From: Huang Ying <ying.huang@xxxxxxxxx> Subject: mm, swap: avoid lock swap_avail_lock when held cluster lock Cluster lock is used to protect the swap_cluster_info and corresponding elements in swap_info_struct->swap_map[]. But it is found that now in scan_swap_map_slots(), swap_avail_lock may be acquired when cluster lock is held. This does no good except making the locking more complex and improving the potential locking contention, because the swap_info_struct->lock is used to protect the data structure operated in the code already. Fix this via moving the corresponding operations in scan_swap_map_slots() out of cluster lock. Link: http://lkml.kernel.org/r/20170317064635.12792-3-ying.huang@xxxxxxxxx Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Acked-by: Tim Chen <tim.c.chen@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/swapfile.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff -puN mm/swapfile.c~mm-swap-avoid-lock-swap_avail_lock-when-held-cluster-lock mm/swapfile.c --- a/mm/swapfile.c~mm-swap-avoid-lock-swap_avail_lock-when-held-cluster-lock +++ a/mm/swapfile.c @@ -672,6 +672,9 @@ checks: else goto done; } + si->swap_map[offset] = usage; + inc_cluster_info_page(si, si->cluster_info, offset); + unlock_cluster(ci); if (offset == si->lowest_bit) si->lowest_bit++; @@ -685,9 +688,6 @@ checks: plist_del(&si->avail_list, &swap_avail_head); spin_unlock(&swap_avail_lock); } - si->swap_map[offset] = usage; - inc_cluster_info_page(si, si->cluster_info, offset); - unlock_cluster(ci); si->cluster_next = offset + 1; slots[n_ret++] = swp_entry(si->type, offset); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
