Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Khazhismel Kumykov <khazhy@google.com>
To:     nborisov@suse.com, akpm@linux-foundation.org
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Khazhismel Kumykov <khazhy@google.com>,
        David Rientjes <rientjes@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Goldwyn Rodrigues <rgoldwyn@suse.de>,
        Jeff Mahoney <jeffm@suse.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH] fs/dcache.c: re-add cond_resched() in shrink_dcache_parent()
Date:   Fri, 13 Apr 2018 13:28:23 -0700
Message-Id: <20180413202823.204377-1-khazhy@google.com>
In-Reply-To: <20180413181350.88831-1-khazhy@google.com>
References: <20180413181350.88831-1-khazhy@google.com>
Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256;
        boundary="f403045dbf568b74990569c0b84a"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

--f403045dbf568b74990569c0b84a

shrink_dcache_parent may spin waiting for a parallel shrink_dentry_list.
In this case we may have 0 dentries to dispose, so we will never
schedule out while waiting for the parallel shrink_dentry_list to
complete.

Tested that this fixes syzbot reports of stalls in shrink_dcache_parent()

Fixes: 32785c0539b7 ("fs/dcache.c: add cond_resched() in shrink_dentry_list()")
Reported-by: syzbot+ae80b790eb412884ca77@syzkaller.appspotmail.com

Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 fs/dcache.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/dcache.c b/fs/dcache.c
index 591b34500e41..3507badeb60a 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1489,6 +1489,7 @@ void shrink_dcache_parent(struct dentry *parent)
 			break;
 
 		shrink_dentry_list(&data.dispose);
+		cond_resched();
 	}
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
-- 
2.17.0.484.g0c8726318c-goog


--f403045dbf568b74990569c0b84a
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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==
--f403045dbf568b74990569c0b84a--