vfs: introduce generic_file_rw_checks()

Factor out helper with some checks on in/out file that are
common to clone_file_range and copy_file_range.

Suggested-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index df2006ba0cfa..a38619a4a6af 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3041,6 +3041,30 @@ int generic_remap_checks(struct file *file_in, loff_t pos_in,
         return 0;
 }
 
+
+/*
+ * Performs common checks before doing a file copy/clone
+ * from @file_in to @file_out.
+ */
+int generic_file_rw_checks(struct file *file_in, struct file *file_out)
+{
+        struct inode *inode_in = file_inode(file_in);
+        struct inode *inode_out = file_inode(file_out);
+
+        /* Don't copy dirs, pipes, sockets... */
+        if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
+                return -EISDIR;
+        if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
+                return -EINVAL;
+
+        if (!(file_in->f_mode & FMODE_READ) ||
+            !(file_out->f_mode & FMODE_WRITE) ||
+            (file_out->f_flags & O_APPEND))
+                return -EBADF;
+
+        return 0;
+}
+
 int pagecache_write_begin(struct file *file, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned flags,
                                 struct page **pagep, void **fsdata)