From: Huang Ying <[email protected]> Previously, swapcache_free_cluster() is used only in the error path of shrink_page_list() to free the swap cluster just allocated if the THP (Transparent Huge Page) is failed to be split. In this patch, it is enhanced to clear the swap cache flag (SWAP_HAS_CACHE) for the swap cluster that holds the contents of THP swapped out.
This will be used in delaying splitting THP after swapping out support. Because there is no THP swapping in as a whole support yet, after clearing the swap cache flag, the swap cluster backing the THP swapped out will be split. So that the swap slots in the swap cluster can be swapped in as normal pages later. Signed-off-by: "Huang, Ying" <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Rik van Riel <[email protected]> --- mm/swapfile.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 8a6cdf9e55f9..4cd02dec6894 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1167,22 +1167,40 @@ static void swapcache_free_cluster(swp_entry_t entry) struct swap_cluster_info *ci; struct swap_info_struct *si; unsigned char *map; - unsigned int i; + unsigned int i, free_entries = 0; + unsigned char val; - si = swap_info_get(entry); + si = _swap_info_get(entry); if (!si) return; ci = lock_cluster(si, offset); map = si->swap_map + offset; for (i = 0; i < SWAPFILE_CLUSTER; i++) { - VM_BUG_ON(map[i] != SWAP_HAS_CACHE); - map[i] = 0; + val = map[i]; + VM_BUG_ON(!(val & SWAP_HAS_CACHE)); + if (val == SWAP_HAS_CACHE) + free_entries++; + } + if (!free_entries) { + for (i = 0; i < SWAPFILE_CLUSTER; i++) + map[i] &= ~SWAP_HAS_CACHE; } unlock_cluster(ci); - mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER); - swap_free_cluster(si, idx); - spin_unlock(&si->lock); + if (free_entries == SWAPFILE_CLUSTER) { + spin_lock(&si->lock); + ci = lock_cluster(si, offset); + memset(map, 0, SWAPFILE_CLUSTER); + unlock_cluster(ci); + mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER); + swap_free_cluster(si, idx); + spin_unlock(&si->lock); + } else if (free_entries) { + for (i = 0; i < SWAPFILE_CLUSTER; i++, entry.val++) { + if (!__swap_entry_free(si, entry, SWAP_HAS_CACHE)) + free_swap_slot(entry); + } + } } #else static inline void swapcache_free_cluster(swp_entry_t entry) -- 2.11.0
