How do we handle the same but uptodated data to disk cache?

["bmoon" <bo@anthologysolutions.com>]

Hello,

I want to write the data to the fixed sector with the same size frequently
just like MD super block, but I do not want to sync and flush the dev
on each write.

For example, to write md super block in /drivers/md/md.c

we do

        fsync_dev(dev);
        bh=getblk(dev, block, size);

        mark_buffer_uptodate(bh,1);
        mark_buffer_dirty(bh);
        ll_rw_block(WRITE,1, &bh);
        wait_on_buffer(bh);
        brelse(bh);
        fsync_dev(dev);

Instead, Can I do as follow

        bh=getblk(dev, block, size);
        if (buffer_uptodate(bh)) { /* still in cache, not flushed yet */
           bh->b_data = new SB data;
            brelse(bh);
        }
        else { /* it must be flushed */
            same as in above
       }

Please provide me your openion or suggestions.

Thanks in advance,

Bo