The patch titled
Subject: percpu: clean up all mappings when pcpu_map_pages() fails
has been added to the -mm mm-unstable branch. Its filename is
percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Subject: percpu: clean up all mappings when pcpu_map_pages() fails
Date: Mon, 11 Mar 2024 19:43:46 +0000
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.
Link: https://lkml.kernel.org/r/20240311194346.2291333-1-yosryahmed@xxxxxxxxxx
Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Acked-by: Dennis Zhou <dennis@xxxxxxxxxx>
Cc: Christoph Lameter (Ampere) <cl@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/percpu-vm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/percpu-vm.c~percpu-clean-up-all-mappings-when-pcpu_map_pages-fails
+++ a/mm/percpu-vm.c
@@ -231,10 +231,10 @@ static int pcpu_map_pages(struct pcpu_ch
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;
_
Patches currently in -mm which might be from yosryahmed@xxxxxxxxxx are
mm-memcg-add-null-check-to-obj_cgroup_put.patch
mm-zswap-remove-unnecessary-check-in-zswap_find_zpool.patch
percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch
