Hello!
On Apr 6, 2015, at 12:02 PM, Al Viro wrote:
> 2) should we ever update the current position when write() returns 0?
> IOW, what effect should zero-length write() on O_APPEND file have upon its
> current position? POSIX seems to imply that it should do nothing, and
> generally that's what happens, but e.g. ext4 *does* update position to
> the EOF, whether we will write anything or not. So does FUSE when server
> requests to bypass the page cache. AFAICS, lustre is the same way,
> but I might be missing something; everything else definitely does not
Lustre is not the same way.
drivers/staging/lustre/lustre/llite/file.c::ll_file_io_generic() has this
if (io-> ci_nob > 0) {
result = io->ci_nob;
*ppos = io->u.ci_wr.wr.crw_pos;
}
and ppos is passed in as &iocb->ki_pos. ci_nob is number of bytes that we managed to read/write,
and if it was 0 (either due to 0 bytes io request or due to error from the get go)
we won't update it.
Bye,
Oleg
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