mm/memory-failure.c clean up around tk pre-allocation

add_to_kill() expects the first 'tk' to be pre-allocated, it makes
subsequent allocations on need basis, this makes the code a bit
difficult to read.

Move all the allocation internal to add_to_kill() and drop the **tk
argument.

Link: http://lkml.kernel.org/r/1565112345-28754-2-git-send-email-jane.chu@oracle.comSigned-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -303,25 +303,19 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
 /*
  * Schedule a process for later kill.
  * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
- * TBD would GFP_NOIO be enough?
  */
 static void add_to_kill(struct task_struct *tsk, struct page *p,
 		       struct vm_area_struct *vma,
-		       struct list_head *to_kill,
-		       struct to_kill **tkc)
+		       struct list_head *to_kill)
 {
 	struct to_kill *tk;
 
-	if (*tkc) {
-		tk = *tkc;
-		*tkc = NULL;
-	} else {
-		tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
-		if (!tk) {
-			pr_err("Memory failure: Out of memory while machine check handling\n");
-			return;
-		}
+	tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
+	if (!tk) {
+		pr_err("Memory failure: Out of memory while machine check handling\n");
+		return;
 	}
+
 	tk->addr = page_address_in_vma(p, vma);
 	if (is_zone_device_page(p))
 		tk->size_shift = dev_pagemap_mapping_shift(p, vma);
@@ -345,6 +339,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
 		kfree(tk);
 		return;
 	}
+
 	get_task_struct(tsk);
 	tk->tsk = tsk;
 	list_add_tail(&tk->nd, to_kill);
@@ -436,7 +431,7 @@ static struct task_struct *task_early_kill(struct task_struct *tsk,
  * Collect processes when the error hit an anonymous page.
  */
 static void collect_procs_anon(struct page *page, struct list_head *to_kill,
-			      struct to_kill **tkc, int force_early)
+				int force_early)
 {
 	struct vm_area_struct *vma;
 	struct task_struct *tsk;
@@ -461,7 +456,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
 			if (!page_mapped_in_vma(page, vma))
 				continue;
 			if (vma->vm_mm == t->mm)
-				add_to_kill(t, page, vma, to_kill, tkc);
+				add_to_kill(t, page, vma, to_kill);
 		}
 	}
 	read_unlock(&tasklist_lock);
@@ -472,7 +467,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
  * Collect processes when the error hit a file mapped page.
  */
 static void collect_procs_file(struct page *page, struct list_head *to_kill,
-			      struct to_kill **tkc, int force_early)
+				int force_early)
 {
 	struct vm_area_struct *vma;
 	struct task_struct *tsk;
@@ -496,7 +491,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
 			 * to be informed of all such data corruptions.
 			 */
 			if (vma->vm_mm == t->mm)
-				add_to_kill(t, page, vma, to_kill, tkc);
+				add_to_kill(t, page, vma, to_kill);
 		}
 	}
 	read_unlock(&tasklist_lock);
@@ -505,26 +500,17 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
 
 /*
  * Collect the processes who have the corrupted page mapped to kill.
- * This is done in two steps for locking reasons.
- * First preallocate one tokill structure outside the spin locks,
- * so that we can kill at least one process reasonably reliable.
  */
 static void collect_procs(struct page *page, struct list_head *tokill,
 				int force_early)
 {
-	struct to_kill *tk;
-
 	if (!page->mapping)
 		return;
 
-	tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
-	if (!tk)
-		return;
 	if (PageAnon(page))
-		collect_procs_anon(page, tokill, &tk, force_early);
+		collect_procs_anon(page, tokill, force_early);
 	else
-		collect_procs_file(page, tokill, &tk, force_early);
-	kfree(tk);
+		collect_procs_file(page, tokill, force_early);
 }
 
 static const char *action_name[] = {