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@xxxxxxxxxx> cc: Steve French <sfrench@xxxxxxxxx> cc: Shyam Prasad N <nspmangalore@xxxxxxxxx> cc: Rohith Surabattula <rohiths.msft@xxxxxxxxx> cc: Tom Talpey <tom@xxxxxxxxxx> cc: Jeff Layton <jlayton@xxxxxxxxxx> cc: linux-cifs@xxxxxxxxxxxxxxx cc: linux-fsdevel@xxxxxxxxxxxxxxx cc: linux-rdma@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/166697256704.61150.17388516338310645808.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # rfc Link: https://lore.kernel.org/r/166732028840.3186319.8512284239779728860.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # rfc --- fs/cifs/smbdirect.c | 224 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 224 insertions(+) diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c index 3e693ffd0662..78a76752fafd 100644 --- a/fs/cifs/smbdirect.c +++ b/fs/cifs/smbdirect.c @@ -44,6 +44,17 @@ static int smbd_post_send_page(struct smbd_connection *info, static void destroy_mr_list(struct smbd_connection *info); static int allocate_mr_list(struct smbd_connection *info); +struct smb_extract_to_rdma { + struct ib_sge *sge; + unsigned int nr_sge; + unsigned int max_sge; + struct ib_device *device; + u32 local_dma_lkey; + enum dma_data_direction direction; +}; +static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len, + struct smb_extract_to_rdma *rdma); + /* SMBD version number */ #define SMBD_V1 0x0100 @@ -2480,3 +2491,216 @@ int smbd_deregister_mr(struct smbd_mr *smbdirect_mr) return rc; } + +static bool smb_set_sge(struct smb_extract_to_rdma *rdma, + struct page *lowest_page, size_t off, size_t len) +{ + struct ib_sge *sge = &rdma->sge[rdma->nr_sge]; + u64 addr; + + addr = ib_dma_map_page(rdma->device, lowest_page, + off, len, rdma->direction); + if (ib_dma_mapping_error(rdma->device, addr)) + return false; + + sge->addr = addr; + sge->length = len; + sge->lkey = rdma->local_dma_lkey; + rdma->nr_sge++; + return true; +} + +/* + * Extract page fragments from a BVEC-class iterator and add them to an RDMA + * element list. The pages are not pinned. + */ +static ssize_t smb_extract_bvec_to_rdma(struct iov_iter *iter, + struct smb_extract_to_rdma *rdma, + ssize_t maxsize) +{ + const struct bio_vec *bv = iter->bvec; + unsigned long start = iter->iov_offset; + unsigned int i, sge_max = rdma->max_sge; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + size_t off, len; + + len = bv[i].bv_len; + if (start >= len) { + start -= len; + continue; + } + + len = min_t(size_t, maxsize, len - start); + off = bv[i].bv_offset + start; + + if (!smb_set_sge(rdma, bv[i].bv_page, off, len)) + return -EIO; + sge_max--; + + ret += len; + maxsize -= len; + if (maxsize <= 0 || sge_max == 0) + break; + start = 0; + } + + return ret; +} + +/* + * Extract fragments from a KVEC-class iterator and add them to an RDMA list. + * This can deal with vmalloc'd buffers as well as kmalloc'd or static buffers. + * The pages are not pinned. + */ +static ssize_t smb_extract_kvec_to_rdma(struct iov_iter *iter, + struct smb_extract_to_rdma *rdma, + ssize_t maxsize) +{ + const struct kvec *kv = iter->kvec; + unsigned long start = iter->iov_offset; + unsigned int i, sge_max = rdma->max_sge; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + struct page *page; + unsigned long kaddr; + size_t off, len, seg; + + len = kv[i].iov_len; + if (start >= len) { + start -= len; + continue; + } + + kaddr = (unsigned long)kv[i].iov_base + start; + off = kaddr & ~PAGE_MASK; + len = min_t(size_t, maxsize, len - start); + kaddr &= PAGE_MASK; + + maxsize -= len; + ret += len; + do { + seg = min_t(size_t, len, PAGE_SIZE - off); + + if (is_vmalloc_or_module_addr((void *)kaddr)) + page = vmalloc_to_page((void *)kaddr); + else + page = virt_to_page(kaddr); + + if (!smb_set_sge(rdma, page, off, len)) + return -EIO; + sge_max--; + + len -= seg; + kaddr += PAGE_SIZE; + off = 0; + } while (len > 0 && sge_max > 0); + + if (maxsize <= 0 || sge_max == 0) + break; + start = 0; + } + + return ret; +} + +/* + * Extract folio fragments from an XARRAY-class iterator and add them to an + * RDMA list. The folios are not pinned. + */ +static ssize_t smb_extract_xarray_to_rdma(struct iov_iter *iter, + struct smb_extract_to_rdma *rdma, + ssize_t maxsize) +{ + struct xarray *xa = iter->xarray; + struct folio *folio; + unsigned int sge_max = rdma->max_sge; + loff_t start = iter->xarray_start + iter->iov_offset; + pgoff_t index = start / PAGE_SIZE; + ssize_t ret = 0; + size_t off, len; + XA_STATE(xas, xa, index); + + rcu_read_lock(); + + xas_for_each(&xas, folio, ULONG_MAX) { + if (xas_retry(&xas, folio)) + continue; + if (WARN_ON(xa_is_value(folio))) + break; + if (WARN_ON(folio_test_hugetlb(folio))) + break; + + off = offset_in_folio(folio, start); + len = min_t(size_t, maxsize, folio_size(folio) - off); + + if (!smb_set_sge(rdma, folio_page(folio, 0), off, len)) { + rcu_read_lock(); + return -EIO; + } + sge_max--; + + maxsize -= len; + ret += len; + if (maxsize <= 0 || sge_max == 0) + break; + } + + rcu_read_unlock(); + return ret; +} + +/* + * Extract page fragments from up to the given amount of the source iterator + * and build up an RDMA list that refers to all of those bits. The RDMA list + * is appended to, up to the maximum number of elements set in the parameter + * block. + * + * The extracted page fragments are not pinned or ref'd in any way; if an + * IOVEC/UBUF-type iterator is to be used, it should be converted to a + * BVEC-type iterator and the pages pinned, ref'd or otherwise held in some + * way. + */ +static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len, + struct smb_extract_to_rdma *rdma) +{ + ssize_t ret; + int before = rdma->nr_sge; + + if (iov_iter_is_discard(iter) || + iov_iter_is_pipe(iter) || + user_backed_iter(iter)) { + WARN_ON_ONCE(1); + return -EIO; + } + + switch (iov_iter_type(iter)) { + case ITER_BVEC: + ret = smb_extract_bvec_to_rdma(iter, rdma, len); + break; + case ITER_KVEC: + ret = smb_extract_kvec_to_rdma(iter, rdma, len); + break; + case ITER_XARRAY: + ret = smb_extract_xarray_to_rdma(iter, rdma, len); + break; + default: + BUG(); + } + + if (ret > 0) { + iov_iter_advance(iter, ret); + } else if (ret < 0) { + while (rdma->nr_sge > before) { + struct ib_sge *sge = &rdma->sge[rdma->nr_sge--]; + + ib_dma_unmap_single(rdma->device, sge->addr, sge->length, + rdma->direction); + sge->addr = 0; + } + } + + return ret; +}
