[PATCH] mm: Support madvise_willneed override by Filesystems

Boaz Harrosh
2019-07-03T01:05:08Z

On 19/06/2019 11:21, Jan Kara wrote:
<>
> Yes, I have patch to make madvise(MADV_WILLNEED) go through ->fadvise() as
> well. I'll post it soon since the rest of the series isn't really dependent
> on it.
>
> Honza
>

Hi Jan

Funny I'm sitting on the same patch since LSF last. I need it too for other
reasons. I have not seen, have you pushed your patch yet?
(Is based on old v4.20)

~~~~~~~~~
From fddb38169e33d23060ddd444ba6f2319f76edc89 Mon Sep 17 00:00:00 2001
From: Boaz Harrosh <boazh@netapp.com>
Date: Thu, 16 May 2019 20:02:14 +0300
Subject: [PATCH] mm: Support madvise_willneed override by Filesystems

In the patchset:
[b833a3660394] ovl: add ovl_fadvise()
[3d8f7615319b] vfs: implement readahead(2) using POSIX_FADV_WILLNEED
[45cd0faae371] vfs: add the fadvise() file operation

Amir Goldstein introduced a way for filesystems to overide fadvise.
Well madvise_willneed is exactly as fadvise_willneed except it always
returns 0.

In this patch we call the FS vector if it exists.

NOTE: I called vfs_fadvise(..,POSIX_FADV_WILLNEED);
(Which is my artistic preference)

I could also selectively call
if (file->f_op->fadvise)
return file->f_op->fadvise(..., POSIX_FADV_WILLNEED);
If we fear theoretical side effects. I don't mind either way.

CC: Amir Goldstein <amir73il@gmail.com>
CC: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Boaz Harrosh <boazh@netapp.com>
---
mm/madvise.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 6cb1ca93e290..6b84ddcaaaf2 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -24,6 +24,7 @@
#include <linux/swapops.h>
#include <linux/shmem_fs.h>
#include <linux/mmu_notifier.h>
+#include <linux/fadvise.h>

#include <asm/tlb.h>

@@ -303,7 +304,8 @@ static long madvise_willneed(struct vm_area_struct *vma,
end = vma->vm_end;
end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;

- force_page_cache_readahead(file->f_mapping, file, start, end - start);
+ vfs_fadvise(file, start << PAGE_SHIFT, (end - start) << PAGE_SHIFT,
+ POSIX_FADV_WILLNEED);
return 0;
}

--
2.20.1