Don't let parts of compound pages/multipage folios be gifted by (vm)splice
into a pipe as the other end may only be expecting single-page gifts (fuse
and virtio console for example).
replace_page_cache_folio(), for example, will do the wrong thing if it
tries to replace a single paged folio with a multipage folio.
Try to avoid this by making add_to_pipe() remove the gift flag on multipage
folios.
Fixes: 7afa6fd037e5 ("[PATCH] vmsplice: allow user to pass in gift pages")
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxx>
cc: Miklos Szeredi <miklos@xxxxxxxxxx>
cc: Amit Shah <amit@xxxxxxxxxx>
cc: linux-fsdevel@xxxxxxxxxxxxxxx
cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
fs/splice.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/splice.c b/fs/splice.c
index 2e76dbb81a8f..8bbd7794d9f0 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -240,6 +240,8 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
} else if (pipe_full(head, tail, pipe->max_usage)) {
ret = -EAGAIN;
} else {
+ if (PageCompound(buf->page))
+ buf->flags &= ~PIPE_BUF_FLAG_GIFT;
pipe->bufs[head & mask] = *buf;
pipe->head = head + 1;
return buf->len;
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