Re: [PATCH v2 5/5] fs: Add inode_assert_locked() and inode_assert_locked_excl()

Matthew Wilcox
2023-10-08T21:05:40Z

On Sun, Oct 08, 2023 at 10:26:40PM +0200, Mateusz Guzik wrote:
> On 10/7/23, Matthew Wilcox (Oracle) <willy@infradead.org> wrote:
> > +static inline void inode_assert_locked_excl(const struct inode *inode)
> > +{
> > + rwsem_assert_held_write(&inode->i_rwsem);
> > +}
> > +
> > static inline void inode_lock_nested(struct inode *inode, unsigned
> > subclass)
> > {
> > down_write_nested(&inode->i_rwsem, subclass);
>
> Why "excl" instead of "write"? Apart from looking weird, it is
> inconsistent with "prior art" in the file: i_mmap_assert_write_locked.

Yes, but that pairs with i_mmap_lock_write() / i_mmap_lock_read().

The problem is that we have inode_lock() / inode_lock_shared()
inode_assert_locked_read/write doesn't make sense with them. But
inode_assert_locked() doesn't make sense as the assertion for
inode_lock() because you'd expect it to assert whether the inode lock
is held at all. So I went with inode_assert_locked_excl().

I wouldn't mind if we converted all the inode_lock()/shared to
inode_lock_read() / inode_lock_write(), and then added
inode_assert_read_locked() / inode_assert_write_locked(). That's
a bit of a bigger job than I want to take on today.