Re: [PATCHv7 3/6] iomap: Refactor some iop related accessor functions

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Jun 05, 2023 at 04:25:03PM +0530, Ritesh Harjani (IBM) wrote:
> We would eventually use iomap_iop_** function naming by the rest of the
> buffered-io iomap code. This patch update function arguments and naming
> from iomap_set_range_uptodate() -> iomap_iop_set_range_uptodate().
> iop_set_range_uptodate() then becomes an accessor function used by
> iomap_iop_** functions.
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>  fs/iomap/buffered-io.c | 111 +++++++++++++++++++++++------------------
>  1 file changed, 63 insertions(+), 48 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 6fffda355c45..136f57ccd0be 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -24,14 +24,14 @@
>  #define IOEND_BATCH_SIZE	4096
>  
>  /*
> - * Structure allocated for each folio when block size < folio size
> - * to track sub-folio uptodate status and I/O completions.
> + * Structure allocated for each folio to track per-block uptodate state
> + * and I/O completions.
>   */
>  struct iomap_page {
>  	atomic_t		read_bytes_pending;
>  	atomic_t		write_bytes_pending;
> -	spinlock_t		uptodate_lock;
> -	unsigned long		uptodate[];
> +	spinlock_t		state_lock;
> +	unsigned long		state[];
>  };
>  
>  static inline struct iomap_page *to_iomap_page(struct folio *folio)
> @@ -43,6 +43,48 @@ static inline struct iomap_page *to_iomap_page(struct folio *folio)
>  
>  static struct bio_set iomap_ioend_bioset;
>  
> +static bool iop_test_full_uptodate(struct folio *folio)

Same comment as Andreas, I think this works better with 'fully', e.g.

iop_test_fully_uptodate()

Why you don't pass the iomap_page directly into this function?  Doesn't
that eliminate the need for iomap_iop_free to keep folio->private set
until the very end?

static inline bool
iomap_iop_is_fully_uptodate(const struct iomap_page *iop,
			    const struct folio *folio)

Same sort of thing for the second function -- we already extracted
folio->private and checked it wasn't null, so we don't need to do that
again.

static inline bool
iomap_io_is_block_uptodate(const struct iomap_page *iop,
			   const struct folio *folio,
			   unsigned int block)

> +{
> +	struct iomap_page *iop = to_iomap_page(folio);
> +	struct inode *inode = folio->mapping->host;
> +
> +	return bitmap_full(iop->state, i_blocks_per_folio(inode, folio));
> +}
> +
> +static bool iop_test_block_uptodate(struct folio *folio, unsigned int block)
> +{
> +	struct iomap_page *iop = to_iomap_page(folio);
> +
> +	return test_bit(block, iop->state);
> +}
> +
> +static void iop_set_range_uptodate(struct inode *inode, struct folio *folio,
> +				   size_t off, size_t len)
> +{
> +	struct iomap_page *iop = to_iomap_page(folio);
> +	unsigned int first_blk = off >> inode->i_blkbits;
> +	unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
> +	unsigned int nr_blks = last_blk - first_blk + 1;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&iop->state_lock, flags);
> +	bitmap_set(iop->state, first_blk, nr_blks);
> +	if (iop_test_full_uptodate(folio))
> +		folio_mark_uptodate(folio);
> +	spin_unlock_irqrestore(&iop->state_lock, flags);
> +}
> +
> +static void iomap_iop_set_range_uptodate(struct inode *inode,

I don't understand why iomap_set_range_uptodate is now
iomap_iop_set_range_uptodate; it doesn't take an iomap_page object as an
argument...?

I thought I understood that iomap_FOO operates on a folio and a range,
whereas iomap_iop_FOO operates on sub-blocks within a folio?  And that
you were renaming the iop_* functions to iomap_iop_*?

I'm also not sure why iop_set_range_uptodate needs to be passed the
struct inode; can't it extract that from folio->mapping->host, like
current upstream does?

