From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
David Woodhouse <dwmw2@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org,
David Howells <dhowells@redhat.com>,
Bernd Schmidt <bernd.schmidt@analog.com>,
Alexander Shishkin <virtuoso@slind.org>
Subject: [BUG] Rewriting backing_dev_info in MTD
Date: Tue, 13 Apr 2010 14:33:01 +0300 [thread overview]
Message-ID: <g2ycc557aab1004130433g537f417ch401a97e5031f77ff@mail.gmail.com> (raw)
I've got NULL-pointer dereference in __mark_inode_dirty() on chmod()
for MTD device node. wb->bdi was NULL in this case.
During investigation I've found that MTD subsystem rewrites
file->f_mapping->backing_dev_info on openning to get mmap() work on
MMU-less systems. But in fact it rewrites
inode->i_mapping->backing_dev_info too, since inode->i_mapping ==
file->f_mapping (see __dentry_open() in fs/open.c). It breaks
writeback of inode changes.
I guess the right way to fix this is changing of __dentry_open() to
create _copy_ of i_mapping to assign to f_mapping since in common case
f_mapping != i_mapping. But I'm not sure were the copy should be
freed.
What do you think?
next reply other threads:[~2010-04-13 11:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-13 11:33 Kirill A. Shutemov [this message]
2010-04-15 17:23 ` [BUG] Rewriting backing_dev_info in MTD Jan Kara
2010-04-21 15:21 ` [PATCH] mtd: Do not corrupt backing device for inode Kirill A. Shutemov
2010-04-22 11:08 ` David Woodhouse
2010-04-22 15:20 ` Jan Kara
2010-05-03 16:56 ` [PATCH] mtd: Do not corrupt backing device of device node inode Kirill A. Shutemov
2010-05-03 18:54 ` Jan Kara
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