The processes names are truncated to 17, while we had the length of the process as name 20 - which meant that while we filled it out with various details - the last 3 characters (which had the queue number) never surfaced to the user-space.
To simplify this and be able to fit the device name, domain id, and the queue number we remove the 'blkback' from the name. Prior to this patch the device name is "blkback.<domid>.<name>" for example: blkback.8.xvda, blkback.11.hda. With the multiqueue block backend we add "-%d" for the queue. But sadly this is already way past the limit so it gets stripped. Possible solution had been identified by Ian: http://lists.xenproject.org/archives/html/xen-devel/2015-05/msg03516.html " If you are pressed for space then the "xvd" is probably a bit redundant in a string which starts blkbk. The guest may not even call the device xvdN (iirc BSD has another prefix) any how, so having blkback say so seems of limited use anyway. Since this seems to not include a partition number how does this work in the split partition scheme? (i.e. one where the guest is given xvda1 and xvda2 rather than xvda with a partition table) [It will be 'blkback.8.xvda1', and 'blkback.11.xvda2'] Perhaps something derived from one of the schemes in http://xenbits.xen.org/docs/unstable/misc/vbd-interface.txt might be a better fit? After a bit of discussion (see http://lists.xenproject.org/archives/html/xen-devel/2015-12/msg01588.html) we settled on dropping the "blback" part. This will make it possible to have the <domid>.<name>-<queue>: [1.xvda-0] [1.xvda-1] And we enough space to make it go up to: [32100.xvdfg9-5] Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> --- drivers/block/xen-blkback/xenbus.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 16e28ee..26aa080 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -23,8 +23,7 @@ #include <xen/grant_table.h> #include "common.h" -/* Enlarge the array size in order to fully show blkback name. */ -#define BLKBACK_NAME_LEN (20) +/* On the XenBus the max length of 'ring-ref%u'. */ #define RINGREF_NAME_LEN (20) struct backend_info { @@ -76,7 +75,7 @@ static int blkback_name(struct xen_blkif *blkif, char *buf) else devname = devpath; - snprintf(buf, BLKBACK_NAME_LEN, "blkback.%d.%s", blkif->domid, devname); + snprintf(buf, TASK_COMM_LEN, "%d.%s", blkif->domid, devname); kfree(devpath); return 0; @@ -85,7 +84,7 @@ static int blkback_name(struct xen_blkif *blkif, char *buf) static void xen_update_blkif_status(struct xen_blkif *blkif) { int err; - char name[BLKBACK_NAME_LEN]; + char name[TASK_COMM_LEN]; struct xen_blkif_ring *ring; int i; -- 2.1.0 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
