staging: lustre: hsm: Use file lease to implement migration
Implement non-blocking migration based on exclusive open instead of group lock. Implemented exclusive close operation to atomically put a lease, swap two layouts and close a file. This allows race-free migrations. Make the caller responsible for retrying on failure (EBUSY, EAGAIN) in non-blocking mode. In blocking mode, allow applications to trigger layout swaps using a grouplock they already own, to prevent race conditions between the actual data copy and the layout swap. Updated lfs accordingly. File leases are also taken in blocking mode, so that lfs migrate can issue a warning if an application attempts to open a file that is being migrated and gets blocked. Timestamps (atime/mtime) are set from userland, after the layout swap is performed, to prevent conflicts with the grouplock. lli_trunc_sem is taken/released in the vvp_io layer, under the DLM lock. This re-ordering fixes the original issue between truncate and migrate. Signed-off-by: Henri Doreau <henri.doreau@cea.fr> Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4840 Reviewed-on: http://review.whamcloud.com/10013Reviewed-by: John L. Hammond <john.hammond@intel.com> Reviewed-by: frank zago <fzago@cray.com> Reviewed-by: Oleg Drokin <oleg.drokin@intel.com> Signed-off-by: James Simmons <jsimmons@infradead.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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