Generally I don't understand why this part of the patch is needed at
all.  Wasn't the point merely to rename uptodate_* to state_* and
introduce the iomap_iop_test_*_uptodate helpers?

--D

> +		struct folio *folio, size_t off, size_t len)
> +{
> +	struct iomap_page *iop = to_iomap_page(folio);
> +
> +	if (iop)
> +		iop_set_range_uptodate(inode, folio, off, len);
> +	else
> +		folio_mark_uptodate(folio);
> +}
> +
>  static struct iomap_page *iomap_iop_alloc(struct inode *inode,
>  				struct folio *folio, unsigned int flags)
>  {
> @@ -58,12 +100,12 @@ static struct iomap_page *iomap_iop_alloc(struct inode *inode,
>  	else
>  		gfp = GFP_NOFS | __GFP_NOFAIL;
>  
> -	iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
> +	iop = kzalloc(struct_size(iop, state, BITS_TO_LONGS(nr_blocks)),
>  		      gfp);
>  	if (iop) {
> -		spin_lock_init(&iop->uptodate_lock);
> +		spin_lock_init(&iop->state_lock);
>  		if (folio_test_uptodate(folio))
> -			bitmap_fill(iop->uptodate, nr_blocks);
> +			bitmap_fill(iop->state, nr_blocks);
>  		folio_attach_private(folio, iop);
>  	}
>  	return iop;
> @@ -72,14 +114,12 @@ static struct iomap_page *iomap_iop_alloc(struct inode *inode,
>  static void iomap_iop_free(struct folio *folio)
>  {
>  	struct iomap_page *iop = to_iomap_page(folio);
> -	struct inode *inode = folio->mapping->host;
> -	unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
>  
>  	if (!iop)
>  		return;
>  	WARN_ON_ONCE(atomic_read(&iop->read_bytes_pending));
>  	WARN_ON_ONCE(atomic_read(&iop->write_bytes_pending));
> -	WARN_ON_ONCE(bitmap_full(iop->uptodate, nr_blocks) !=
> +	WARN_ON_ONCE(iop_test_full_uptodate(folio) !=
>  			folio_test_uptodate(folio));
>  	folio_detach_private(folio);
>  	kfree(iop);
> @@ -111,7 +151,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  
>  		/* move forward for each leading block marked uptodate */
>  		for (i = first; i <= last; i++) {
> -			if (!test_bit(i, iop->uptodate))
> +			if (!iop_test_block_uptodate(folio, i))
>  				break;
>  			*pos += block_size;
>  			poff += block_size;
> @@ -121,7 +161,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  
>  		/* truncate len if we find any trailing uptodate block(s) */
>  		for ( ; i <= last; i++) {
> -			if (test_bit(i, iop->uptodate)) {
> +			if (iop_test_block_uptodate(folio, i)) {
>  				plen -= (last - i + 1) * block_size;
>  				last = i - 1;
>  				break;
> @@ -145,30 +185,6 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  	*lenp = plen;
>  }
>  
> -static void iomap_iop_set_range_uptodate(struct folio *folio,
> -		struct iomap_page *iop, size_t off, size_t len)
> -{
> -	struct inode *inode = folio->mapping->host;
> -	unsigned first = off >> inode->i_blkbits;
> -	unsigned last = (off + len - 1) >> inode->i_blkbits;
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&iop->uptodate_lock, flags);
> -	bitmap_set(iop->uptodate, first, last - first + 1);
> -	if (bitmap_full(iop->uptodate, i_blocks_per_folio(inode, folio)))
> -		folio_mark_uptodate(folio);
> -	spin_unlock_irqrestore(&iop->uptodate_lock, flags);
> -}
> -
> -static void iomap_set_range_uptodate(struct folio *folio,
> -		struct iomap_page *iop, size_t off, size_t len)
> -{
> -	if (iop)
> -		iomap_iop_set_range_uptodate(folio, iop, off, len);
> -	else
> -		folio_mark_uptodate(folio);
> -}
> -
>  static void iomap_finish_folio_read(struct folio *folio, size_t offset,
