Messages in this thread Patch in this message | | | Subject | Re: [PATCH v4] mtd: Do not corrupt backing device of device node inode | From | David Woodhouse <> | Date | Fri, 14 May 2010 02:04:34 +0100 |
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On Wed, 2010-05-05 at 18:40 +0300, Kirill A. Shutemov wrote: > We cannot modify file->f_mapping->backing_dev_info, because it will corrupt > backing device of device node inode, since file->f_mapping is equal to > inode->i_mapping (see __dentry_open() in fs/open.c). > > Let's introduce separate inode for MTD device with appropriate backing > device.
I hate the fact that we have to do this -- is it really the only option?
Is it _just_ for the backing_device_info? Can't that be done differently?
> @@ -85,11 +88,27 @@ static int mtd_open(struct inode *inode, struct file *file) > goto out; > } > > - if (mtd->backing_dev_info) > - file->f_mapping->backing_dev_info = mtd->backing_dev_info; > + if (!mtd->inode) { > + mtd->inode = new_inode(mtd_inode_mnt->mnt_sb);
I believe that would be a race condition, if it wasn't for the BKL.
And what happens when you close the chardevice and call iput() on the inode so it's destroyed, and then you re-open the device? You never set mtd->inode = NULL, so won't it now try to igrab a stale pointer?
You won't have seen this in your testing unless you made it prune the icache between the close and open calls.
-- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation
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