Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > Apparently, it is permitted for gss_krb5_cts_crypt() to do a > kmalloc(GFP_NOFS) in the context from where gss_krb5_aes_encrypt() is > being invoked, and so I don't see why it wouldn't be possible to > simply kmalloc() a scatterlist[] of the appropriate size, populate it > with all the pages, bufs and whatever else gets passed into the > skcipher, and pass it into the skcipher in one go. I never said it wasn't possible. But doing a pair of order-1 allocations from there might have a significant detrimental effect on performance - in which case Trond and co. will say "no". Remember: to crypt 1MiB of data on a 64-bit machine requires 2 x minimum 8KiB scatterlist arrays. That's assuming the pages in the middle are contiguous, which might not be the case for a direct I/O read/write. So for the DIO case, it could be involve an order-2 allocation (or chaining of single pages). David
