Looking at the conditional lock acquire functions in the kernel due to
the new sparse support (see commit 4a557a5d1a61 "sparse: introduce
conditional lock acquire function attribute"), it became obvious that
the lockref code has a couple of them, but they don't match the usual
naming convention for the other ones, and their return value logic is
also reversed.

In the other very similar places, the naming pattern is '*_and_lock()'
(eg 'atomic_put_and_lock()' and 'refcount_dec_and_lock()'), and the
function returns true when the lock is taken.

The lockref code is superficially very similar to the refcount code,
only with the special "atomic wrt the embedded lock" semantics.  But
instead of the '*_and_lock()' naming it uses '*_or_lock()'.

And instead of returning true in case it took the lock, it returns true
if it *didn't* take the lock.

Now, arguably the reflock code is quite logical: it really is a "either
decrement _or_ lock" kind of situation - and the return value is about
whether the operation succeeded without any special care needed.

So despite the similarities, the differences do make some sense, and
maybe it's not worth trying to unify the different conditional locking
primitives in this area.

But while looking at this all, it did become obvious that the
'lockref_get_or_lock()' function hasn't actually had any users for
almost a decade.

The only user it ever had was the shortlived 'd_rcu_to_refcount()'
function, and it got removed and replaced with 'lockref_get_not_dead()'
back in 2013 in commits 0d98439ea3c6 ("vfs: use lockred 'dead' flag to
mark unrecoverably dead dentries") and e5c832d55588 ("vfs: fix dentry
RCU to refcounting possibly sleeping dput()")

In fact, that single use was removed less than a week after the whole
function was introduced in commit b3abd80250c1 ("lockref: add
'lockref_get_or_lock() helper") so this function has been around for a
decade, but only had a user for six days.

Let's just put this mis-designed and unused function out of its misery.

We can think about the naming and semantic oddities of the remaining
'lockref_put_or_lock()' later, but at least that function has users.

And while the naming is different and the return value doesn't match,
that function matches the whole '{atomic,refcount}_dec_and_test()'
pattern much better (ie the magic happens when the count goes down to
zero, not when it is incremented from zero).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The kernel tends to try to avoid conditional locking semantics because
it makes it harder to think about and statically check locking rules,
but we do have a few fundamental locking primitives that take locks
conditionally - most obviously the 'trylock' functions.

That has always been a problem for 'sparse' checking for locking
imbalance, and we've had a special '__cond_lock()' macro that we've used
to let sparse know how the locking works:

    # define __cond_lock(x,c)        ((c) ? ({ __acquire(x); 1; }) : 0)

so that you can then use this to tell sparse that (for example) the
spinlock trylock macro ends up acquiring the lock when it succeeds, but
not when it fails:

    #define raw_spin_trylock(lock)  __cond_lock(lock, _raw_spin_trylock(lock))

and then sparse can follow along the locking rules when you have code like

        if (!spin_trylock(&dentry->d_lock))
                return LRU_SKIP;
	.. sparse sees that the lock is held here..
        spin_unlock(&dentry->d_lock);

and sparse ends up happy about the lock contexts.

However, this '__cond_lock()' use does result in very ugly header files,
and requires you to basically wrap the real function with that macro
that uses '__cond_lock'.  Which has made PeterZ NAK things that try to
fix sparse warnings over the years [1].

To solve this, there is now a very experimental patch to sparse that
basically does the exact same thing as '__cond_lock()' did, but using a
function attribute instead.  That seems to make PeterZ happy [2].

Note that this does not replace existing use of '__cond_lock()', but
only exposes the new proposed attribute and uses it for the previously
unannotated 'refcount_dec_and_lock()' family of functions.

For existing sparse installations, this will make no difference (a
negative output context was ignored), but if you have the experimental
sparse patch it will make sparse now understand code that uses those
functions, the same way '__cond_lock()' makes sparse understand the very
similar 'atomic_dec_and_lock()' uses that have the old '__cond_lock()'
annotations.

Note that in some cases this will silence existing context imbalance
warnings.  But in other cases it may end up exposing new sparse warnings
for code that sparse just didn't see the locking for at all before.

This is a trial, in other words.  I'd expect that if it ends up being
successful, and new sparse releases end up having this new attribute,
we'll migrate the old-style '__cond_lock()' users to use the new-style
'__cond_acquires' function attribute.

The actual experimental sparse patch was posted in [3].

Link: https://lore.kernel.org/all/20130930134434.GC12926@twins.programming.kicks-ass.net/ [1]
Link: https://lore.kernel.org/all/Yr60tWxN4P568x3W@worktop.programming.kicks-ass.net/ [2]
Link: https://lore.kernel.org/all/CAHk-=wjZfO9hGqJ2_hGQG3U_XzSh9_XaXze=HgPdvJbgrvASfA@mail.gmail.com/ [3]
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Aring <aahringo@redhat.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull xfs fixes from Darrick Wong:
 "This fixes some stalling problems and corrects the last of the
  problems (I hope) observed during testing of the new atomic xattr
  update feature.

   - Fix statfs blocking on background inode gc workers

   - Fix some broken inode lock assertion code

   - Fix xattr leaf buffer leaks when cancelling a deferred xattr update
     operation

   - Clean up xattr recovery to make it easier to understand.

