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authorDavid Hildenbrand <david@redhat.com>2022-03-25 04:13:46 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-25 05:06:51 +0300
commit363106c4cefe7d08ca67cc77f3d38d4213190f31 (patch)
tree5e27f91949ff00469e7d62448f052ebb3fef38a1
parent3bff7e3f1f16dc7305d12905c51c278b54970f0e (diff)
downloadlinux-363106c4cefe7d08ca67cc77f3d38d4213190f31.tar.xz
mm/khugepaged: remove reuse_swap_page() usage
reuse_swap_page() currently indicates if we can write to an anon page without COW. A COW is required if the page is shared by multiple processes (either already mapped or via swap entries) or if there is concurrent writeback that cannot tolerate concurrent page modifications. However, in the context of khugepaged we're not actually going to write to a read-only mapped page, we'll copy the page content to our newly allocated THP and map that THP writable. All we have to make sure is that the read-only mapped page we're about to copy won't get reused by another process sharing the page, otherwise, page content would get modified. But that is already guaranteed via multiple mechanisms (e.g., holding a reference, holding the page lock, removing the rmap after copying the page). The swapcache handling was introduced in commit 10359213d05a ("mm: incorporate read-only pages into transparent huge pages") and it sounds like it merely wanted to mimic what do_swap_page() would do when trying to map a page obtained via the swapcache writable. As that logic is unnecessary, let's just remove it, removing the last user of reuse_swap_page(). Link: https://lkml.kernel.org/r/20220131162940.210846-7-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: David Rientjes <rientjes@google.com> Cc: Don Dutile <ddutile@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Liang Zhang <zhangliang5@huawei.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: Rik van Riel <riel@surriel.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/trace/events/huge_memory.h1
-rw-r--r--mm/khugepaged.c11
2 files changed, 0 insertions, 12 deletions
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 4fdb14a81108..d651f3437367 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -29,7 +29,6 @@
EM( SCAN_VMA_NULL, "vma_null") \
EM( SCAN_VMA_CHECK, "vma_check_failed") \
EM( SCAN_ADDRESS_RANGE, "not_suitable_address_range") \
- EM( SCAN_SWAP_CACHE_PAGE, "page_swap_cache") \
EM( SCAN_DEL_PAGE_LRU, "could_not_delete_page_from_lru")\
EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1cdf7c38b9e5..a4e5eaf3eb01 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -46,7 +46,6 @@ enum scan_result {
SCAN_VMA_NULL,
SCAN_VMA_CHECK,
SCAN_ADDRESS_RANGE,
- SCAN_SWAP_CACHE_PAGE,
SCAN_DEL_PAGE_LRU,
SCAN_ALLOC_HUGE_PAGE_FAIL,
SCAN_CGROUP_CHARGE_FAIL,
@@ -683,16 +682,6 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
result = SCAN_PAGE_COUNT;
goto out;
}
- if (!pte_write(pteval) && PageSwapCache(page) &&
- !reuse_swap_page(page)) {
- /*
- * Page is in the swap cache and cannot be re-used.
- * It cannot be collapsed into a THP.
- */
- unlock_page(page);
- result = SCAN_SWAP_CACHE_PAGE;
- goto out;
- }
/*
* Isolate the page to avoid collapsing an hugepage