Alexander Viro wrote:
> > 1) overlapping concurrent write operations violate Nfsv2.
>
> Yes, that is serious.
> > 3) do not forget f_pos when you implement a synchonization: even
> > concurrent reads are not allowed if both use the same file pointer.
>
> Ditto. It's a separate issue.
These are 2 pending problems which must be fixed before 2.4
If you fix them, then you will add synchonization to sys_write(), and
raw-io will be affected since raw-io is accessed through sys_write() to
a special character device driver.
Other pending problems are O_APPEND, mandantory file locks.
Eg mandantory file locks:
process A: backup. It make multi-megabyte read operations. During these
long operations, the kernel schedules around.
process B: uses the database. Mandantory file locks.
it calls lock(), read(), write(), write(), unlock().
^^^
kernel schedules back to process A, it reads the data.
--> data corruption. Mandantory file locks must not return if there are
pending read operations in the affected area.
> > Eg I'm pretty sure that Stephen will not like it if raw-io is slowed
> > down by a multiple reader-single writer synchonization.
>
> Erm? Writer access is for truncate() and I don't see where the raw-io
> comes into the picture.
Not yet, but if you fix all synchonization, then it will come into the
picture.
> Huh? It's not a sys_write(), it's generic_file_write(). Pipes do not come
> even close to that place.
Not yet, but after you have fixed f_pos, it will come into the picture.
> And I'm talking about 2.3 - 2.2 is _way_ too
> different.
I know that, but 2.3 is broken, 2.2 is ugly.
I wanted to say that we should NOT make the same fault again. Flags are
needed.
-- Manfred
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/