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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8de5ed06c6bsm21142376d6.18.2026.06.19.05.13.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jun 2026 05:13:20 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1waY63-00000004THz-2S2T; Fri, 19 Jun 2026 09:13:19 -0300 Date: Fri, 19 Jun 2026 09:13:19 -0300 From: Jason Gunthorpe To: "Liam R. Howlett" Cc: Rik van Riel , linux-kernel@vger.kernel.org, kernel-team@meta.com, robin.murphy@arm.com, joro@8bytes.org, will@kernel.org, iommu@lists.linux.dev, kyle@mcmartin.ca, Rik van Riel , maple-tree@lists.infradead.org Subject: Re: [PATCH v3 3/3] iova: defer maple tree erase on GFP_ATOMIC failure Message-ID: <20260619121319.GK231643@ziepe.ca> References: <20260612180303.GO1066031@ziepe.ca> <20260615115633.GQ1066031@ziepe.ca> <20260617180419.GA231643@ziepe.ca> <20260618152451.GE231643@ziepe.ca> <76xtcbn5hxv3z2w6zbbudr5exjqdgjan4dkcsvrpgagdfpc45x@7prb5j6ivh4w> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <76xtcbn5hxv3z2w6zbbudr5exjqdgjan4dkcsvrpgagdfpc45x@7prb5j6ivh4w> On Fri, Jun 19, 2026 at 12:54:13AM -0400, Liam R. Howlett wrote: > On 26/06/18 11:51PM, Rik van Riel wrote: > > On Thu, 2026-06-18 at 12:24 -0300, Jason Gunthorpe wrote: > > > > > > - I like your idea for Rik to try to store NULL to erase, on failure > > >   store ZERO_ENTRY, and then set a note on the next alloc to clean > > > the > > >   ZERO_ENTRYs? > > > > > Is there any efficient way to find those XA_ZERO_ENTRYs? > > > > Without a good way to find them, we might still need the > > llist to clean them up, though I agree that cleaning them > > up from the allocator side looks cleaner than doing it > > from an external worker, and I did make that change for v4. > > no, but how often is there a failure? Would walking the list and > writing NULLs be out of the question (I really don't know, sorry if it's > a dumb one)? Yeah, this is what I was thinking. Should never happen? I wouldn't burn memory in each node to make an emergency recovery run faster. The idea of keeping track of the high/low along with the flag makes sense, it will narrow the IOVA range to search. Jason