[$] Dropping the page cache for filesystems

VFS maintainer Christian Brauner led a discussion about the possibility ofselectively dropping the contents of the page cache for a filesystem in asession at the2024 Linux Storage,Filesystem, Memory Management, and BPF Summit. As he described in histopicproposal, the use case that started him down this path comes fromGNOME, which wants to be able to safely suspend access to an encrypted homedirectory. While it is known to kerneldevelopers, it is surprising to others that reads from encryptedfilesystems that have been suspended will succeed if the data to be readstill exists in the page cache.