ba6a24026c
Early versions of ZFS coordinated the creation and destruction of device minors from userspace. This was inherently racy and in late 2009 these ioctl()s were removed leaving everything up to the kernel. This significantly simplified the code. However, we never picked up these changes in ZoL since we'd already significantly adjusted this code for Linux. This patch aims to rectify that by finally removing ZFC_IOC_*_MINOR ioctl()s and moving all the functionality down in to the kernel. Since this cleanup will change the kernel/user ABI it's being done in the same tag as the previous libzfs_core ABI changes. This will minimize, but not eliminate, the disruption to end users. Once merged ZoL, Illumos, and FreeBSD will basically be back in sync in regards to handling ZVOLs in the common code. While each platform must have its own custom zvol.c implemenation the interfaces provided are consistent. NOTES: 1) This patch introduces one subtle change in behavior which could not be easily avoided. Prior to this change callers of 'zfs create -V ...' were guaranteed that upon exit the /dev/zvol/ block device link would be created or an error returned. That's no longer the case. The utilities will no longer block waiting for the symlink to be created. Callers are now responsible for blocking, this is why a 'udev_wait' call was added to the 'label' function in scripts/common.sh. 2) The read-only behavior of a ZVOL now solely depends on if the ZVOL_RDONLY bit is set in zv->zv_flags. The redundant policy setting in the gendisk structure was removed. This both simplifies the code and allows us to safely leverage set_disk_ro() to issue a KOBJ_CHANGE uevent. See the comment in the code for futher details on this. 3) Because __zvol_create_minor() and zvol_alloc() may now be called in a sync task they must use KM_PUSHPAGE. References: illumos/illumos-gate@681d9761e8 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #1969 |
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