Re: [RESEND PATCH] gfs2: do not evict glocks with populated address spaces

Andreas Gruenbacher <[email protected]> wrote:
> There are two GLOCK_BUG_ON() assertions in __gfs2_glock_put(). I
> assume you are talking about this one:
> 
> GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
> 
> This should never trigger because each holder has a glock reference
> (see the gfs2_glock_hold() in __gfs2_holder_init()), and so
> gl->gl_lockref should never reach zero while there are holders.
> 
> If none of the holders has the HIF_HOLDER flag set, we don't know if
> the glock is actually locked.
Sorry, yes has two GLOCK_BUG_ON() assertions. I talk about the second
GLOCK_BUG_ON on __gfs2_glock_put(): 
`GLOCK_BUG_ON(gl, !mapping_empty(mapping))`. 

NOT ABOUT `GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));` (the first
GLOCK_BUG_ON())

The dump_stack() indicates a memory pressure and the
gfs2_glock_put_eventually() on fs/gfs2/super.c is called.
But when the __gfs2_glock_put() was called, the glock was has a private folios. 
I test by this way:
```
struct address_space *mapping = ...;
pgoff_t index;
struct folio *folio;
xa_for_each(&mapping->i_pages, index, folio) {
	if (folio_test_private(folio)) 
		pr_err("I have private folios")
}
```

And, I can see the glock is about metadata:
`gl->gl_name.ln_type != LM_TYPE_INODE`

the truncate_inode_pages_final() failed silently when the folio is private.

I guess maybe evict metadata (or locked) glock is not a good idea.

Thanks, Guilherme