On Wednesday April 23, Paul.Clements@SteelEye.com wrote: > Neil Brown wrote: > > On Tuesday April 22, Paul.Clements@SteelEye.com wrote: > > > Following is a simple patch to remove deprecated MOD_INC_USE_COUNT from > > > md.c. > > > > > > If it looks good, please apply. > > > > I don't think it is that easy. > > Well, I think that it's safe to remove the MOD_INC_USE_COUNT...here's > why: > > We're protected while a device is open (by the infrastructure in the > block layer that takes a module reference when an md device is opened > and keeps it until the device is closed). > > So, while any ioctl is being done, there's an md device open...and...the > ioctls are currently the only way to activate md devices (autorun, > RUN_ARRAY, etc.). > > Now, none of these ioctls will succeed (activate a device) unless there > is an underlying raid personality module (raid0, raid1, et al.) for the > array already loaded. The underlying raid modules also take module > references against md, so by the time a device is activated, md is > already pinned into memory... > > So we're safe from every angle...the MOD_INC_USE_COUNT/MOD_DEC_USE_COUNT > appears to have been superfluous in the first place...(at least with the > way 2.5 kernel module refs work) Almost.. but not quite. It is possible for an array to be half-assembled. To have some drives attached, but not to have been started. This can happen (for example) if you use mdadm to assemble a raid5 array without given all of the drives, and without giving --run. In this case you don't want 'md' to be unloaded, but you haven't loaded a personality module yet. So you need to take a reference to the md module whenever you start putting an md array together. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
