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mm/ksm: convert scan_get_next_rmap_item() from follow_page() to folio_walk

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Let's use folio_walk instead, for example avoiding taking temporary folio
references if the folio does obviously not even apply and getting rid of
one more follow_page() user.  We cannot move all handling under the PTL,
so leave the rmap handling (which implies an allocation) out.

Note that zeropages obviously don't apply: old code could just have
specified FOLL_DUMP.  Further, we don't care about losing the secretmem
check in follow_page(): these are never anon pages and
vma_ksm_compatible() would never consider secretmem vmas (VM_SHARED |
VM_MAYSHARE must be set for secretmem, see secretmem_mmap()).

Link: https://lkml.kernel.org/r/20240802155524.517137-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-08-02 17:55:19 +02:00 committed by Andrew Morton
parent 184e916c62
commit b1d3e9bbcc
1 changed files with 24 additions and 14 deletions
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38
mm/ksm.c
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@ -2564,36 +2564,46 @@ next_mm:
ksm_scan.address = vma->vm_end;
while (ksm_scan.address < vma->vm_end) {
struct page *tmp_page = NULL;
struct folio_walk fw;
struct folio *folio;
if (ksm_test_exit(mm))
break;
*page = follow_page(vma, ksm_scan.address, FOLL_GET);
if (IS_ERR_OR_NULL(*page)) {
ksm_scan.address += PAGE_SIZE;
cond_resched();
continue;
folio = folio_walk_start(&fw, vma, ksm_scan.address, 0);
if (folio) {
if (!folio_is_zone_device(folio) &&
folio_test_anon(folio)) {
folio_get(folio);
tmp_page = fw.page;
}
folio_walk_end(&fw, vma);
}
if (is_zone_device_page(*page))
goto next_page;
if (PageAnon(*page)) {
flush_anon_page(vma, *page, ksm_scan.address);
flush_dcache_page(*page);
if (tmp_page) {
flush_anon_page(vma, tmp_page, ksm_scan.address);
flush_dcache_page(tmp_page);
rmap_item = get_next_rmap_item(mm_slot,
ksm_scan.rmap_list, ksm_scan.address);
if (rmap_item) {
ksm_scan.rmap_list =
&rmap_item->rmap_list;
if (should_skip_rmap_item(*page, rmap_item))
if (should_skip_rmap_item(tmp_page, rmap_item)) {
folio_put(folio);
goto next_page;
}
ksm_scan.address += PAGE_SIZE;
} else
put_page(*page);
*page = tmp_page;
} else {
folio_put(folio);
}
mmap_read_unlock(mm);
return rmap_item;
}
next_page:
put_page(*page);
ksm_scan.address += PAGE_SIZE;
cond_resched();
}