Messages in this thread | | | Date | Fri, 21 Aug 2020 07:17:52 +0100 | From | Christoph Hellwig <> | Subject | Re: [RFC PATCH V3] iomap: add support to track dirty state of sub pages |
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> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index bcfc288dba3f..b6a7457d8581 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -21,15 +21,20 @@ > > #include "../internal.h" > > +#define DIRTY_BITS(x) ((x) + PAGE_SIZE / SECTOR_SIZE) > /*
Nit: please keep an empty line between a definition and a comment.
> + * 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 * 2 / SECTOR_SIZE); > }; > > static inline struct iomap_page *to_iomap_page(struct page *page) > @@ -52,8 +57,8 @@ iomap_page_create(struct inode *inode, struct page *page) > iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL); > atomic_set(&iop->read_count, 0); > atomic_set(&iop->write_count, 0); > - spin_lock_init(&iop->uptodate_lock); > - bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE); > + spin_lock_init(&iop->state_lock); > + bitmap_zero(iop->state, PAGE_SIZE * 2 / SECTOR_SIZE);
Maybe add a
#define IOMAP_STATE_ARRAY_SIZE (PAGE_SIZE * 2 / SECTOR_SIZE)
and use? That isn't much shorter, but a little easier to read at least.
> + spin_lock_irqsave(&iop->state_lock, flags); > + for (i = first; i <= last; i++) > + set_bit(i, iop->state);
I think Matthew had some patches to move the these days pointlessly atomic bitops to use the bitmap_* routines. It might make sense to start out that way for new code as well.
> + > + if (last >= first) > + iomap_set_page_dirty(page); > + > + spin_unlock_irqrestore(&iop->state_lock, flags);
As aready pointed out, this probably needs to move out of the lock.
> +static void > +iomap_set_range_dirty(struct page *page, unsigned int off, > + unsigned int len) > +{ > + if (PageError(page)) > + return; > + > + if (page_has_private(page)) > + iomap_iop_set_range_dirty(page, off, len);
I'd be tempted to merge this function and iomap_iop_set_range_dirty, and just return early if there is an error or no iomap_page structure, relying on the fact that to_iomap_page returns NULL for that case.
> +static void > +iomap_iop_clear_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 first = DIRTY_BITS(off >> inode->i_blkbits); > + unsigned int last = DIRTY_BITS((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++) > + clear_bit(i, iop->state);
should probably use bitmap_clear().
> +static void > +iomap_clear_range_dirty(struct page *page, unsigned int off, > + unsigned int len) > +{ > + if (PageError(page)) > + return; > + > + if (page_has_private(page)) > + iomap_iop_clear_range_dirty(page, off, len); > +}
Same comment about merging the two functions as above.
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