[PATCH 1/6] iomap: correct the range of a partial dirty clear

[Zhang Yi]

From: Zhang Yi <yi.zhang@xxxxxxxxxx>

The block range calculation in ifs_clear_range_dirty() is incorrect when
partial clear a range in a folio. We can't clear the dirty bit of the
first block or the last block if the start or end offset is blocksize
unaligned, this has not yet caused any issue since we always clear a
whole folio in iomap_writepage_map()->iomap_clear_range_dirty(). Fix
this by round up the first block and round down the last block and
correct the calculation of nr_blks.

Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
 fs/iomap/buffered-io.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d46558990279..a896d15c191a 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -138,11 +138,14 @@ static void ifs_clear_range_dirty(struct folio *folio,
 {
 	struct inode *inode = folio->mapping->host;
 	unsigned int blks_per_folio = i_blocks_per_folio(inode, 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 int first_blk = DIV_ROUND_UP(off, i_blocksize(inode));
+	unsigned int last_blk = (off + len) >> inode->i_blkbits;
+	unsigned int nr_blks = last_blk - first_blk;
 	unsigned long flags;
 
+	if (!nr_blks)
+		return;
+
 	spin_lock_irqsave(&ifs->state_lock, flags);
 	bitmap_clear(ifs->state, first_blk + blks_per_folio, nr_blks);
 	spin_unlock_irqrestore(&ifs->state_lock, flags);
-- 
2.39.2