On Thu, 7 Aug 2014 10:25:49 +0900 Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx> wrote: > This patch implements iSCSI multipath support in sheepdog backing > store driver. Below is a brief description of the feature: > > The main problem of enabling iSCSI multipath for sheepdog's VDI is > keeping coherence of tgtd's internal inode data structure. Assume tgt > A and B have logical units which point same sheepdog VDI. After > initialization of the logical units, A and B have copies of inode > object in their address space (let's X denote this object). When an > initiator sends write request to A and the request causes COW, A > creates a new object and updates the inode object X (let's X' denote > the updated one). > > After the update by A, A can die with hardware faults. In such a case, > the initiator detects a connection error and switch its target to B if > iSCSI multipath is configured correctly. But the problem can arise at > this point. Because B doesn't know the update caused by A and its > internal inode object is still X, not X'. B creates requests based on > X, so it can read obsolete data which is already hidden by X' or > update X' in wrong manner. > > For solving the above problem, sheepdog implements inode object > coherence protocol which mocks MSI protocol of shared memory multicore > processors. With this mechanism sheepdog can prevent requests which > are based on obsolete inode objects. This patch let sheepdog driver of > tgtd adopt the coherence protocol. > > Signed-off-by: Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx> > --- > usr/bs_sheepdog.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 81 insertions(+), 16 deletions(-) Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
