Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] netfs: Fix lockdep warning from taking sb_writers whilst holding mmap_lock | Date | Tue, 07 Dec 2021 13:32:13 +0000 |
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Matthew Wilcox <willy@infradead.org> wrote:
> On Tue, Dec 07, 2021 at 11:19:35AM +0000, David Howells wrote: > > Taking sb_writers whilst holding mmap_lock isn't allowed and will result in > > a lockdep warning like that below. The problem comes from cachefiles > > needing to take the sb_writers lock in order to do a write to the cache, > > but being asked to do this by netfslib called from readpage, readahead or > > write_begin[1]. > > Isn't it taking sb_writers _on a different filesystem_? So there's not > a real deadlock here, just a need to tell lockdep that this is a > different subclass of lock?
Jann thinks it can be turned into a real deadlock. See the link I put in the patch description:
> > Link: https://lore.kernel.org/r/20210922110420.GA21576@quack2.suse.cz/ [1]
David
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