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Is it guaranteed that a struct file pointer won't be deallocated and reallocated somewhere else in memory during its open to close lifecycle?

I want to uniquely identify file structs that are passed to a device driver (through read/write/open etc) and was wondering if I could just use the pointer to the file struct for identification. The only other alternative I see would be to store a unique identifier in private_data, if it is not guaranteed that the struct file pointer will not change.

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I assume you mean just through the lifecycle (open->close) of a file, and not, as in, will it never be deallocated? – Ben Zotto 1 hour ago
Yeah just through the lifecycle. – Michael 1 hour ago
IIUC, the {devicenumber,inodenumber} is the natural key for files. In a datamodelling sense, the pointers are functionally dependent on them. The raw pointer value could be stable in time, but I would not trust on it. Disclaimer: Dammit, Jim, I am a DBA, not a kernel hacker. – wildplasser 1 hour ago
The file struct indicate an open file in a process, not the actual file in the filesystem which is indicated by devnumber/inodenumber. So you could have multiple file structs pointing to the same device/inode. – Michael 1 hour ago
In that case (I think) you have a hierarchy inversion. The file structure should not exist at the device driver level, it is a different level of abstraction, IMHO. – wildplasser 32 mins ago
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