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Dave Chinner authored
In the next patches we are going to make the CIL list itself per-cpu, and so we cannot use list_empty() to check is the list is empty. Replace the list_empty() checks with a flag in the CIL to indicate we have committed at least one transaction to the CIL and hence the CIL is not empty. We need this flag to be an atomic so that we can clear it without holding any locks in the commit fast path, but we also need to be careful to avoid atomic operations in the fast path. Hence we use the fact that test_bit() is not an atomic op to first check if the flag is set and then run the atomic test_and_clear_bit() operation to clear it and steal the initial unit reservation for the CIL context checkpoint. When we are switching to a new context in a push, we place the setting of the XLOG_CIL_EMPTY flag under the xc_push_lock. THis allows all the other places that need to check whether the CIL is empty to use test_bit() and still be serialised correctly with the CIL context swaps that set the bit. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
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