Am Mittwoch, 24. Dezember 2014, 16:12:53 schrieb Stephan Mueller: Hi Christophe, > Am Mittwoch, 24. Dezember 2014, 15:10:14 schrieb leroy christophe: > > Hi leroy, > > > Le 24/12/2014 10:03, Stephan Mueller a écrit : > > > Am Dienstag, 23. Dezember 2014, 18:16:01 schrieb leroy christophe: > > > > > > Hi leroy, > > > > > >> Le 20/12/2014 07:37, Stephan Mueller a écrit : > > >>> Am Donnerstag, 18. Dezember 2014, 13:22:20 schrieb leroy christophe: > > >>> > > >>> Hi Christophe, > > >>> > > >>>> Le 18/12/2014 13:15, Stephan Mueller a écrit : > > >>>>> Hi Herbert, > > >>>>> > > >>>>> While testing the vmsplice/splice interface of algif_hash I was made > > >>>>> aware of the problem that data blobs larger than 16 pages do not > > >>>>> seem > > >>>>> to > > >>>>> be hashed properly. > > >>>>> > > >>>>> For testing, a file is mmap()ed and handed to vmsplice / splice. If > > >>>>> the > > >>>>> file is smaller than 2**16, the interface returns the proper hash. > > >>>>> However, when the file is larger, only the first 2**16 bytes seem to > > >>>>> be > > >>>>> used. > > >>>>> > > >>>>> When adding printk's to hash_sendpage, I see that this function is > > >>>>> invoked exactly 16 times where the first 15 invocations have the > > >>>>> MSG_MORE flag set and the last invocation does not have MSG_MORE. > > >>>> > > >>>> Hi Stephan, > > >>>> > > >>>> I have already noticed the same issue and proposed a patch, but I > > >>>> never > > >>>> got any feedback and it has never been merged, allthought I pinged it > > >>>> a > > >>>> few times. > > >>>> > > >>>> See https://lkml.org/lkml/2014/4/18/276 > > >>> > > >>> After testing, this patch does not work for me. The operation still > > >>> stops > > >>> after 16 pages. > > >> > > >> Yes, it looks like the function I fixed is exclusively used by > > >> sendfile() system call. > > >> So there is probably the same kind of fix to be done in another > > >> function. > > > > > > I do not believe that is the case. IMHO the blocking issue is found in > > > the > > > following code: > > > > > > splice_from_pipe_feed walks the pipe->nrbufs. And vmsplice_to_pipe > > > defines > > > the maximum number of nrbufs as PIPE_DEF_BUFFERS -- which is 16. As > > > subsequent functions allocate memory based on PIPE_DEF_BUFFERS, there is > > > no trivial way to increase the number of pages to be processed. > > > > > > Thus I see that the vmsplice/splice combo can at most operate on a chunk > > > of 16 pages. Thus, you have to segment your input buffer into chunks of > > > that size and invoke the vmsplice/splice syscalls for each segment. > > > > Yes your are probably right. There splice needs to be called with > > SPLICE_F_MORE flag, hope that works. > > That is not the only one. Vmsplice works on a pipe. A pipe is backed by 16 > pages max. Thus, you have to call vmsplice once per 16 pages. The current > code I am testing which seems to work is the following: > > while (inlen) { > size_t datalen = (inlen > MAXLEN) ? MAXLEN : inlen; > > iov.iov_len = datalen; > ret = _kcapi_common_vmsplice_data(handle, &iov, 1, datalen, > 1); > if (0 > ret) > return ret; > processed += ret; > iov.iov_base = (void*)(uintptr_t)(in + processed); > inlen -= ret; > } > return _kcapi_common_read_data(handle, out, outlen); As I do not see an easy fix where a single vmsplice/splice syscall combo can be applied to an input data stream of arbitrary length, I added appropriate handling code in libkcapi version 0.6.2 [1]. This code follows the aforementioned approach to segment the input into 16 PAGE_SIZE segments and send them to the kernel individually. [1] http://www.chronox.de/libkcapi.html -- Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
