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b=r9UnyXZIV7L8ZEOOeJT1nl62EE6F8j9PcBYhYDgjuXdqLWdOasVD1Vd2xaxL5PqfE cHv1LnDQ9uXSc7KHeS91rdLs1uhyk0KakkBPQKfX1uspq/dM0doSGkbkcJxkqogn+b PoEcIOSBZeHC8NGZAaCohSy30TRBPO6BLUrqCI+UnSI8GGfhz/c5NmV3iq3pYPDItR F9FFuDHirpkbyfWCeUHIUy/iO5DbQvU6hFMlZQTQKemyHm76gGYOhO83Ek8lg7vWmH JVxDDl6VYryFXKGDdGPRB7+r4Lue0oZ8GpEjDBZjtpZh0t2rHd0q+bIBNP+kvf53ii V+6mOW30QW9kA== Message-ID: <5c1630ac-d304-4854-9ba6-5c9cc1f78be5@kernel.org> Date: Thu, 20 Nov 2025 21:23:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] fs/writeback: skip inodes with potential writeback hang in wait_sb_inodes() To: Joanne Koong , akpm@linux-foundation.org Cc: linux-mm@kvack.org, shakeel.butt@linux.dev, athul.krishna.kr@protonmail.com, miklos@szeredi.hu, stable@vger.kernel.org References: <20251120184211.2379439-1-joannelkoong@gmail.com> <20251120184211.2379439-3-joannelkoong@gmail.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251120184211.2379439-3-joannelkoong@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D4267C001A X-Stat-Signature: 56s5k9pixaoitbbntxiwpr6oruwfeacq X-Rspam-User: X-HE-Tag: 1763670235-705554 X-HE-Meta: U2FsdGVkX18tJdIO8Mi1Tbhj6WxCLvcz6RGK3sFXcoGMf44VCKVVAPQYa3AE9mMQiRVbkThm//Nwc5x+S91XDQZ8vms46F+pErgsy3C2Jf3IJgfGziSs8Q/IzpCPsnCWhPRwZrA0TYXkQCFwVkraTomQBwVVsvfi2kP0kxIIceHcamLPxzUDQI9p1JWGGdA+T2WmcvMBmI0Cl3uxXFmW+AqUT1Sn5H4C+t2qKvgFcbwuqqxbRipUy4qD+9MHx4+sHmNQ+wkMcYBjc2s5l31hUCoyq2ugOMJzOWmjgDwC0EBZPhHb7e6A2WsQ54Tg7yY0Qbe4YKJRpBgzwrMrtWRqp1N/XseWUVgeRmxXzWQYEI55xUBS8m6f5EgKZXMvqTWcTjkKeeOS18wz2Ume4VwaBxvJ6aEx5lqxuuw8wNiC639xlcXg7yvkOEWxkgqRXw1w7ZdzxUbv+rsEDNhj1D/6bQB0EH9qF91bynf51VhfVgQaPIZ+WZmlS++lb9HSuO8+CRrLAxO+ycZFvmHY6A/qZRS9+26nwaZndGRDPetgrfPNg7gYAvvUD28/+jE5uFT85OMxv+4k90TkePQL3jXoWMJ1Dt4sLwMqYIdrlafDbZdIOZ07Suvkeb4qiKTmo5o6VVXUp7Y25wY1M4ed6tZbQiO4beJBn+gW20N6m6UDo7jpPhVEEG5taKnrwSZKhxYNk1E91wZaycyiE0gt66QfARQERYLsWTzEAfvHWoLMPYYD7Iq15D0N7xjOlpZieufO4SUIQHGhvziA9X3+xidxSbAbSPHKAcEqdUaJquognjy6iUT8WyQ6GlvvIJZmrI4SRLAK2HTi62r8k0MhBouxpQXBYPxgi7JtDlHBaGFLaK1LNANaOJQZ1W1fVVhNHLrvApS+ieoKvfFgzTI9zWcEKWCa363dyQsV3R0zZXdqY9uar0/I4TB4zFlTIYMVULfyUm4ftvrclW0mUg4lvjq UlTpHQLH te4FbfnLRYHxy9EY7ojZAu7Q9lHNSyELcuTxtBMe83kv4BaMxW4mMy0mRQnEmkM3bsrxAoHUvaeaeb9q8+djuRMuXMCwKuulG/AF6DyQ31/aKwXHuv/3Q/7iv2NCwDHxIWwt1uOVeJ1S9kVqUooB+SBt8f4mor/Zs3NMO0bg5n1bZjWCsnxeHbvz7MgKxQZwaqu/AnL/XzsO9vJOQJxAWm/PCDHuMgZIg48x5cKY000biV+guAsBJtu9cFXI9LNEIFZxD7TQME1KyiKdNe4R2TV45qccG0ClxLKQppL8Whr1nE+zIhs/+by3D8YQmByKcYgGSk3V8x9G1UlQInhslsQGDYEmwVEvtgGRfIGu2qXIVIeDWJHhyuDeOKT5nr8YpF5BX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/20/25 19:42, Joanne Koong wrote: > During superblock writeback waiting, skip inodes where writeback may > take an indefinite amount of time or hang, as denoted by the > AS_WRITEBACK_MAY_HANG mapping flag. > > Currently, fuse is the only filesystem with this flag set. For a > properly functioning fuse server, writeback requests are completed and > there is no issue. However, if there is a bug in the fuse server and it > hangs on writeback, then without this change, wait_sb_inodes() will wait > forever. > > Signed-off-by: Joanne Koong > Fixes: 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb tree") > Reported-by: Athul Krishna > --- > fs/fs-writeback.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 2b35e80037fe..eb246e9fbf3d 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -2733,6 +2733,9 @@ static void wait_sb_inodes(struct super_block *sb) > if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) > continue; > > + if (mapping_writeback_may_hang(mapping)) > + continue; I think I raised it in the past, but simply because it could happen, why would we unconditionally want to do that for all fuse mounts? That just seems wrong :( To phrase it in a different way, if any writeback could theoretically hang, why are we even waiting on writeback in the first place? -- Cheers David