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Subject: [RFC PATCH 2/2] iov_iter: Drop the X argument from
 iterate_all_kinds() and use B instead
From:   David Howells <dhowells@redhat.com>
To:     viro@zeniv.linux.org.uk
Cc:     dhowells@redhat.com, willy@infradead.org, jlayton@kernel.org,
        hch@lst.de, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-cachefs@redhat.com, v9fs-developer@lists.sourceforge.net,
        linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org,
        linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Fri, 09 Apr 2021 19:11:06 +0100
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Drop the X argument from iterate_all_kinds() and use the B argument instead
as it's always the same unless the ITER_XARRAY is handled specially.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 lib/iov_iter.c |   42 ++++++++++++------------------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 93e9838c128d..144abdac11db 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -79,8 +79,8 @@
 #define iterate_xarray(i, n, __v, skip, STEP) {		\
 	struct page *head = NULL;				\
 	size_t wanted = n, seg, offset;				\
-	loff_t start = i->xarray_start + skip;			\
-	pgoff_t index = start >> PAGE_SHIFT;			\
+	loff_t xarray_start = i->xarray_start + skip;		\
+	pgoff_t index = xarray_start >> PAGE_SHIFT;		\
 	int j;							\
 								\
 	XA_STATE(xas, i->xarray, index);			\
@@ -113,7 +113,7 @@
 	n = wanted - n;						\
 }
 
-#define iterate_all_kinds(i, n, v, I, B, K, X) {		\
+#define iterate_all_kinds(i, n, v, I, B, K) {			\
 	if (likely(n)) {					\
 		size_t skip = i->iov_offset;			\
 		if (unlikely(i->type & ITER_BVEC)) {		\
@@ -127,7 +127,7 @@
 		} else if (unlikely(i->type & ITER_DISCARD)) {	\
 		} else if (unlikely(i->type & ITER_XARRAY)) {	\
 			struct bio_vec v;			\
-			iterate_xarray(i, n, v, skip, (X));	\
+			iterate_xarray(i, n, v, skip, (B));	\
 		} else {					\
 			const struct iovec *iov;		\
 			struct iovec v;				\
@@ -842,9 +842,7 @@ bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 		0;}),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
-		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
-				 v.bv_offset, v.bv_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 	)
 
 	iov_iter_advance(i, bytes);
@@ -927,9 +925,7 @@ bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 		0;}),
 		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
-		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
-				 v.bv_offset, v.bv_len)
+		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 	)
 
 	iov_iter_advance(i, bytes);
@@ -1058,9 +1054,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 		copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
 		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
 				 v.bv_offset, v.bv_len),
-		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
-		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
-				 v.bv_offset, v.bv_len)
+		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
 	)
 	kunmap_atomic(kaddr);
 	return bytes;
@@ -1349,8 +1343,7 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
 	iterate_all_kinds(i, size, v,
 		(res |= (unsigned long)v.iov_base | v.iov_len, 0),
 		res |= v.bv_offset | v.bv_len,
-		res |= (unsigned long)v.iov_base | v.iov_len,
-		res |= v.bv_offset | v.bv_len
+		res |= (unsigned long)v.iov_base | v.iov_len
 	)
 	return res;
 }
@@ -1372,9 +1365,7 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
 		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
 			(size != v.bv_len ? size : 0)),
 		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
-			(size != v.iov_len ? size : 0)),
-		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
-			(size != v.bv_len ? size : 0))
+			(size != v.iov_len ? size : 0))
 		);
 	return res;
 }
@@ -1530,8 +1521,7 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 		return v.bv_len;
 	}),({
 		return -EFAULT;
-	}),
-	0
+	})
 	)
 	return 0;
 }
@@ -1665,7 +1655,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		return v.bv_len;
 	}),({
 		return -EFAULT;
-	}), 0
+	})
 	)
 	return 0;
 }
@@ -1751,13 +1741,6 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
 				      v.iov_base, v.iov_len,
 				      sum, off);
 		off += v.iov_len;
-	}), ({
-		char *p = kmap_atomic(v.bv_page);
-		sum = csum_and_memcpy((to += v.bv_len) - v.bv_len,
-				      p + v.bv_offset, v.bv_len,
-				      sum, off);
-		kunmap_atomic(p);
-		off += v.bv_len;
 	})
 	)
 	*csum = sum;
@@ -1892,8 +1875,7 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
 			- p / PAGE_SIZE;
 		if (npages >= maxpages)
 			return maxpages;
-	}),
-	0
+	})
 	)
 	return npages;
 }