On Fri, Jul 12, 2024 at 02:27:20PM +0800, Zhihao Cheng wrote: > Problem description > =================== > > The inode reclaiming process(See function prune_icache_sb) collects all > reclaimable inodes and mark them with I_FREEING flag at first, at that > time, other processes will be stuck if they try getting these inodes(See > function find_inode_fast), then the reclaiming process destroy the > inodes by function dispose_list(). > Some filesystems(eg. ext4 with ea_inode feature, ubifs with xattr) may > do inode lookup in the inode evicting callback function, if the inode > lookup is operated under the inode lru traversing context, deadlock > problems may happen. > > Case 1: In function ext4_evict_inode(), the ea inode lookup could happen > if ea_inode feature is enabled, the lookup process will be stuck under > the evicting context like this: > > 1. File A has inode i_reg and an ea inode i_ea > 2. getfattr(A, xattr_buf) // i_ea is added into lru // lru->i_ea > 3. Then, following three processes running like this: > > PA PB > echo 2 > /proc/sys/vm/drop_caches > shrink_slab > prune_dcache_sb > // i_reg is added into lru, lru->i_ea->i_reg > prune_icache_sb > list_lru_walk_one > inode_lru_isolate > i_ea->i_state |= I_FREEING // set inode state > i_ea->i_state |= I_FREEING // set inode state Um, I don't see how this can happen. If the ea_inode is in use, i_count will be greater than zero, and hence the inode will never be go down the rest of the path in inode_lru_inode(): if (atomic_read(&inode->i_count) || ...) { list_lru_isolate(lru, &inode->i_lru); spin_unlock(&inode->i_lock); this_cpu_dec(nr_unused); return LRU_REMOVED; } Do you have an actual reproduer which triggers this? Or would this happen be any chance something that was dreamed up with DEPT? - Ted