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| author | Kairui Song <kasong@tencent.com> | 2022-12-20 02:58:37 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-18 17:12:44 -0800 |
| commit | 3f79b187ad2f677047a1f1104bfb8a81b58b67d5 (patch) | |
| tree | c8e8abd6d245bc1efbc633c6e449e7828dcce950 /mm/swapfile.c | |
| parent | 497b099d9a166f819e667f4bf258e7a00ea2e78a (diff) | |
| download | linux-stable-3f79b187ad2f677047a1f1104bfb8a81b58b67d5.tar.gz linux-stable-3f79b187ad2f677047a1f1104bfb8a81b58b67d5.tar.bz2 linux-stable-3f79b187ad2f677047a1f1104bfb8a81b58b67d5.zip | |
swapfile: get rid of volatile and avoid redundant read
Patch series "Clean up and fixes for swap", v2.
This series cleans up some code paths, saves a few cycles and reduces the
object size by a bit. It also fixes some rare race issue with statistics.
This patch (of 4):
Convert a volatile variable to more readable READ_ONCE. And this actually
avoids the code from reading the variable twice redundantly when it races.
Link: https://lkml.kernel.org/r/20221219185840.25441-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20221219185840.25441-2-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 908a529bca12..6d3f60bd383b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1835,13 +1835,13 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, pte_t *pte; struct swap_info_struct *si; int ret = 0; - volatile unsigned char *swap_map; si = swap_info[type]; pte = pte_offset_map(pmd, addr); do { struct folio *folio; unsigned long offset; + unsigned char swp_count; if (!is_swap_pte(*pte)) continue; @@ -1852,7 +1852,6 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, offset = swp_offset(entry); pte_unmap(pte); - swap_map = &si->swap_map[offset]; folio = swap_cache_get_folio(entry, vma, addr); if (!folio) { struct page *page; @@ -1869,8 +1868,10 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, folio = page_folio(page); } if (!folio) { - if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD) + swp_count = READ_ONCE(si->swap_map[offset]); + if (swp_count == 0 || swp_count == SWAP_MAP_BAD) goto try_next; + return -ENOMEM; } |