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. To invoke the vmsplice/splice interface, I use my current implementation of libkcapi available at [1]. That library uses the following calls: vmsplice(handle->pipes[1], iov, iovlen, SPLICE_F_GIFT); splice(handle->pipes[0], NULL, handle->opfd, NULL, inlen, 0); read(handle->opfd, out, outlen); The return code of splice() is always 65536 irrespectively of the following variations: - have one iovec pointing to the entire buffer of the mmap()ed file - have multiple iovecs with all pointing to at most 2**16 bytes - invoke splice/read multiple times with at most 2**16 bytes My guess of the problem is that the maximum buffer size for the pipe is 16 pages. These 16 pages are filled with the repeated invocation of hash_sendpage. Is there a specific way of how the splice interface is to be called so that the pages are released? Or is there a need to change hash_sendpage such that after the af_alg_wait_for_completion call, some form of "releasing/putting" of the used page needs to be added? Note, hashing the large mmap()ed file with one iovec using the sendmsg() interface works flawlessly. [1] http://www.chronox.de/libkcapi.html Thanks 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
