ovl: add ovl_fadvise()

Implement stacked fadvise to fix syscalls readahead(2) and fadvise64(2)
on an overlayfs file.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: d1d04ef8572b ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index a4acd84591d4..aeaefd2a551b 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -331,6 +331,25 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
         return ret;
 }
 
+static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+        struct fd real;
+        const struct cred *old_cred;
+        int ret;
+
+        ret = ovl_real_fdget(file, &real);
+        if (ret)
+                return ret;
+
+        old_cred = ovl_override_creds(file_inode(file)->i_sb);
+        ret = vfs_fadvise(real.file, offset, len, advice);
+        revert_creds(old_cred);
+
+        fdput(real);
+
+        return ret;
+}
+
 static long ovl_real_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg)
 {
@@ -499,6 +518,7 @@ const struct file_operations ovl_file_operations = {
         .fsync          = ovl_fsync,
         .mmap           = ovl_mmap,
         .fallocate      = ovl_fallocate,
+        .fadvise        = ovl_fadvise,
         .unlocked_ioctl = ovl_ioctl,
         .compat_ioctl   = ovl_compat_ioctl,