mm, swap: avoid lock swap_avail_lock when held cluster lock
authorHuang Ying <ying.huang@intel.com>
Wed, 3 May 2017 21:54:39 +0000 (14:54 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 3 May 2017 22:52:10 +0000 (15:52 -0700)
commit2872bb2d0a4952ffb721e703555cb73d40b2c2f0
tree6f7936193bf981d5aff8f1af8b723dd0c0dabb2b
parent0ef017d117d79eb765cb490a8d7e323752a13f4a
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@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/swapfile.c