[PATCH v4 13/36] iomap: Support arbitrarily many blocks per page

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

Size the uptodate array dynamically.  Now that this array is protected
by a spinlock, we can use bitmap functions to set the bits in this array
instead of a loop around set_bit().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/iomap/buffered-io.c | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 4bc37bf8d057..4a79061073eb 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -22,14 +22,14 @@
 #include "../internal.h"
 
 /*
- * Structure allocated for each page when block size < PAGE_SIZE to track
+ * Structure allocated for each page when block size < page size to track
  * sub-page uptodate status and I/O completions.
  */
 struct iomap_page {
 	atomic_t		read_count;
 	atomic_t		write_count;
 	spinlock_t		uptodate_lock;
-	DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
+	unsigned long		uptodate[];
 };
 
 static inline struct iomap_page *to_iomap_page(struct page *page)
@@ -45,15 +45,14 @@ static struct iomap_page *
 iomap_page_create(struct inode *inode, struct page *page)
 {
 	struct iomap_page *iop = to_iomap_page(page);
+	unsigned int nr_blocks = i_blocks_per_page(inode, page);
 
-	if (iop || i_blocks_per_page(inode, page) <= 1)
+	if (iop || nr_blocks <= 1)
 		return iop;
 
-	iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
-	atomic_set(&iop->read_count, 0);
-	atomic_set(&iop->write_count, 0);
+	iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
+				GFP_NOFS | __GFP_NOFAIL);
 	spin_lock_init(&iop->uptodate_lock);
-	bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
 
 	/*
 	 * migrate_page_move_mapping() assumes that pages with private data have
@@ -146,20 +145,12 @@ iomap_iop_set_range_uptodate(struct page *page, unsigned off, unsigned len)
 	struct iomap_page *iop = to_iomap_page(page);
 	struct inode *inode = page->mapping->host;
 	unsigned first = off >> inode->i_blkbits;
-	unsigned last = (off + len - 1) >> inode->i_blkbits;
-	bool uptodate = true;
+	unsigned count = len >> inode->i_blkbits;
 	unsigned long flags;
-	unsigned int i;
 
 	spin_lock_irqsave(&iop->uptodate_lock, flags);
-	for (i = 0; i < i_blocks_per_page(inode, page); i++) {
-		if (i >= first && i <= last)
-			set_bit(i, iop->uptodate);
-		else if (!test_bit(i, iop->uptodate))
-			uptodate = false;
-	}
-
-	if (uptodate)
+	bitmap_set(iop->uptodate, first, count);
+	if (bitmap_full(iop->uptodate, i_blocks_per_page(inode, page)))
 		SetPageUptodate(page);
 	spin_unlock_irqrestore(&iop->uptodate_lock, flags);
 }
-- 
2.26.2