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SubjectRe: [PATCH] xfs: Fix tail rounding in xfs_alloc_file_space()
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On 26.09.19 16:37, Darrick J. Wong wrote:
> On Thu, Sep 26, 2019 at 04:22:38PM +0200, Max Reitz wrote:
>> To ensure that all blocks touched by the range [offset, offset + count)
>> are allocated, we need to calculate the block count from the difference
>> of the range end (rounded up) and the range start (rounded down).
>>
>> Before this patch, we just round up the byte count, which may lead to
>> unaligned ranges not being fully allocated:
>>
>> $ touch test_file
>> $ block_size=$(stat -fc '%S' test_file)
>> $ fallocate -o $((block_size / 2)) -l $block_size test_file
>> $ xfs_bmap test_file
>> test_file:
>> 0: [0..7]: 1396264..1396271
>> 1: [8..15]: hole
>>
>> There should not be a hole there. Instead, the first two blocks should
>> be fully allocated.
>>
>> With this patch applied, the result is something like this:
>>
>> $ touch test_file
>> $ block_size=$(stat -fc '%S' test_file)
>> $ fallocate -o $((block_size / 2)) -l $block_size test_file
>> $ xfs_bmap test_file
>> test_file:
>> 0: [0..15]: 11024..11039
>
> Code looks ok; by any chance do you have an xfstest we could add to the
> regresion test suite?
I’ll look into it.

Max

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