Daniel,

prev_chunk->dirents is an empty list.  The num_entries say 112, but the next and prev suggest an empty list.  I did not find any code that decrements num_entries as dirents are removed.  Only a reset back to zero if the whole list is emptied.

1. Should the code below check for empty list?  If empty go backwards to the prev_chunk’s prev or just set reload_ck to whence
2. Does the code in unchunk_dirent that removes from chunk also need to decrement num_entries
3. Will not decrementing the num_entries have an effect on the split logic in place_new_dirent – or at least that code need to handle empty chunks
4. Do empty chunks get cleaned up?

***** Code snippet for 1 and core:  mdcache_get_chunk. ****

if (prev_chunk) {

                chunk->reload_ck = glist_last_entry(&prev_chunk->dirents,

                                                    mdcache_dir_entry_t,

>>>>Line 914                                                     chunk_list)->ck;

/* unref prev_chunk as we had got a ref on prev_chunk

                * at the beginning of this function

                */

                mdcache_lru_unref_chunk(prev_chunk);

        } else {

                chunk->reload_ck = whence;

        }

Note:  This core had a ref_count of 1 for the prev_chunk.  A different core had a ref_count of 1 for prev_chunk

******* core *****

(gdb) info locals

lru = 0x0

chunk = 0x75320370

__func__ = "mdcache_get_chunk"

(gdb) info args

parent = 0x2f837f60

prev_chunk = 0x2f70dc50

whence = 18525227

(gdb) print *chunk

$2 = {chunks = {next = 0x2f838200, prev = 0x40ab5700}, dirents = {next = 0x75320380, prev = 0x75320380}, parent = 0x2f837f60,

chunk_lru = {q = {next = 0x0, prev = 0x0}, qid = LRU_ENTRY_NONE, refcnt = 0, flags = 0, lane = 0, cf = 0}, reload_ck = 0,

next_ck = 0, num_entries = 0}

(gdb) print *prev_chunk

$3 = {chunks = {next = 0x39a24aa0, prev = 0x55ed7f00}, dirents = {next = 0x2f70dc60, prev = 0x2f70dc60}, parent = 0x0,

chunk_lru = {q = {next = 0x0, prev = 0x0}, qid = LRU_ENTRY_L1, refcnt = 1, flags = 0, lane = 0, cf = 0}, reload_ck = 0,

next_ck = 0, num_entries = 112}

(gdb) bt

#0 mdcache_get_chunk (parent=0x2f837f60, prev_chunk=0x2f70dc50, whence=18525227)

at /src/src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_lru.c:914

#1 0x0000000000541da9 in mdcache_populate_dir_chunk (directory=0x2f837f60, whence=18525227, dirent=0x7f0edeea3940,

prev_chunk=0x2f70dc50, eod_met=0x7f0edeea393f) at /src/src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:2554

#2 0x00000000005437cd in mdcache_readdir_chunked (directory=0x2f837f60, whence=18525227, dir_state=0x7f0edeea3af0,

cb=0x4325fd <populate_dirent>, attrmask=0, eod_met=0x7f0edeea3feb)

at /src/src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:2985

#3 0x0000000000531b60 in mdcache_readdir (dir_hdl=0x2f837f98, whence=0x7f0edeea3ad0, dir_state=0x7f0edeea3af0,

cb=0x4325fd <populate_dirent>, attrmask=0, eod_met=0x7f0edeea3feb)

at /src/src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:559

#4 0x0000000000432f24 in fsal_readdir (directory=0x2f837f98, cookie=18525227, nbfound=0x7f0edeea3fec, eod_met=0x7f0edeea3feb,

attrmask=0, cb=0x491f59 <nfs3_readdir_callback>, opaque=0x7f0edeea3fa0) at /src/src/FSAL/fsal_helper.c:1164

#5 0x0000000000491d41 in nfs3_readdir (arg=0x7534a418, req=0x75349d10, res=0x75289cf0)

at /src/src/Protocols/NFS/nfs3_readdir.c:289

#6 0x0000000000457e26 in nfs_rpc_process_request (reqdata=0x75349d10) at /src/src/MainNFSD/nfs_worker_thread.c:1328

#7 0x00000000004585e5 in nfs_rpc_valid_NFS (req=0x75349d10) at /src/src/MainNFSD/nfs_worker_thread.c:1548

#8 0x00007f0ee83c4034 in svc_vc_decode (req=0x75349d10) at /src/src/libntirpc/src/svc_vc.c:829

#9 0x000000000044afd5 in nfs_rpc_decode_request (xprt=0x1453b20, xdrs=0x75363020)

at /src/src/MainNFSD/nfs_rpc_dispatcher_thread.c:1345

#10 0x00007f0ee83c3f45 in svc_vc_recv (xprt=0x1453b20) at /src/src/libntirpc/src/svc_vc.c:802

#11 0x00007f0ee83c0689 in svc_rqst_xprt_task (wpe=0x1453d38) at /src/src/libntirpc/src/svc_rqst.c:769

#12 0x00007f0ee83c0ae6 in svc_rqst_epoll_events (sr_rec=0x1434020, n_events=1) at /src/src/libntirpc/src/svc_rqst.c:941

#13 0x00007f0ee83c0d7b in svc_rqst_epoll_loop (sr_rec=0x1434020) at /src/src/libntirpc/src/svc_rqst.c:1014

#14 0x00007f0ee83c0e2e in svc_rqst_run_task (wpe=0x1434020) at /src/src/libntirpc/src/svc_rqst.c:1050

#15 0x00007f0ee83c97f6 in work_pool_thread (arg=0x144d470) at /src/src/libntirpc/src/work_pool.c:181

#16 0x00007f0ee73e7de5 in start_thread () from /lib64/libpthread.so.0

#17 0x00007f0ee6ceef1d in clone () from /lib64/libc.so.6