Re: [PATCH] splice: fix wrong __splice_from_pipe() usage

OGAWA Hirofumi
2007-07-16T10:53:17Z

Jens Axboe <jens.axboe@oracle.com> writes:

> On Mon, Jul 16 2007, OGAWA Hirofumi wrote:
>> Hi,
>>
>> I've noticed the nfsd read corruption by recent change. And this patch
>> fixes the problem for me, is this right fix?
>> --
>> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>>
>>
>> __splice_from_pipe() is updating the sd->pos for the actor, but those
>> functions are passing the sd of reader side directory. So, splice
>> updates sd->pos twice.
>>
>> This fixes usage of __splice_from_pipe().
>
> For sendfile() usage, or the nfsd path that uses splice to send?

nfsd_vfs_read() path.

nfsd_vfs_read()
splice_direct_to_actor()
while(len) {
do_splice_to() [update sd->pos]
-> generic_file_splice_read() [read from sd->pos]
nfsd_direct_splice_actor()
-> __splice_from_pipe() [update sd->pos]
}

do_splice_to() updates sd->pos for read, and pass updated sd to
__splice_from_pipe(), and __splice_from_pipe() updates sd->pos for
write. So, next do_splice_to() read from wrong position.