Re: [PATCH v2 0/8] Support Clang context analysis for ext2

[Nathan Chancellor]

On Tue, Aug 18, 2026 at 11:58:20AM +0200, Jan Kara wrote:
> On Tue 11-08-26 12:03:28, Timothy Day wrote:
> > This description is mostly copied from v1:
> > 
> > This series adds annotations for Clang's context analysis to ext2.
> > Clang context analysis was recently added in a series by Marco
> > Elver [1]. This allows the compiler to validate different
> > locking patterns at compile time.
> > 
> > This series enables context analysis, fixes pre-existing warnings,
> > and adds new annotations. It is inspired by similar series in the
> > block layer (NVMe host driver, for example [2]).
> > 
> > I'm starting with ext2 since it's smaller and simpler compared to
> > ext4/btrfs/etc. After ext2, I'd be interested in converting the
> > other filesystems and infrastructure code in fs/. I think the ultimate
> > goal would be to enable this by default across all of fs/.
> > 
> > The series was built and tested with Clang 23 with
> > CONFIG_WARN_CONTEXT_ANALYSIS enabled. I based on 7.2-rc7.
> 
> Thanks for the patches! They look good to me. Once the merge window is over
> I'll queue them to my tree. The only thing I'm not fully sure is how much I
> like the spinlock_init scoped guards - they looked quite confusing to me at
> the first sight (as much as I understand the convenience, conceptually how
> can initialization of a global lock be scoped?). I'll sleep over it, maybe
> I'll change them to just spinlock_init() + scoped_guard for the lock itself
> or maybe I'll get used to them. Anyway, no action on your side needed :).

This series is now in -next, where I see the following warnings (or errors with
CONFIG_WERROR=y / W=e) with various configurations, such as ARCH=arm
allmodconfig, when building with LLVM 23.1.0

  fs/ext2/xattr.c:825:6: error: rw_semaphore 'EXT2_I().xattr_sem' is not held on every path through here [-Werror,-Wthread-safety-analysis]
    825 |         if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
        |             ^
  include/asm-generic/bug.h:180:2: note: expanded from macro 'WARN_ON_ONCE'
    180 |         DO_ONCE_LITE_IF(condition, WARN_ON, 1)
        |         ^
  include/linux/once_lite.h:30:7: note: expanded from macro 'DO_ONCE_LITE_IF'
     30 |                 if (__ONCE_LITE_IF(__ret_do_once))                      \
        |                     ^
  include/linux/once_lite.h:23:3: note: expanded from macro '__ONCE_LITE_IF'
     23 |                 unlikely(__ret_once);                                   \
        |                 ^
  include/linux/compiler.h:77:22: note: expanded from macro 'unlikely'
     77 | # define unlikely(x)    __builtin_expect(!!(x), 0)
        |                         ^
  fs/ext2/xattr.c:825:20: note: rw_semaphore acquired here
    825 |         if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
        |                           ^

  fs/ext2/super.c:1149:3: error: calling function 'ext2_rsv_window_add' requires holding spinlock 'EXT2_SB(sb).s_rsv_window_lock' exclusively [-Werror,-Wthread-safety-precise]
   1149 |                 ext2_rsv_window_add(sb, &sbi->s_rsv_window_head);
        |                 ^
  fs/ext2/super.c:1149:3: note: found near match '_res->s_rsv_window_lock'

-- 
Cheers,
Nathan