>  		size_t len, int error)
>  {
> @@ -178,7 +194,8 @@ static void iomap_finish_folio_read(struct folio *folio, size_t offset,
>  		folio_clear_uptodate(folio);
>  		folio_set_error(folio);
>  	} else {
> -		iomap_set_range_uptodate(folio, iop, offset, len);
> +		iomap_iop_set_range_uptodate(folio->mapping->host, folio,
> +					     offset, len);
>  	}
>  
>  	if (!iop || atomic_sub_and_test(len, &iop->read_bytes_pending))
> @@ -214,7 +231,6 @@ struct iomap_readpage_ctx {
>  static int iomap_read_inline_data(const struct iomap_iter *iter,
>  		struct folio *folio)
>  {
> -	struct iomap_page *iop;
>  	const struct iomap *iomap = iomap_iter_srcmap(iter);
>  	size_t size = i_size_read(iter->inode) - iomap->offset;
>  	size_t poff = offset_in_page(iomap->offset);
> @@ -232,15 +248,14 @@ static int iomap_read_inline_data(const struct iomap_iter *iter,
>  	if (WARN_ON_ONCE(size > iomap->length))
>  		return -EIO;
>  	if (offset > 0)
> -		iop = iomap_iop_alloc(iter->inode, folio, iter->flags);
> -	else
> -		iop = to_iomap_page(folio);
> +		iomap_iop_alloc(iter->inode, folio, iter->flags);
>  
>  	addr = kmap_local_folio(folio, offset);
>  	memcpy(addr, iomap->inline_data, size);
>  	memset(addr + size, 0, PAGE_SIZE - poff - size);
>  	kunmap_local(addr);
> -	iomap_set_range_uptodate(folio, iop, offset, PAGE_SIZE - poff);
> +	iomap_iop_set_range_uptodate(iter->inode, folio, offset,
> +				     PAGE_SIZE - poff);
>  	return 0;
>  }
>  
> @@ -277,7 +292,7 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
>  
>  	if (iomap_block_needs_zeroing(iter, pos)) {
>  		folio_zero_range(folio, poff, plen);
> -		iomap_set_range_uptodate(folio, iop, poff, plen);
> +		iomap_iop_set_range_uptodate(iter->inode, folio, poff, plen);
>  		goto done;
>  	}
>  
> @@ -452,7 +467,7 @@ bool iomap_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
>  	last = (from + count - 1) >> inode->i_blkbits;
>  
>  	for (i = first; i <= last; i++)
> -		if (!test_bit(i, iop->uptodate))
> +		if (!iop_test_block_uptodate(folio, i))
>  			return false;
>  	return true;
>  }
> @@ -591,7 +606,7 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>  			if (status)
>  				return status;
>  		}
> -		iomap_set_range_uptodate(folio, iop, poff, plen);
> +		iomap_iop_set_range_uptodate(iter->inode, folio, poff, plen);
>  	} while ((block_start += plen) < block_end);
>  
>  	return 0;
> @@ -698,7 +713,6 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
>  static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
>  		size_t copied, struct folio *folio)
>  {
> -	struct iomap_page *iop = to_iomap_page(folio);
>  	flush_dcache_folio(folio);
>  
>  	/*
> @@ -714,7 +728,8 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
>  	 */
>  	if (unlikely(copied < len && !folio_test_uptodate(folio)))
>  		return 0;
> -	iomap_set_range_uptodate(folio, iop, offset_in_folio(folio, pos), len);
> +	iomap_iop_set_range_uptodate(inode, folio, offset_in_folio(folio, pos),
> +				     len);
>  	filemap_dirty_folio(inode->i_mapping, folio);
>  	return copied;
>  }
> @@ -1630,7 +1645,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	 * invalid, grab a new one.
>  	 */
>  	for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
> -		if (iop && !test_bit(i, iop->uptodate))
> +		if (iop && !iop_test_block_uptodate(folio, i))
>  			continue;
>  
>  		error = wpc->ops->map_blocks(wpc, inode, pos);
> -- 
> 2.40.1
>