mm-support-posix_fadv_noreuse.patch removed from -mm tree

The quilt patch titled
Subject: mm: support POSIX_FADV_NOREUSE
has been removed from the -mm tree. Its filename was
mm-support-posix_fadv_noreuse.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Yu Zhao <[email protected]>
Subject: mm: support POSIX_FADV_NOREUSE
Date: Fri, 30 Dec 2022 14:52:52 -0700

This patch adds POSIX_FADV_NOREUSE to vma_has_recency() so that the LRU algorithm can ignore access to mapped files marked by this flag.

The advantages of POSIX_FADV_NOREUSE are:
1. Unlike MADV_SEQUENTIAL and MADV_RANDOM, it does not alter the default readahead behavior.
2. Unlike MADV_SEQUENTIAL and MADV_RANDOM, it does not split VMAs and therefore does not take mmap_lock.
3. Unlike MADV_COLD, setting it has a negligible cost, regardless of how many pages it affects.

Its limitations are:
1. Like POSIX_FADV_RANDOM and POSIX_FADV_SEQUENTIAL, it currently does not support range. IOW, its scope is the entire file.
2. It currently does not ignore access through file descriptors. Specifically, for the active/inactive LRU, given a file page shared by two users and one of them having set POSIX_FADV_NOREUSE on the file, this page will be activated upon the second user accessing it. This corner case can be covered by checking POSIX_FADV_NOREUSE before calling folio_mark_accessed() on the read path. But it is considered not worth the effort.

There have been a few attempts to support POSIX_FADV_NOREUSE, e.g., [1]. This time the goal is to fill a niche: a few desktop applications, e.g., large file transferring and video encoding/decoding, want fast file streaming with mmap() rather than direct IO. Among those applications, an SVT-AV1 regression was reported when running with MGLRU [2]. The following test can reproduce that regression.

  kb=$(awk '/MemTotal/ { print $2 }' /proc/meminfo)
  kb=$((kb - 8*1024*1024))

modprobe brd rd_nr=1 rd_size=$kb
dd if=/dev/zero of=/dev/ram0 bs=1M

mkfs.ext4 /dev/ram0
mount /dev/ram0 /mnt/
swapoff -a

fallocate -l 8G /mnt/swapfile
mkswap /mnt/swapfile
swapon /mnt/swapfile

  wget http://ultravideo.cs.tut.fi/video/Bosphorus_3840x2160_120fps_420_8bit_YUV_Y4M.7z
  7z e -o/mnt/ Bosphorus_3840x2160_120fps_420_8bit_YUV_Y4M.7z
  SvtAv1EncApp --preset 12 -w 3840 -h 2160 \
               -i /mnt/Bosphorus_3840x2160.y4m

For MGLRU, the following change showed a [9-11]% increase in FPS, which makes it on par with the active/inactive LRU.

  patch Source/App/EncApp/EbAppMain.c <<EOF
  31a32
  > #include <fcntl.h>
  35d35
  < #include <fcntl.h> /* _O_BINARY */
  117a118
  >             posix_fadvise(config->mmap.fd, 0, 0, POSIX_FADV_NOREUSE);
  EOF

[1] https://lore.kernel.org/r/[email protected]/
[2] https://openbenchmarking.org/result/2209259-PTS-MGLRU8GB57

---

 include/linux/fs.h        |    2 ++
 include/linux/mm_inline.h |    3 +++
 mm/fadvise.c              |    5 ++++-
 3 files changed, 9 insertions(+), 1 deletion(-)

@@ -166,6 +166,8 @@ typedef int (dio_iodone_t)(struct kiocb
 /* 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)
 

@@ -599,6 +599,9 @@ static inline bool vma_has_recency(struc
 	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;
 }
 

@@ -80,7 +80,7 @@ int generic_fadvise(struct file *file, l
 	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, l
 		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,

_

Patches currently in -mm which might be from [email protected] are

mm-multi-gen-lru-fix-crash-during-cgroup-migration.patch