On Dec 11, 2007 6:40 PM, Scott James Remnant <scott@xxxxxxxxxx> wrote: > > On Tue, 2007-12-11 at 18:35 +0100, Kay Sievers wrote: > > > On Dec 11, 2007 5:08 PM, Scott James Remnant <scott@xxxxxxxxxx> wrote: > > > This is a patch we've written and applied in Ubuntu to improve the > > > atomicity of devmapper device creation somewhat, and avoid races with > > > udev. > > > > Without synchronization between libdevmapper and udev, you can't > > predict which one will win in creating the node, right? > > So this patch makes is more likely to create a valid device node, but > > it can still happen, that libdevmapper replaces the udev nodes, which > > is not what we want, right? > > > No, the patch is slightly skewed so that udev always wins. udev will > always adopt an existing device node, adjusting permissions as > necessary. The patch makes devmapper "back off" if the device node > exists. > > So you end up with either: > > 1) devmapper creates device node > 2) udev adopts device node and sets permissions > > or: > > 1) udev creates device node and sets permissions > 2) devmapper no-ops since it already exists There is a window between stat() and rename() in libdevmapper, how can you konw that "udev always wins"? Kay -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
