iov_iter: make the amount already copied available to iterator callbacks
Making iterator macros keep track of the amount of data copied is pretty
easy and it has several benefits:
1) we no longer need the mess like (from += v.iov_len) - v.iov_len
in the callbacks - initial value + total amount copied so far would do
just fine.
2) less obviously, we no longer need to remember the initial amount
of data we wanted to copy; the loops in iterator macros are along the lines
of
wanted = bytes;
while (bytes) {
copy some
bytes -= copied
if short copy
break
}
bytes = wanted - bytes;
Replacement is
offs = 0;
while (bytes) {
copy some
offs += copied
bytes -= copied
if short copy
break
}
bytes = offs;
That wouldn't be a win per se, but unlike the initial value of bytes, the amount
copied so far *is* useful in callbacks.
3) in some cases (csum_and_copy_..._iter()) we already had offs manually
maintained by the callbacks. With that change we can drop that.
Less boilerplate and more readable code...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
parent
21b56c8477
commit
622838f3fd
120
lib/iov_iter.c
120
lib/iov_iter.c
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@ -17,15 +17,14 @@
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#define PIPE_PARANOIA /* for now */
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/* covers iovec and kvec alike */
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#define iterate_iovec(i, n, __v, __p, skip, STEP) { \
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size_t left; \
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size_t wanted = n; \
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#define iterate_iovec(i, n, __v, __off, __p, skip, STEP) { \
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size_t __off = 0; \
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do { \
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__v.iov_len = min(n, __p->iov_len - skip); \
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if (likely(__v.iov_len)) { \
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__v.iov_base = __p->iov_base + skip; \
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left = (STEP); \
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__v.iov_len -= left; \
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__v.iov_len -= (STEP); \
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__off += __v.iov_len; \
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skip += __v.iov_len; \
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n -= __v.iov_len; \
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if (skip < __p->iov_len) \
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@ -34,11 +33,11 @@
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__p++; \
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skip = 0; \
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} while (n); \
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n = wanted - n; \
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n = __off; \
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}
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#define iterate_bvec(i, n, __v, p, skip, STEP) { \
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size_t wanted = n; \
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#define iterate_bvec(i, n, __v, __off, p, skip, STEP) { \
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size_t __off = 0; \
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while (n) { \
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unsigned offset = p->bv_offset + skip; \
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unsigned left; \
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@ -50,6 +49,7 @@
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left = (STEP); \
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kunmap_local(kaddr); \
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__v.iov_len -= left; \
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__off += __v.iov_len; \
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skip += __v.iov_len; \
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if (skip == p->bv_len) { \
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skip = 0; \
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@ -59,13 +59,14 @@
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if (left) \
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break; \
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} \
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n = wanted - n; \
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n = __off; \
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}
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#define iterate_xarray(i, n, __v, skip, STEP) { \
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#define iterate_xarray(i, n, __v, __off, skip, STEP) { \
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__label__ __out; \
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size_t __off = 0; \
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struct page *head = NULL; \
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size_t wanted = n, seg, offset; \
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size_t seg, offset; \
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loff_t start = i->xarray_start + skip; \
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pgoff_t index = start >> PAGE_SHIFT; \
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int j; \
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@ -84,25 +85,26 @@
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for (j = (head->index < index) ? index - head->index : 0; \
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j < thp_nr_pages(head); j++) { \
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void *kaddr = kmap_local_page(head + j); \
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offset = (i->xarray_start + skip) % PAGE_SIZE; \
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offset = (start + __off) % PAGE_SIZE; \
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__v.iov_base = kaddr + offset; \
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seg = PAGE_SIZE - offset; \
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__v.iov_len = min(n, seg); \
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left = (STEP); \
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kunmap_local(kaddr); \
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__v.iov_len -= left; \
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__off += __v.iov_len; \
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n -= __v.iov_len; \
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skip += __v.iov_len; \
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if (left || n == 0) \
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goto __out; \
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} \
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} \
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__out: \
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rcu_read_unlock(); \
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n = wanted - n; \
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skip += __off; \
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n = __off; \
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}
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#define __iterate_and_advance(i, n, v, I, K) { \
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#define __iterate_and_advance(i, n, v, off, I, K) { \
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if (unlikely(i->count < n)) \
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n = i->count; \
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if (likely(n)) { \
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@ -110,31 +112,31 @@ __out: \
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if (likely(iter_is_iovec(i))) { \
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const struct iovec *iov = i->iov; \
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struct iovec v; \
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iterate_iovec(i, n, v, iov, skip, (I)) \
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iterate_iovec(i, n, v, off, iov, skip, (I)) \
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i->nr_segs -= iov - i->iov; \
