On Wed, Mar 22 2006, Alasdair G Kergon wrote: > On Wed, Mar 22, 2006 at 12:32:35PM +0100, Jens Axboe wrote: > > Why isn't this just handled in the merge callback? Can a single page bio > > span > 2 targets? > > Yes. (Unit of size if the sector - and things don't have to > be aligned nicely, just aligned to sector.) > > IIRC the merge function assumes the number of bytes that can > be added is only a function of the offset: but in our case > it's also a function of time. To make this work it should > reserve those bytes with device-mapper, and guarantee either to > supply them to us subsequently (and preferably quickly) or to > cancel that reservation. Device-mapper for its part would > guarantee to accept the bio without needing to split it. > Or dm could have a rejection mechanism that refuses bios > that are too big (because the max number of bytes we accept > got reduced between the initial call and the bio actually being > presented) and they go back and get processed again. > > Alasdair > -- > agk@xxxxxxxxxx > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Jens Axboe -- dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
