block: partitions: replace __get_free_page() with kmalloc()

check_partition() allocates a buffer to use as backing memory for
seq_buf.

This buffer can be allocated with kmalloc() as there's nothing special
about it to go directly to the page allocator.

kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.

For a single allocation on the cold path the performance difference between
kmalloc() and __get_free_pages() is not measurable as both allocators take
an object/page from a per-CPU list for fast path allocations.

For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.

Replace use of __get_free_page() with kmalloc() and free_page() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260527-block-v2-1-8e06f914c484@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/partitions/core.c b/block/partitions/core.c
index 5d5332ce586b6b292325e7dc02dca7e41f7ef6bc..b5c59b79ca7cbb28d4d93478ee1c80908f76ee9f 100644 (file)
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -124,7 +124,7 @@ static struct parsed_partitions *check_partition(struct gendisk *hd)
        state = allocate_partitions(hd);
        if (!state)
                return NULL;
-       state->pp_buf.buffer = (char *)__get_free_page(GFP_KERNEL);
+       state->pp_buf.buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!state->pp_buf.buffer) {
                free_partitions(state);
                return NULL;
@@ -154,7 +154,7 @@ static struct parsed_partitions *check_partition(struct gendisk *hd)
        if (res > 0) {
                printk(KERN_INFO "%s", seq_buf_str(&state->pp_buf));
 
-               free_page((unsigned long)state->pp_buf.buffer);
+               kfree(state->pp_buf.buffer);
                return state;
        }
        if (state->access_beyond_eod)
@@ -170,7 +170,7 @@ static struct parsed_partitions *check_partition(struct gendisk *hd)
                printk(KERN_INFO "%s", seq_buf_str(&state->pp_buf));
        }
 
-       free_page((unsigned long)state->pp_buf.buffer);
+       kfree(state->pp_buf.buffer);
        free_partitions(state);
        return ERR_PTR(res);
 }