If filelayout_decode_layout fail, _filelayout_free_lseg will causes
a double freeing of fh_array.

[ 1179.279800] BUG: unable to handle kernel NULL pointer dereference at           (null)
[ 1179.280198] IP: [<ffffffffa027222d>] filelayout_free_fh_array.isra.11+0x1d/0x70 [nfs_layout_nfsv41_files]
[ 1179.281010] PGD 0
[ 1179.281443] Oops: 0000 [#1]
[ 1179.281831] Modules linked in: nfs_layout_nfsv41_files(OE) nfsv4(OE) nfs(OE) fscache(E) xfs libcrc32c coretemp nfsd crct10dif_pclmul ppdev crc32_pclmul crc32c_intel auth_rpcgss ghash_clmulni_intel nfs_acl lockd vmw_balloon grace sunrpc parport_pc vmw_vmci parport shpchp i2c_piix4 vmwgfx drm_kms_helper ttm drm serio_raw mptspi scsi_transport_spi mptscsih e1000 mptbase ata_generic pata_acpi [last unloaded: fscache]
[ 1179.283891] CPU: 0 PID: 13336 Comm: cat Tainted: G           OE   4.3.0-rc1-pnfs+ #244
[ 1179.284323] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/20/2014
[ 1179.285206] task: ffff8800501d48c0 ti: ffff88003e3c4000 task.ti: ffff88003e3c4000
[ 1179.285668] RIP: 0010:[<ffffffffa027222d>]  [<ffffffffa027222d>] filelayout_free_fh_array.isra.11+0x1d/0x70 [nfs_layout_nfsv41_files]
[ 1179.286612] RSP: 0018:ffff88003e3c77f8  EFLAGS: 00010202
[ 1179.287092] RAX: 0000000000000000 RBX: ffff88001fe78900 RCX: 0000000000000000
[ 1179.287731] RDX: ffffea0000f40760 RSI: ffff88001fe789c8 RDI: ffff88001fe789c0
[ 1179.288383] RBP: ffff88003e3c7810 R08: ffffea0000f40760 R09: 0000000000000000
[ 1179.289170] R10: 0000000000000000 R11: 0000000000000001 R12: ffff88001fe789c8
[ 1179.289959] R13: ffff88001fe789c0 R14: ffff88004ec05a80 R15: ffff88004f935b88
[ 1179.290791] FS:  00007f4e66bb5700(0000) GS:ffffffff81c29000(0000) knlGS:0000000000000000
[ 1179.291580] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1179.292209] CR2: 0000000000000000 CR3: 00000000203f8000 CR4: 00000000001406f0
[ 1179.292731] Stack:
[ 1179.293195]  ffff88001fe78900 00000000000000d0 ffff88001fe78178 ffff88003e3c7868
[ 1179.293676]  ffffffffa0272737 0000000000000001 0000000000000001 ffff88001fe78800
[ 1179.294151]  00000000614fffce ffffffff81727671 ffff88001fe78100 ffff88001fe78100
[ 1179.294623] Call Trace:
[ 1179.295092]  [<ffffffffa0272737>] filelayout_alloc_lseg+0xa7/0x2d0 [nfs_layout_nfsv41_files]
[ 1179.295625]  [<ffffffff81727671>] ? out_of_line_wait_on_bit+0x81/0xb0
[ 1179.296133]  [<ffffffffa040407e>] pnfs_layout_process+0xae/0x320 [nfsv4]
[ 1179.296632]  [<ffffffffa03e0a01>] nfs4_proc_layoutget+0x2b1/0x360 [nfsv4]
[ 1179.297134]  [<ffffffffa0402983>] pnfs_update_layout+0x853/0xb30 [nfsv4]
[ 1179.297632]  [<ffffffffa039db24>] ? nfs_get_lock_context+0x74/0x170 [nfs]
[ 1179.298158]  [<ffffffffa0271807>] filelayout_pg_init_read+0x37/0x50 [nfs_layout_nfsv41_files]
[ 1179.298834]  [<ffffffffa03a72d9>] __nfs_pageio_add_request+0x119/0x460 [nfs]
[ 1179.299385]  [<ffffffffa03a6bd7>] ? nfs_create_request.part.9+0x37/0x2e0 [nfs]
[ 1179.299872]  [<ffffffffa03a7cc3>] nfs_pageio_add_request+0xa3/0x1b0 [nfs]
[ 1179.300362]  [<ffffffffa03a8635>] readpage_async_filler+0x85/0x260 [nfs]
[ 1179.300907]  [<ffffffff81180cb1>] read_cache_pages+0x91/0xd0
[ 1179.301391]  [<ffffffffa03a85b0>] ? nfs_read_completion+0x220/0x220 [nfs]
[ 1179.301867]  [<ffffffffa03a8dc8>] nfs_readpages+0x128/0x200 [nfs]
[ 1179.302330]  [<ffffffff81180ef3>] __do_page_cache_readahead+0x203/0x280
[ 1179.302784]  [<ffffffff81180dc8>] ? __do_page_cache_readahead+0xd8/0x280
[ 1179.303413]  [<ffffffff81181116>] ondemand_readahead+0x1a6/0x2f0
[ 1179.303855]  [<ffffffff81181371>] page_cache_sync_readahead+0x31/0x50
[ 1179.304286]  [<ffffffff811750a6>] generic_file_read_iter+0x4a6/0x5c0
[ 1179.304711]  [<ffffffffa03a0316>] ? __nfs_revalidate_mapping+0x1f6/0x240 [nfs]
[ 1179.305132]  [<ffffffffa039ccf2>] nfs_file_read+0x52/0xa0 [nfs]
[ 1179.305540]  [<ffffffff811e343c>] __vfs_read+0xcc/0x100
[ 1179.305936]  [<ffffffff811e3d15>] vfs_read+0x85/0x130
[ 1179.306326]  [<ffffffff811e4a98>] SyS_read+0x58/0xd0
[ 1179.306708]  [<ffffffff8172caaf>] entry_SYSCALL_64_fastpath+0x12/0x76
[ 1179.307094] Code: c4 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 53 8b 07 49 89 f4 85 c0 74 47 48 8b 06 49 89 fd <48> 8b 38 48 85 ff 74 22 31 db eb 0c 48 63 d3 48 8b 3c d0 48 85
[ 1179.308357] RIP  [<ffffffffa027222d>] filelayout_free_fh_array.isra.11+0x1d/0x70 [nfs_layout_nfsv41_files]
[ 1179.309177]  RSP <ffff88003e3c77f8>
[ 1179.309582] CR2: 0000000000000000
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>