Re: [PATCH v1 2/2] nvme-pci: handle dma_opt_mapping_size() returning 0

[Christoph Hellwig]

On Mon, Mar 16, 2026 at 10:39:56PM +0200, Ionut Nechita (Wind River) wrote:
> From: Ionut Nechita <ionut.nechita@xxxxxxxxxxxxx>
> 
> After the previous commit, dma_opt_mapping_size() returns 0 when no DMA
> backend provides an optimal mapping size hint (e.g. IOMMU in passthrough
> mode with no ops->opt_mapping_size callback).
> 
> The NVMe PCI driver used min_t(u32, NVME_MAX_BYTES >> SECTOR_SHIFT,
> dma_opt_mapping_size() >> 9) to cap max_hw_sectors.  With a 0 return
> value this would set max_hw_sectors to 0, which is invalid.

... which means that if you want to change it, you need to combine
both patches into one to not create a regression.