Merge tag 'ovl-fixes-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fixes from Miklos Szeredi:
 "This fixes a regression in the recent file stacking update, reported
  and fixed by Amir Goldstein. The fix is fairly trivial, but involves
  adding a fadvise() f_op and the associated churn in the vfs. As
  discussed on -fsdevel, there are other possible uses for this method,
  than allowing proper stacking for overlays.

  And there's one other fix for a syzkaller detected oops"

* tag 'ovl-fixes-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix oopses in ovl_fill_super() failure paths
  ovl: add ovl_fadvise()
  vfs: implement readahead(2) using POSIX_FADV_WILLNEED
  vfs: add the fadvise() file operation
  Documentation/filesystems: update documentation of file_operations
  ovl: fix GPF in swapfile_activate of file from overlayfs over xfs
  ovl: respect FIEMAP_FLAG_SYNC flag

include/linux/fs.h

@@ -1763,6 +1763,7 @@ struct file_operations {
 			u64);
 	int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,
 			u64);
+	int (*fadvise)(struct file *, loff_t, loff_t, int);
 } __randomize_layout;
 
 struct inode_operations {
@@ -3459,4 +3460,8 @@ static inline bool dir_relax_shared(struct inode *inode)
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);
 
+/* mm/fadvise.c */
+extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
+		       int advice);
+
 #endif /* _LINUX_FS_H */