Re: [Patch v2 10/15] CIFS: SMBD: Support page offset in memory registration
From: Tom Talpey
Date: Sat Jun 23 2018 - 22:24:39 EST
On 5/30/2018 3:48 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>
Change code to pass the correct page offset during memory registration for
RDMA read/write.
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
fs/cifs/smb2pdu.c | 18 ++++++++-----
fs/cifs/smbdirect.c | 76 +++++++++++++++++++++++++++++++----------------------
fs/cifs/smbdirect.h | 2 +-
3 files changed, 58 insertions(+), 38 deletions(-)
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index f603fbe..fc30774 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2623,8 +2623,8 @@ smb2_new_read_req(void **buf, unsigned int *total_len,
rdata->mr = smbd_register_mr(
server->smbd_conn, rdata->pages,
- rdata->nr_pages, rdata->tailsz,
- true, need_invalidate);
+ rdata->nr_pages, rdata->page_offset,
+ rdata->tailsz, true, need_invalidate);
if (!rdata->mr)
return -ENOBUFS;
@@ -3013,16 +3013,22 @@ smb2_async_writev(struct cifs_writedata *wdata,
wdata->mr = smbd_register_mr(
server->smbd_conn, wdata->pages,
- wdata->nr_pages, wdata->tailsz,
- false, need_invalidate);
+ wdata->nr_pages, wdata->page_offset,
+ wdata->tailsz, false, need_invalidate);
if (!wdata->mr) {
rc = -ENOBUFS;
goto async_writev_out;
}
req->Length = 0;
req->DataOffset = 0;
- req->RemainingBytes =
- cpu_to_le32((wdata->nr_pages-1)*PAGE_SIZE + wdata->tailsz);
+ if (wdata->nr_pages > 1)
+ req->RemainingBytes =
+ cpu_to_le32(
+ (wdata->nr_pages - 1) * wdata->pagesz -
+ wdata->page_offset + wdata->tailsz
+ );
+ else
+ req->RemainingBytes = cpu_to_le32(wdata->tailsz);
Again, I think a helper that computed and returned this size would be
much clearer and compact. And I still am incredulous that a single page
io always has an offset of zero. :-)
req->Channel = SMB2_CHANNEL_RDMA_V1_INVALIDATE;
if (need_invalidate)
req->Channel = SMB2_CHANNEL_RDMA_V1;
diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index ba53c52..e459c97 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -2299,37 +2299,37 @@ static void smbd_mr_recovery_work(struct work_struct *work)
if (smbdirect_mr->state == MR_INVALIDATED ||
smbdirect_mr->state == MR_ERROR) {
- if (smbdirect_mr->state == MR_INVALIDATED) {
+ /* recover this MR entry */
+ rc = ib_dereg_mr(smbdirect_mr->mr);
+ if (rc) {
+ log_rdma_mr(ERR,
+ "ib_dereg_mr failed rc=%x\n",
+ rc);
+ smbd_disconnect_rdma_connection(info);
+ continue;
+ }
Ok, we discussed this ib_dereg_mr() call at the plugfest last week.
It's unnecessary - the MR is reusable and does not need to be destroyed
after each use.
+
+ smbdirect_mr->mr = ib_alloc_mr(
+ info->pd, info->mr_type,
+ info->max_frmr_depth);
+ if (IS_ERR(smbdirect_mr->mr)) {
+ log_rdma_mr(ERR,
+ "ib_alloc_mr failed mr_type=%x "
+ "max_frmr_depth=%x\n",
+ info->mr_type,
+ info->max_frmr_depth);
+ smbd_disconnect_rdma_connection(info);
+ continue;
+ }
+
Not needed, for the same reason above.
+ if (smbdirect_mr->state == MR_INVALIDATED)
ib_dma_unmap_sg(
info->id->device, smbdirect_mr->sgl,
smbdirect_mr->sgl_count,
smbdirect_mr->dir);
- smbdirect_mr->state = MR_READY;
As we observed, the smbdirect_mr is not protected by a lock, therefore
this MR_READY state transition needs a memory barrier in front of it!
- } else if (smbdirect_mr->state == MR_ERROR) {
-
- /* recover this MR entry */
- rc = ib_dereg_mr(smbdirect_mr->mr);
- if (rc) {
- log_rdma_mr(ERR,
- "ib_dereg_mr failed rc=%x\n",
- rc);
- smbd_disconnect_rdma_connection(info);
- }
Why are you deleting the MR_ERROR handling? It seems this is precisely
the place where the MR needs to be destroyed, to prevent any later RDMA
operations from potentially reaching the original memory.
