Description of problem:

For the background to this bug and a reproducer, see bug 914931.

[   58.734603] guestfsd invoked oom-killer: gfp_mask=0x201da, order=0, oom_score_adj=0
[   58.735833] guestfsd cpuset=/ mems_allowed=0
[   58.736484] Pid: 118, comm: guestfsd Not tainted 3.7.6-201.fc18.x86_64 #1
[   58.737534] Call Trace:
[   58.737951]  [<ffffffff810d2d91>] ? cpuset_print_task_mems_allowed+0x91/0xa0
[   58.738998]  [<ffffffff8162dc81>] dump_header+0x79/0x1b3
[   58.739839]  [<ffffffff810f795e>] ? __delayacct_freepages_end+0x2e/0x30
[   58.740862]  [<ffffffff812ecac3>] ? ___ratelimit+0xa3/0x120
[   58.741748]  [<ffffffff811337d7>] oom_kill_process+0x1c7/0x310
[   58.742661]  [<ffffffff8106ad05>] ? has_ns_capability_noaudit+0x15/0x20
[   58.743679]  [<ffffffff81133fa7>] out_of_memory+0x437/0x470
[   58.744540]  [<ffffffff811399ee>] __alloc_pages_nodemask+0x83e/0x990
[   58.745480]  [<ffffffff81176680>] alloc_pages_current+0xb0/0x120
[   58.746409]  [<ffffffff8112fae7>] __page_cache_alloc+0xd7/0x100
[   58.747341]  [<ffffffff811302fc>] ? find_get_page+0x3c/0x110
[   58.748230]  [<ffffffff8113237a>] filemap_fault+0x2aa/0x480
[   58.749097]  [<ffffffff81156a71>] __do_fault+0x71/0x550
[   58.749855]  [<ffffffff81159af5>] handle_pte_fault+0x95/0xb10
[   58.750747]  [<ffffffff813b20e3>] ? uart_write+0xe3/0x110
[   58.751596]  [<ffffffff812fbb21>] ? list_del+0x11/0x40
[   58.752405]  [<ffffffff816344cd>] ? mutex_lock+0x1d/0x50
[   58.753187]  [<ffffffff8115aeb1>] handle_mm_fault+0x261/0x330
[   58.754076]  [<ffffffff8163a922>] __do_page_fault+0x172/0x4e0
[   58.754954]  [<ffffffff8115ed18>] ? __vm_enough_memory+0x38/0x190
[   58.755907]  [<ffffffff810975af>] ? __dequeue_entity+0x2f/0x50
[   58.756818]  [<ffffffff810135d1>] ? __switch_to+0x181/0x4a0
[   58.757645]  [<ffffffff8163ac9e>] do_page_fault+0xe/0x10
[   58.758476]  [<ffffffff8163a425>] do_async_page_fault+0x35/0xa0
[   58.759398]  [<ffffffff81637308>] async_page_fault+0x28/0x30
[   58.760306] Mem-Info:
[   58.760654] Node 0 DMA per-cpu:
[   58.761280] CPU    0: hi:    0, btch:   1 usd:   0
[   58.761976] Node 0 DMA32 per-cpu:
[   58.762547] CPU    0: hi:  186, btch:  31 usd:  68
[   58.763309] active_anon:116672 inactive_anon:0 isolated_anon:0
[   58.763309]  active_file:0 inactive_file:17 isolated_file:0
[   58.763309]  unevictable:313 dirty:0 writeback:0 unstable:0
[   58.763309]  free:1186 slab_reclaimable:1442 slab_unreclaimable:1875
[   58.763309]  mapped:4 shmem:0 pagetables:335 bounce:0
[   58.763309]  free_cma:0
[   58.767852] Node 0 DMA free:2004kB min:88kB low:108kB high:132kB active_anon:13848kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15652kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:4kB slab_unreclaimable:28kB kernel_stack:0kB pagetables:20kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
[   58.773531] lowmem_reserve[]: 0 476 476 476
[   58.774309] Node 0 DMA32 free:2740kB min:2744kB low:3428kB high:4116kB active_anon:452840kB inactive_anon:0kB active_file:0kB inactive_file:68kB unevictable:1252kB isolated(anon):0kB isolated(file):0kB present:487872kB mlocked:0kB dirty:0kB writeback:0kB mapped:16kB shmem:0kB slab_reclaimable:5764kB slab_unreclaimable:7472kB kernel_stack:408kB pagetables:1320kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:252 all_unreclaimable? yes
[   58.780259] lowmem_reserve[]: 0 0 0 0
[   58.780947] Node 0 DMA: 5*4kB 0*8kB 0*16kB 0*32kB 1*64kB 1*128kB 1*256kB 1*512kB 1*1024kB 0*2048kB 0*4096kB = 2004kB
[   58.782808] Node 0 DMA32: 181*4kB 0*8kB 0*16kB 1*32kB 1*64kB 1*128kB 1*256kB 1*512kB 1*1024kB 0*2048kB 0*4096kB = 2740kB
[   58.784755] 332 total pagecache pages
[   58.785347] 0 pages in swap cache
[   58.785833] Swap cache stats: add 0, delete 0, find 0/0
[   58.786648] Free swap  = 0kB
[   58.787082] Total swap = 0kB
[   58.788590] 127984 pages RAM
[   58.789069] 5158 pages reserved
[   58.789538] 18 pages shared
[   58.789998] 121415 pages non-shared
[   58.790524] [ pid ]   uid  tgid total_vm      rss nr_ptes swapents oom_score_adj name
[   58.791742] [   57]     0    57     9133      120      22        0         -1000 systemd-udevd
[   58.793079] [  118]     0   118   144642   116456     273        0             0 guestfsd
[   58.794319] [  125]     0   125     5435       49      25        0             0 tar
[   58.795485] Out of memory: Kill process 118 (guestfsd) score 920 or sacrifice child
[   58.796640] Killed process 118 (guestfsd) total-vm:578568kB, anon-rss:465816kB, file-rss:8kB
/init: line 158:   118 Killed                  $vg guestfsd
Rebooting.
[   58.985384] Unregister pv shared memory for cpu 0
[   58.986168] sd 2:0:1:0: [sdb] Synchronizing SCSI cache
[   58.987490] sd 2:0:0:0: [sda] Synchronizing SCSI cache
[   59.044312] Disabling non-boot CPUs ...
[   59.044918] Restarting system.
[   59.045405] reboot: machine restart
libguestfs: child_cleanup: 0x18031e0: child process died

Version-Release number of selected component (if applicable):

libguestfs 1.20.2

How reproducible:

100%

Steps to Reproduce:
1. 'data1.raw' is a disk containing several gigabytes of data.
2. guestfish -a data1.raw -m /dev/sda1 -- tar-out / - | guestfish -v -a data2.raw -m /dev/VG/LV -- tar-in - / >& /tmp/log