On Fri, 26 Oct 2007 16:37:36 -0700
Mike Waychison <mikew@xxxxxxxxxx> wrote:
> Attempt to deal with races with truncate paths.
>
> I'm not really sure on the locking here, but these seem to be taken
> by the truncate path. BKL is left as some filesystem may(?) still
> require it.
>
> Signed-off-by: Mike Waychison <mikew@xxxxxxxxxx>
> fs/ioctl.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> Index: linux-2.6.23/fs/ioctl.c
> ===================================================================
> --- linux-2.6.23.orig/fs/ioctl.c 2007-10-26 15:27:29.000000000
> -0700 +++ linux-2.6.23/fs/ioctl.c 2007-10-26
> 16:16:28.000000000 -0700 @@ -43,13 +43,21 @@ static long
> do_ioctl(struct file *filp, static int do_fibmap(struct address_space
> *mapping, sector_t block, sector_t *phys_block)
> {
> + struct inode *inode = mapping->host;
> +
> if (!capable(CAP_SYS_RAWIO))
> return -EPERM;
> if (!mapping->a_ops->bmap)
> return -EINVAL;
>
> lock_kernel();
> + /* Avoid races with truncate */
> + mutex_lock(&inode->i_mutex);
> + /* FIXME: Do we really need i_alloc_sem? */
> + down_read(&inode->i_alloc_sem);
i_alloc_sem will avoid races with filesystems filling holes inside
writepage (where i_mutex isn't held). I'd expect everyone to currently
give some consistent result (either the old value or the new but not
garbage), but I wouldn't expect taking the semaphore to hurt anything.
-chris
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