On Thu 14-07-22 17:17:02, Ritesh Harjani wrote: > On 22/07/12 12:54PM, Jan Kara wrote: > > 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@xxxxxxxxxxxxxxx > > Fixes: 82939d7999df ("ext4: convert to mbcache2") > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > --- > > 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) { > > On taking a look at this patchset again. I think if we move this "if" condition > of checking refcnt to above i.e. before we delete the entry from c_list. > Then we can avoid => > removing of the entry -> checking it's refcnt under lock -> adding it back > if the refcnt is elevated. > > Thoughts? Well, but synchronization would get more complicated because we don't want to acquire hlist_bl_lock() under c_list_lock (technically we could at this point in the series but it would make life harder for the last patch in the series). And we need c_list_lock to remove entry from the LRU list. It could be all done but I don't think what you suggest is really that simpler and this code will go away later in the patchset anyway... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR