From: Zhang Yi The block range calculation in ifs_clear_range_dirty() is incorrect when partially clearing a range in a folio. We cannot clear the dirty bit of the first block or the last block if the start or end offset is not blocksize-aligned. This has not yet caused any issues since we always clear a whole folio in iomap_writeback_folio(). Fix this by rounding up the first block to blocksize alignment, and calculate the last block by rounding down (using truncation). Correct the nr_blks calculation accordingly. Signed-off-by: Zhang Yi --- This is modified from: https://lore.kernel.org/linux-fsdevel/20240812121159.3775074-2-yi.zhang@huaweicloud.com/ Changes: - Use round_up() instead of DIV_ROUND_UP() to prevent wasted integer division. fs/iomap/buffered-io.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index d7b648421a70..64351a448a8b 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -176,13 +176,17 @@ 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 = round_up(off, i_blocksize(inode)) >> + inode->i_blkbits; + unsigned int last_blk = (off + len) >> inode->i_blkbits; unsigned long flags; + if (first_blk >= last_blk) + return; + spin_lock_irqsave(&ifs->state_lock, flags); - bitmap_clear(ifs->state, first_blk + blks_per_folio, nr_blks); + bitmap_clear(ifs->state, first_blk + blks_per_folio, + last_blk - first_blk); spin_unlock_irqrestore(&ifs->state_lock, flags); } -- 2.52.0