[LTP] [PATCH v2 2/2] aio_tio: determine alignment based on target filesystem
Tue Feb 26 16:37:00 CET 2019
On 22/02/2019 15:33, Cyril Hrubis wrote:
>> The alignment for O_DIRECT operations has to match the blocksize of the
>> underlying filesystem. Determine the alignment from the target file's
>> file system.
>> aio_tio test cases 1 and 2 failed (nondeterministic) on aarch64 when run
>> on a 4096 byte blocksize filesystem and with an alignment of 512 bytes.
> Is this really about the filesystem? Citing man open:
> Under Linux 2.4, transfer sizes, and the alignment of the user buffer
> and the file offset must all be multiples of the logical block size of
> the filesystem. Since Linux 2.6.0, alignment to the logical block size
> of the underlying storage (typically 512 bytes) suffices. The logical
> block size can be determined using the ioctl(2) BLKSSZGET operation or
> from the shell using the command:
> blockdev --getss
> So unless you are running ancient 2.4 kernel the aligment restrictions should
> be result of the blocksize of the device rather than of the filesystem.
Yes. You are right. The blocksize of the device is what I was referring
to. Sorry for that.
In particular the test hits the alignment check in fs/direct-io.c
(do_blockdev_direct_IO) , which makes the direct io operation fail in
my case with EINVAL.
> What does the blockdev command return on the particular system?
I will update the patch to correct comment and commit message.
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