[PATCH 01/10] mbcache: Don't reclaim used entries

Jan Kara
2022-06-14T16:06:15Z

Do not reclaim entries that are currently used by somebody from a
shrinker. Firstly, these entries are likely useful. Secondly, we will
need to keep such entries to protect pending increment of xattr block
refcount.

CC: stable@vger.kernel.org
Fixes: 82939d7999df ("ext4: convert to mbcache2")
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/mbcache.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/mbcache.c b/fs/mbcache.c
index 97c54d3a2227..cfc28129fb6f 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -288,7 +288,7 @@ static unsigned long mb_cache_shrink(struct mb_cache *cache,
while (nr_to_scan-- && !list_empty(&cache->c_list)) {
entry = list_first_entry(&cache->c_list,
struct mb_cache_entry, e_list);
- if (entry->e_referenced) {
+ if (entry->e_referenced || atomic_read(&entry->e_refcnt) > 2) {
entry->e_referenced = 0;
list_move_tail(&entry->e_list, &cache->c_list);
continue;
@@ -302,6 +302,14 @@ static unsigned long mb_cache_shrink(struct mb_cache *cache,
spin_unlock(&cache->c_list_lock);
head = mb_cache_entry_head(cache, entry->e_key);
hlist_bl_lock(head);
+ /* Now a reliable check if the entry didn't get used... */
+ if (atomic_read(&entry->e_refcnt) > 2) {
+ hlist_bl_unlock(head);
+ spin_lock(&cache->c_list_lock);
+ list_add_tail(&entry->e_list, &cache->c_list);
+ cache->c_entry_count++;
+ continue;
+ }
if (!hlist_bl_unhashed(&entry->e_hash_list)) {
hlist_bl_del_init(&entry->e_hash_list);
atomic_dec(&entry->e_refcnt);
--
2.35.3