fs: factor out backing_file_mmap() helper

Assert that the file object is allocated in a backing_file container
so that file_user_path() could be used to display the user path and
not the backing file's path in /proc/<pid>/maps.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>

diff --git a/fs/backing-file.c b/fs/backing-file.c
index ddd35c1d6c71fac43fa3e1fef62db53aadeda43b..a681f38d84d8e170bcca715c6045811c7c7f163b 100644 (file)
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -11,6 +11,7 @@
 #include <linux/fs.h>
 #include <linux/backing-file.h>
 #include <linux/splice.h>
+#include <linux/mm.h>
 
 #include "internal.h"
 
@@ -296,6 +297,32 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 }
 EXPORT_SYMBOL_GPL(backing_file_splice_write);
 
+int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
+                     struct backing_file_ctx *ctx)
+{
+       const struct cred *old_cred;
+       int ret;
+
+       if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) ||
+           WARN_ON_ONCE(ctx->user_file != vma->vm_file))
+               return -EIO;
+
+       if (!file->f_op->mmap)
+               return -ENODEV;
+
+       vma_set_file(vma, file);
+
+       old_cred = override_creds(ctx->cred);
+       ret = call_mmap(vma->vm_file, vma);
+       revert_creds(old_cred);
+
+       if (ctx->accessed)
+               ctx->accessed(ctx->user_file);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(backing_file_mmap);
+
 static int __init backing_aio_init(void)
 {
        backing_aio_cachep = kmem_cache_create("backing_aio",

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 69b52d2f9c74e5cff20d991f34c4a6f0220a74fb..05536964d37fdfae71508d15dbfab9bf2f75f38e 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -10,7 +10,6 @@
 #include <linux/uio.h>
 #include <linux/uaccess.h>
 #include <linux/security.h>
-#include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/backing-file.h>
 #include "overlayfs.h"
@@ -415,23 +414,13 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 {
        struct file *realfile = file->private_data;
-       const struct cred *old_cred;
-       int ret;
-
-       if (!realfile->f_op->mmap)
-               return -ENODEV;
-
-       if (WARN_ON(file != vma->vm_file))
-               return -EIO;
-
-       vma_set_file(vma, realfile);
-
-       old_cred = ovl_override_creds(file_inode(file)->i_sb);
-       ret = call_mmap(vma->vm_file, vma);
-       revert_creds(old_cred);
-       ovl_file_accessed(file);
+       struct backing_file_ctx ctx = {
+               .cred = ovl_creds(file_inode(file)->i_sb),
+               .user_file = file,
+               .accessed = ovl_file_accessed,
+       };
 
-       return ret;
+       return backing_file_mmap(realfile, vma, &ctx);
 }
 
 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)

diff --git a/include/linux/backing-file.h b/include/linux/backing-file.h
index 0546d5b1c9f59b73aed7a0389f3ac91c50194191..3f1fe1774f1b6984ad0edc64f21e12a7abe7f7c4 100644 (file)
--- a/include/linux/backing-file.h
+++ b/include/linux/backing-file.h
@@ -36,5 +36,7 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
                                  struct file *out, loff_t *ppos, size_t len,
                                  unsigned int flags,
                                  struct backing_file_ctx *ctx);
+int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
+                     struct backing_file_ctx *ctx);
 
 #endif /* _LINUX_BACKING_FILE_H */