[PATCH v6 3/7] mm: check fatal signal pending of target process

[Minchan Kim]

Bail out to prevent unnecessary CPU overhead if target process has
pending fatal signal during (MADV_COLD|MADV_PAGEOUT) operation.

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 mm/madvise.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index f29155b8185d..def1507c2030 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -36,6 +36,7 @@
 struct madvise_walk_private {
 	struct mmu_gather *tlb;
 	bool pageout;
+	struct task_struct *target_task;
 };
 
 /*
@@ -316,6 +317,10 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 	if (fatal_signal_pending(current))
 		return -EINTR;
 
+	if (private->target_task &&
+			fatal_signal_pending(private->target_task))
+		return -EINTR;
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (pmd_trans_huge(*pmd)) {
 		pmd_t orig_pmd;
@@ -471,12 +476,14 @@ static const struct mm_walk_ops cold_walk_ops = {
 };
 
 static void madvise_cold_page_range(struct mmu_gather *tlb,
+			     struct task_struct *task,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end)
 {
 	struct madvise_walk_private walk_private = {
 		.pageout = false,
 		.tlb = tlb,
+		.target_task = task,
 	};
 
 	tlb_start_vma(tlb, vma);
@@ -484,7 +491,8 @@ static void madvise_cold_page_range(struct mmu_gather *tlb,
 	tlb_end_vma(tlb, vma);
 }
 
-static long madvise_cold(struct vm_area_struct *vma,
+static long madvise_cold(struct task_struct *task,
+			struct vm_area_struct *vma,
 			struct vm_area_struct **prev,
 			unsigned long start_addr, unsigned long end_addr)
 {
@@ -497,19 +505,21 @@ static long madvise_cold(struct vm_area_struct *vma,
 
 	lru_add_drain();
 	tlb_gather_mmu(&tlb, mm, start_addr, end_addr);
-	madvise_cold_page_range(&tlb, vma, start_addr, end_addr);
+	madvise_cold_page_range(&tlb, task, vma, start_addr, end_addr);
 	tlb_finish_mmu(&tlb, start_addr, end_addr);
 
 	return 0;
 }
 
 static void madvise_pageout_page_range(struct mmu_gather *tlb,
+			     struct task_struct *task,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end)
 {
 	struct madvise_walk_private walk_private = {
 		.pageout = true,
 		.tlb = tlb,
+		.target_task = task,
 	};
 
 	tlb_start_vma(tlb, vma);
@@ -533,7 +543,8 @@ static inline bool can_do_pageout(struct vm_area_struct *vma)
 		inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
 }
 
-static long madvise_pageout(struct vm_area_struct *vma,
+static long madvise_pageout(struct task_struct *task,
+			struct vm_area_struct *vma,
 			struct vm_area_struct **prev,
 			unsigned long start_addr, unsigned long end_addr)
 {
@@ -549,7 +560,7 @@ static long madvise_pageout(struct vm_area_struct *vma,
 
 	lru_add_drain();
 	tlb_gather_mmu(&tlb, mm, start_addr, end_addr);
-	madvise_pageout_page_range(&tlb, vma, start_addr, end_addr);
+	madvise_pageout_page_range(&tlb, task, vma, start_addr, end_addr);
 	tlb_finish_mmu(&tlb, start_addr, end_addr);
 
 	return 0;
@@ -929,7 +940,8 @@ static int madvise_inject_error(int behavior,
 #endif
 
 static long
-madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
+madvise_vma(struct task_struct *task, struct vm_area_struct *vma,
+		struct vm_area_struct **prev,
 		unsigned long start, unsigned long end, int behavior)
 {
 	switch (behavior) {
@@ -938,9 +950,9 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 	case MADV_WILLNEED:
 		return madvise_willneed(vma, prev, start, end);
 	case MADV_COLD:
-		return madvise_cold(vma, prev, start, end);
+		return madvise_cold(task, vma, prev, start, end);
 	case MADV_PAGEOUT:
-		return madvise_pageout(vma, prev, start, end);
+		return madvise_pageout(task, vma, prev, start, end);
 	case MADV_FREE:
 	case MADV_DONTNEED:
 		return madvise_dontneed_free(vma, prev, start, end, behavior);
@@ -1140,7 +1152,8 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
 			tmp = end;
 
 		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
-		error = madvise_vma(vma, &prev, start, tmp, behavior);
+		error = madvise_vma(target_task, vma, &prev,
+					start, tmp, behavior);
 		if (error)
 			goto out;
 		start = tmp;
-- 
2.25.0.265.gbab2e86ba0-goog