On Mon, Sep 09 2019, Guoqing Jiang wrote:
> On 9/9/19 8:57 AM, NeilBrown wrote:
>>
>> If the drives in a RAID0 are not all the same size, the array is
>> divided into zones.
>> The first zone covers all drives, to the size of the smallest.
>> The second zone covers all drives larger than the smallest, up to
>> the size of the second smallest - etc.
>>
>> A change in Linux 3.14 unintentionally changed the layout for the
>> second and subsequent zones. All the correct data is still stored, but
>> each chunk may be assigned to a different device than in pre-3.14 kernels.
>> This can lead to data corruption.
>>
>> It is not possible to determine what layout to use - it depends which
>> kernel the data was written by.
>> So we add a module parameter to allow the old (0) or new (1) layout to be
>> specified, and refused to assemble an affected array if that parameter is
>> not set.
>>
>> Fixes: 20d0189b1012 ("block: Introduce new bio_split()")
>> cc: sta...@vger.kernel.org (3.14+)
>> Signed-off-by: NeilBrown <ne...@suse.de>
>> ---
>>
>> This and the next patch are my proposal for how to address
>> this problem. I haven't actually tested .....
>>
>> NeilBrown
>>
>> drivers/md/raid0.c | 28 +++++++++++++++++++++++++++-
>> drivers/md/raid0.h | 14 ++++++++++++++
>> 2 files changed, 41 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
>> index bf5cf184a260..a8888c12308a 100644
>> --- a/drivers/md/raid0.c
>> +++ b/drivers/md/raid0.c
>> @@ -19,6 +19,9 @@
>> #include "raid0.h"
>> #include "raid5.h"
>>
>> +static int default_layout = -1;
>> +module_param(default_layout, int, 0644);
>> +
>> #define UNSUPPORTED_MDDEV_FLAGS \
>> ((1L << MD_HAS_JOURNAL) | \
>> (1L << MD_JOURNAL_CLEAN) | \
>> @@ -139,6 +142,19 @@ static int create_strip_zones(struct mddev *mddev,
>> struct r0conf **private_conf)
>> }
>> pr_debug("md/raid0:%s: FINAL %d zones\n",
>> mdname(mddev), conf->nr_strip_zones);
>> +
>> + if (conf->nr_strip_zones == 1) {
>> + conf->layout = RAID0_ORIG_LAYOUT;
>> + } else if (default_layout == RAID0_ORIG_LAYOUT ||
>> + default_layout == RAID0_ALT_MULTIZONE_LAYOUT) {
>> + conf->layout = default_layout;
>> + } else {
>> + pr_err("md/raid0:%s: cannot assemble multi-zone RAID0 with
>> default_layout setting\n",
>> + mdname(mddev));
>> + pr_err("md/raid0: please set raid.default_layout to 0 or 1\n");
>
> Maybe "1 or 2" to align with the definition of below r0layout?
Thanks. Fixed.
NeilBrown
>
> [snip]
>
>> +enum r0layout {
>> + RAID0_ORIG_LAYOUT = 1,
>> + RAID0_ALT_MULTIZONE_LAYOUT = 2,
>> +};
>> struct r0conf {
>> struct strip_zone *strip_zone;
>> struct md_rdev **devlist; /* lists of rdevs, pointed to
>> * by strip_zone->dev */
>> int nr_strip_zones;
>> + enum r0layout layout;
>> };
>>
>> #endif
>>
>
> Thanks,
> Guoqing
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