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> As someone not familiar with the filesystem related parts of the kernel, it's quite surprising to hear this. It sounds like filesystems are a lot more integra
by cesarb 3y ago
> As someone not familiar with the filesystem related parts of the kernel, it's quite surprising to hear this. It sounds like filesystems are a lot more integrated (or at least less modular) than other kernel subsystems.
AFAIK, on Linux filesystems are closely coupled with the memory management subsystem and the directory and inode caches. It's part of the reason why filesystem access on Linux is so fast.
> But other than that issue, I don't really understand why it's difficult to simply rip out support for a specific filesystem. Compared to something like a driver for a PCIe or USB device, what makes filesystems so much more integrated and difficult to remove?
It's not that unusual for users to have a partition containing a filesystem (sometimes, but not always, on an external drive) surviving unchanged through several migrations to newer Linux distributions and/or hardware. Compared to something like a PCIe or USB device, filesystems have a longer life.
- tyingq 3y agoBuffer cache also. An article that goes into detail with an example of the coupling you're describing: https://lwn.net/Articles/930173/ https://lwn.net/Articles/930173/
- yencabulator 3y agoThat's more of a reason why it's hard to change the core MM/page cache/etc logic, as you have to change all the users of it (every filesystem, etc). Ripping out a filesystem is, technically, near-trivial. The downsides are fully human: the Linux kernel-userspace ABI is normally considered a golden promise that shall not be broken. The developers don't want users to have a bad morning on which their old filesystems no longer work.