[PATCH net] s390/ism: Properly fix receive message buffer allocation

Gerd Bayer
2024-04-15T13:15:26Z

Since [1], dma_alloc_coherent() does not accept requests for GFP_COMP
anymore, even on archs that may be able to fulfill this. Functionality that
relied on the receive buffer being a compound page broke at that point:
The SMC-D protocol, that utilizes the ism device driver, passes receive
buffers to the splice processor in a struct splice_pipe_desc with a
single entry list of struct pages. As the buffer is no longer a compound
page, the splice processor now rejects requests to handle more than a
page worth of data.

Replace dma_alloc_coherent() and allocate a buffer with folio_alloc and
create a DMA map for it with dma_map_page(). Since only receive buffers
on ISM devices use DMA, qualify the mapping as FROM_DEVICE.
Since ISM devices are available on arch s390, only, and on that arch all
DMA is coherent, there is no need to introduce and export some kind of
dma_sync_to_cpu() method to be called by the SMC-D protocol layer.

Analogously, replace dma_free_coherent by a two step dma_unmap_page,
then folio_put to free the receive buffer.

[1] https://lore.kernel.org/all/20221113163535.884299-1-hch@lst.de/

Fixes: c08004eede4b ("s390/ism: don't pass bogus GFP_ flags to dma_alloc_coherent")
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>

---

Hi all,

this is the next iteration (v3 so to speak) of the fix [2] whose v2 [3] was
picked - then reverted - while there was still one comment outstanding. Here the
last review comment is addressed and proper error checking is done after
allocating the folio.

Please consider this complete patch for inclusion into the next 6.9 rc.

Thank you,
Gerd

[2] https://lore.kernel.org/all/20240328154144.272275-1-gbayer@linux.ibm.com/
[3] https://lore.kernel.org/all/20240405111606.1785928-1-gbayer@linux.ibm.com/

https://lore.kernel.org/all/20240405111222.1785248-1-gbayer@linux.ibm.com/
---
drivers/s390/net/ism_drv.c | 37 ++++++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index 2c8e964425dc..43778b088ffa 100644
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -292,13 +292,16 @@ static int ism_read_local_gid(struct ism_dev *ism)
static void ism_free_dmb(struct ism_dev *ism, struct ism_dmb *dmb)
{
clear_bit(dmb->sba_idx, ism->sba_bitmap);
- dma_free_coherent(&ism->pdev->dev, dmb->dmb_len,
- dmb->cpu_addr, dmb->dma_addr);
+ dma_unmap_page(&ism->pdev->dev, dmb->dma_addr, dmb->dmb_len,
+ DMA_FROM_DEVICE);
+ folio_put(virt_to_folio(dmb->cpu_addr));
}

static int ism_alloc_dmb(struct ism_dev *ism, struct ism_dmb *dmb)
{
+ struct folio *folio;
unsigned long bit;
+ int rc;

if (PAGE_ALIGN(dmb->dmb_len) > dma_get_max_seg_size(&ism->pdev->dev))
return -EINVAL;
@@ -315,14 +318,30 @@ static int ism_alloc_dmb(struct ism_dev *ism, struct ism_dmb *dmb)
test_and_set_bit(dmb->sba_idx, ism->sba_bitmap))
return -EINVAL;

- dmb->cpu_addr = dma_alloc_coherent(&ism->pdev->dev, dmb->dmb_len,
- &dmb->dma_addr,
- GFP_KERNEL | __GFP_NOWARN |
- __GFP_NOMEMALLOC | __GFP_NORETRY);
- if (!dmb->cpu_addr)
- clear_bit(dmb->sba_idx, ism->sba_bitmap);
+ folio = folio_alloc(GFP_KERNEL | __GFP_NOWARN | __GFP_NOMEMALLOC |
+ __GFP_NORETRY, get_order(dmb->dmb_len));

- return dmb->cpu_addr ? 0 : -ENOMEM;
+ if (!folio) {
+ rc = -ENOMEM;
+ goto out_bit;
+ }
+
+ dmb->cpu_addr = folio_address(folio);
+ dmb->dma_addr = dma_map_page(&ism->pdev->dev,
+ virt_to_page(dmb->cpu_addr), 0,
+ dmb->dmb_len, DMA_FROM_DEVICE);
+ if (dma_mapping_error(&ism->pdev->dev, dmb->dma_addr)) {
+ rc = -ENOMEM;
+ goto out_free;
+ }
+
+ return 0;
+
+out_free:
+ kfree(dmb->cpu_addr);
+out_bit:
+ clear_bit(dmb->sba_idx, ism->sba_bitmap);
+ return rc;
}

int ism_register_dmb(struct ism_dev *ism, struct ism_dmb *dmb,
--
2.44.0