[merged mm-stable] percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch removed from -mm tree

[merged mm-stable] percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: percpu: clean up all mappings when pcpu_map_pages() fails
has been removed from the -mm tree.  Its filename was
     percpu-clean-up-all-mappings-when-pcpu_map_pages-fails.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Yosry Ahmed <yosryahmed@google.com>
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@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Christoph Lameter (Ampere) <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@google.com are

mm-zswap-always-shrink-in-zswap_store-if-zswap_pool_reached_full.patch
mm-zswap-refactor-limit-checking-from-zswap_store.patch
mm-zswap-move-more-same-filled-pages-checks-outside-of-zswap_store.patch
mm-zswap-remove-same_filled-module-params.patch
mm-zswap-remove-same_filled-module-params-fix.patch