0;
> +}
I think we need more justification for why you'd want to expose
dm_table_prealloc_integrity() as a public interface. Makes DM a bit
more brittle with unknown gain at the moment. Why not just move the
dm_table_prealloc_integrity() call to dm_table_complete() -- just before
dm_table_alloc_md_mempools()?
> static DEFINE_MUTEX(_event_lock);
> void dm_table_event_callback(struct dm_table *t,
> void (*fn)(void *), void *context)
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 1381cd9..95fea4c 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -215,6 +215,18 @@ void dm_set_mdptr(struct mapped_device *md, void *ptr);
> void *dm_get_mdptr(struct mapped_device *md);
>
> /*
> + * Export the device via the ioctl interface
> + */
> +int dm_ioctl_export(struct mapped_device *md, const char *name,
> + const char *uuid);
> +
> +/*
> + * Suspend feature flags
> + */
> +#define DM_SUSPEND_LOCKFS_FLAG (1 << 0)
> +#define DM_SUSPEND_NOFLUSH_FLAG (1 << 1)
You're missing the matching removal of these flags from drivers/md/dm.h
Regards,
Mike
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