[v2,01/12] get rid of unlikely() on page_copy_sane() calls

Commit Message

Al Viro Oct. 28, 2022, 2:33 a.m. UTC

Signed-off-by: Al Viro <[e-mail]>
---
 lib/iov_iter.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

Comments

Christoph Hellwig Oct. 30, 2022, 8:12 a.m. UTC | #1

This could explain why your are dropping the unlikely, 'cause just
from the page this is non-obvious.  Especially as the patch seems to
do a lot more than just removing an unlikely.

Patch

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index c3ca28ca68a6..e9a8fc9ee8ee 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -703,17 +703,16 @@  static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
 	head = compound_head(page);
 	v += (page - head) << PAGE_SHIFT;
 
-	if (likely(n <= v && v <= (page_size(head))))
-		return true;
-	WARN_ON(1);
-	return false;
+	if (WARN_ON(n > v || v > page_size(head)))
+		return false;
+	return true;
 }
 
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i)
 {
 	size_t res = 0;
-	if (unlikely(!page_copy_sane(page, offset, bytes)))
+	if (!page_copy_sane(page, offset, bytes))
 		return 0;
 	if (unlikely(iov_iter_is_pipe(i)))
 		return copy_page_to_iter_pipe(page, offset, bytes, i);
@@ -808,7 +807,7 @@  size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt
 				  struct iov_iter *i)
 {
 	char *kaddr = kmap_atomic(page), *p = kaddr + offset;
-	if (unlikely(!page_copy_sane(page, offset, bytes))) {
+	if (!page_copy_sane(page, offset, bytes)) {
 		kunmap_atomic(kaddr);
 		return 0;
 	}