On Thu, Sep 13, 2018 at 04:51:35PM +0100, David Howells wrote: > > Hi Al, > > Here's a set of patches that adds two new iov_iter types and then makes AFS > use them to do I/O. The iov_iter changes are: > > (1) Separate the type from the direction in the iov_iter struct and > provide accessor functions to wrap type checking. > > (2) Renumber the type constants to be contiguous small unsigned integers, > starting from 0 and then use switch-statements rather than if-else > chains using bit-testing. > > Note that the compiler can optimise this better by using CMP rather > than AND/TEST, say, as comparing integers requires fewer CMP > instructions or can use jump tables. > > (3) Change iov_offset from size_t to loff_t. This allows iov_offset to be > then used as a byte offset with ITER_MAPPING and allows 4GiB and larger > reads and writes to be proposed. > > This makes no difference on a 64-bit system, but does make a 32-bit > compilation a bit larger. > > (4) Add an ITER_MAPPING iterator type. This provides an iterator that > directly accesses an address_space, and assumes that the target pages > are in some way locked (eg. PG_lock or PG_writeback). > > (5) Add an ITER_DISCARD iterator type. This provides an iterator that > simply discards anything written to it. It cannot be used as a data > source. Hmm... I'll take a look in about an hour (need to finish the sodding tty-ioctl stuff first), will post review then. Sorry, I remember seeing it posted several weeks ago, slipped through the cracks then ;-/
