On Mon, Apr 07, 2025 at 12:07:11AM -0700, Christoph Hellwig wrote: > On Sun, Apr 06, 2025 at 03:40:04PM -0400, Sean Anderson wrote: > > - What about bv_offset? > > bv_offset is a memory offset and must only be aligned to the > dma_alignment limit. > > > - Is it possible to have a bio where the total length is a multiple of > > logical_sector_size, but the data is split across several segments > > where each segment is a multiple of SECTOR_SIZE? > > Yes. > > > - Is is possible to have segments not even aligned to SECTOR_SIZE? > > No. O_DIRECT only requires each user iovec be a multiple of the logical block size with the address aligned to the dma_alignment. If the dma_alignment is smaller than the logical block size, then this could create bvec segments that are smaller. For nvme where we have 4-byte dma alignment, you could have the first segment be the last 4 bytes of a page, then the remaing 508 bytes from a different page in the next segment.
