The patch titled
Subject: mm, swap: avoid lock swap_avail_lock when held cluster lock
has been removed from the -mm tree. Its filename was
mm-swap-avoid-lock-swap_avail_lock-when-held-cluster-lock.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
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);
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
mm-swap-use-kvzalloc-to-allocate-some-swap-data-structure.patch
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