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i->iov = iov; \
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} else if (iov_iter_is_bvec(i)) { \
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const struct bio_vec *bvec = i->bvec; \
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struct kvec v; \
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iterate_bvec(i, n, v, bvec, skip, (K)) \
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iterate_bvec(i, n, v, off, bvec, skip, (K)) \
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i->nr_segs -= bvec - i->bvec; \
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i->bvec = bvec; \
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} else if (iov_iter_is_kvec(i)) { \
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const struct kvec *kvec = i->kvec; \
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struct kvec v; \
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iterate_iovec(i, n, v, kvec, skip, (K)) \
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iterate_iovec(i, n, v, off, kvec, skip, (K)) \
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i->nr_segs -= kvec - i->kvec; \
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i->kvec = kvec; \
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} else if (iov_iter_is_xarray(i)) { \
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struct kvec v; \
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iterate_xarray(i, n, v, skip, (K)) \
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iterate_xarray(i, n, v, off, skip, (K)) \
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} \
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i->count -= n; \
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i->iov_offset = skip; \
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} \
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}
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#define iterate_and_advance(i, n, v, I, K) \
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__iterate_and_advance(i, n, v, I, ((void)(K),0))
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#define iterate_and_advance(i, n, v, off, I, K) \
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__iterate_and_advance(i, n, v, off, I, ((void)(K),0))
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static int copyout(void __user *to, const void *from, size_t n)
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{
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@ -607,14 +609,13 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
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size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
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{
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const char *from = addr;
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if (unlikely(iov_iter_is_pipe(i)))
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return copy_pipe_to_iter(addr, bytes, i);
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if (iter_is_iovec(i))
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might_fault();
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iterate_and_advance(i, bytes, v,
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copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
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memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
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iterate_and_advance(i, bytes, v, off,
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copyout(v.iov_base, addr + off, v.iov_len),
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memcpy(v.iov_base, addr + off, v.iov_len)
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)
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return bytes;
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@ -703,17 +704,13 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
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*/
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size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
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{
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const char *from = addr;
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if (unlikely(iov_iter_is_pipe(i)))
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return copy_mc_pipe_to_iter(addr, bytes, i);
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if (iter_is_iovec(i))
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might_fault();
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__iterate_and_advance(i, bytes, v,
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copyout_mc(v.iov_base, (from += v.iov_len) - v.iov_len,
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v.iov_len),
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copy_mc_to_kernel(v.iov_base, (from += v.iov_len)
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- v.iov_len, v.iov_len)
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__iterate_and_advance(i, bytes, v, off,
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copyout_mc(v.iov_base, addr + off, v.iov_len),
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copy_mc_to_kernel(v.iov_base, addr + off, v.iov_len)
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)
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return bytes;
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@ -723,16 +720,15 @@ EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
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size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
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{
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char *to = addr;
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if (unlikely(iov_iter_is_pipe(i))) {
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WARN_ON(1);
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return 0;
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}
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if (iter_is_iovec(i))
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might_fault();
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iterate_and_advance(i, bytes, v,
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copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
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memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
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iterate_and_advance(i, bytes, v, off,
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copyin(addr + off, v.iov_base, v.iov_len),
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memcpy(addr + off, v.iov_base, v.iov_len)
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)
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return bytes;
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@ -741,15 +737,14 @@ EXPORT_SYMBOL(_copy_from_iter);
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size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
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{
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char *to = addr;
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if (unlikely(iov_iter_is_pipe(i))) {
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WARN_ON(1);
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return 0;
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}
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iterate_and_advance(i, bytes, v,
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__copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len,
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iterate_and_advance(i, bytes, v, off,
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__copy_from_user_inatomic_nocache(addr + off,
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v.iov_base, v.iov_len),
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memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
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memcpy(addr + off, v.iov_base, v.iov_len)
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)
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return bytes;
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@ -773,16 +768,13 @@ EXPORT_SYMBOL(_copy_from_iter_nocache);
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*/
