Hi Shaohua,
On Wed, Mar 1, 2017 at 7:37 AM, Shaohua Li <shli@xxxxxxxxxx> wrote:
> On Tue, Feb 28, 2017 at 11:41:36PM +0800, Ming Lei wrote:
>> Now we allocate one page array for managing resync pages, instead
>> of using bio's vec table to do that, and the old way is very hacky
>> and won't work any more if multipage bvec is enabled.
>>
>> The introduced cost is that we need to allocate (128 + 16) * raid_disks
>> bytes per r1_bio, and it is fine because the inflight r1_bio for
>> resync shouldn't be much, as pointed by Shaohua.
>>
>> Also the bio_reset() in raid1_sync_request() is removed because
>> all bios are freshly new now and not necessary to reset any more.
>>
>> This patch can be thought as a cleanup too
>>
>> Suggested-by: Shaohua Li <shli@xxxxxxxxxx>
>> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
>> ---
>> drivers/md/raid1.c | 83 ++++++++++++++++++++++++++++++++++--------------------
>> 1 file changed, 53 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
>> index c442b4657e2f..900144f39630 100644
>> --- a/drivers/md/raid1.c
>> +++ b/drivers/md/raid1.c
>> @@ -77,6 +77,16 @@ static void lower_barrier(struct r1conf *conf, sector_t sector_nr);
>> #define raid1_log(md, fmt, args...) \
>> do { if ((md)->queue) blk_add_trace_msg((md)->queue, "raid1 " fmt, ##args); } while (0)
>>
>> +static inline struct resync_pages *get_resync_pages(struct bio *bio)
>> +{
>> + return bio->bi_private;
>> +}
>> +
>> +static inline struct r1bio *get_resync_r1bio(struct bio *bio)
>> +{
>> + return get_resync_pages(bio)->raid_bio;
>> +}
>
> This is a weird between bio, r1bio and the resync_pages. I'd like the pages are
It is only a bit weird inside allocating and freeing r1bio, once all
are allocated, you
can see everthing is clean and simple:
- r1bio includes lots of bioes,
- and one bio is attached by one resync_pages via .bi_private
> embedded in r1bio. Maybe a pointer of r1bio to the pages. It's cleaner and more
> straightforward.
In theory, the cleanest way is to allocate one resync_pages for each resync bio,
but that isn't efficient. That is why this patch allocates all
resync_pages together
in r1buf_pool_alloc(), and split them into bio.
BTW, the only trick is just that the whole page array is stored in .bi_private
of the 1st bio, then we can avoid to add one pointer into r1bio.
>
> I think the patch 6, 7 8 should be in a same patch. Otherwise bisect will be broken.
>
No, it won't. Both patch 7 and patch 8 just replacing reading from bvec table
with reading from the pre-allocated page array. Both should be fine, but the
latter is cleaner and simpler to do.
Thanks,
Ming
