In pcpu_map_pages(), if __pcpu_map_pages() fails on a CPU, we call
__pcpu_unmap_pages() to clean up mappings on all CPUs where mappings
were created, but not on the CPU where __pcpu_map_pages() fails.
__pcpu_map_pages() and __pcpu_unmap_pages() are wrappers around
vmap_pages_range_noflush() and vunmap_range_noflush(). All other callers
of vmap_pages_range_noflush() call vunmap_range_noflush() when mapping
fails, except pcpu_map_pages(). The reason could be that partial
mappings may be left behind from a failed mapping attempt.
Call __pcpu_unmap_pages() for the failed CPU as well in
pcpu_map_pages().
This was found by code inspection, no failures or bugs were observed.
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
---
Perhaps the reason __pcpu_unmap_pages() is not currently being called
for the failed CPU is that the size and alignment requirements make sure
we never leave any partial mappings behind? I have no idea. Nonetheless,
I think we want this change as that could be fragile, and is
inconsistent with other callers.
---
mm/percpu-vm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index 2054c9213c433..cd69caf6aa8d8 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -231,10 +231,10 @@ static int pcpu_map_pages(struct pcpu_chunk *chunk,
return 0;
err:
for_each_possible_cpu(tcpu) {
- if (tcpu == cpu)
- break;
__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
page_end - page_start);
+ if (tcpu == cpu)
+ break;
}
pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);
return err;
--
2.44.0.278.ge034bb2e1d-goog
