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Subject: [PATCH 18/29] iov_iter: Split iov_iter_single_seg_count()
From:   David Howells <dhowells@redhat.com>
To:     Pavel Begunkov <asml.silence@gmail.com>,
        Matthew Wilcox <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Cc:     dhowells@redhat.com,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Sat, 21 Nov 2020 14:15:42 +0000
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Split iov_iter_single_seg_count() by type.

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

 lib/iov_iter.c |   31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index b8e3da20547e..90291188ace5 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1415,18 +1415,23 @@ static void discard_revert(struct iov_iter *i, size_t unroll)
 /*
  * Return the count of just the current iov_iter segment.
  */
-static size_t xxx_single_seg_count(const struct iov_iter *i)
+static size_t iovec_kvec_single_seg_count(const struct iov_iter *i)
 {
-	if (unlikely(iov_iter_is_pipe(i)))
-		return i->count;	// it is a silly place, anyway
 	if (i->nr_segs == 1)
 		return i->count;
-	if (unlikely(iov_iter_is_discard(i)))
+	return min(i->count, i->iov->iov_len - i->iov_offset);
+}
+
+static size_t bvec_single_seg_count(const struct iov_iter *i)
+{
+	if (i->nr_segs == 1)
 		return i->count;
-	else if (iov_iter_is_bvec(i))
-		return min(i->count, i->bvec->bv_len - i->iov_offset);
-	else
-		return min(i->count, i->iov->iov_len - i->iov_offset);
+	return min(i->count, i->bvec->bv_len - i->iov_offset);
+}
+
+static size_t simple_single_seg_count(const struct iov_iter *i)
+{
+	return i->count;
 }
 
 void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
@@ -2110,7 +2115,7 @@ static const struct iov_iter_ops iovec_iter_ops = {
 	.advance			= iovec_advance,
 	.revert				= iovec_kvec_revert,
 	.fault_in_readable		= iovec_fault_in_readable,
-	.single_seg_count		= xxx_single_seg_count,
+	.single_seg_count		= iovec_kvec_single_seg_count,
 	.copy_page_to_iter		= iovec_copy_page_to_iter,
 	.copy_page_from_iter		= iovec_copy_page_from_iter,
 	.copy_to_iter			= iovec_copy_to_iter,
@@ -2144,7 +2149,7 @@ static const struct iov_iter_ops kvec_iter_ops = {
 	.advance			= kvec_advance,
 	.revert				= iovec_kvec_revert,
 	.fault_in_readable		= no_fault_in_readable,
-	.single_seg_count		= xxx_single_seg_count,
+	.single_seg_count		= iovec_kvec_single_seg_count,
 	.copy_page_to_iter		= bkvec_copy_page_to_iter,
 	.copy_page_from_iter		= bkvec_copy_page_from_iter,
 	.copy_to_iter			= kvec_copy_to_iter,
@@ -2178,7 +2183,7 @@ static const struct iov_iter_ops bvec_iter_ops = {
 	.advance			= bvec_iov_advance,
 	.revert				= bvec_revert,
 	.fault_in_readable		= no_fault_in_readable,
-	.single_seg_count		= xxx_single_seg_count,
+	.single_seg_count		= bvec_single_seg_count,
 	.copy_page_to_iter		= bkvec_copy_page_to_iter,
 	.copy_page_from_iter		= bkvec_copy_page_from_iter,
 	.copy_to_iter			= bvec_copy_to_iter,
@@ -2212,7 +2217,7 @@ static const struct iov_iter_ops pipe_iter_ops = {
 	.advance			= pipe_advance,
 	.revert				= pipe_revert,
 	.fault_in_readable		= no_fault_in_readable,
-	.single_seg_count		= xxx_single_seg_count,
+	.single_seg_count		= simple_single_seg_count,
 	.copy_page_to_iter		= pipe_copy_page_to_iter,
 	.copy_page_from_iter		= no_copy_page_from_iter,
 	.copy_to_iter			= pipe_copy_to_iter,
@@ -2246,7 +2251,7 @@ static const struct iov_iter_ops discard_iter_ops = {
 	.advance			= discard_advance,
 	.revert				= discard_revert,
 	.fault_in_readable		= no_fault_in_readable,
-	.single_seg_count		= xxx_single_seg_count,
+	.single_seg_count		= simple_single_seg_count,
 	.copy_page_to_iter		= discard_copy_page_to_iter,
 	.copy_page_from_iter		= no_copy_page_from_iter,
 	.copy_to_iter			= discard_copy_to_iter,