6.17-stable review patch. If anyone has any objections, please let me know.
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From: Youngjun Park youngjun.park@lge.com
[ Upstream commit f5e31a196edcd1f1bb44f26b6f9299b9a5b9b3c4 ]
After commit 4f78252da887, nr_swap_pages is decremented in swap_range_alloc(). Since cluster_alloc_swap_entry() calls swap_range_alloc() internally, the decrement in get_swap_page_of_type() causes double-decrementing.
As a representative userspace-visible runtime example of the impact, /proc/meminfo reports increasingly inaccurate SwapFree values. The discrepancy grows with each swap allocation, and during hibernation when large amounts of memory are written to swap, the reported value can deviate significantly from actual available swap space, misleading users and monitoring tools.
Remove the duplicate decrement.
Link: https://lkml.kernel.org/r/20251102082456.79807-1-youngjun.park@lge.com Fixes: 4f78252da887 ("mm: swap: move nr_swap_pages counter decrement from folio_alloc_swap() to swap_range_alloc()") Signed-off-by: Youngjun Park youngjun.park@lge.com Acked-by: Chris Li chrisl@kernel.org Reviewed-by: Barry Song baohua@kernel.org Reviewed-by: Kairui Song kasong@tencent.com Acked-by: Nhat Pham nphamcs@gmail.com Cc: Baoquan He bhe@redhat.com Cc: Kemeng Shi shikemeng@huaweicloud.com Cc: stable@vger.kernel.org [6.17+] Signed-off-by: Andrew Morton akpm@linux-foundation.org [ adjusted context ] Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/swapfile.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
--- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1866,10 +1866,8 @@ swp_entry_t get_swap_page_of_type(int ty if (get_swap_device_info(si)) { if (si->flags & SWP_WRITEOK) { offset = cluster_alloc_swap_entry(si, 0, 1); - if (offset) { + if (offset) entry = swp_entry(si->type, offset); - atomic_long_dec(&nr_swap_pages); - } } put_swap_device(si); }