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cifs: Add a function to build an RDMA SGE list from an iterator
Add a function to add elements onto an RDMA SGE list representing page fragments extracted from a BVEC-, KVEC- or XARRAY-type iterator and DMA mapped until the maximum number of elements is reached. Nothing is done to make sure the pages remain present - that must be done by the caller. Signed-off-by: David Howells <dhowells@redhat.com> cc: Steve French <sfrench@samba.org> cc: Shyam Prasad N <nspmangalore@gmail.com> cc: Rohith Surabattula <rohiths.msft@gmail.com> cc: Tom Talpey <tom@talpey.com> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-rdma@vger.kernel.org Link: https://lore.kernel.org/r/166697256704.61150.17388516338310645808.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166732028840.3186319.8512284239779728860.stgit@warthog.procyon.org.uk/ # rfc Signed-off-by: Steve French <stfrench@microsoft.com>
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1 changed files with 214 additions and 0 deletions
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@ -44,6 +44,17 @@ static int smbd_post_send_page(struct smbd_connection *info,
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static void destroy_mr_list(struct smbd_connection *info);
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static int allocate_mr_list(struct smbd_connection *info);
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struct smb_extract_to_rdma {
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struct ib_sge *sge;
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unsigned int nr_sge;
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unsigned int max_sge;
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struct ib_device *device;
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u32 local_dma_lkey;
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enum dma_data_direction direction;
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};
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static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len,
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struct smb_extract_to_rdma *rdma);
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/* SMBD version number */
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#define SMBD_V1 0x0100
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@ -2492,3 +2503,206 @@ int smbd_deregister_mr(struct smbd_mr *smbdirect_mr)
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return rc;
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}
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static bool smb_set_sge(struct smb_extract_to_rdma *rdma,
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struct page *lowest_page, size_t off, size_t len)
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{
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struct ib_sge *sge = &rdma->sge[rdma->nr_sge];
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u64 addr;
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addr = ib_dma_map_page(rdma->device, lowest_page,
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off, len, rdma->direction);
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if (ib_dma_mapping_error(rdma->device, addr))
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return false;
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sge->addr = addr;
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sge->length = len;
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sge->lkey = rdma->local_dma_lkey;
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rdma->nr_sge++;
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return true;
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}
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/*
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* Extract page fragments from a BVEC-class iterator and add them to an RDMA
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* element list. The pages are not pinned.
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*/
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static ssize_t smb_extract_bvec_to_rdma(struct iov_iter *iter,
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struct smb_extract_to_rdma *rdma,
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ssize_t maxsize)
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{
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const struct bio_vec *bv = iter->bvec;
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unsigned long start = iter->iov_offset;
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unsigned int i;
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ssize_t ret = 0;
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for (i = 0; i < iter->nr_segs; i++) {
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size_t off, len;
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len = bv[i].bv_len;
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if (start >= len) {
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start -= len;
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continue;
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}
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len = min_t(size_t, maxsize, len - start);
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off = bv[i].bv_offset + start;
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if (!smb_set_sge(rdma, bv[i].bv_page, off, len))
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return -EIO;
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ret += len;
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maxsize -= len;
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if (rdma->nr_sge >= rdma->max_sge || maxsize <= 0)
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break;
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start = 0;
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}
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return ret;
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}
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/*
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* Extract fragments from a KVEC-class iterator and add them to an RDMA list.
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* This can deal with vmalloc'd buffers as well as kmalloc'd or static buffers.
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* The pages are not pinned.
