Assigning the newly allocated page to pipe->tmp_page, only to
unconditionally clear ->tmp_page a little later, seems somewhat odd.
It made sense prior to commit a194dfe6e6f6 ("pipe: Rearrange sequence
in pipe_write() to preallocate slot"), when a user copy was done
between the allocation and the buf->page = page assignment, and a
failure there would then just leave the pipe's one-element page cache
populated. Now, the same purpose is served by the page being inserted
as a size-0 buffer, and the next write attempting to merge with that
buffer.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
fs/pipe.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 4d0799e4e719..097400cce241 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -508,13 +508,14 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
struct page *page = pipe->tmp_page;
int copied;
- if (!page) {
+ if (page) {
+ pipe->tmp_page = NULL;
+ } else {
page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
if (unlikely(!page)) {
ret = ret ? : -ENOMEM;
break;
}
- pipe->tmp_page = page;
}
/* Allocate a slot in the ring in advance and attach an
@@ -534,7 +535,6 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
buf->flags = PIPE_BUF_FLAG_PACKET;
else
buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
- pipe->tmp_page = NULL;
copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
--
2.48.1
