graphdriver/btrfs: depend on kernel UAPI instead of libbtrfs#44761
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graphdriver/btrfs: depend on kernel UAPI instead of libbtrfs#44761neersighted merged 5 commits intomoby:masterfrom
neersighted merged 5 commits intomoby:masterfrom
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This is actually quite meaningless as we are reporting the libbtrfs version, but we do not use libbtrfs. We only use the kernel interface to btrfs instead. While we could report the version of the kernel headers in play, they're rather all-or-nothing: they provide the structures and defines we need, or they don't. As such, drop all version information as the host kernel version is the only thing that matters. Signed-off-by: Bjorn Neergaard <[email protected]>
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By relying on the kernel UAPI (userspace API), we can drop a dependency and simplify building Moby, while also ensuring that we are using a stable/supported source of the C types and defines we need. btrfs-progs mirrors the kernel headers, but the headers it ships with are not the canonical source and as [we have seen before][44698], could be subject to changes. Depending on the canonical headers from the kernel both is more idiomatic, and ensures we are protected by the kernel's promise to not break userspace. [44698]: moby#44698 Signed-off-by: Bjorn Neergaard <[email protected]>
While the Cgo in this entire file is quite questionable, that is a task for another day. Signed-off-by: Bjorn Neergaard <[email protected]>
We only need suitable UAPI headers now. They are available on kernel 4.7 and newer; out of the distributions currently in support that users might be interested in, only Enterprise Linux 7 has too old a kernel (3.10). Users of Enterprise Linux 7 distros can compile using a newer platform, disable the Btrfs graphdriver as documented in this file, or use newer kernel headers on their older distro. Signed-off-by: Bjorn Neergaard <[email protected]>
This is no longer necessary after the switch to the kernel UAPI. Signed-off-by: Bjorn Neergaard <[email protected]>
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This was referenced Jan 7, 2023
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- What I did
Use the kernel UAPI to provide the Btrfs headers, instead of btrfs-progs/libbtrfs
- How I did it
Given #44707 this was a very straightforward substitution with most of the work in research/verification.
- How to verify it
Verify the assumptions (e.g. kernel versions) and use containers to test building on platforms of interest (e.g. EL 7 with newer kernel headers).
- Description for the changelog
- A picture of a cute animal (not mandatory but encouraged)
