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2019-04-02filemon: fix watch IDs to avoid potential wraparound issuesDaniel P. Berrangé
Watch IDs are allocated from incrementing a int counter against the QFileMonitor object. In very long life QEMU processes with a huge amount of USB MTP activity creating & deleting directories it is just about conceivable that the int counter can wrap around. This would result in incorrect behaviour of the file monitor watch APIs due to clashing watch IDs. Instead of trying to detect this situation, this patch changes the way watch IDs are allocated. It is turned into an int64_t variable where the high 32 bits are set from the underlying inotify "int" ID. This gives an ID that is guaranteed unique for the directory as a whole, and we can rely on the kernel to enforce this. QFileMonitor then sets the low 32 bits from a per-directory counter. The USB MTP device only sets watches on the directory as a whole, not files within, so there is no risk of guest triggered wrap around on the low 32 bits. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2019-04-02filemon: ensure watch IDs are unique to QFileMonitor scopeDaniel P. Berrangé
The watch IDs are mistakenly only unique within the scope of the directory being monitored. This is not useful for clients which are monitoring multiple directories. They require watch IDs to be unique globally within the QFileMonitor scope. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Tested-by: Bandan Das <bsd@redhat.com> Reviewed-by: Bandan Das <bsd@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2019-04-02tests: refactor file monitor test to make it more understandableDaniel P. Berrangé
The current file monitor unit tests are too clever for their own good making it hard to understand the desired output. Instead of trying to infer the expected events, explicitly list the events we expect in the operation sequence. Instead of dynamically building a matrix of tests, just have one giant operation sequence that validates all scenarios in a single test. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2019-02-26util: add helper APIs for dealing with inotify in portable mannerDaniel P. Berrangé
The inotify userspace API for reading events is quite horrible, so it is useful to wrap it in a more friendly API to avoid duplicating code across many users in QEMU. Wrapping it also allows introduction of a platform portability layer, so that we can add impls for non-Linux based equivalents in future. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>