Hi, Jens Axboe, Alasdair Kergon, Mike Snitzer: What's your opinion? On 2020/8/21 15:05, Coly Li wrote: > On 2020/8/21 14:48, Leizhen (ThunderTown) wrote: >> >> >> On 8/21/2020 12:11 PM, Coly Li wrote: >>> On 2020/8/21 10:03, Zhen Lei wrote: >>>> There are too many PAGE_SECTORS definitions, and all of them are the >>>> same. It looks a bit of a mess. So why not move it into <linux/blkdev.h>, >>>> to achieve a basic and unique definition. >>>> >>>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx> >>> >>> >>> A lazy question about page size > 4KB: currently in bcache code the >>> sector size is assumed to be 512 sectors, if kernel page > 4KB, it is >>> possible that PAGE_SECTORS in bcache will be a number > 8 ? >> >> Sorry, I don't fully understand your question. I known that the sector size >> can be 512 or 4K, and the PAGE_SIZE can be 4K or 64K. So even if sector size >> is 4K, isn't it greater than 8 for 64K pages? >> >> I'm not sure if the question you're asking is the one Matthew Wilcox has >> answered before: >> https://www.spinics.net/lists/raid/msg64345.html > > Thank you for the above information. Currently bcache code assumes > sector size is always 512 bytes, you may see how many "<< 9" or ">> 9" > are used. Therefore I doubt whether current code may stably work on e.g. > 4Kn SSDs (this is only doubt because I don't have such SSD). > > Anyway your patch is fine to me. This change to bcache doesn't make > thins worse or better, maybe it can be helpful to trigger my above > suspicious early if people do have this kind of problem on 4Kn sector SSDs. > > For the bcache part of this patch, you may add, > Acked-by: Coly Li <colyli@xxxxxxx> > > Thanks. > > Coly Li > >>>> --- >>>> drivers/block/brd.c | 1 - >>>> drivers/block/null_blk_main.c | 1 - >>>> drivers/md/bcache/util.h | 2 -- >>>> include/linux/blkdev.h | 5 +++-- >>>> include/linux/device-mapper.h | 1 - >>>> 5 files changed, 3 insertions(+), 7 deletions(-) >>>> >>> >>> [snipped] >>> >>>> diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h >>>> index c029f7443190805..55196e0f37c32c6 100644 >>>> --- a/drivers/md/bcache/util.h >>>> +++ b/drivers/md/bcache/util.h >>>> @@ -15,8 +15,6 @@ >>>> >>>> #include "closure.h" >>>> >>>> -#define PAGE_SECTORS (PAGE_SIZE / 512) >>>> - >>>> struct closure; >>>> >>>> #ifdef CONFIG_BCACHE_DEBUG >>>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h >>>> index bb5636cc17b91a7..b068dfc5f2ef0ab 100644 >>>> --- a/include/linux/blkdev.h >>>> +++ b/include/linux/blkdev.h >>>> @@ -949,11 +949,12 @@ static inline struct request_queue *bdev_get_queue(struct block_device *bdev) >>>> * multiple of 512 bytes. Hence these two constants. >>>> */ >>>> #ifndef SECTOR_SHIFT >>>> -#define SECTOR_SHIFT 9 >>>> +#define SECTOR_SHIFT 9 >>>> #endif >>>> #ifndef SECTOR_SIZE >>>> -#define SECTOR_SIZE (1 << SECTOR_SHIFT) >>>> +#define SECTOR_SIZE (1 << SECTOR_SHIFT) >>>> #endif >>>> +#define PAGE_SECTORS (PAGE_SIZE / SECTOR_SIZE) >>>> >>>> /* >>>> * blk_rq_pos() : the current sector >>> [snipped] >>> >>> >> > > > . >
