If there are several shrinkers working on a single sbi there can be easily a
situation when a neighbor shrinkers reclaimed a bunch of extents and thus a
bunch inoes from the s_es_list but we don't honor this and iterate over
sbi->s_es_list the number of times equal to the initial number of inodes in
s_es_list.

Before each iteration, check if we are going to iterate more than the number of
inodes in the list and adjust nr_to_walk accordingly.

https://jira.sw.ru/browse/PSBM-83335

Signed-off-by: Konstantin Khorenko <khore...@virtuozzo.com>
---
 fs/ext4/extents_status.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index a3b9c480ec20..ed1f63eef74c 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -998,6 +998,14 @@ static int __es_shrink(struct ext4_sb_info *sbi, int 
nr_to_scan,
                        spin_unlock(&sbi->s_es_lock);
                        goto out;
                }
+               /*
+                * Another shrinker can remove a bunch of extents in parallel,
+                * we don't have to iterate more than the current number of
+                * inodes in the list.
+                */
+               if (nr_to_walk > sbi->s_es_nr_inode)
+                       nr_to_walk = sbi->s_es_nr_inode;
+
                ei = list_first_entry(&sbi->s_es_list, struct ext4_inode_info,
                                      i_es_list);
                /* Move the inode to the tail */
-- 
2.15.1

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