Merge tag 'vfs-6.7.iov_iter' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

Pull iov_iter updates from Christian Brauner:
 "This contain's David's iov_iter cleanup work to convert the iov_iter
  iteration macros to inline functions:

   - Remove last_offset from iov_iter as it was only used by ITER_PIPE

   - Add a __user tag on copy_mc_to_user()'s dst argument on x86 to
     match that on powerpc and get rid of a sparse warning

   - Convert iter->user_backed to user_backed_iter() in the sound PCM
     driver

   - Convert iter->user_backed to user_backed_iter() in a couple of
     infiniband drivers

   - Renumber the type enum so that the ITER_* constants match the order
     in iterate_and_advance*()

   - Since the preceding patch puts UBUF and IOVEC at 0 and 1, change
     user_backed_iter() to just use the type value and get rid of the
     extra flag

   - Convert the iov_iter iteration macros to always-inline functions to
     make the code easier to follow. It uses function pointers, but they
     get optimised away

   - Move the check for ->copy_mc to _copy_from_iter() and
     copy_page_from_iter_atomic() rather than in memcpy_from_iter_mc()
     where it gets repeated for every segment. Instead, we check once
     and invoke a side function that can use iterate_bvec() rather than
     iterate_and_advance() and supply a different step function

   - Move the copy-and-csum code to net/ where it can be in proximity
     with the code that uses it

   - Fold memcpy_and_csum() in to its two users

   - Move csum_and_copy_from_iter_full() out of line and merge in
     csum_and_copy_from_iter() since the former is the only caller of
     the latter

   - Move hash_and_copy_to_iter() to net/ where it can be with its only
     caller"

* tag 'vfs-6.7.iov_iter' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs:
  iov_iter, net: Move hash_and_copy_to_iter() to net/
  iov_iter, net: Merge csum_and_copy_from_iter{,_full}() together
  iov_iter, net: Fold in csum_and_memcpy()
  iov_iter, net: Move csum_and_copy_to/from_iter() to net/
  iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()
  iov_iter: Convert iterate*() to inline funcs
  iov_iter: Derive user-backedness from the iterator type
  iov_iter: Renumber ITER_* constants
  infiniband: Use user_backed_iter() to see if iterator is UBUF/IOVEC
  sound: Fix snd_pcm_readv()/writev() to use iov access functions
  iov_iter, x86: Be consistent about the __user tag on copy_mc_to_user()
  iov_iter: Remove last_offset from iov_iter as it was for ITER_PIPE

