On Monday 16 November 2009, Christoph Hellwig wrote:
> As mentioned before making generic_file_llseek the new default is
> probably a bad idea. The majority of our file_operations instances
> don't actually support seeking, so no_llseek should become the new
> default if you spend some effort on converting things. Anything that
> wants to allow seeking will have to set a llseek method. This also
> mirrors what we do for other file operations. None of the major ones
> has a non-trivial default, it's either silently succeeding for a
> selected few like open or release or returning an error for operatings
> that actually do something like read and write.
Ok, good point.
Do you think we should also prevent pread/pwrite for devices without
an llseek operation, like nonseekable_open does? I guess that would
be consistent.
Then there is the point that (I forgot who) brought up that changing
code to do no_llseek is actually an ABI change. Even if the file
position is never used anywhere, some random user application might
expect a chardev not to return an error when its llseek method is
called, resulting in regressions.
Arnd <><
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