When io_check_coalesce_buffer() meets a single page buffer it bails out
and tells that it can be coalesced. That's fine for registered buffers
as io_coalesce_buffer() wouldn't change anything, but the region code
now uses the function to decided on whether to vmap the buffer or not.
Report that a single page buffer is trivially coalescable and let
io_sqe_buffer_register() to filter them.
Fixes: cc2f1a864c27a ("io_uring/memmap: optimise single folio regions")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
io_uring/rsrc.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 9208cf77c41e..0f1cd0a1d880 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -675,14 +675,9 @@ bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
unsigned int count = 1, nr_folios = 1;
int i;
- if (nr_pages <= 1)
- return false;
-
data->nr_pages_mid = folio_nr_pages(folio);
- if (data->nr_pages_mid == 1)
- return false;
-
data->folio_shift = folio_shift(folio);
+
/*
* Check if pages are contiguous inside a folio, and all folios have
* the same page count except for the head and tail.
@@ -750,8 +745,10 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
}
/* If it's huge page(s), try to coalesce them into fewer bvec entries */
- if (io_check_coalesce_buffer(pages, nr_pages, &data))
- coalesced = io_coalesce_buffer(&pages, &nr_pages, &data);
+ if (nr_pages > 1 && io_check_coalesce_buffer(pages, nr_pages, &data)) {
+ if (data.nr_pages_mid != 1)
+ coalesced = io_coalesce_buffer(&pages, &nr_pages, &data);
+ }
imu = kvmalloc(struct_size(imu, bvec, nr_pages), GFP_KERNEL);
if (!imu)
--
2.47.1
