[PATCH 6.18 020/270] smb: client/smbdirect: fix MR registration for coalesced SG lists

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yi Kuo <yi@yikuo.dev>

commit 9900b9fee5a0e0f72d7c744b37c7c851d5785ac6 upstream.
The stable backport to < 7.1 patches a different file. Also
the Fixes tag below is adjusted for the old code path.

ib_dma_map_sg() modifies the provided scatterlist and returns the
number of mapped entries, which can be fewer than the requested
mr->sgt.nents if the DMA controller coalesces contiguous memory
segments. Passing the original, uncoalesced count to ib_map_mr_sg()
causes memory registration failures if coalescing actually occurs.

Capture the actual mapped count returned by ib_dma_map_sg() and pass it
to ib_map_mr_sg() to ensure correct MR registration.

Also update the ib_dma_map_sg() error logging to drop the error
pointer formatting, since the return value is an integer count
rather than an error code.

Ensure a proper error code (-EIO) is assigned when DMA mapping or
MR registration fails.

Fixes: c7398583340a ("CIFS: SMBD: Implement RDMA memory registration")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221408
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Yi Kuo <yi@yikuo.dev>
Signed-off-by: Steve French <stfrench@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/client/smbdirect.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
index ff44a2dc49938..e2b20219ba2c7 100644
--- a/fs/smb/client/smbdirect.c
+++ b/fs/smb/client/smbdirect.c
@@ -2895,7 +2895,7 @@ struct smbdirect_mr_io *smbd_register_mr(struct smbd_connection *info,
 	struct smbdirect_socket *sc = &info->socket;
 	struct smbdirect_socket_parameters *sp = &sc->parameters;
 	struct smbdirect_mr_io *mr;
-	int rc, num_pages;
+	int rc, num_pages, num_mapped;
 	struct ib_reg_wr *reg_wr;
 
 	num_pages = iov_iter_npages(iter, sp->max_frmr_depth + 1);
@@ -2923,18 +2923,21 @@ struct smbdirect_mr_io *smbd_register_mr(struct smbd_connection *info,
 		    num_pages, iov_iter_count(iter), sp->max_frmr_depth);
 	smbd_iter_to_mr(iter, &mr->sgt, sp->max_frmr_depth);
 
-	rc = ib_dma_map_sg(sc->ib.dev, mr->sgt.sgl, mr->sgt.nents, mr->dir);
-	if (!rc) {
-		log_rdma_mr(ERR, "ib_dma_map_sg num_pages=%x dir=%x rc=%x\n",
-			    num_pages, mr->dir, rc);
+	num_mapped = ib_dma_map_sg(sc->ib.dev, mr->sgt.sgl, mr->sgt.nents, mr->dir);
+	if (!num_mapped) {
+		log_rdma_mr(ERR, "ib_dma_map_sg num_pages=%x dir=%x num_mapped=%x\n",
+			    num_pages, mr->dir, num_mapped);
+		rc = -EIO;
 		goto dma_map_error;
 	}
 
-	rc = ib_map_mr_sg(mr->mr, mr->sgt.sgl, mr->sgt.nents, NULL, PAGE_SIZE);
-	if (rc != mr->sgt.nents) {
+	rc = ib_map_mr_sg(mr->mr, mr->sgt.sgl, num_mapped, NULL, PAGE_SIZE);
+	if (rc != num_mapped) {
 		log_rdma_mr(ERR,
-			    "ib_map_mr_sg failed rc = %d nents = %x\n",
-			    rc, mr->sgt.nents);
+			    "ib_map_mr_sg failed rc = %d num_mapped = %x\n",
+			    rc, num_mapped);
+		if (rc >= 0)
+			rc = -EIO;
 		goto map_mr_error;
 	}
 
-- 
2.53.0