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b=VSnEPKWPkGYfgsbBCkycraDrTgZUJS3vjZs0plA5/JOOin935OlbvZml8Kf2FF8AG 4Laa4y6xXHx9N+pVIo6AjEUQYhihc6CrCGi22v4o0vJVOu6JHrIeBzt/UPFVoVBuvM MXoFG0AVuuMJP1HO7hFDcAnXT9biAB3IzIabrXCg= Date: Thu, 14 Dec 2023 14:23:20 -0800 From: Andrew Morton To: Yosry Ahmed Cc: Chengming Zhou , Nhat Pham , Chris Li , Johannes Weiner , Seth Jennings , Dan Streetman , Vitaly Wool , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 5/5] mm/zswap: cleanup zswap_reclaim_entry() Message-Id: <20231214142320.f5cf319e619dbb2127c423e9@linux-foundation.org> In-Reply-To: References: <20231213-zswap-dstmem-v1-0-896763369d04@bytedance.com> <20231213-zswap-dstmem-v1-5-896763369d04@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 5D6392001E X-Rspam-User: X-Stat-Signature: zphzwk7msu5pxzjcuzno5uodn7w67t4i X-Rspamd-Server: rspam03 X-HE-Tag: 1702592605-576826 X-HE-Meta: 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 dNqJUJyK R+VFT0Ou0ngThb7v/3pShMIbZeNaUGqOeD2ey4kx2P/YNGOQExGAa3LojDEgjLBAeFYHVNxic5pGBAt7wBOjfQ3WCdbch+SXzmchuLGvwBsKwSNqvUnM0X5MU0t4vzG+mn5pBbfImyrpSxx98PrOscETHFwCLf1r4jPth69jRl1gXmsUWdDISncsgN2GySb9T7GpOhcTrvmmXWQvZEnwE/jSyi3BDmaYlh/x0tZEXFlrjGsmE1SvhG8cLRCtwGh6Qvf8ixITbfGkr2BQwmVch7gKpFEny1VNuFXGLfVmQVH+umv4FJLYqfEqVG44qXZM0Q70haldSbj/PM46Djautp7ikl2uJWuVoDGfp 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 Wed, 13 Dec 2023 17:02:25 -0800 Yosry Ahmed wrote: > On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou > wrote: > > > > Also after the common decompress part goes to __zswap_load(), we can > > cleanup the zswap_reclaim_entry() a little. > > I think you mean zswap_writeback_entry(), same for the commit title. I updated my copy of the changelog, thanks. > > - /* > > - * If we get here because the page is already in swapcache, a > > - * load may be happening concurrently. It is safe and okay to > > - * not free the entry. It is also okay to return !0. > > - */ > > This comment should be moved above the failure check of > __read_swap_cache_async() above, not completely removed. This? --- a/mm/zswap.c~mm-zswap-cleanup-zswap_reclaim_entry-fix +++ a/mm/zswap.c @@ -1457,8 +1457,14 @@ static int zswap_writeback_entry(struct mpol = get_task_policy(current); page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, NO_INTERLEAVE_INDEX, &page_was_allocated, true); - if (!page) + if (!page) { + /* + * If we get here because the page is already in swapcache, a + * load may be happening concurrently. It is safe and okay to + * not free the entry. It is also okay to return !0. + */ return -ENOMEM; + } /* Found an existing page, we raced with load/swapin */ if (!page_was_allocated) {