diff options
Diffstat (limited to 'lib/iov_iter.c')
-rw-r--r-- | lib/iov_iter.c | 52 |
1 files changed, 33 insertions, 19 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 1b0a349fbcd9..650554964f18 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1836,24 +1836,38 @@ int import_single_range(int rw, void __user *buf, size_t len, } EXPORT_SYMBOL(import_single_range); -int iov_iter_for_each_range(struct iov_iter *i, size_t bytes, - int (*f)(struct kvec *vec, void *context), - void *context) +/** + * iov_iter_restore() - Restore a &struct iov_iter to the same state as when + * iov_iter_save_state() was called. + * + * @i: &struct iov_iter to restore + * @state: state to restore from + * + * Used after iov_iter_save_state() to bring restore @i, if operations may + * have advanced it. + * + * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC + */ +void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state) { - struct kvec w; - int err = -EINVAL; - if (!bytes) - return 0; - - iterate_all_kinds(i, bytes, v, -EINVAL, ({ - w.iov_base = kmap(v.bv_page) + v.bv_offset; - w.iov_len = v.bv_len; - err = f(&w, context); - kunmap(v.bv_page); - err;}), ({ - w = v; - err = f(&w, context);}) - ) - return err; + if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) && + !iov_iter_is_kvec(i)) + return; + i->iov_offset = state->iov_offset; + i->count = state->count; + /* + * For the *vec iters, nr_segs + iov is constant - if we increment + * the vec, then we also decrement the nr_segs count. Hence we don't + * need to track both of these, just one is enough and we can deduct + * the other from that. ITER_KVEC and ITER_IOVEC are the same struct + * size, so we can just increment the iov pointer as they are unionzed. + * ITER_BVEC _may_ be the same size on some archs, but on others it is + * not. Be safe and handle it separately. + */ + BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec)); + if (iov_iter_is_bvec(i)) + i->bvec -= state->nr_segs - i->nr_segs; + else + i->iov -= state->nr_segs - i->nr_segs; + i->nr_segs = state->nr_segs; } -EXPORT_SYMBOL(iov_iter_for_each_range); |