From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: [PATCH] mtd: Do not corrupt backing device for inode Date: Thu, 22 Apr 2010 12:08:55 +0100 Message-ID: <1271934535.11751.1550.camel@macbook.infradead.org> References: <20100415172300.GF3561@quack.suse.cz> <1271863269-5423-1-git-send-email-kirill@shutemov.name> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Jan Kara , Alexander Viro , David Howells , Alexander Shishkin , linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: "Kirill A. Shutemov" Return-path: In-Reply-To: <1271863269-5423-1-git-send-email-kirill@shutemov.name> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 2010-04-21 at 18:21 +0300, Kirill A. Shutemov wrote: > + /* > + * We cannot modify file->f_mapping->backing_dev_info directly, > + * because it will corrupt backing device for inode, since > + * inode->i_mapping is equal to file->f_mapping. So we have to > + * copy f_mapping first. > + */ > + file->f_mapping = kmalloc(sizeof(*file->f_mapping), GFP_KERNEL); > + memcpy(file->f_mapping, inode->i_mapping, > + sizeof(*file->f_mapping)); > file->f_mapping->backing_dev_info = mtd->backing_dev_info; > + } Ick. What about the rest of file->f_mapping? That'll still be inherited. Jan pointed at drivers/char/raw.c as an example, but that doesn't do anything as ugly as this -- that sets file->f_mapping to point at bdev->bd_inode->i_mapping instead. I suspect we should do something similar -- have an inode for the MTD device, with a valid i_data of its own. -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation