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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> 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> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 1F02C1C0008 X-Stat-Signature: kezspw4f6rrfnfejbrf6ccthq54958o1 X-HE-Tag: 1708404510-236496 X-HE-Meta: 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 LSZ+obI8 Z2XqL1tCBJycWeazmpE/CoID5zAdLaelxNMGVSrDANVeS8hFzB++WLf1tN3xtKTlyv/P9tXDC2vsujeISatUlkaEzdLWvAOtav/l8Nyyap3I9ifVLn2z0ZoIeyu/sfcXoj/OD+22IcehsGHztPSalZPS+2T/KQTrpJ6/IXItP2Psq8S4T3sWt+R2HlSgxEpvs4EDLdbO+fXd+aGsNOxIQB6T9nBnfPx6SiCyD11p2OTKPaaSzF23FFBOKBHcm8KhWEUTCVzCD/cteqQse9x5dGDanQ1nSXXYVtOeojLI+aMp5mJEsFnX3pChsJVbdNDM4SDt2xwkFruZd4Xdz5qzwwtnIKB0li7hIAGymYXQV+8/aJQ8mUN72gGGGxw6jylxsOhlpas+wGnWBLG1rcrP4cpf0itZzkA2XbQCJhuVRYIB/Gy+qdz0/adzv9A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.036944, 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 (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); > - }