This patch introduces a new way of attaching an external buffer to a mbuf.
Attaching an external buffer is quite similar to mbuf indirection in
replacing buffer addresses and length of a mbuf, but a few differences:
- When an indirect mbuf is attached, refcnt of the direct mbuf would be
2 as long as the direct mbuf itself isn't freed after the attachment.
In such cases, the buffer area of a direct mbuf must be read-only. But
external buffer has its own refcnt and it starts from 1. Unless
multiple mbufs are attached to a mbuf having an external buffer, the
external buffer is writable.
- There's no need to allocate buffer from a mempool. Any buffer can be
attached with appropriate free callback.
- Smaller metadata is required to maintain shared data such as refcnt.
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
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