On Wed, Nov 08, 2006 at 03:43:26PM +0100, Rafael J. Wysocki wrote: > Will it be enough to cover the interactions with dm? There are cases where you *cannot* freeze the filesystem (unless you wait for userspace processes to finish what they are doing) - and only dm can tell you that. The freeze_filesystems() code ought to do it's best in any given circumstances within the constraints. So: Get the filesystem's block device. Check the full tree of devices that that block device depends upon and for any device that belongs to device-mapper check if it is suspended. If it is, skip the original device. struct mapped_device *dm_get_md(dev_t dev); int dm_suspended(struct mapped_device *md); void dm_put(struct mapped_device *md); Handling the tree is the difficult bit, but sysfs could help. [You can get the device-mapper dependencies with: struct mapped_device *dm_get_md(dev_t dev); struct dm_table *dm_get_table(struct mapped_device *md); struct list_head *dm_table_get_devices(struct dm_table *t); void dm_table_put(struct dm_table *t); void dm_put(struct mapped_device *md); ] Consider that you could have an already-frozen filesystem containing a loop device containing a device-mapper device containing a not-frozen filesystem. You won't be able to freeze that top filesystem because the I/O would queue lower down the stack. (Similar problem if the device-mapper device in the stack was suspended.) Alasdair -- agk@xxxxxxxxxx -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
