Revert "mm: shrinkers: make count and scan in shrinker debugfs lockless"

This reverts commit 20cd1892fcc3efc10a7ac327cc3790494bec46b5.

Kernel test robot reports -88.8% regression in stress-ng.ramfs.ops_per_sec
test case [1], which is caused by commit f95bdb700bc6 ("mm: vmscan: make
global slab shrink lockless").  The root cause is that SRCU has to be
careful to not frequently check for SRCU read-side critical section exits.
Therefore, even if no one is currently in the SRCU read-side critical
section, synchronize_srcu() cannot return quickly.  That's why
unregister_shrinker() has become slower.

We will try to use the refcount+RCU method [2] proposed by Dave Chinner to
continue to re-implement the lockless slab shrink.  So revert the
shrinker_srcu related changes first.

[1]. https://lore.kernel.org/lkml/[email protected]/
[2]. https://lore.kernel.org/lkml/[email protected]/

Link: https://lkml.kernel.org/r/[email protected]
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Signed-off-by: Qi Zheng <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Kirill Tkhai <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions