Messages in this thread | | | Date | Mon, 29 Oct 2007 09:36:18 -0400 | From | Chris Mason <> | Subject | Re: [patch 4/6][RFC] Attempt to plug race with truncate |
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On Fri, 26 Oct 2007 16:37:36 -0700 Mike Waychison <mikew@google.com> 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@google.com> > 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.
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