On Tue, Aug 18, 2020 at 04:53:05PM +0100, Matthew Wilcox wrote: > On Tue, Aug 18, 2020 at 09:46:18PM +0800, Yu Kuai wrote: > > changes from v1: > > - separate set dirty and clear dirty functions > > - don't test uptodate bit in iomap_writepage_map() > > - use one bitmap array for uptodate and dirty. > > This looks much better. > > > + spinlock_t state_lock; > > + /* > > + * The first half bits are used to track sub-page uptodate status, > > + * the second half bits are for dirty status. > > + */ > > + DECLARE_BITMAP(state, PAGE_SIZE / 256); > > It would be better to use the same wording as below: > > > + bitmap_zero(iop->state, PAGE_SIZE * 2 / SECTOR_SIZE);
ISTR there was some reason why '512' was hardcoded in here instead of SECTOR_SIZE. I /think/ it was so that iomap.h did not then have a hard dependency on blkdev.h and everything else that requires... https://lore.kernel.org/linux-xfs/20181215105155.gd1...@lst.de/ --D > > [...] > > > +static void > > +iomap_iop_set_range_dirty(struct page *page, unsigned int off, > > + unsigned int len) > > +{ > > + struct iomap_page *iop = to_iomap_page(page); > > + struct inode *inode = page->mapping->host; > > + unsigned int total = PAGE_SIZE / SECTOR_SIZE; > > + unsigned int first = off >> inode->i_blkbits; > > + unsigned int last = (off + len - 1) >> inode->i_blkbits; > > + unsigned long flags; > > + unsigned int i; > > + > > + spin_lock_irqsave(&iop->state_lock, flags); > > + for (i = first; i <= last; i++) > > + set_bit(i + total, iop->state); > > + spin_unlock_irqrestore(&iop->state_lock, flags); > > +} > > How about: > > - unsigned int total = PAGE_SIZE / SECTOR_SIZE; > ... > + first += PAGE_SIZE / SECTOR_SIZE; > + last += PAGE_SIZE / SECTOR_SIZE; > ... > for (i = first; i <= last; i++) > - set_bit(i + total, iop->state); > + set_bit(i, iop->state); > > We might want > > #define DIRTY_BITS(x) ((x) + PAGE_SIZE / SECTOR_SIZE) > > and then we could do: > > + unsigned int last = DIRTY_BITS((off + len - 1) >> inode->i_blkbits); > > That might be overthinking things a bit though. > > > @@ -705,6 +767,7 @@ __iomap_write_end(struct inode *inode, loff_t pos, > > unsigned len, > > if (unlikely(copied < len && !PageUptodate(page))) > > return 0; > > iomap_set_range_uptodate(page, offset_in_page(pos), len); > > + iomap_set_range_dirty(page, offset_in_page(pos), len); > > iomap_set_page_dirty(page); > > I would move the call to iomap_set_page_dirty() into > iomap_set_range_dirty() to parallel iomap_set_range_uptodate more closely. > We don't want a future change to add a call to iomap_set_range_dirty() > and miss the call to iomap_set_page_dirty(). > > > return copied; > > } > > @@ -1030,6 +1093,7 @@ iomap_page_mkwrite_actor(struct inode *inode, loff_t > > pos, loff_t length, > > WARN_ON_ONCE(!PageUptodate(page)); > > iomap_page_create(inode, page); > > set_page_dirty(page); > > + iomap_set_range_dirty(page, offset_in_page(pos), length); > > I would move all this from the mkwrite_actor() to iomap_page_mkwrite() > and call it once with (0, PAGE_SIZE) rather than calling it once for > each extent in the page. > > > @@ -1435,6 +1500,8 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc, > > */ > > set_page_writeback_keepwrite(page); > > } else { > > + iomap_clear_range_dirty(page, 0, > > + end_offset - page_offset(page) + 1); > > clear_page_dirty_for_io(page); > > set_page_writeback(page); > > I'm not sure it's worth doing this calculation. Better to just clear > the dirty bits on the entire page? Opinions?
