lkml.org 
[lkml]   [2017]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: udf: allow implicit blocksize specification during mount
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.

Honza

--
Jan Kara <jack@suse.com>
SUSE Labs, CR

\
 
 \ /
  Last update: 2017-06-15 10:35    [W:0.057 / U:0.736 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site