x86, bts, mm: clean up buffer allocation

The current mm interface is asymetric. One function allocates a locked
buffer, another function only refunds the memory.

Change this to have two functions for accounting and refunding locked
memory, respectively; and do the actual buffer allocation in ptrace.

[ Impact: refactor BTS buffer allocation code ]

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090424095143.A30265@sedona.ch.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 47 insertions, 34 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index d5252ae6c520..09ecbde91c13 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -617,17 +617,28 @@ struct bts_context {
         struct work_struct      work;
 };
 
-static inline void alloc_bts_buffer(struct bts_context *context,
-                                    unsigned int size)
+static int alloc_bts_buffer(struct bts_context *context, unsigned int size)
 {
-        void *buffer;
+        void *buffer = NULL;
+        int err = -ENOMEM;
 
-        buffer = alloc_locked_buffer(size);
-        if (buffer) {
-                context->buffer = buffer;
-                context->size = size;
-                context->mm = get_task_mm(current);
-        }
+        err = account_locked_memory(current->mm, current->signal->rlim, size);
+        if (err < 0)
+                return err;
+
+        buffer = kzalloc(size, GFP_KERNEL);
+        if (!buffer)
+                goto out_refund;
+
+        context->buffer = buffer;
+        context->size = size;
+        context->mm = get_task_mm(current);
+
+        return 0;
+
+ out_refund:
+        refund_locked_memory(current->mm, size);
+        return err;
 }
 
 static inline void free_bts_buffer(struct bts_context *context)
@@ -638,7 +649,7 @@ static inline void free_bts_buffer(struct bts_context *context)
         kfree(context->buffer);
         context->buffer = NULL;
 
-        refund_locked_buffer_memory(context->mm, context->size);
+        refund_locked_memory(context->mm, context->size);
         context->size = 0;
 
         mmput(context->mm);
@@ -786,13 +797,15 @@ static int ptrace_bts_config(struct task_struct *child,
         context->tracer = NULL;
 
         if ((cfg.flags & PTRACE_BTS_O_ALLOC) && (cfg.size != context->size)) {
+                int err;
+
                 free_bts_buffer(context);
                 if (!cfg.size)
                         return 0;
 
-                alloc_bts_buffer(context, cfg.size);
-                if (!context->buffer)
-                        return -ENOMEM;
+                err = alloc_bts_buffer(context, cfg.size);
+                if (err < 0)
+                        return err;
         }
 
         if (cfg.flags & PTRACE_BTS_O_TRACE)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a3963ba23a6d..009eabd3c21c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -19,6 +19,7 @@ struct anon_vma;
 struct file_ra_state;
 struct user_struct;
 struct writeback_control;
+struct rlimit;
 
 #ifndef CONFIG_DISCONTIGMEM          /* Don't use mapnrs, do it properly */
 extern unsigned long max_mapnr;
@@ -1319,7 +1320,8 @@ int vmemmap_populate_basepages(struct page *start_page,
 int vmemmap_populate(struct page *start_page, unsigned long pages, int node);
 void vmemmap_populate_print_last(void);
 
-extern void *alloc_locked_buffer(size_t size);
-extern void refund_locked_buffer_memory(struct mm_struct *mm, size_t size);
+extern int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
+                                 size_t size);
+extern void refund_locked_memory(struct mm_struct *mm, size_t size);
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
diff --git a/mm/mlock.c b/mm/mlock.c
index 28be15ead9c1..ac130433c7d3 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -629,38 +629,36 @@ void user_shm_unlock(size_t size, struct user_struct *user)
         free_uid(user);
 }
 
-void *alloc_locked_buffer(size_t size)
+int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
+                          size_t size)
 {
-        unsigned long rlim, vm, pgsz;
-        void *buffer = NULL;
+        unsigned long lim, vm, pgsz;
+        int error = -ENOMEM;
 
         pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
-        down_write(&current->mm->mmap_sem);
-
-        rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
-        vm   = current->mm->total_vm + pgsz;
-        if (rlim < vm)
-                goto out;
+        down_write(&mm->mmap_sem);
 
-        rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
-        vm   = current->mm->locked_vm + pgsz;
-        if (rlim < vm)
+        lim = rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
+        vm   = mm->total_vm + pgsz;
+        if (lim < vm)
                 goto out;
 
-        buffer = kzalloc(size, GFP_KERNEL);
-        if (!buffer)
+        lim = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
+        vm   = mm->locked_vm + pgsz;
+        if (lim < vm)
                 goto out;
 
-        current->mm->total_vm  += pgsz;
-        current->mm->locked_vm += pgsz;
+        mm->total_vm  += pgsz;
+        mm->locked_vm += pgsz;
 
+        error = 0;
  out:
-        up_write(&current->mm->mmap_sem);
-        return buffer;
+        up_write(&mm->mmap_sem);
+        return error;
 }
 
-void refund_locked_buffer_memory(struct mm_struct *mm, size_t size)
+void refund_locked_memory(struct mm_struct *mm, size_t size)
 {
         unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;