nfsd: don't fsync nfsd_files on last close
Most of the time, NFSv4 clients issue a COMMIT before the final CLOSE of an open stateid, so with NFSv4, the fsync in the nfsd_file_free path is usually a no-op and doesn't block. We have a customer running knfsd over very slow storage (XFS over Ceph RBD). They were using the "async" export option because performance was more important than data integrity for this application. That export option turns NFSv4 COMMIT calls into no-ops. Due to the fsync in this codepath however, their final CLOSE calls would still stall (since a CLOSE effectively became a COMMIT). I think this fsync is not strictly necessary. We only use that result to reset the write verifier. Instead of fsync'ing all of the data when we free an nfsd_file, we can just check for writeback errors when one is acquired and when it is freed. If the client never comes back, then it'll never see the error anyway and there is no point in resetting it. If an error occurs after the nfsd_file is removed from the cache but before the inode is evicted, then it will reset the write verifier on the next nfsd_file_acquire, (since there will be an unseen error). The only exception here is if something else opens and fsyncs the file during that window. Given that local applications work with this limitation today, I don't see that as an issue. Link: https://bugzilla.redhat.com/show_bug.cgi?id=2166658 Fixes: ac3a2585 ("nfsd: rework refcounting in filecache") Reported-and-tested-by:Pierguido Lambri <plambri@redhat.com> Signed-off-by:
Jeff Layton <jlayton@kernel.org> Signed-off-by:
Chuck Lever <chuck.lever@oracle.com>
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