   - Fix xattr leaf block verifiers tripping over empty blocks.

   - Remove complicated and error prone xattr leaf block bholding mess.

   - Fix a bug where an rt extent crossing EOF was treated as "posteof"
     blocks and cleaned unnecessarily.

   - Fix a UAF when log shutdown races with unmount"

* tag 'xfs-5.19-fixes-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: prevent a UAF when log IO errors race with unmount
  xfs: dont treat rt extents beyond EOF as eofblocks to be cleared
  xfs: don't hold xattr leaf buffers across transaction rolls
  xfs: empty xattr leaf header blocks are not corruption
  xfs: clean up the end of xfs_attri_item_recover
  xfs: always free xattri_leaf_bp when cancelling a deferred op
  xfs: use invalidate_lock to check the state of mmap_lock
  xfs: factor out the common lock flags assert
  xfs: introduce xfs_inodegc_push()
  xfs: bound maximum wait time for inodegc work

Pull nfsd fixes from Chuck Lever:
 "Notable regression fixes:

   - Fix NFSD crash during NFSv4.2 READ_PLUS operation

   - Fix incorrect status code returned by COMMIT operation"

* tag 'nfsd-5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux:
  SUNRPC: Fix READ_PLUS crasher
  NFSD: restore EINVAL error translation in nfsd_commit()

Pull parisc architecture fixes from Helge Deller:
 "Two important fixes for bugs in code which was added in 5.18:

   - Fix userspace signal failures on 32-bit kernel due to a bug in vDSO

   - Fix 32-bit load-word unalignment exception handler which returned
     wrong values"

* tag 'for-5.19/parisc-4' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: Fix vDSO signal breakage on 32-bit kernel
  parisc/unaligned: Fix emulate_ldw() breakage

Addition of vDSO support for parisc in kernel v5.18 suddenly broke glibc
signal testcases on a 32-bit kernel.

The trampoline code (sigtramp.S) which is mapped into userspace includes
an offset to the context data on the stack, which is used by gdb and
glibc to get access to registers.

In a 32-bit kernel we used by mistake the offset into the compat context
(which is valid on a 64-bit kernel only) instead of the offset into the
"native" 32-bit context.

Reported-by: John David Anglin <dave.anglin@bell.net>
Tested-by: John David Anglin <dave.anglin@bell.net>
Fixes: 	df24e1783e6e ("parisc: Add vDSO support")
CC: stable@vger.kernel.org # 5.18
Signed-off-by: Helge Deller <deller@gmx.de>

Pull perf tools fixes from Arnaldo Carvalho de Melo:

 - BPF program info linear (BPIL) data is accessed assuming 64-bit
   alignment resulting in undefined behavior as the data is just byte
   aligned. Fix it, Found using -fsanitize=undefined.

 - Fix 'perf offcpu' build on old kernels wrt task_struct's
   state/__state field.

 - Fix perf_event_attr.sample_type setting on the 'offcpu-time' event
   synthesized by the 'perf offcpu' tool.

 - Don't bail out when synthesizing PERF_RECORD_ events for pre-existing
   threads when one goes away while parsing its procfs entries.

 - Don't sort the task scan result from /proc, its not needed and
   introduces bugs when the main thread isn't the first one to be
   processed.

 - Fix uninitialized 'offset' variable on aarch64 in the unwind code.

 - Sync KVM headers with the kernel sources.

* tag 'perf-tools-fixes-for-v5.19-2022-07-02' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
  perf synthetic-events: Ignore dead threads during event synthesis
  perf synthetic-events: Don't sort the task scan result from /proc
  perf unwind: Fix unitialized 'offset' variable on aarch64
  tools headers UAPI: Sync linux/kvm.h with the kernel sources
  perf bpf: 8 byte align bpil data
  tools kvm headers arm64: Update KVM headers from the kernel sources
  perf offcpu: Accept allowed sample types only
  perf offcpu: Fix build failure on old kernels

Pull powerpc fixes from Michael Ellerman:

 - Fix BPF uapi confusion about the correct type of bpf_user_pt_regs_t.

 - Fix virt_addr_valid() when memory is hotplugged above the boot-time
   high_memory value.

 - Fix a bug in 64-bit Book3E map_kernel_page() which would incorrectly
   allocate a PMD page at PUD level.

 - Fix a couple of minor issues found since we enabled KASAN for 64-bit
   Book3S.

Thanks to Aneesh Kumar K.V, Cédric Le Goater, Christophe Leroy, Kefeng
Wang, Liam Howlett, Nathan Lynch, and Naveen N. Rao.

* tag 'powerpc-5.19-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/memhotplug: Add add_pages override for PPC
  powerpc/bpf: Fix use of user_pt_regs in uapi
  powerpc/prom_init: Fix kernel config grep
  powerpc/book3e: Fix PUD allocation size in map_kernel_page()
  powerpc/xive/spapr: correct bitmap allocation size

When it synthesize various task events, it scans the list of task
first and then accesses later.  There's a window threads can die
between the two and proc entries may not be available.

Instead of bailing out, we can ignore that thread and move on.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220701205458.985106-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>