Not neccesarily. If a program needs to know the block size, it should request the geometry using ioctl, and use that value. Even without that change, different block devices have different block sizes that the programs must work with. IMHO this should affect only memory consumption by filesystem drivers (and only for those platforms using the ftl driver to translate mtd2block) and write efficiency (the latter for the better).
In your opinion, how could this affect an existing program? Carlos On Thu, Apr 9, 2026 at 5:39 PM Sebastien Lorquet <[email protected]> wrote: > > Hello, > > My initial feeling just by reading your email is that it could break a > LOT of existing programs if that was changed without a lot of care. > > Sebastien > > > On 4/9/26 17:36, Carlos Sanchez wrote: > > Hi all, > > > > I want to request opinions on the block size returned by the FTL layer. > > > > MTD drivers expose two "block sizes" on the geometry data: erase block > > size (the "flash page" size, which must be erased before writing) and > > the read/write block size (used for read/write operations). > > > > Classical block devices export just one block size. This is normal > > because this size is used for random access disks where you do not > > need to "erase" before writing. > > > > When the FTL driver exports a MTD "to look like" a block device, it > > passes (read/write) block size directly as the "simulated" block > > device's block size. This means file systems attaching to the > > FTL-exposed block device will typically try to break read/write > > operations in chunks of that size. As the underlying MTD requires > > erasing before writing, and erase size is typically N * block size, > > this results in multiple erase operations per write. > > > > I was thinking it might be better to use "erase block size" as "block > > size" when exporting an MTD as a block device through FTL. > > Functionality will not be affected; some filesystems (which size their > > buffer based on block device size) might use more buffers, but > > minimizing erases is usually the goal when accessing an MTD. > > > > Thoughts? > > > > Carlos -- Carlos Sanchez Geotab Senior Team Lead, Embedded Development | Europe Visit www.geotab.com YouTube | LinkedIn Celebrating 25 years of innovation and impact
