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iomap: correct the range of a partial dirty clear

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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.

Fixes: 4ce02c6797 ("iomap: Add per-block dirty state tracking to improve performance")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260714082325.325163-2-yi.zhang@huaweicloud.com
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Zhang Yi 2026-07-14 16:23:21 +08:00 committed by Christian Brauner
parent 1590cf0329
commit 88c2651531
1 changed files with 8 additions and 4 deletions
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12
fs/iomap/buffered-io.c
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@ -177,13 +177,17 @@ 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);
}