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Mon, 19 Feb 2024 20:48:30 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:8998:e92c:64ca:f09f]) by smtp.gmail.com with ESMTPSA id ok3-20020a17090b1d4300b00299d619bf2dsm811441pjb.9.2024.02.19.20.48.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Feb 2024 20:48:29 -0800 (PST) Date: Tue, 20 Feb 2024 13:48:25 +0900 From: Sergey Senozhatsky To: Chengming Zhou Cc: nphamcs@gmail.com, yosryahmed@google.com, Sergey Senozhatsky , Minchan Kim , Andrew Morton , hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] mm/zsmalloc: remove migrate_write_lock_nested() Message-ID: <20240220044825.GD11472@google.com> References: <20240219-b4-szmalloc-migrate-v1-0-34cd49c6545b@bytedance.com> <20240219-b4-szmalloc-migrate-v1-2-34cd49c6545b@bytedance.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20240219-b4-szmalloc-migrate-v1-2-34cd49c6545b@bytedance.com> On (24/02/19 13:33), Chengming Zhou wrote: > static void migrate_write_unlock(struct zspage *zspage) > { > write_unlock(&zspage->lock); > @@ -2003,19 +1997,17 @@ static unsigned long __zs_compact(struct zs_pool *pool, > dst_zspage = isolate_dst_zspage(class); > if (!dst_zspage) > break; > - migrate_write_lock(dst_zspage); > } > > src_zspage = isolate_src_zspage(class); > if (!src_zspage) > break; > > - migrate_write_lock_nested(src_zspage); > - > + migrate_write_lock(src_zspage); > migrate_zspage(pool, src_zspage, dst_zspage); > - fg = putback_zspage(class, src_zspage); > migrate_write_unlock(src_zspage); > > + fg = putback_zspage(class, src_zspage); Hmm. Lockless putback doesn't look right to me. We modify critical zspage fileds in putback_zspage(). > if (fg == ZS_INUSE_RATIO_0) { > free_zspage(pool, class, src_zspage); > pages_freed += class->pages_per_zspage; > @@ -2025,7 +2017,6 @@ static unsigned long __zs_compact(struct zs_pool *pool, > if (get_fullness_group(class, dst_zspage) == ZS_INUSE_RATIO_100 > || spin_is_contended(&pool->lock)) { > putback_zspage(class, dst_zspage); > - migrate_write_unlock(dst_zspage); > dst_zspage = NULL; > > spin_unlock(&pool->lock); > @@ -2034,15 +2025,12 @@ static unsigned long __zs_compact(struct zs_pool *pool, > } > } > > - if (src_zspage) { > + if (src_zspage) > putback_zspage(class, src_zspage); > - migrate_write_unlock(src_zspage); > - } > > - if (dst_zspage) { > + if (dst_zspage) > putback_zspage(class, dst_zspage); > - migrate_write_unlock(dst_zspage); > - }