On Fri, 07 Jun 2013 23:47:33 -0400 Richard Yao <r...@gentoo.org> wrote:
> When you use dm-crypt, block IO requests to a dm-* device will invoke > dm_request_fn() -> map_request() -> crypt_map(). If a BIO is a write > barrier, crypt_map() will return DM_MAPIO_REMAPPED to map_request(), > which will immediately queue it to the device. > > If a few dozen IOs are queued in rapid succession with multiple write > barriers, all write barriers will be executed before any actual write > BIOs occur because the write IOs will be processed asynchronously in a > work queue. Since the barriers will be long gone by the time the write > IOs are queued, they can be queued in any order. > > Am I misunderstanding this or is dm-crypt ignoring proper write barrier > semantics? > http://www.saout.de/pipermail/dm-crypt/2012-April/002441.html http://lwn.net/Articles/400541/ -- Sergei
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