Should a block device enforce block atomicity?

[Erez Zilber]

Hi,

I have a question about block devices and whether they are required to
enforce block atomicity:

I read the code of drivers/block/brd.c, and I didn't see any locking
when blocks are read/written. I also looked at the block layer code
that calls brd and didn't find any locking there. Does it mean that
there's no block atomicity (i.e. multiple threads can write a single
block at the same time)? Is there any hidden assumption here? Is this
the responsibility of the application to do that (e.g. not start a
WRITE request before other READ/WRITE requests to the same block were
completed)?

Thanks,
Erez
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