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Subjectmnt_want_write_file() has problem?
Date
Hi,

While I'm reading some code, I suspected that mnt_want_write_file() may
have wrong assumption. I think mnt_want_write_file() is assuming it
increments ->mnt_writers if (file->f_mode & FMODE_WRITE). But, if it's
special_file(), it is false?

Sorry, I'm still not checking all of those though. E.g. I'm thinking the
below.

static inline int __get_file_write_access(struct inode *inode,
struct vfsmount *mnt)
{
[...]
if (!special_file(inode->i_mode)) {
/*
* Balanced in __fput()
*/
error = mnt_want_write(mnt);
if (error)
put_write_access(inode);
}
return error;
}

Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>



Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---

fs/namespace.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN fs/namespace.c~mnt_want_write-wrong-assume fs/namespace.c
--- linux-2.6/fs/namespace.c~mnt_want_write-wrong-assume 2009-08-03 04:33:35.000000000 +0900
+++ linux-2.6-hirofumi/fs/namespace.c 2009-08-03 04:31:34.000000000 +0900
@@ -316,7 +316,8 @@ EXPORT_SYMBOL_GPL(mnt_clone_write);
*/
int mnt_want_write_file(struct file *file)
{
- if (!(file->f_mode & FMODE_WRITE))
+ struct inode *inode = file->f_dentry->d_inode;
+ if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
return mnt_want_write(file->f_path.mnt);
else
return mnt_clone_write(file->f_path.mnt);
_

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