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Subject[PATCH 5.3 326/344] mm: Handle MADV_WILLNEED through vfs_fadvise()
Date
From: Jan Kara <jack@suse.cz>

commit 692fe62433d4ca47605b39f7c416efd6679ba694 upstream.

Currently handling of MADV_WILLNEED hint calls directly into readahead
code. Handle it by calling vfs_fadvise() instead so that filesystem can
use its ->fadvise() callback to acquire necessary locks or otherwise
prepare for the request.

Suggested-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Boaz Harrosh <boazh@netapp.com>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/madvise.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)

--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -14,6 +14,7 @@
#include <linux/userfaultfd_k.h>
#include <linux/hugetlb.h>
#include <linux/falloc.h>
+#include <linux/fadvise.h>
#include <linux/sched.h>
#include <linux/ksm.h>
#include <linux/fs.h>
@@ -275,6 +276,7 @@ static long madvise_willneed(struct vm_a
unsigned long start, unsigned long end)
{
struct file *file = vma->vm_file;
+ loff_t offset;

*prev = vma;
#ifdef CONFIG_SWAP
@@ -298,12 +300,20 @@ static long madvise_willneed(struct vm_a
return 0;
}

- start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
- if (end > vma->vm_end)
- 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);
+ /*
+ * Filesystem's fadvise may need to take various locks. We need to
+ * explicitly grab a reference because the vma (and hence the
+ * vma's reference to the file) can go away as soon as we drop
+ * mmap_sem.
+ */
+ *prev = NULL; /* tell sys_madvise we drop mmap_sem */
+ get_file(file);
+ up_read(&current->mm->mmap_sem);
+ offset = (loff_t)(start - vma->vm_start)
+ + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+ vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
+ fput(file);
+ down_read(&current->mm->mmap_sem);
return 0;
}


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