3 files changed, 281 insertions, 30 deletions

diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
new file mode 100644
index 000000000000..270454a6703d
--- /dev/null
+++ b/include/linux/iov_iter.h
@@ -0,0 +1,274 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* I/O iterator iteration building functions.
+ *
+ * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_IOV_ITER_H
+#define _LINUX_IOV_ITER_H
+
+#include <linux/uio.h>
+#include <linux/bvec.h>
+
+typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len,
+			     void *priv, void *priv2);
+typedef size_t (*iov_ustep_f)(void __user *iter_base, size_t progress, size_t len,
+			      void *priv, void *priv2);
+
+/*
+ * Handle ITER_UBUF.
+ */
+static __always_inline
+size_t iterate_ubuf(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_ustep_f step)
+{
+	void __user *base = iter->ubuf;
+	size_t progress = 0, remain;
+
+	remain = step(base + iter->iov_offset, 0, len, priv, priv2);
+	progress = len - remain;
+	iter->iov_offset += progress;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_IOVEC.
+ */
+static __always_inline
+size_t iterate_iovec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		     iov_ustep_f step)
+{
+	const struct iovec *p = iter->__iov;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t part = min(len, p->iov_len - skip);
+
+		if (likely(part)) {
+			remain = step(p->iov_base + skip, progress, part, priv, priv2);
+			consumed = part - remain;
+			progress += consumed;
+			skip += consumed;
+			len -= consumed;
+			if (skip < p->iov_len)
+				break;
+		}
+		p++;
+		skip = 0;
+	} while (len);
+
+	iter->nr_segs -= p - iter->__iov;
+	iter->__iov = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_KVEC.
+ */
+static __always_inline
+size_t iterate_kvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_step_f step)
+{
+	const struct kvec *p = iter->kvec;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t part = min(len, p->iov_len - skip);
+
+		if (likely(part)) {
+			remain = step(p->iov_base + skip, progress, part, priv, priv2);
+			consumed = part - remain;
+			progress += consumed;
+			skip += consumed;
+			len -= consumed;
+			if (skip < p->iov_len)
+				break;
+		}
+		p++;
+		skip = 0;
+	} while (len);
+
+	iter->nr_segs -= p - iter->kvec;
+	iter->kvec = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_BVEC.
+ */
+static __always_inline
+size_t iterate_bvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_step_f step)
+{
+	const struct bio_vec *p = iter->bvec;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t offset = p->bv_offset + skip, part;
+		void *kaddr = kmap_local_page(p->bv_page + offset / PAGE_SIZE);
+
+		part = min3(len,
+			   (size_t)(p->bv_len - skip),
+			   (size_t)(PAGE_SIZE - offset % PAGE_SIZE));
+		remain = step(kaddr + offset % PAGE_SIZE, progress, part, priv, priv2);
+		kunmap_local(kaddr);
+		consumed = part - remain;
+		len -= consumed;
+		progress += consumed;
+		skip += consumed;
+		if (skip >= p->bv_len) {
+			skip = 0;
+			p++;
+		}
+		if (remain)
+			break;
+	} while (len);
+
+	iter->nr_segs -= p - iter->bvec;
+	iter->bvec = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_XARRAY.
+ */
+static __always_inline
+size_t iterate_xarray(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		      iov_step_f step)
+{
+	struct folio *folio;
+	size_t progress = 0;
+	loff_t start = iter->xarray_start + iter->iov_offset;
+	pgoff_t index = start / PAGE_SIZE;
+	XA_STATE(xas, iter->xarray, index);
+
+	rcu_read_lock();
+	xas_for_each(&xas, folio, ULONG_MAX) {
+		size_t remain, consumed, offset, part, flen;
+
+		if (xas_retry(&xas, folio))
+			continue;
+		if (WARN_ON(xa_is_value(folio)))
+			break;
+		if (WARN_ON(folio_test_hugetlb(folio)))
+			break;
+
+		offset = offset_in_folio(folio, start + progress);
+		flen = min(folio_size(folio) - offset, len);
+
+		while (flen) {
+			void *base = kmap_local_folio(folio, offset);
+
+			part = min_t(size_t, flen,
+				     PAGE_SIZE - offset_in_page(offset));
+			remain = step(base, progress, part, priv, priv2);
+			kunmap_local(base);
+
+			consumed = part - remain;
+			progress += consumed;
+			len -= consumed;
+
+			if (remain || len == 0)
+				goto out;
+			flen -= consumed;
+			offset += consumed;
+		}
+	}
+
+out:
+	rcu_read_unlock();
+	iter->iov_offset += progress;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_DISCARD.
+ */
+static __always_inline
+size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		      iov_step_f step)
+{
+	size_t progress = len;
+
+	iter->count -= progress;
+	return progress;
+}
+
+/**
+ * iterate_and_advance2 - Iterate over an iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @priv2: More data for the step functions.
+ * @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
+ * @step: Function for other iterators; given kernel addresses.
+ *
+ * Iterate over the next part of an iterator, up to the specified length.  The
+ * buffer is presented in segments, which for kernel iteration are broken up by
+ * physical pages and mapped, with the mapped address being presented.
+ *
+ * Two step functions, @step and @ustep, must be provided, one for handling
+ * mapped kernel addresses and the other is given user addresses which have the
+ * potential to fault since no pinning is performed.
+ *
+ * The step functions are passed the address and length of the segment, @priv,
+ * @priv2 and the amount of data so far iterated over (which can, for example,
+ * be added to @priv to point to the right part of a second buffer).  The step
+ * functions should return the amount of the segment they didn't process (ie. 0
+ * indicates complete processsing).
+ *
+ * This function returns the amount of data processed (ie. 0 means nothing was
+ * processed and the value of @len means processes to completion).
+ */
+static __always_inline
+size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
+			    void *priv2, iov_ustep_f ustep, iov_step_f step)
+{
+	if (unlikely(iter->count < len))
+		len = iter->count;
+	if (unlikely(!len))
+		return 0;
+
+	if (likely(iter_is_ubuf(iter)))
+		return iterate_ubuf(iter, len, priv, priv2, ustep);
+	if (likely(iter_is_iovec(iter)))
+		return iterate_iovec(iter, len, priv, priv2, ustep);
+	if (iov_iter_is_bvec(iter))
+		return iterate_bvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_kvec(iter))
+		return iterate_kvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_xarray(iter))
+		return iterate_xarray(iter, len, priv, priv2, step);
+	return iterate_discard(iter, len, priv, priv2, step);
+}
+
+/**
+ * iterate_and_advance - Iterate over an iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
+ * @step: Function for other iterators; given kernel addresses.
+ *
+ * As iterate_and_advance2(), but priv2 is always NULL.
+ */
+static __always_inline
+size_t iterate_and_advance(struct iov_iter *iter, size_t len, void *priv,
+			   iov_ustep_f ustep, iov_step_f step)
+{
+	return iterate_and_advance2(iter, len, priv, NULL, ustep, step);
+}
+
+#endif /* _LINUX_IOV_ITER_H */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 97bfef071255..27998f73183e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3679,6 +3679,9 @@ static inline int __must_check skb_put_padto(struct sk_buff *skb, unsigned int l
 	return __skb_put_padto(skb, len, true);
 }
 
+bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i)
+	__must_check;
+
 static inline int skb_add_data(struct sk_buff *skb,
 			       struct iov_iter *from, int copy)
 {
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 42bce38a8e87..b6214cbf2a43 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -21,12 +21,12 @@ struct kvec {
 
 enum iter_type {
 	/* iter types */
+	ITER_UBUF,
 	ITER_IOVEC,
-	ITER_KVEC,
 	ITER_BVEC,
+	ITER_KVEC,
 	ITER_XARRAY,
 	ITER_DISCARD,
-	ITER_UBUF,
 };
 
 #define ITER_SOURCE	1	// == WRITE
@@ -43,11 +43,7 @@ struct iov_iter {
 	bool copy_mc;
 	bool nofault;
 	bool data_source;
-	bool user_backed;
-	union {
-		size_t iov_offset;
-		int last_offset;
-	};
+	size_t iov_offset;
 	/*
 	 * Hack alert: overlay ubuf_iovec with iovec + count, so
 	 * that the members resolve correctly regardless of the type
@@ -143,7 +139,7 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
 
 static inline bool user_backed_iter(const struct iov_iter *i)
 {
-	return i->user_backed;
+	return iter_is_ubuf(i) || iter_is_iovec(i);
 }
 
 /*
@@ -342,27 +338,6 @@ iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
 	return npages;
 }
 
-struct csum_state {
-	__wsum csum;
-	size_t off;
-};
-
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csstate, struct iov_iter *i);
-size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
-
-static __always_inline __must_check
-bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
-				  __wsum *csum, struct iov_iter *i)
-{
-	size_t copied = csum_and_copy_from_iter(addr, bytes, csum, i);
-	if (likely(copied == bytes))
-		return true;
-	iov_iter_revert(i, copied);
-	return false;
-}
-size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
-		struct iov_iter *i);
-
 struct iovec *iovec_from_user(const struct iovec __user *uvector,
 		unsigned long nr_segs, unsigned long fast_segs,
 		struct iovec *fast_iov, bool compat);
@@ -383,7 +358,6 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
 	*i = (struct iov_iter) {
 		.iter_type = ITER_UBUF,
 		.copy_mc = false,
-		.user_backed = true,
 		.data_source = direction,
 		.ubuf = buf,
 		.count = count,