people have been asking for quota support in tmpfs many times in the past mostly to avoid one malicious user, or misbehaving user/program to consume all of the system memory. This has been partially solved with the size mount option, but some problems still prevail. One of the problems is the fact that /dev/shm is still generally unprotected with this and another is administration overhead of managing multiple tmpfs mounts and lack of more fine grained control. Quota support can solve all these problems in a somewhat standard way people are already familiar with from regular file systems. It can give us more fine grained control over how much memory user/groups can consume. Additionally it can also control number of inodes and with special quota mount options introduced with a second patch we can set global limits allowing us to replace the size mount option with quota entirely. Currently the standard userspace quota tools (quota, xfs_quota) are only using quotactl ioctl which is expecting a block device. I patched quota [1] and xfs_quota [2] to use quotactl_fd in case we want to run the tools on mount point directory to work nicely with tmpfs. The implementation was tested on patched version of xfstests [3]. Thoughts? -Lukas [1] https://github.com/lczerner/quota/tree/quotactl_fd_support [2] https://github.com/lczerner/xfsprogs/tree/quotactl_fd_support [3] https://github.com/lczerner/xfstests/tree/tmpfs_quota_support
