[PATCH 11/39] Revert "Revert "ovl: get_write_access() in truncate""

[Miklos Szeredi]

This reverts commit 31c3a7069593b072bd57192b63b62f9a7e994e9a.

Re-add functionality dealing with i_writecount on truncate to overlayfs.
This patch shouldn't have any observable effects, since we just re-assert
the writecout that vfs_truncate() already got for us.

This is in preparation for moving overlay functionality out of the VFS.

Signed-off-by: Miklos Szeredi <mszer...@redhat.com>
---
 fs/overlayfs/inode.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 24fc27683a57..0116ec12451d 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -39,10 +39,27 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
        if (err)
                goto out;
 
+       if (attr->ia_valid & ATTR_SIZE) {
+               struct inode *realinode = d_inode(ovl_dentry_real(dentry));
+
+               err = -ETXTBSY;
+               if (atomic_read(&realinode->i_writecount) < 0)
+                       goto out_drop_write;
+       }
+
        err = ovl_copy_up(dentry);
        if (!err) {
+               struct inode *winode = NULL;
+
                upperdentry = ovl_dentry_upper(dentry);
 
+               if (attr->ia_valid & ATTR_SIZE) {
+                       winode = d_inode(upperdentry);
+                       err = get_write_access(winode);
+                       if (err)
+                               goto out_drop_write;
+               }
+
                if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
                        attr->ia_valid &= ~ATTR_MODE;
 
@@ -53,7 +70,11 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
                if (!err)
                        ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
                inode_unlock(upperdentry->d_inode);
+
+               if (winode)
+                       put_write_access(winode);
        }
+out_drop_write:
        ovl_drop_write(dentry);
 out:
        return err;
-- 
2.14.3