When interrupting an application which was allocating DMAable
memory, it was possible, that the DMA memory was deallocated twice, leading
to the error symptoms below.

BugLink: http://bugs.launchpad.net/bugs/1559194

Thanks to Gerald, who analyzed the problem and provided this
patch.

I agree with his analysis of the problem: ddcb_cmd_fixups() ->
genwqe_alloc_sync_sgl() (fails in f/lpage, but sgl->sgl != NULL
and f/lpage maybe also != NULL) -> ddcb_cmd_cleanup() ->
genwqe_free_sync_sgl() (double free, because sgl->sgl != NULL and
f/lpage maybe also != NULL)

In this scenario we would have exactly the kind of double free that
would explain the WARNING / Bad page state, and as expected it is
caused by broken error handling (cleanup).

Using the Ubuntu git source, tag Ubuntu-4.4.0-33.52, he was able to reproduce
the "Bad page state" issue, and with the patch on top he could not reproduce
it any more.

------------[ cut here ]------------
WARNING: at /build/linux-o03cxz/linux-4.4.0/arch/s390/include/asm/pci_dma.h:141
Modules linked in: qeth_l2 ghash_s390 prng aes_s390 des_s390 des_generic sha512_s390 sha256_s390 sha1_s390 sha_common genwqe_card qeth crc_itu_t qdio ccwgroup vmur dm_multipath dasd_eckd_mod dasd_mod
CPU: 2 PID: 3293 Comm: genwqe_gunzip Not tainted 4.4.0-33-generic #52-Ubuntu
task: 0000000032c7e270 ti: 00000000324e4000 task.ti: 00000000324e4000
Krnl PSW : 0404c00180000000 0000000000156346 (dma_update_cpu_trans+0x9e/0xa8)
           R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 EA:3
Krnl GPRS: 00000000324e7bcd 0000000000c3c34a 0000000027628298 000000003215b400
           0000000000000400 0000000000001fff 0000000000000400 0000000116853000
           07000000324e7b1e 0000000000000001 0000000000000001 0000000000000001
           0000000000001000 0000000116854000 0000000000156402 00000000324e7a38
Krnl Code: 000000000015633a: 95001000           cli     0(%r1),0
           000000000015633e: a774ffc3           brc     7,1562c4
          #0000000000156342: a7f40001           brc     15,156344
          >0000000000156346: 92011000           mvi     0(%r1),1
           000000000015634a: a7f4ffbd           brc     15,1562c4
           000000000015634e: 0707               bcr     0,%r7
           0000000000156350: c00400000000       brcl    0,156350
           0000000000156356: eb7ff0500024       stmg    %r7,%r15,80(%r15)
Call Trace:
([<00000000001563e0>] dma_update_trans+0x90/0x228)
 [<00000000001565dc>] s390_dma_unmap_pages+0x64/0x160
 [<00000000001567c2>] s390_dma_free+0x62/0x98
 [<000003ff801310ce>] __genwqe_free_consistent+0x56/0x70 [genwqe_card]
 [<000003ff801316d0>] genwqe_free_sync_sgl+0xf8/0x160 [genwqe_card]
 [<000003ff8012bd6e>] ddcb_cmd_cleanup+0x86/0xa8 [genwqe_card]
 [<000003ff8012c1c0>] do_execute_ddcb+0x110/0x348 [genwqe_card]
 [<000003ff8012c914>] genwqe_ioctl+0x51c/0xc20 [genwqe_card]
 [<000000000032513a>] do_vfs_ioctl+0x3b2/0x518
 [<0000000000325344>] SyS_ioctl+0xa4/0xb8
 [<00000000007b86c6>] system_call+0xd6/0x264
 [<000003ff9e8e520a>] 0x3ff9e8e520a
Last Breaking-Event-Address:
 [<0000000000156342>] dma_update_cpu_trans+0x9a/0xa8
---[ end trace 35996336235145c8 ]---
BUG: Bad page state in process jbd2/dasdb1-8  pfn:3215b
page:000003d100c856c0 count:-1 mapcount:0 mapping:          (null) index:0x0
flags: 0x3fffc0000000000()
page dumped because: nonzero _count
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>