From: David Sterba <dsterba@suse.cz>
To: Nikolay Borisov <nborisov@suse.com>
Cc: Josef Bacik <josef@toxicpanda.com>,
kernel-team@fb.com, linux-btrfs@vger.kernel.org,
Zdenek Sojka <zsojka@seznam.cz>
Subject: Re: [PATCH] btrfs: nofs inode allocations
Date: Tue, 1 Oct 2019 20:06:13 +0200 [thread overview]
Message-ID: <20191001180613.GF2751@twin.jikos.cz> (raw)
In-Reply-To: <a4f375b2-b610-ed0b-4dcf-147da15065ef@suse.com>
On Mon, Sep 09, 2019 at 05:28:11PM +0300, Nikolay Borisov wrote:
> > This is because btrfs_new_inode() calls new_inode() under the
> > transaction. We could probably move the new_inode() outside of this but
> > for now just wrap it in memalloc_nofs_save().
>
> If I'm understanding correctly what happens here is that symlinking
> wants to instantiate a new inode
> (new_inode->btrfs_alloc_inode->kmem_cache_alloc with GFP_KERNEL) but it
> triggers background reclaim, hence goes to sleep, while holding a
> transaction. At the same time background reclaim joins the same
> transaction which is now blocked by the symlinking thread, hence it's
> prone to deadlock ?
Yes, that's the pattern, GFP_KERNEL inside
start_transaction/commit_transaction. The more generic fix is in the works.
next prev parent reply other threads:[~2019-10-01 18:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 14:12 [PATCH] btrfs: nofs inode allocations Josef Bacik
2019-09-09 14:28 ` Nikolay Borisov
2019-10-01 18:06 ` David Sterba [this message]
2019-09-11 9:37 ` Filipe Manana
2019-10-01 18:11 ` David Sterba
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