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size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
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{
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char *to = addr;
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if (unlikely(iov_iter_is_pipe(i))) {
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WARN_ON(1);
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return 0;
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}
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iterate_and_advance(i, bytes, v,
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__copy_from_user_flushcache((to += v.iov_len) - v.iov_len,
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v.iov_base, v.iov_len),
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memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base,
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v.iov_len)
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iterate_and_advance(i, bytes, v, off,
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__copy_from_user_flushcache(addr + off, v.iov_base, v.iov_len),
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memcpy_flushcache(addr + off, v.iov_base, v.iov_len)
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)
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return bytes;
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@ -911,7 +903,7 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
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{
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if (unlikely(iov_iter_is_pipe(i)))
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return pipe_zero(bytes, i);
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iterate_and_advance(i, bytes, v,
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iterate_and_advance(i, bytes, v, count,
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clear_user(v.iov_base, v.iov_len),
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memset(v.iov_base, 0, v.iov_len)
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)
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@ -933,9 +925,9 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt
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WARN_ON(1);
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return 0;
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}
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iterate_and_advance(i, bytes, v,
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copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
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memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
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iterate_and_advance(i, bytes, v, off,
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copyin(p + off, v.iov_base, v.iov_len),
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memcpy(p + off, v.iov_base, v.iov_len)
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)
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kunmap_atomic(kaddr);
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return bytes;
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@ -1656,28 +1648,22 @@ EXPORT_SYMBOL(iov_iter_get_pages_alloc);
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size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
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struct iov_iter *i)
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{
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char *to = addr;
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__wsum sum, next;
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size_t off = 0;
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sum = *csum;
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if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
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WARN_ON(1);
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return 0;
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}
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iterate_and_advance(i, bytes, v, ({
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iterate_and_advance(i, bytes, v, off, ({
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next = csum_and_copy_from_user(v.iov_base,
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(to += v.iov_len) - v.iov_len,
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addr + off,
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v.iov_len);
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if (next) {
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if (next)
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sum = csum_block_add(sum, next, off);
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off += v.iov_len;
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}
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next ? 0 : v.iov_len;
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}), ({
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sum = csum_and_memcpy((to += v.iov_len) - v.iov_len,
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v.iov_base, v.iov_len,
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sum = csum_and_memcpy(addr + off, v.iov_base, v.iov_len,
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sum, off);
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off += v.iov_len;
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})
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)
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*csum = sum;
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@ -1689,33 +1675,27 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
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struct iov_iter *i)
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{
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struct csum_state *csstate = _csstate;
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const char *from = addr;
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__wsum sum, next;
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size_t off;
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if (unlikely(iov_iter_is_pipe(i)))
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return csum_and_copy_to_pipe_iter(addr, bytes, _csstate, i);
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sum = csum_shift(csstate->csum, csstate->off);
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off = 0;
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if (unlikely(iov_iter_is_discard(i))) {
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WARN_ON(1); /* for now */
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return 0;
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}
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iterate_and_advance(i, bytes, v, ({
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next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
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iterate_and_advance(i, bytes, v, off, ({
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next = csum_and_copy_to_user(addr + off,
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v.iov_base,
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v.iov_len);
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if (next) {
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if (next)
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sum = csum_block_add(sum, next, off);
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off += v.iov_len;
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}
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next ? 0 : v.iov_len;
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}), ({
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sum = csum_and_memcpy(v.iov_base,
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(from += v.iov_len) - v.iov_len,
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addr + off,
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v.iov_len, sum, off);
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off += v.iov_len;
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})
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)
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csstate->csum = csum_shift(sum, csstate->off);
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