From: David Sterba <dsterba@suse.cz>
To: Nikolay Borisov <nborisov@suse.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 6/7] btrfs: Replace open-coded maths with DIV_ROUND_UP
Date: Thu, 3 Jan 2019 15:44:32 +0100 [thread overview]
Message-ID: <20190103144432.GH23615@twin.jikos.cz> (raw)
In-Reply-To: <20190103085005.32053-7-nborisov@suse.com>
On Thu, Jan 03, 2019 at 10:50:04AM +0200, Nikolay Borisov wrote:
> In a couple of places it's required to calculate the number of pages
> given a start and end offsets. Currently this is opencoded, unify the
> code base by replacing all such sites with the DIV_ROUND_UP macro. Also,
> current open-coded sites were buggy in that they were adding
> 'PAGE_SIZE', rather than 'PAGE_SIZE - 1'.
Didn't you find it strange that it's so consistently wrong? After a
closer inspection, you'd find that the end of the range is inclusive. So
the math is correct and your patch introduces a bug.
end - start + PAGE_SIZE = end + 1 - start + PAGE_SIZE - 1
Check eg. writepage_delalloc how it sets up page_end.
The correct use in DIV_ROUND_UP needs +1 adjustment.
next prev parent reply other threads:[~2019-01-03 14:45 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-03 8:49 [PATCH 0/7] More misc fixes Nikolay Borisov
2019-01-03 8:49 ` [PATCH 1/7] btrfs: Remove inode argument from async_cow_submit Nikolay Borisov
2019-01-05 6:02 ` Anand Jain
2019-01-07 10:12 ` Johannes Thumshirn
2019-01-03 8:50 ` [PATCH 2/7] btrfs: Remove isize local variable in compress_file_range Nikolay Borisov
2019-01-05 6:17 ` Anand Jain
2019-01-07 10:17 ` Johannes Thumshirn
2019-01-07 17:41 ` David Sterba
2019-01-03 8:50 ` [PATCH 3/7] btrfs: Use ihold instead of igrab in cow_file_range_async Nikolay Borisov
2019-01-04 15:29 ` David Sterba
2019-01-03 8:50 ` [PATCH 4/7] btrfs: Remove WARN_ON in btrfs_alloc_delalloc_work Nikolay Borisov
2019-01-04 15:30 ` David Sterba
2019-01-07 10:19 ` Johannes Thumshirn
2019-01-03 8:50 ` [PATCH 5/7] btrfs: Document logic in async_cow_submit Nikolay Borisov
2019-01-03 8:50 ` [PATCH 6/7] btrfs: Replace open-coded maths with DIV_ROUND_UP Nikolay Borisov
2019-01-03 14:44 ` David Sterba [this message]
2019-01-03 15:33 ` Nikolay Borisov
2019-01-07 15:29 ` David Sterba
2019-01-03 8:50 ` [PATCH 7/7] btrfs: Refactor shrink_delalloc Nikolay Borisov
2019-01-04 15:35 ` David Sterba
2019-01-07 17:58 ` David Sterba
2019-01-07 17:59 ` [PATCH 0/7] More misc fixes David Sterba
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