Commit a1d767c1 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: introduce helpers for subpage uptodate status 



Introduce the following functions to handle subpage uptodate status:

- btrfs_subpage_set_uptodate()
- btrfs_subpage_clear_uptodate()
- btrfs_subpage_test_uptodate()
  These helpers can only be called when the page has subpage attached
  and the range is ensured to be inside the page.

- btrfs_page_set_uptodate()
- btrfs_page_clear_uptodate()
- btrfs_page_test_uptodate()
  These helpers can handle both regular sector size and subpage.
  Although caller should still ensure that the range is inside the page.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 09bc1f0f

fs/btrfs/subpage.c

+113 −0
Original line number Diff line number Diff line
@@ -101,3 +101,116 @@ void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info, 
	ASSERT(atomic_read(&subpage->eb_refs));

	atomic_dec(&subpage->eb_refs);

}



/*

 * Convert the [start, start + len) range into a u16 bitmap

 *

 * For example: if start == page_offset() + 16K, len = 16K, we get 0x00f0.

 */

static u16 btrfs_subpage_calc_bitmap(const struct btrfs_fs_info *fs_info,

		struct page *page, u64 start, u32 len)

{

	const int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits;

	const int nbits = len >> fs_info->sectorsize_bits;



	/* Basic checks */

	ASSERT(PagePrivate(page) && page->private);

	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&

	       IS_ALIGNED(len, fs_info->sectorsize));



	/*

	 * The range check only works for mapped page, we can still have

	 * unmapped page like dummy extent buffer pages.

	 */

	if (page->mapping)

		ASSERT(page_offset(page) <= start &&

		       start + len <= page_offset(page) + PAGE_SIZE);

	/*

	 * Here nbits can be 16, thus can go beyond u16 range. We make the

	 * first left shift to be calculate in unsigned long (at least u32),

	 * then truncate the result to u16.

	 */

	return (u16)(((1UL << nbits) - 1) << bit_start);

}



void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info,

		struct page *page, u64 start, u32 len)

{

	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;

	const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);

	unsigned long flags;



	spin_lock_irqsave(&subpage->lock, flags);

	subpage->uptodate_bitmap |= tmp;

	if (subpage->uptodate_bitmap == U16_MAX)

		SetPageUptodate(page);

	spin_unlock_irqrestore(&subpage->lock, flags);

}



void btrfs_subpage_clear_uptodate(const struct btrfs_fs_info *fs_info,

		struct page *page, u64 start, u32 len)

{

	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;

	const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);

	unsigned long flags;



	spin_lock_irqsave(&subpage->lock, flags);

	subpage->uptodate_bitmap &= ~tmp;

	ClearPageUptodate(page);

	spin_unlock_irqrestore(&subpage->lock, flags);

}



/*

 * Unlike set/clear which is dependent on each page status, for test all bits

 * are tested in the same way.

 */

#define IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(name)				\

bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len)			\

{									\

	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; \

	const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); \

	unsigned long flags;						\

	bool ret;							\

									\

	spin_lock_irqsave(&subpage->lock, flags);			\

	ret = ((subpage->name##_bitmap & tmp) == tmp);			\

	spin_unlock_irqrestore(&subpage->lock, flags);			\

	return ret;							\

}

IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate);



/*

 * Note that, in selftests (extent-io-tests), we can have empty fs_info passed

 * in.  We only test sectorsize == PAGE_SIZE cases so far, thus we can fall

 * back to regular sectorsize branch.

 */

#define IMPLEMENT_BTRFS_PAGE_OPS(name, set_page_func, clear_page_func,	\

			       test_page_func)				\

void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\

		struct page *page, u64 start, u32 len)			\

{									\

	if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) {	\

		set_page_func(page);					\

		return;							\

	}								\

	btrfs_subpage_set_##name(fs_info, page, start, len);		\

}									\

void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len)			\

{									\

	if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) {	\

		clear_page_func(page);					\

		return;							\

	}								\

	btrfs_subpage_clear_##name(fs_info, page, start, len);		\

}									\

bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len)			\

{									\

	if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE)	\

		return test_page_func(page);				\

	return btrfs_subpage_test_##name(fs_info, page, start, len);	\

}

IMPLEMENT_BTRFS_PAGE_OPS(uptodate, SetPageUptodate, ClearPageUptodate,

			 PageUptodate);

fs/btrfs/subpage.h

+27 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
struct btrfs_subpage {

	/* Common members for both data and metadata pages */

	spinlock_t lock;

	u16 uptodate_bitmap;

	union {

		/*

		 * Structures only used by metadata
@@ -51,4 +52,30 @@ void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info, 
void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,

			    struct page *page);



/*

 * Template for subpage related operations.

 *

 * btrfs_subpage_*() are for call sites where the page has subpage attached and

 * the range is ensured to be inside the page.

 *

 * btrfs_page_*() are for call sites where the page can either be subpage

 * specific or regular page. The function will handle both cases.

 * But the range still needs to be inside the page.

 */

#define DECLARE_BTRFS_SUBPAGE_OPS(name)					\

void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len);			\

void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len);			\

bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len);			\

void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\

		struct page *page, u64 start, u32 len);			\

void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len);			\

bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,	\

		struct page *page, u64 start, u32 len);



DECLARE_BTRFS_SUBPAGE_OPS(uptodate);



#endif