Description of problem: Help, lvm2 snapshot and XFS , using xfs_freeze to do this, but then lvcreate hang. I use lvm2 and xfs both. If I do not use xfs_freeze before, I can use lvcreate snapshot the lv. And it work fine for some static files or lv, but not for running system such as / (root) which will generate a log of I/O error. So I heard that xfs should run xfs_freeze before create snapshot. However, after xfs_freeze -f, then lvcreate hang all the time. And I still can not kill (-9) the lvcreate process.
what version of kernel/lvm are you using. manual xfs_freeze has been unnecessary for quite some time, as lvm automatically freezes the things it's about to snapshot. lvm is probably hung waiting for the filesystem to unfreeze so that -it- can freeze it. dm_suspend lock_fs freeze_bdev sb->s_op->write_super_lockfs xfs_fs_lockfs etc...
Without any further information from the submitter, it appears that xfs_freeze was manually invoked prior to taking the lvm snapshot, which then also tried to freeze the filesystem, and got stuck behind xfs_freeze. For newer lvm, no manual xfs_freeze is necessary, and in fact if you do it, it will lock out the lvm snapshot. If recent lvm snapshots are generating IO errors for you, perhaps you can open a new bug with that information, as that seems like a separate, and more serious, problem. Thanks, -Eric