APPLIED: [SRU][J:linux-bluefield][PATCH 0/1] Bluefield 5.15.0-1084.86 build failure: nfsd4_get_drc_mem assertion with GCC 9

[Alessio Faina]

On Mon, Feb 23, 2026 at 04:10:07PM +1100, Satya Jhaveri wrote:
> From: sjhaveri <satya.jhaveri at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2142422
> 
> SRU Justification:
> 
> [ Impact ]
> 
> The Bluefield 5.15 kernel fails to build from source on GCC 9.
> 
> The Bluefield kernel has backported newer implementations in the `minmax.h`
> header, which enforce strict compile-time checks on `clamp_t()`. However,
> the legacy function `nfsd4_get_drc_mem()` in `fs/nfsd/nfs4state.c` code
> contains logic where `max < min` is theoretically possible, causing the
> compile-time assertions to fail.
> 
> This blocks the Bluefield 5.15 Kernel from successfully building in 
> environments with GCC 9 (such as Ubuntu Focal). Although GCC 9 is the
> only version that fails to build with this issue, it is present
> regardless, and future GCC versions may be capable of identifying this
> issue as well.
> 
> [ Fix ]
> 
> Apply the backport of the upstream fix. Commit: "nfsd: Replace clamp_t
> in nfsd4_get_drc_mem()"
> 
> As noted in the commit description, this patch was created specifically
> for LTS Kernels to permit the application of the updated `minmax.h` header
> without breaking the build, by replacing the clamp usage with open-coded
> if-else logic to more safely and explicitly handle cases where `max < min`.
> 
> commit 5f4720ac8e67f41020cb39c678e4a3bdc26114fe
> From: NeilBrown <neil at brown.name>
> Date: Fri, 14 Nov 2025 16:19:22 -0500
> Subject: nfsd: Replace clamp_t in nfsd4_get_drc_mem()
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5f4720ac8e67
> 
> [ Test Plan ]
> 
> 1. Setup a clean build environment with GCC 9 (for example, Focal)
> 2. Clone the `linux-bluefield` source.
> 3. Checkout the tag `Ubuntu-bluefield-5.15.0-1084.86`
> 4. Attempt to build the kernel.
> 5. Observe build failure at `fs/nfsd/nfs4state.c`.
> 6. Apply patch.
> 7. Attempt a clean build of the kernel.
> 8. Build succeeds.
> 
> [ Where problems could occur ]
> 
> The likelihood of problems occuring is very low. The upstream patch for this
> issue was specifically created by upstream maintainers for this scenario. The
> patch replaces the usage of the `clamp_t` macro with open-coded logic that
> performs the same runtime operation, but avoids the compile-time assertion.
> 
> 
> NeilBrown (1):
>   nfsd: Replace clamp_t in nfsd4_get_drc_mem()
> 
>  fs/nfsd/nfs4state.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> -- 
> 2.43.0
> 
> 
> -- 
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Applied to j:linux-bluefield 

Thanks!
- Alessio Faina