Re: [PATCH v2] smb: smbdirect: fix MR registration for coalesced SG lists

[Namjae Jeon]

On Wed, Apr 29, 2026 at 7:00 PM Yi Kuo <yi@xxxxxxxxx> wrote:
>
> 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: de5ef8ec3c46 ("smb: smbdirect: introduce smbdirect_mr.c with client mr code")
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221408
> Signed-off-by: Yi Kuo <yi@xxxxxxxxx>
Acked-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Thanks!