> -----Original Message----- > From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] > Sent: Monday, August 18, 2014 5:57 PM > To: Gao, Yunpeng > Cc: linux-mmc; Dong, Chuanxiao > Subject: Re: [PATCH] mmc: core: resolve divded by zero panic > > On 14 August 2014 12:29, Yunpeng Gao <yunpeng.gao@xxxxxxxxx> wrote: > > From: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> > > > > With one special SD card, below divide by zero error observed: > > ... > > [ 2.144300] divide error: 0000 [#1] PREEMPT SMP > > [ 2.148860] Modules linked in: > > [ 2.151898] > > [ 2.152685] Set up 4031 stolen pages starting at 0x0001f000, GTT offset > 0K > > [ 2.157330] Set up 0 CI stolen pages starting at 0x00000000, GTT offset > 131072K > > [ 2.167581] Pid: 5, comm: kworker/u:0 Not tainted > 3.0.8-138216-g974a2ab #1 > > [ 2.169506] [drm] PSB GTT mem manager ready, tt_start 4031, tt_size > 28737 pages > > [ 2.169906] [drm] SGX core id = 0x00000000 > > [ 2.169920] [drm] SGX core rev major = 0x00, minor = 0x00 > > [ 2.169934] [drm] SGX core rev maintenance = 0x00, designer = 0x00 > > [ 2.197370] Intel Corporation Medfield/iCDKB > > [ 2.201716] EIP: 0060:[<c1697ca6>] EFLAGS: 00010246 CPU: 1 > > [ 2.207198] EIP is at mmc_init_erase+0x76/0x150 > > [ 2.211704] EAX: 00002000 EBX: dcd1b400 ECX: 00002000 EDX: > 00000000 > > [ 2.217957] ESI: 00000000 EDI: dcd5c800 EBP: dd867e84 ESP: dd867e7c > > [ 2.224214] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 > > [ 2.229605] Process kworker/u:0 (pid: 5, ti=dd866000 task=dd868000 > task.ti=dd866000) > > [ 2.237325] Stack: > > [ 2.239322] dcd1b400 00000000 dd867eb0 c16a06da c1ab7c44 > dd995aa8 00000003 00000000 > > [ 2.247054] 00000000 00000000 dcd5c800 00000000 dcd1b400 > dd867ef8 c16a1012 c1698b00 > > [ 2.254785] 00000029 00000001 c194eb80 dcd5c9ec dd867e00 > c1239b00 00000000 00000000 > > [ 2.262519] Call Trace: > > [ 2.264975] [<c16a06da>] mmc_sd_setup_card+0x1da/0x4f0 > > [ 2.270183] [<c16a1012>] mmc_sd_init_card+0x192/0xc40 > > [ 2.275304] [<c1698b00>] ? __mmc_claim_host+0x160/0x160 > > [ 2.280610] [<c1239b00>] ? __schedule_bug+0x50/0x80 > > [ 2.285556] [<c16a1b89>] mmc_attach_sd+0xc9/0x230 > > [ 2.290333] [<c169b6ef>] mmc_rescan+0x25f/0x2c0 > > [ 2.294943] [<c1274223>] process_one_work+0x103/0x400 > > [ 2.300065] [<c12670fd>] ? mod_timer+0x1ad/0x3c0 > > [ 2.304756] [<c169b490>] ? mmc_suspend_host+0x1a0/0x1a0 > > [ 2.310056] [<c127502d>] worker_thread+0x12d/0x4a0 > > [ 2.314921] [<c18fcfbd>] ? preempt_schedule+0x2d/0x50 > > [ 2.320047] [<c1274f00[ 2.323976] ---[ end trace > 5398ec2720494438 ]--- > > ... > > > > So, seems this bad SD card does not set valid value in related SSR / CSD > register fields. > > And then the driver will set card->erase_size to 0. > > Then it triggered this divided by zero error when calculate card->pref_erase. > > > > Submit this patch to fix the issue. > > > > Signed-off-by: Yunpeng Gao <yunpeng.gao@xxxxxxxxx> > > Signed-off-by: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> > > --- > > drivers/mmc/core/core.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index > > 7dc0c85..385373db 100644 > > --- a/drivers/mmc/core/core.c > > +++ b/drivers/mmc/core/core.c > > @@ -1761,7 +1761,7 @@ void mmc_init_erase(struct mmc_card *card) > > card->erase_shift = ffs(card->ssr.au) - 1; > > } else if (card->ext_csd.hc_erase_size) { > > card->pref_erase = card->ext_csd.hc_erase_size; > > - } else { > > + } else if (card->erase_size) { > > sz = (card->csd.capacity << (card->csd.read_blkbits - 9)) >> > 11; > > if (sz < 128) > > card->pref_erase = 512 * 1024 / 512; @@ > > -1778,7 +1778,8 @@ void mmc_init_erase(struct mmc_card *card) > > if (sz) > > card->pref_erase += > card->erase_size - sz; > > } > > - } > > + } else > > + card->pref_erase = 0; > > } > > > > Overall this seems like a good idea. Though I wonder what happens with the > QUEUE_FLAG_DISCARD? I suppose we would to prevent it from being set when > initiating the blk dev queue, right? In mmc_init_queue() of file queue.c, it will first check 'if (mmc_can_erase(card))' and then call mmc_queue_setup_discard(), and which function will set QUEUE_FLAG_DISCARD flag. Since inside mmc_can_erase(card), it will check 'card->erase_size' and will return '0' if 'card->erase_size' is 0, that means QUEUE_FLAG_DISCARD flag will not be set if 'card->erase_size' is 0. So, yes, if this case - to SD card, 'card->erase_size' is 0 - then QUEUE_FLAG_DISCARD flag will not be set. This has already been implemented in current driver. Thanks. Yunpeng > Kind regards > Uffe ��.n��������+%������w��{.n�����{��i��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
