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e12a0edafe
Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT open flag of guest applications will be discarded by virtiofsd. While this behavior makes it consistent with the virtio-9p scheme when guest applications use direct I/O, we no longer have any chance to bypass the host page cache. Therefore, we add a flag 'allow_direct_io' to lo_data. If '-o no_allow_direct_io' option is added, or none of '-o allow_direct_io' or '-o no_allow_direct_io' is added, the 'allow_direct_io' will be set to 0, and virtiofsd discards O_DIRECT as before. If '-o allow_direct_io' is added to the starting command-line, 'allow_direct_io' will be set to 1, so that the O_DIRECT flags will be retained and host page cache can be bypassed. Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20200824105957.61265-1-zhangjiachen.jaycee@bytedance.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>