On Fri, Aug 09, 2013 at 09:18:15PM +0100, Steven Whitehouse wrote: > 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,
Thanks! Turns out ext3 seems to do it as well (now I feel kind of dumb for asking -- had tried with ext2, and had tried some writes with a file descriptor with O_SYNC set, but I was kind of shooting in the dark.) And my code appears to work too. -- 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/
