linux-kernel - fs/netfs/read_retry.c:235:20: error: variable 'subreq' is uninitialized when used here [-Werror,-Wuninitialized]

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Message-ID: <CA+G9fYuLXDh8GDmgdhmA1NAhsma3=FoH1n93gmkHAGGFKbNGeQ@mail.gmail.com>
Date: Tue, 26 Nov 2024 13:55:11 +0530
From: Naresh Kamboju <naresh.kamboju@...aro.org>
To: netfs@...ts.linux.dev, linux-fsdevel@...r.kernel.org, 
	open list <linux-kernel@...r.kernel.org>, lkft-triage@...ts.linaro.org
Cc: Jeff Layton <jlayton@...nel.org>, David Howells <dhowells@...hat.com>, 
	Dan Carpenter <dan.carpenter@...aro.org>, Anders Roxell <anders.roxell@...aro.org>, 
	Arnd Bergmann <arnd@...db.de>
Subject: fs/netfs/read_retry.c:235:20: error: variable 'subreq' is
 uninitialized when used here [-Werror,-Wuninitialized]

The x86_64 builds failed with clang-19 and clang-nightly on the Linux
next-20241125 tag.
Same build pass with gcc-13.

First seen on Linux next-20241125 tag.
  Good: next-20241122
  Bad:  next-20241125 and next-20241126

x86_64:
  build:
    * clang-19-lkftconfig
    * clang-nightly-lkftconfig-lto-full
    * clang-nightly-lkftconfig
    * clang-19-lkftconfig-kcsan
    * korg-clang-19-lkftconfig-lto-full
    * clang-nightly-lkftconfig-lto-thing
    * clang-nightly-lkftconfig-kselftest
    * clang-19-x86_64_defconfig
    * rustclang-nightly-lkftconfig-kselftest
    * clang-19-lkftconfig-no-kselftest-frag
    * korg-clang-19-lkftconfig-hardening
    * korg-clang-19-lkftconfig-lto-thing
    * clang-19-lkftconfig-compat
    * clang-nightly-lkftconfig-hardening
    * clang-nightly-x86_64_defconfig

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>

Build error:
---------
fs/netfs/read_retry.c:235:20: error: variable 'subreq' is
uninitialized when used here [-Werror,-Wuninitialized]
  235 |         if (list_is_last(&subreq->rreq_link, &stream->subrequests))
      |                           ^~~~~~
fs/netfs/read_retry.c:28:36: note: initialize the variable 'subreq' to
silence this warning
   28 |         struct netfs_io_subrequest *subreq;
      |                                           ^
      |                                            = NULL
1 error generated.
make[5]: *** [scripts/Makefile.build:194: fs/netfs/read_retry.o] Error 1

Build image:
-----------
- https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20241126/testrun/26060810/suite/build/test/clang-19-lkftconfig/log
- https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20241126/testrun/26060810/suite/build/test/clang-19-lkftconfig/details/
- https://storage.tuxsuite.com/public/linaro/lkft/builds/2pNKzjvChfT6aOWplZaZeQzbYCX/

Steps to reproduce:
------------
- tuxmake --runtime podman --target-arch x86_64 --toolchain clang-19
--kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2pNKzjvChfT6aOWplZaZeQzbYCX/config
LLVM=1 LLVM_IAS=1

The git log shows
$ git log --oneline  next-20241122..next-20241125 -- fs/netfs/read_retry.c
1bd9011ee163e netfs: Change the read result collector to only use one work item
5c962f9982cd9 netfs: Don't use bh spinlock
3c8a83f74e0ea netfs: Drop the was_async arg from netfs_read_subreq_terminated()
2029a747a14d2 netfs: Abstract out a rolling folio buffer implementation

metadata:
----
  git describe: next-20241125 and next-20241126
  git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
  git sha: ed9a4ad6e5bd3a443e81446476718abebee47e82
  kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/2pNKzjvChfT6aOWplZaZeQzbYCX/config
  build url: https://storage.tuxsuite.com/public/linaro/lkft/builds/2pNKzjvChfT6aOWplZaZeQzbYCX/
  toolchain: clang-19 and clang-nightly
  config: defconfig, lkftconfig etc
  arch: x86_64

--
Linaro LKFT
https://lkft.linaro.org