- smbdirect_mr->mr = ib_alloc_mr(
- info->pd, info->mr_type,
- info->max_frmr_depth);
- if (IS_ERR(smbdirect_mr->mr)) {
- log_rdma_mr(ERR,
- "ib_alloc_mr failed mr_type=%x "
- "max_frmr_depth=%x\n",
- info->mr_type,
- info->max_frmr_depth);
- smbd_disconnect_rdma_connection(info);
- }
+ smbdirect_mr->state = MR_READY;
- smbdirect_mr->state = MR_READY;
- }
/* smbdirect_mr->state is updated by this function
* and is read and updated by I/O issuing CPUs trying
* to get a MR, the call to atomic_inc_return
@@ -2475,7 +2475,7 @@ static struct smbd_mr *get_mr(struct smbd_connection *info)
*/
struct smbd_mr *smbd_register_mr(
struct smbd_connection *info, struct page *pages[], int num_pages,
- int tailsz, bool writing, bool need_invalidate)
+ int offset, int tailsz, bool writing, bool need_invalidate)
{
struct smbd_mr *smbdirect_mr;
int rc, i;
@@ -2498,17 +2498,31 @@ struct smbd_mr *smbd_register_mr(
smbdirect_mr->sgl_count = num_pages;
sg_init_table(smbdirect_mr->sgl, num_pages);
- for (i = 0; i < num_pages - 1; i++)
- sg_set_page(&smbdirect_mr->sgl[i], pages[i], PAGE_SIZE, 0);
+ log_rdma_mr(INFO, "num_pages=0x%x offset=0x%x tailsz=0x%x\n",
+ num_pages, offset, tailsz);
+ if (num_pages == 1) {
+ sg_set_page(&smbdirect_mr->sgl[0], pages[0], tailsz, offset);
+ goto skip_multiple_pages;
A simple "else" would be much preferable to this "goto".
+ }
+
+ /* We have at least two pages to register */
+ sg_set_page(
+ &smbdirect_mr->sgl[0], pages[0], PAGE_SIZE - offset, offset);
+ i = 1;
+ while (i < num_pages - 1) {
+ sg_set_page(&smbdirect_mr->sgl[i], pages[i], PAGE_SIZE, 0);
+ i++;
+ }
sg_set_page(&smbdirect_mr->sgl[i], pages[i],
tailsz ? tailsz : PAGE_SIZE, 0);
+skip_multiple_pages:
dir = writing ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
smbdirect_mr->dir = dir;
rc = ib_dma_map_sg(info->id->device, smbdirect_mr->sgl, num_pages, dir);
if (!rc) {
- log_rdma_mr(INFO, "ib_dma_map_sg num_pages=%x dir=%x rc=%x\n",
+ log_rdma_mr(ERR, "ib_dma_map_sg num_pages=%x dir=%x rc=%x\n",
num_pages, dir, rc);
goto dma_map_error;
}
@@ -2516,8 +2530,8 @@ struct smbd_mr *smbd_register_mr(
rc = ib_map_mr_sg(smbdirect_mr->mr, smbdirect_mr->sgl, num_pages,
NULL, PAGE_SIZE);
if (rc != num_pages) {
- log_rdma_mr(INFO,
- "ib_map_mr_sg failed rc = %x num_pages = %x\n",
+ log_rdma_mr(ERR,
+ "ib_map_mr_sg failed rc = %d num_pages = %x\n",
rc, num_pages);
goto map_mr_error;
}
diff --git a/fs/cifs/smbdirect.h b/fs/cifs/smbdirect.h
index f9038da..1e419c2 100644
--- a/fs/cifs/smbdirect.h
+++ b/fs/cifs/smbdirect.h
@@ -321,7 +321,7 @@ struct smbd_mr {
/* Interfaces to register and deregister MR for RDMA read/write */
struct smbd_mr *smbd_register_mr(
struct smbd_connection *info, struct page *pages[], int num_pages,
- int tailsz, bool writing, bool need_invalidate);
+ int offset, int tailsz, bool writing, bool need_invalidate);
int smbd_deregister_mr(struct smbd_mr *mr);
#else