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dkim=pass header.d=gmail.com header.s=20210112 header.b=micluZpS; spf=pass (imf14.hostedemail.com: domain of huangzhaoyang@gmail.com designates 209.85.167.41 as permitted sender) smtp.mailfrom=huangzhaoyang@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1666061570-677285 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: On Mon, Oct 17, 2022 at 11:55 PM Matthew Wilcox wrote: > > On Mon, Oct 17, 2022 at 01:34:13PM +0800, Zhaoyang Huang wrote: > > On Fri, Oct 14, 2022 at 8:12 PM Matthew Wilcox wrote: > > > > > > On Fri, Oct 14, 2022 at 01:30:48PM +0800, zhaoyang.huang wrote: > > > > From: Zhaoyang Huang > > > > > > > > Bellowing RCU stall is reported where kswapd traps in a live lock when shrink > > > > superblock's inode list. The direct reason is zombie page keeps staying on the > > > > xarray's slot and make the check and retry loop permanently. The root cause is unknown yet > > > > and supposed could be an xa update without synchronize_rcu etc. I would like to > > > > suggest skip this page to break the live lock as a workaround. > > > > > > No, the underlying bug should be fixed. > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Understand. IMHO, find_get_entry actruely works as an open API dealing with different kinds of address_spaces page cache, which requires high robustness to deal with any corner cases. Take the current problem as example, the inode with fault page(refcount=0) could remain on the sb's list without live lock problem. > > > OK, could I move the xas like below? > > > > + if (!folio_try_get_rcu(folio)) { > > + xas_next_offset(xas); > > goto reset; > > + }