On Tue, 20 Jun 2023 15:53:20 +0100 David Howells wrote: > If sendmsg() is passed MSG_SPLICE_PAGES and is given a buffer that contains > some data that's resident in the slab, copy it rather than returning EIO. How did that happen? I thought MSG_SPLICE_PAGES comes from former sendpage users and sendpage can't operate on slab pages. > This can be made use of by a number of drivers in the kernel, including: > iwarp, ceph/rds, dlm, nvme, ocfs2, drdb. It could also be used by iscsi, > rxrpc, sunrpc, cifs and probably others. > > skb_splice_from_iter() is given it's own fragment allocator as > page_frag_alloc_align() can't be used because it does no locking to prevent > parallel callers from racing. The locking is to local_bh_disable(). Does the milliont^w new frag allocator have any additional benefits? > alloc_skb_frag() uses a separate folio for > each cpu and locks to the cpu whilst allocating, reenabling cpu migration > around folio allocation.
