On Mon, Jul 27, 2020 at 6:18 PM Xiao Ni <xni@xxxxxxxxxx> wrote:
>
>
>
> On 07/28/2020 01:33 AM, Song Liu wrote:
> > On Tue, Jun 30, 2020 at 12:55 AM Xiao Ni <xni@xxxxxxxxxx> wrote:
> >> One super1.0 raid array wants to grow size, it needs to check the device max usable
> >> size. If the requested size is bigger than max usable size, it will return an error.
> >>
> >> Now it uses rdev->sectors for max usable size. If one disk is 500G and the raid device
> >> only uses the 100GB of this disk. rdev->sectors can't tell the real max usable size.
> >> The max usable size should be dev_size-(superblock_size+bitmap_size+badblock_size).
> >>
> >> Signed-off-by: Xiao Ni <xni@xxxxxxxxxx>
> > Thanks for the fix!
> >
> >> ---
> >> drivers/md/md.c | 26 +++++++++++++++++++++++---
> >> 1 file changed, 23 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/md/md.c b/drivers/md/md.c
> >> index f567f53..d2c5984 100644
> >> --- a/drivers/md/md.c
> >> +++ b/drivers/md/md.c
> >> @@ -2183,10 +2183,30 @@ super_1_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
> >> return 0;
> >> } else {
> >> /* minor version 0; superblock after data */
> >> - sector_t sb_start;
> >> - sb_start = (i_size_read(rdev->bdev->bd_inode) >> 9) - 8*2;
> >> + sector_t sb_start, bm_space;
> >> + sector_t dev_size = i_size_read(rdev->bdev->bd_inode) >> 9;
> >> +
> >> + /* 8K is for superblock */
> >> + sb_start = dev_size - 8*2;
> >> sb_start &= ~(sector_t)(4*2 - 1);
> >> - max_sectors = rdev->sectors + sb_start - rdev->sb_start;
> >> +
> >> + /* if the device is bigger than 8Gig, save 64k for bitmap usage,
> >> + * if bigger than 200Gig, save 128k
> >> + */
> >> + if (dev_size < 64*2)
> >> + bm_space = 0;
> >> + else if (dev_size - 64*2 >= 200*1024*1024*2)
> >> + bm_space = 128*2;
> >> + else if (dev_size - 4*2 > 8*1024*1024*2)
> >> + bm_space = 64*2;
> >> + else
> >> + bm_space = 4*2;
> > Could you explain the handling of bitmap space?
> Hi Song
>
> This calculation of bitmap is decided by mdadm. In mdadm super1.c
> choose_bm_space function,
> it uses this way to calculate bitmap space. Do I need to add comments
> here to describe this?
> Something like "mdadm function choose_bm_space decides the bitmap space"?
Thanks for the explanation.
I merged the two patches, made some changes, and applied it to md-next. Please
let me know whether it looks good.
Song
