Hi, On Fri, 2013-08-09 at 14:09 -0500, scame...@beardog.cce.hp.com wrote: > So, I'm working on a block driver using the make_request_fn > interface, and have to handle a bio that comes in with > (bi_rw & REQ_FLUSH) set AND data to transfer. > > According to Documentation/block/writeback_cache_control.txt: > > The REQ_FLUSH flag can be OR ed into the r/w flags of a > bio submitted from the filesystem and will make sure the > volatile cache of the storage device has been flushed > before the actual I/O operation is started. > > So I've written code that handles that case, along with the > various error cases I might encounter, I think, which leads > to my question: > > How do I get such a bio with a data transfer AND the REQ_FLUSH bit > set to come into the driver? Just wondering how to test this case. > GFS2 does this... if you look at the log flush code and the function log_write_header() in particular, you'll see that it sets this on each log header that gets written. You don't need a cluster to generate this kind of i/o, just supply mkfs.gfs2 with -p lock_nolock and mount it as a local filesystem. The combination of touch foo; sync should be enough to generate a log flush writing a log header with this flag set,
Steve. > Thanks, > > (I cc'ed Tejun Heo just because his name is in block/blk-flush.c) > > -- steve > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
