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Subject[PATCH 2/2] Introduce __cond_lock_err
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

The __cond_lock macro expects the function to return 'true' if the lock
was acquired and 'false' if it wasn't. We have another common calling
convention in the kernel, which is returning 0 on success and an errno
on failure. It's hard to use the existing __cond_lock macro for those
kinds of functions, so introduce __cond_lock_err() and convert the
two existing users.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/compiler_types.h | 2 ++
include/linux/mm.h | 9 ++-------
mm/memory.c | 9 ++-------
3 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 6b79a9bba9a7..ff3c41c78efa 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -16,6 +16,7 @@
# define __acquire(x) __context__(x,1)
# define __release(x) __context__(x,-1)
# define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
+# define __cond_lock_err(x,c) ((c) ? 1 : ({ __acquire(x); 0; }))
# define __percpu __attribute__((noderef, address_space(3)))
# define __rcu __attribute__((noderef, address_space(4)))
# define __private __attribute__((noderef))
@@ -42,6 +43,7 @@ extern void __chk_io_ptr(const volatile void __iomem *);
# define __acquire(x) (void)0
# define __release(x) (void)0
# define __cond_lock(x,c) (c)
+# define __cond_lock_err(x,c) (c)
# define __percpu
# define __rcu
# define __private
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 94a9d2149bd6..2ccdc980296b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1328,13 +1328,8 @@ static inline int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
unsigned long *start, unsigned long *end,
pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
{
- int res;
-
- /* (void) is needed to make gcc happy */
- (void) __cond_lock(*ptlp,
- !(res = __follow_pte_pmd(mm, address, start, end,
- ptepp, pmdpp, ptlp)));
- return res;
+ return __cond_lock_err(*ptlp, __follow_pte_pmd(mm, address, start, end,
+ ptepp, pmdpp, ptlp));
}

static inline void unmap_shared_mapping_range(struct address_space *mapping,
diff --git a/mm/memory.c b/mm/memory.c
index cb433662af21..92d58309cf45 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4269,13 +4269,8 @@ int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
static inline int follow_pte(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, spinlock_t **ptlp)
{
- int res;
-
- /* (void) is needed to make gcc happy */
- (void) __cond_lock(*ptlp,
- !(res = __follow_pte_pmd(mm, address, NULL, NULL,
- ptepp, NULL, ptlp)));
- return res;
+ return __cond_lock_err(*ptlp, __follow_pte_pmd(mm, address, NULL, NULL,
+ ptepp, NULL, ptlp));
}

/**
--
2.15.1
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