btrfs: subpage: pack all subpage bitmaps into a larger bitmap

Currently we use u16 bitmap to make 4k sectorsize work for 64K page
size.

But this u16 bitmap is not large enough to contain larger page size like
128K, nor is space efficient for 16K page size.

To handle both cases, here we pack all subpage bitmaps into a larger
bitmap, now btrfs_subpage::bitmaps[] will be the ultimate bitmap for
subpage usage.

Each sub-bitmap will has its start bit number recorded in
btrfs_subpage_info::*_start, and its bitmap length will be recorded in
btrfs_subpage_info::bitmap_nr_bits.

All subpage bitmap operations will be converted from using direct u16
operations to bitmap operations, with above *_start calculated.

For 64K page size with 4K sectorsize, this should not cause much
difference.

While for 16K page size, we will only need 1 unsigned long (u32) to
store all the bitmaps, which saves quite some space.

Furthermore, this allows us to support larger page size like 128K and
258K.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 81 insertions, 45 deletions

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index f127bac6d610..51f873a680ea 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -133,10 +133,13 @@ struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
 					  enum btrfs_subpage_type type)
 {
 	struct btrfs_subpage *ret;
+	unsigned int real_size;
 
 	ASSERT(fs_info->sectorsize < PAGE_SIZE);
 
-	ret = kzalloc(sizeof(struct btrfs_subpage), GFP_NOFS);
+	real_size = struct_size(ret, bitmaps,
+			BITS_TO_LONGS(fs_info->subpage_info->total_nr_bits));
+	ret = kzalloc(real_size, GFP_NOFS);
 	if (!ret)
 		return ERR_PTR(-ENOMEM);
 
@@ -319,37 +322,59 @@ void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
 		unlock_page(page);
 }
 
-/*
- * 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)
+static bool bitmap_test_range_all_set(unsigned long *addr, unsigned int start,
+				      unsigned int nbits)
 {
-	const int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits;
-	const int nbits = len >> fs_info->sectorsize_bits;
+	unsigned int found_zero;
 
-	btrfs_subpage_assert(fs_info, page, start, len);
+	found_zero = find_next_zero_bit(addr, start + nbits, start);
+	if (found_zero == start + nbits)
+		return true;
+	return false;
+}
 
-	/*
-	 * 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);
+static bool bitmap_test_range_all_zero(unsigned long *addr, unsigned int start,
+				       unsigned int nbits)
+{
+	unsigned int found_set;
+
+	found_set = find_next_bit(addr, start + nbits, start);
+	if (found_set == start + nbits)
+		return true;
+	return false;
 }
 
+#define subpage_calc_start_bit(fs_info, page, name, start, len)		\
+({									\
+	unsigned int start_bit;						\
+									\
+	btrfs_subpage_assert(fs_info, page, start, len);		\
+	start_bit = offset_in_page(start) >> fs_info->sectorsize_bits;	\
+	start_bit += fs_info->subpage_info->name##_offset;		\
+	start_bit;							\
+})
+
+#define subpage_test_bitmap_all_set(fs_info, subpage, name)		\
+	bitmap_test_range_all_set(subpage->bitmaps,			\
+			fs_info->subpage_info->name##_offset,		\
+			fs_info->subpage_info->bitmap_nr_bits)
+
+#define subpage_test_bitmap_all_zero(fs_info, subpage, name)		\
+	bitmap_test_range_all_zero(subpage->bitmaps,			\
+			fs_info->subpage_info->name##_offset,		\
+			fs_info->subpage_info->bitmap_nr_bits)
+
 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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							uptodate, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->uptodate_bitmap |= tmp;
-	if (subpage->uptodate_bitmap == U16_MAX)
+	bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+	if (subpage_test_bitmap_all_set(fs_info, subpage, uptodate))
 		SetPageUptodate(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -358,11 +383,12 @@ 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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							uptodate, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->uptodate_bitmap &= ~tmp;
+	bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
 	ClearPageUptodate(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -371,11 +397,12 @@ void btrfs_subpage_set_error(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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							error, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->error_bitmap |= tmp;
+	bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
 	SetPageError(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -384,12 +411,13 @@ void btrfs_subpage_clear_error(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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							error, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->error_bitmap &= ~tmp;
-	if (subpage->error_bitmap == 0)
+	bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+	if (subpage_test_bitmap_all_zero(fs_info, subpage, error))
 		ClearPageError(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -398,11 +426,12 @@ void btrfs_subpage_set_dirty(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)
 {
 	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
-	u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+	unsigned int start_bit = subpage_calc_start_bit(fs_info, page,
+							dirty, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->dirty_bitmap |= tmp;
+	bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 	set_page_dirty(page);
 }
@@ -421,13 +450,14 @@ bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)
 {
 	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
-	u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+	unsigned int start_bit = subpage_calc_start_bit(fs_info, page,
+							dirty, start, len);
 	unsigned long flags;
 	bool last = false;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->dirty_bitmap &= ~tmp;
-	if (subpage->dirty_bitmap == 0)
+	bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+	if (subpage_test_bitmap_all_zero(fs_info, subpage, dirty))
 		last = true;
 	spin_unlock_irqrestore(&subpage->lock, flags);
 	return last;
@@ -447,11 +477,12 @@ void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)
 {
 	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
-	u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+	unsigned int start_bit = subpage_calc_start_bit(fs_info, page,
+							writeback, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->writeback_bitmap |= tmp;
+	bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
 	set_page_writeback(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -460,12 +491,13 @@ void btrfs_subpage_clear_writeback(const struct btrfs_fs_info *fs_info,
 		struct page *page, u64 start, u32 len)
 {
 	struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
-	u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
+	unsigned int start_bit = subpage_calc_start_bit(fs_info, page,
+							writeback, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->writeback_bitmap &= ~tmp;
-	if (subpage->writeback_bitmap == 0) {
+	bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+	if (subpage_test_bitmap_all_zero(fs_info, subpage, writeback)) {
 		ASSERT(PageWriteback(page));
 		end_page_writeback(page);
 	}
@@ -476,11 +508,12 @@ void btrfs_subpage_set_ordered(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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							ordered, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->ordered_bitmap |= tmp;
+	bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
 	SetPageOrdered(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -489,12 +522,13 @@ void btrfs_subpage_clear_ordered(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 int start_bit = subpage_calc_start_bit(fs_info, page,
+							ordered, start, len);
 	unsigned long flags;
 
 	spin_lock_irqsave(&subpage->lock, flags);
-	subpage->ordered_bitmap &= ~tmp;
-	if (subpage->ordered_bitmap == 0)
+	bitmap_clear(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
+	if (subpage_test_bitmap_all_zero(fs_info, subpage, ordered))
 		ClearPageOrdered(page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -507,12 +541,14 @@ 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 int start_bit = subpage_calc_start_bit(fs_info, page,	\
+						name, start, len);	\
 	unsigned long flags;						\
 	bool ret;							\
 									\
 	spin_lock_irqsave(&subpage->lock, flags);			\
-	ret = ((subpage->name##_bitmap & tmp) == tmp);			\
+	ret = bitmap_test_range_all_set(subpage->bitmaps, start_bit,	\
+				len >> fs_info->sectorsize_bits);	\
 	spin_unlock_irqrestore(&subpage->lock, flags);			\
 	return ret;							\
 }
@@ -609,5 +645,5 @@ void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
 		return;
 
 	ASSERT(PagePrivate(page) && page->private);
-	ASSERT(subpage->dirty_bitmap == 0);
+	ASSERT(subpage_test_bitmap_all_zero(fs_info, subpage, dirty));
 }