by Josh Boyer

[permalink] [raw]

Subject: Re: cgroup/loop Bad page state oops in Linux v4.2-rc3-136-g45b4b782e848

On Mon, Aug 3, 2015 at 12:56 PM, Josh Boyer <[email protected]> wrote:
> On Mon, Aug 3, 2015 at 10:28 AM, Mike Snitzer <[email protected]> wrote:
>> On Sun, Aug 02 2015 at 10:01P -0400,
>> Josh Boyer <[email protected]> wrote:
>>
>>> On Fri, Jul 31, 2015 at 2:58 PM, Josh Boyer <[email protected]> wrote:
>>> > On Thu, Jul 30, 2015 at 8:19 PM, Mike Snitzer <[email protected]> wrote:
>>> >>
>>> >> The only commit that looks even remotely related (given 32bit concerns)
>>> >> would be 1c220c69ce0dcc0f234a9f263ad9c0864f971852
>>> >
>>> > Confirmed. I built kernels for our tester that started with the
>>> > working snapshot and applied the patches above one at a time. The
>>> > failing patch was the commit you suspected.
>>> >
>>> > I can try and build a 4.2-rc4 kernel with that reverted, but it would
>>> > be good if someone could start thinking about how that could cause
>>> > this issue.
>>>
>>> A revert on top of 4.2-rc4 booted. So this is currently causing
>>> issues with upstream as well.
>>
>> Hi Josh,
>>
>> I've staged the following fix in linux-next (for 4.2-rc6 inclusion):
>> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=76270d574acc897178a5c8be0bd2a743a77e4bac
>>
>> Can you please verify that it works for your 32bit testcase against
>> 4.2-rc4 (or rc5)?
>
> Sure, I'll get a kernel with this included spun up and ask Adam to test.

Adam tested this with success. If you're still collecting patch
metadata, adding:

Tested-by: Adam Williamson <[email protected]>

would be appreciated.

josh

>> From: Mike Snitzer <[email protected]>
>> Date: Mon, 3 Aug 2015 09:54:58 -0400
>> Subject: [PATCH] dm: fix dm_merge_bvec regression on 32 bit systems
>>
>> A DM regression on 32 bit systems was reported against v4.2-rc3 here:
>> https://lkml.org/lkml/2015/7/29/401
>>
>> Fix this by reverting both commit 1c220c69 ("dm: fix casting bug in
>> dm_merge_bvec()") and 148e51ba ("dm: improve documentation and code
>> clarity in dm_merge_bvec"). This combined revert is done to eliminate
>> the possibility of a partial revert in stable@ kernels.
>>
>> In hindsight the correct fix, at the time 1c220c69 was applied to fix
>> the regression that 148e51ba introduced, should've been to simply revert
>> 148e51ba.
>>
>> Reported-by: Josh Boyer <[email protected]>
>> Acked-by: Joe Thornber <[email protected]>
>> Signed-off-by: Mike Snitzer <[email protected]>
>> Cc: [email protected] # 3.19+
>> ---
>> drivers/md/dm.c | 27 ++++++++++-----------------
>> 1 file changed, 10 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>> index ab37ae1..0d7ab20 100644
>> --- a/drivers/md/dm.c
>> +++ b/drivers/md/dm.c
>> @@ -1729,7 +1729,8 @@ static int dm_merge_bvec(struct request_queue *q,
>> struct mapped_device *md = q->queuedata;
>> struct dm_table *map = dm_get_live_table_fast(md);
>> struct dm_target *ti;
>> - sector_t max_sectors, max_size = 0;
>> + sector_t max_sectors;
>> + int max_size = 0;
>>
>> if (unlikely(!map))
>> goto out;
>> @@ -1742,18 +1743,10 @@ static int dm_merge_bvec(struct request_queue *q,
>> * Find maximum amount of I/O that won't need splitting
>> */
>> max_sectors = min(max_io_len(bvm->bi_sector, ti),
>> - (sector_t) queue_max_sectors(q));
>> + (sector_t) BIO_MAX_SECTORS);
>> max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
>> -
>> - /*
>> - * FIXME: this stop-gap fix _must_ be cleaned up (by passing a sector_t
>> - * to the targets' merge function since it holds sectors not bytes).
>> - * Just doing this as an interim fix for stable@ because the more
>> - * comprehensive cleanup of switching to sector_t will impact every
>> - * DM target that implements a ->merge hook.
>> - */
>> - if (max_size > INT_MAX)
>> - max_size = INT_MAX;
>> + if (max_size < 0)
>> + max_size = 0;
>>
>> /*
>> * merge_bvec_fn() returns number of bytes
>> @@ -1761,13 +1754,13 @@ static int dm_merge_bvec(struct request_queue *q,
>> * max is precomputed maximal io size
>> */
>> if (max_size && ti->type->merge)
>> - max_size = ti->type->merge(ti, bvm, biovec, (int) max_size);
>> + max_size = ti->type->merge(ti, bvm, biovec, max_size);
>> /*
>> * If the target doesn't support merge method and some of the devices
>> - * provided their merge_bvec method (we know this by looking for the
>> - * max_hw_sectors that dm_set_device_limits may set), then we can't
>> - * allow bios with multiple vector entries. So always set max_size
>> - * to 0, and the code below allows just one page.
>> + * provided their merge_bvec method (we know this by looking at
>> + * queue_max_hw_sectors), then we can't allow bios with multiple vector
>> + * entries. So always set max_size to 0, and the code below allows
>> + * just one page.
>> */
>> else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
>> max_size = 0;
>> --
>> 2.3.2 (Apple Git-55)
>>