[Bugs] [Bug 1438424] [Ganesha + EC] : Input/ Output Error while creating LOTS of smallfiles

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1438424



--- Comment #1 from Pranith Kumar K <pkarampu at redhat.com> ---
    Problem:
    local->loc.gfid in dht_lookup_directory() will be null-gfid for a fresh
lookup.
    dht_lookup_dir_cbk() updates local->loc.gfid while in other thread
dht_lookup_directory()
    is still winding lookup calls to subvolumes so there is a chance of partial
gfid being
    seen by EC.

    We saw in 12x(4+2) volume, ec is receiving an loc where the gfid has last
12 bytes matching
    with the gfid of the directory and the first 4 bytes are all-zeros. This is
leading to EC
    erroring out the lookup with EINVAL which leads to NFS failing lookup with
EIO.

    snip from gdb:
    $37 = (dht_local_t *) 0x7fde5de5b3cc
    (gdb) p /x $37->loc.gfid
    $39 = {0x3b, 0x82, 0x10, 0x5e, 0x40, 0x65, 0x43, 0x14, 0xa0, 0xc6, 0x8,
0xf5,
    0x6c, 0x2c, 0xb8, 0x56}
    (gdb) fr 7
    state=<optimized out>) at ec-generic.c:837
    837                     ec_lookup_rebuild(fop->xl->private, fop, cbk);
    (gdb) p /x fop->loc[0].gfid
    $40 = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x43, 0x14, 0xa0, 0xc6, 0x8, 0xf5,
0x6c,
    0x2c, 0xb8, 0x56}

    snip from log:
    [2017-01-29 03:22:30.132328] W [MSGID: 122019]
    [ec-helpers.c:354:ec_loc_gfid_check] 0-butcher-disperse-4: Mismatching
GFID's
    in loc [2017-01-29 03:22:30.132709] W [MSGID: 112199]
    [nfs3-helpers.c:3515:nfs3_log_newfh_res] 0-nfs-nfsv3:
    /linux-4.9.5/Documentation => (XID: b27b9474, MKDIR: NFS: 5(I/O error),
POSIX:
    5(Input/output error)), FH: exportid 00000000-0000-0000-0000-000000000000,
gfid
    00000000-0000-0000-0000-000000000000, mountid
    00000000-0000-0000-0000-000000000000 [Invalid argument]

    Fix:
    update local->loc.gfid in last-call to make sure there are no races.

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