On Thursday 15 June 2017 10:34:27 Jan Kara wrote: > On Wed 14-06-17 21:36:45, Pali Rohár wrote: > > On Tuesday 13 June 2017 14:59:55 Jan Kara wrote: > > > Hi, > > > > > > On Mon 12-06-17 22:40:14, Pali Rohár wrote: > > > > Hi! I found that following UDF patch was included into linus tree: > > > > https://patchwork.kernel.org/patch/9524557/ > > > > > > > > It is really a good improvement to recognize UDF file system which > > > > have block size different from disk sector size and also different > > > > from 2048. > > > > > > > > But should not detection on 4K native disks (4096/4096) try to also > > > > use block size of 512 bytes? Because current loop is from logical > > > > sector size to 4096. > > > > > > By definition, bdev_logical_block_size() is the smallest block size a > > > device can support. So if it is larger than 512, the device driver > > > had explicitely declared that it cannot handle smaller blocks... > > > > Ok, but it is a really problem when trying to read data from filesystem > > which has smaller blocks as the smallest block size of a device? > > > > In the worst case filesystem driver needs to read 512 bytes, but device > > can send only block of 4096 bytes (as it does not support smaller > > block). Driver receives 4096 bytes, then it process just first 512 bytes > > and do not care about remaining data... > > Well, as much as I agree this is possible in principle, the block layer, > block device page cache etc. don't handle this so it would be a non-trivial > effort to support this. Ok, so it is not a problem in UDF driver nor hardware, just it is limitation of kernel block layer which do not support it. -- Pali Rohár pali.rohar@xxxxxxxxx
