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Message-ID: <d56e3183-a27e-fbbb-4203-28e8e10127cb@huaweicloud.com>
Date: Tue, 13 Aug 2024 10:14:40 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, hch@...radead.org, brauner@...nel.org,
david@...morbit.com, jack@...e.cz, willy@...radead.org, yi.zhang@...wei.com,
chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v2 1/6] iomap: correct the range of a partial dirty clear
On 2024/8/13 0:33, Darrick J. Wong wrote:
> On Mon, Aug 12, 2024 at 08:11:54PM +0800, Zhang Yi wrote:
>> From: Zhang Yi <yi.zhang@...wei.com>
>>
>> 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@...wei.com>
>> ---
>> 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 f420c53d86ac..4da453394aaf 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));
>
> Is there a round up macro that doesn't involve integer division?
>
Sorry, I don't find a common macro now, if we want to avoid integer division,
how about open code here?
first_blk = round_up(off, i_blocksize(inode)) >> inode->i_blkbits;
Thanks,
Yi.
>
>> + 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
>>
>>
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