[PATCH 2/2] mm: support POSIX_FADV_NOREUSE for generic fadvise handler

[Yuanchu Xie <yuanchu@google.com>]

From: Yu Zhao <yuzhao@google.com>

POSIX_FADV_NOREUSE allows an application to specify that accesses to
file data does not follow LRU and is used only once. Since 2.6.18 this
is a no-op. We add FMODE_NOREUSE, checked in vma_has_locality to prevent
LRU activation.

Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Yuanchu Xie <yuanchu@google.com>
---
 include/linux/fs.h        | 2 ++
 include/linux/mm_inline.h | 3 +++
 mm/fadvise.c              | 5 ++++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 066555ad1bf8..5660ed0edf1a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -166,6 +166,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 /* File supports DIRECT IO */
 #define	FMODE_CAN_ODIRECT	((__force fmode_t)0x400000)
 
+#define	FMODE_NOREUSE		((__force fmode_t)0x800000)
+
 /* File was opened by fanotify and shouldn't generate fanotify events */
 #define FMODE_NONOTIFY		((__force fmode_t)0x4000000)
 
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 80c0f6901ead..024f834d952d 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -583,6 +583,9 @@ static inline bool vma_has_locality(struct vm_area_struct *vma)
 	if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))
 		return false;
 
+	if (vma->vm_file && (vma->vm_file->f_mode & FMODE_NOREUSE))
+		return false;
+
 	return true;
 }
 
diff --git a/mm/fadvise.c b/mm/fadvise.c
index bf04fec87f35..fb7c5f43fd2a 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -80,7 +80,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 	case POSIX_FADV_NORMAL:
 		file->f_ra.ra_pages = bdi->ra_pages;
 		spin_lock(&file->f_lock);
-		file->f_mode &= ~FMODE_RANDOM;
+		file->f_mode &= ~(FMODE_RANDOM | FMODE_NOREUSE);
 		spin_unlock(&file->f_lock);
 		break;
 	case POSIX_FADV_RANDOM:
@@ -107,6 +107,9 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 		force_page_cache_readahead(mapping, file, start_index, nrpages);
 		break;
 	case POSIX_FADV_NOREUSE:
+		spin_lock(&file->f_lock);
+		file->f_mode |= FMODE_NOREUSE;
+		spin_unlock(&file->f_lock);
 		break;
 	case POSIX_FADV_DONTNEED:
 		__filemap_fdatawrite_range(mapping, offset, endbyte,
-- 
2.39.0.314.g84b9a713c41-goog