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*/
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static ssize_t smb_extract_kvec_to_rdma(struct iov_iter *iter,
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struct smb_extract_to_rdma *rdma,
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ssize_t maxsize)
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{
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const struct kvec *kv = iter->kvec;
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unsigned long start = iter->iov_offset;
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unsigned int i;
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ssize_t ret = 0;
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for (i = 0; i < iter->nr_segs; i++) {
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struct page *page;
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unsigned long kaddr;
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size_t off, len, seg;
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len = kv[i].iov_len;
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if (start >= len) {
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start -= len;
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continue;
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}
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kaddr = (unsigned long)kv[i].iov_base + start;
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off = kaddr & ~PAGE_MASK;
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len = min_t(size_t, maxsize, len - start);
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kaddr &= PAGE_MASK;
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maxsize -= len;
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do {
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seg = min_t(size_t, len, PAGE_SIZE - off);
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if (is_vmalloc_or_module_addr((void *)kaddr))
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page = vmalloc_to_page((void *)kaddr);
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else
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page = virt_to_page(kaddr);
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if (!smb_set_sge(rdma, page, off, seg))
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return -EIO;
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ret += seg;
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len -= seg;
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kaddr += PAGE_SIZE;
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off = 0;
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} while (len > 0 && rdma->nr_sge < rdma->max_sge);
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if (rdma->nr_sge >= rdma->max_sge || maxsize <= 0)
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break;
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start = 0;
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}
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return ret;
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}
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/*
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* Extract folio fragments from an XARRAY-class iterator and add them to an
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* RDMA list. The folios are not pinned.
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*/
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static ssize_t smb_extract_xarray_to_rdma(struct iov_iter *iter,
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struct smb_extract_to_rdma *rdma,
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ssize_t maxsize)
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{
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struct xarray *xa = iter->xarray;
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struct folio *folio;
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loff_t start = iter->xarray_start + iter->iov_offset;
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pgoff_t index = start / PAGE_SIZE;
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ssize_t ret = 0;
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size_t off, len;
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XA_STATE(xas, xa, index);
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rcu_read_lock();
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xas_for_each(&xas, folio, ULONG_MAX) {
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if (xas_retry(&xas, folio))
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continue;
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if (WARN_ON(xa_is_value(folio)))
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break;
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if (WARN_ON(folio_test_hugetlb(folio)))
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break;
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off = offset_in_folio(folio, start);
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len = min_t(size_t, maxsize, folio_size(folio) - off);
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if (!smb_set_sge(rdma, folio_page(folio, 0), off, len)) {
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rcu_read_unlock();
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return -EIO;
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}
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maxsize -= len;
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ret += len;
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if (rdma->nr_sge >= rdma->max_sge || maxsize <= 0)
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break;
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}
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rcu_read_unlock();
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return ret;
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}
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/*
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* Extract page fragments from up to the given amount of the source iterator
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* and build up an RDMA list that refers to all of those bits. The RDMA list
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* is appended to, up to the maximum number of elements set in the parameter
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* block.
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*
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* The extracted page fragments are not pinned or ref'd in any way; if an
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* IOVEC/UBUF-type iterator is to be used, it should be converted to a
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* BVEC-type iterator and the pages pinned, ref'd or otherwise held in some
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* way.
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*/
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static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len,
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struct smb_extract_to_rdma *rdma)
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{
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ssize_t ret;
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int before = rdma->nr_sge;
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switch (iov_iter_type(iter)) {
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case ITER_BVEC:
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ret = smb_extract_bvec_to_rdma(iter, rdma, len);
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break;
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case ITER_KVEC:
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ret = smb_extract_kvec_to_rdma(iter, rdma, len);
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break;
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case ITER_XARRAY:
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ret = smb_extract_xarray_to_rdma(iter, rdma, len);
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break;
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default:
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WARN_ON_ONCE(1);
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return -EIO;
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}
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if (ret > 0) {
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iov_iter_advance(iter, ret);
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} else if (ret < 0) {
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while (rdma->nr_sge > before) {
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struct ib_sge *sge = &rdma->sge[rdma->nr_sge--];
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ib_dma_unmap_single(rdma->device, sge->addr, sge->length,
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rdma->direction);
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sge->addr = 0;
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}
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}
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return ret;
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}
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