Played a bit with that bz again - fts_read error is being set on lib/fts.c:2000 - hardcoding ENOENT to errno. Error occurs when ".." entry is not cached yet, so with more repeating after mount, it seems to be possible to get rid off those errors and to get correct result. It seems that check on fts.c:1997/1998 has to be extended to handle properly that situation with NetApp .snapshot dir. Using du -Lsh also helps in some cases.
Played a bit with that bz again - fts_read error is being set on lib/fts.c:2000 - hardcoding ENOENT to errno. Error occurs when ".." entry is not cached yet, so with more repeating after mount, it seems to be possible to get rid off those errors and to get correct result. It seems that check on fts.c:1997/1998 has to be extended to handle properly that situation with NetApp .snapshot dir. Using du -Lsh also helps in some cases.