From 622838f3fde2c3671a718dc6196c19087ebe9b11 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 2 May 2021 11:13:09 -0400 Subject: [PATCH] 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 --- lib/iov_iter.c | 120 ++++++++++++++++++++++++--------------------------------- 1 file changed, 50 insertions(+), 70 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 74e20d6..0e04abe 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -17,15 +17,14 @@ #define PIPE_PARANOIA /* for now */ /* covers iovec and kvec alike */ -#define iterate_iovec(i, n, __v, __p, skip, STEP) { \ - size_t left; \ - size_t wanted = n; \ +#define iterate_iovec(i, n, __v, __off, __p, skip, STEP) { \ + size_t __off = 0; \ do { \ __v.iov_len = min(n, __p->iov_len - skip); \ if (likely(__v.iov_len)) { \ __v.iov_base = __p->iov_base + skip; \ - left = (STEP); \ - __v.iov_len -= left; \ + __v.iov_len -= (STEP); \ + __off += __v.iov_len; \ skip += __v.iov_len; \ n -= __v.iov_len; \ if (skip < __p->iov_len) \ @@ -34,11 +33,11 @@ __p++; \ skip = 0; \ } while (n); \ - n = wanted - n; \ + n = __off; \ } -#define iterate_bvec(i, n, __v, p, skip, STEP) { \ - size_t wanted = n; \ +#define iterate_bvec(i, n, __v, __off, p, skip, STEP) { \ + size_t __off = 0; \ while (n) { \ unsigned offset = p->bv_offset + skip; \ unsigned left; \ @@ -50,6 +49,7 @@ left = (STEP); \ kunmap_local(kaddr); \ __v.iov_len -= left; \ + __off += __v.iov_len; \ skip += __v.iov_len; \ if (skip == p->bv_len) { \ skip = 0; \ @@ -59,13 +59,14 @@ if (left) \ break; \ } \ - n = wanted - n; \ + n = __off; \ } -#define iterate_xarray(i, n, __v, skip, STEP) { \ +#define iterate_xarray(i, n, __v, __off, skip, STEP) { \ __label__ __out; \ + size_t __off = 0; \ struct page *head = NULL; \ - size_t wanted = n, seg, offset; \ + size_t seg, offset; \ loff_t start = i->xarray_start + skip; \ pgoff_t index = start >> PAGE_SHIFT; \ int j; \ @@ -84,25 +85,26 @@ for (j = (head->index < index) ? index - head->index : 0; \ j < thp_nr_pages(head); j++) { \ void *kaddr = kmap_local_page(head + j); \ - offset = (i->xarray_start + skip) % PAGE_SIZE; \ + offset = (start + __off) % PAGE_SIZE; \ __v.iov_base = kaddr + offset; \ seg = PAGE_SIZE - offset; \ __v.iov_len = min(n, seg); \ left = (STEP); \ kunmap_local(kaddr); \ __v.iov_len -= left; \ + __off += __v.iov_len; \ n -= __v.iov_len; \ - skip += __v.iov_len; \ if (left || n == 0) \ goto __out; \ } \ } \ __out: \ rcu_read_unlock(); \ - n = wanted - n; \ + skip += __off; \ + n = __off; \ } -#define __iterate_and_advance(i, n, v, I, K) { \ +#define __iterate_and_advance(i, n, v, off, I, K) { \ if (unlikely(i->count < n)) \ n = i->count; \ if (likely(n)) { \ @@ -110,31 +112,31 @@ __out: \ if (likely(iter_is_iovec(i))) { \ const struct iovec *iov = i->iov; \ struct iovec v; \ - iterate_iovec(i, n, v, iov, skip, (I)) \ + iterate_iovec(i, n, v, off, iov, skip, (I)) \ i->nr_segs -= iov - i->iov; \ i->iov = iov; \ } else if (iov_iter_is_bvec(i)) { \ const struct bio_vec *bvec = i->bvec; \ struct kvec v; \ - iterate_bvec(i, n, v, bvec, skip, (K)) \ + iterate_bvec(i, n, v, off, bvec, skip, (K)) \ i->nr_segs -= bvec - i->bvec; \ i->bvec = bvec; \ } else if (iov_iter_is_kvec(i)) { \ const struct kvec *kvec = i->kvec; \ struct kvec v; \ - iterate_iovec(i, n, v, kvec, skip, (K)) \ + iterate_iovec(i, n, v, off, kvec, skip, (K)) \ i->nr_segs -= kvec - i->kvec; \ i->kvec = kvec; \ } else if (iov_iter_is_xarray(i)) { \ struct kvec v; \ - iterate_xarray(i, n, v, skip, (K)) \ + iterate_xarray(i, n, v, off, skip, (K)) \ } \ i->count -= n; \ i->iov_offset = skip; \ } \ } -#define iterate_and_advance(i, n, v, I, K) \ - __iterate_and_advance(i, n, v, I, ((void)(K),0)) +#define iterate_and_advance(i, n, v, off, I, K) \ + __iterate_and_advance(i, n, v, off, I, ((void)(K),0)) static int copyout(void __user *to, const void *from, size_t n) { @@ -607,14 +609,13 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes, size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { - const char *from = addr; if (unlikely(iov_iter_is_pipe(i))) return copy_pipe_to_iter(addr, bytes, i); if (iter_is_iovec(i)) might_fault(); - iterate_and_advance(i, bytes, v, - copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len), - memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len) + iterate_and_advance(i, bytes, v, off, + copyout(v.iov_base, addr + off, v.iov_len), + memcpy(v.iov_base, addr + off, v.iov_len) ) return bytes; @@ -703,17 +704,13 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes, */ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { - const char *from = addr; - if (unlikely(iov_iter_is_pipe(i))) return copy_mc_pipe_to_iter(addr, bytes, i); if (iter_is_iovec(i)) might_fault(); - __iterate_and_advance(i, bytes, v, - copyout_mc(v.iov_base, (from += v.iov_len) - v.iov_len, - v.iov_len), - copy_mc_to_kernel(v.iov_base, (from += v.iov_len) - - v.iov_len, v.iov_len) + __iterate_and_advance(i, bytes, v, off, + copyout_mc(v.iov_base, addr + off, v.iov_len), + copy_mc_to_kernel(v.iov_base, addr + off, v.iov_len) ) return bytes; @@ -723,16 +720,15 @@ EXPORT_SYMBOL_GPL(_copy_mc_to_iter); size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) { - char *to = addr; if (unlikely(iov_iter_is_pipe(i))) { WARN_ON(1); return 0; } if (iter_is_iovec(i)) might_fault(); - iterate_and_advance(i, bytes, v, - copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len), - memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len) + iterate_and_advance(i, bytes, v, off, + copyin(addr + off, v.iov_base, v.iov_len), + memcpy(addr + off, v.iov_base, v.iov_len) ) return bytes; @@ -741,15 +737,14 @@ EXPORT_SYMBOL(_copy_from_iter); size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i) { - char *to = addr; if (unlikely(iov_iter_is_pipe(i))) { WARN_ON(1); return 0; } - iterate_and_advance(i, bytes, v, - __copy_from_user_inatomic_nocache((to += v.iov_len) - v.iov_len, + iterate_and_advance(i, bytes, v, off, + __copy_from_user_inatomic_nocache(addr + off, v.iov_base, v.iov_len), - memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len) + memcpy(addr + off, v.iov_base, v.iov_len) ) return bytes; @@ -773,16 +768,13 @@ EXPORT_SYMBOL(_copy_from_iter_nocache); */ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i) { - char *to = addr; if (unlikely(iov_iter_is_pipe(i))) { WARN_ON(1); return 0; } - iterate_and_advance(i, bytes, v, - __copy_from_user_flushcache((to += v.iov_len) - v.iov_len, - v.iov_base, v.iov_len), - memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base, - v.iov_len) + iterate_and_advance(i, bytes, v, off, + __copy_from_user_flushcache(addr + off, v.iov_base, v.iov_len), + memcpy_flushcache(addr + off, v.iov_base, v.iov_len) ) return bytes; @@ -911,7 +903,7 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i) { if (unlikely(iov_iter_is_pipe(i))) return pipe_zero(bytes, i); - iterate_and_advance(i, bytes, v, + iterate_and_advance(i, bytes, v, count, clear_user(v.iov_base, v.iov_len), memset(v.iov_base, 0, v.iov_len) ) @@ -933,9 +925,9 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt WARN_ON(1); return 0; } - iterate_and_advance(i, bytes, v, - copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len), - memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len) + iterate_and_advance(i, bytes, v, off, + copyin(p + off, v.iov_base, v.iov_len), + memcpy(p + off, v.iov_base, v.iov_len) ) kunmap_atomic(kaddr); return bytes; @@ -1656,28 +1648,22 @@ EXPORT_SYMBOL(iov_iter_get_pages_alloc); size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i) { - char *to = addr; __wsum sum, next; - size_t off = 0; sum = *csum; if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) { WARN_ON(1); return 0; } - iterate_and_advance(i, bytes, v, ({ + iterate_and_advance(i, bytes, v, off, ({ next = csum_and_copy_from_user(v.iov_base, - (to += v.iov_len) - v.iov_len, + addr + off, v.iov_len); - if (next) { + if (next) sum = csum_block_add(sum, next, off); - off += v.iov_len; - } next ? 0 : v.iov_len; }), ({ - sum = csum_and_memcpy((to += v.iov_len) - v.iov_len, - v.iov_base, v.iov_len, + sum = csum_and_memcpy(addr + off, v.iov_base, v.iov_len, sum, off); - off += v.iov_len; }) ) *csum = sum; @@ -1689,33 +1675,27 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate, struct iov_iter *i) { struct csum_state *csstate = _csstate; - const char *from = addr; __wsum sum, next; - size_t off; if (unlikely(iov_iter_is_pipe(i))) return csum_and_copy_to_pipe_iter(addr, bytes, _csstate, i); sum = csum_shift(csstate->csum, csstate->off); - off = 0; if (unlikely(iov_iter_is_discard(i))) { WARN_ON(1); /* for now */ return 0; } - iterate_and_advance(i, bytes, v, ({ - next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len, + iterate_and_advance(i, bytes, v, off, ({ + next = csum_and_copy_to_user(addr + off, v.iov_base, v.iov_len); - if (next) { + if (next) sum = csum_block_add(sum, next, off); - off += v.iov_len; - } next ? 0 : v.iov_len; }), ({ sum = csum_and_memcpy(v.iov_base, - (from += v.iov_len) - v.iov_len, + addr + off, v.iov_len, sum, off); - off += v.iov_len; }) ) csstate->csum = csum_shift(sum, csstate->off); -- 2.7.4