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. -- 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
