ext4: change LRU to round-robin in extent status tree shrinker

In this commit we discard the lru algorithm for inodes with extent
status tree because it takes significant effort to maintain a lru list
in extent status tree shrinker and the shrinker can take a long time to
scan this lru list in order to reclaim some objects.

We replace the lru ordering with a simple round-robin.  After that we
never need to keep a lru list.  That means that the list needn't be
sorted if the shrinker can not reclaim any objects in the first round.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 4 insertions, 7 deletions

diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index cd37a584ee88..6cfb841fea7c 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -2450,15 +2450,14 @@ TRACE_EVENT(ext4_collapse_range,
 
 TRACE_EVENT(ext4_es_shrink,
         TP_PROTO(struct super_block *sb, int nr_shrunk, u64 scan_time,
-                 int skip_precached, int nr_skipped, int retried),
+                 int nr_skipped, int retried),
 
-        TP_ARGS(sb, nr_shrunk, scan_time, skip_precached, nr_skipped, retried),
+        TP_ARGS(sb, nr_shrunk, scan_time, nr_skipped, retried),
 
         TP_STRUCT__entry(
                 __field(        dev_t,          dev             )
                 __field(        int,            nr_shrunk       )
                 __field(        unsigned long long, scan_time   )
-                __field(        int,            skip_precached  )
                 __field(        int,            nr_skipped      )
                 __field(        int,            retried         )
         ),
@@ -2467,16 +2466,14 @@ TRACE_EVENT(ext4_es_shrink,
                 __entry->dev            = sb->s_dev;
                 __entry->nr_shrunk      = nr_shrunk;
                 __entry->scan_time      = div_u64(scan_time, 1000);
-                __entry->skip_precached = skip_precached;
                 __entry->nr_skipped     = nr_skipped;
                 __entry->retried        = retried;
         ),
 
-        TP_printk("dev %d,%d nr_shrunk %d, scan_time %llu skip_precached %d "
+        TP_printk("dev %d,%d nr_shrunk %d, scan_time %llu "
                   "nr_skipped %d retried %d",
                   MAJOR(__entry->dev), MINOR(__entry->dev), __entry->nr_shrunk,
-                  __entry->scan_time, __entry->skip_precached,
-                  __entry->nr_skipped, __entry->retried)
+                  __entry->scan_time, __entry->nr_skipped, __entry->retried)
 );
 
 #endif /* _TRACE_EXT4_H */