Readynas RN314 iscsi errors

I created an iscsi share on my ReadyNAS RN 314.

The NAS and the linux client are connected via dedicated Gigabit Ethernet.

Under write load, there are i/o errors writing to the file system.

The memory on the NAS system does not get very full during the write operations, however I seem to get out of memory errors from the linux kernel on the NAS.

I found this in dmesg of the NAS:

[540798.949288] iscsi_trx: page allocation failure: order:4, mode:0x40d0
[540798.949299] CPU: 0 PID: 20599 Comm: iscsi_trx Tainted: P O 4.1.21.x86_64.1 #1
[540798.949302] Hardware name: NETGEAR ReadyNAS 314 /ReadyNAS 314 , BIOS 4.6.5 06/11/2013
[540798.949306] 0000000000000000 ffff88004f247b38 ffffffff889b0fe5 00000000000040d0
[540798.949312] 0000000000000000 ffff88004f247bc8 ffffffff880ed1c9 00000010fffffff0
[540798.949317] 00000004000040d0 00000000000003c0 ffff88007ba73640 0000000000000004
[540798.949323] Call Trace:
[540798.949334] [<ffffffff889b0fe5>] dump_stack+0x4d/0x63
[540798.949341] [<ffffffff880ed1c9>] warn_alloc_failed+0xd9/0x130
[540798.949346] [<ffffffff880ef49b>] __alloc_pages_nodemask+0x14b/0x760
[540798.949353] [<ffffffff880efb82>] alloc_kmem_pages+0x12/0x20
[540798.949358] [<ffffffff88102f53>] kmalloc_order+0x13/0x50
[540798.949363] [<ffffffff88122264>] __kmalloc+0xc4/0x100
[540798.949369] [<ffffffff88614799>] target_alloc_sgl+0x49/0x150
[540798.949374] [<ffffffff88614922>] transport_generic_new_cmd+0x82/0x250
[540798.949382] [<ffffffff8863835c>] iscsit_process_scsi_cmd+0xec/0x110
[540798.949387] [<ffffffff8863afd9>] iscsi_target_rx_thread+0x569/0xf10
[540798.949392] [<ffffffff8863aa70>] ? iscsi_target_tx_thread+0x1d0/0x1d0
[540798.949398] [<ffffffff88082624>] kthread+0xc4/0xe0
[540798.949403] [<ffffffff88082560>] ? __kthread_parkme+0x80/0x80
[540798.949408] [<ffffffff889b9012>] ret_from_fork+0x42/0x70
[540798.949413] [<ffffffff88082560>] ? __kthread_parkme+0x80/0x80
[540798.949417] Mem-Info:
[540798.949425] active_anon:3511 inactive_anon:3273 isolated_anon:0
[540798.949425] active_file:205579 inactive_file:245427 isolated_file:0
[540798.949425] unevictable:0 dirty:19162 writeback:0 unstable:0
[540798.949425] slab_reclaimable:19185 slab_unreclaimable:7866
[540798.949425] mapped:4114 shmem:1491 pagetables:1245 bounce:0
[540798.949425] free:18203 free_pcp:0 free_cma:0
[540798.949478] DMA free:8236kB min:316kB low:392kB high:472kB active_anon:28kB inactive_anon:112kB active_file:876kB inactive_file:1764kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15976kB managed:15892kB mlocked:0kB dirty:44kB writeback:0kB mapped:0kB shmem:40kB slab_reclaimable:2768kB slab_unreclaimable:1644kB kernel_stack:112kB pagetables:96kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
[540798.949484] lowmem_reserve[]: 0 1969 1969 1969
[540798.949522] DMA32 free:64576kB min:40332kB low:50412kB high:60496kB active_anon:14016kB inactive_anon:12980kB active_file:821440kB inactive_file:979944kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2069212kB managed:2017564kB mlocked:0kB dirty:76604kB writeback:0kB mapped:16456kB shmem:5924kB slab_reclaimable:73972kB slab_unreclaimable:29820kB kernel_stack:2896kB pagetables:4884kB unstable:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:20 all_unreclaimable? no
[540798.949533] lowmem_reserve[]: 0 0 0 0
[540798.949571] DMA: 31*4kB (UEM) 18*8kB (UEM) 53*16kB (UEM) 46*32kB (UEM) 16*64kB (UE) 4*128kB (M) 0*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB (R) = 8220kB
[540798.949596] DMA32: 7187*4kB (UEM) 3268*8kB (UM) 29*16kB (UM) 15*32kB (UR) 23*64kB (UR) 2*128kB (R) 0*256kB 0*512kB 1*1024kB (R) 1*2048kB (R) 1*4096kB (R) = 64732kB
[540798.949622] 453591 total pagecache pages
[540798.949627] 1063 pages in swap cache
[540798.949633] Swap cache stats: add 16654, delete 15591, find 75022/77542
[540798.949637] Free swap = 1009140kB
[540798.949640] Total swap = 1047420kB
[540798.949643] 521297 pages RAM
[540798.949646] 0 pages HighMem/MovableOnly
[540798.949649] 12933 pages reserved

Any idea how to avoid this problem?