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X-CSE-ConnectionGUID: nlg2ZjUhSDqofTLAHV6bog== X-CSE-MsgGUID: 8ngfco/2RUe/Rjex3UWTyg== X-IronPort-AV: E=McAfee;i="6700,10204,11221"; a="28128571" X-IronPort-AV: E=Sophos;i="6.11,195,1725346800"; d="scan'208";a="28128571" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2024 23:39:32 -0700 X-CSE-ConnectionGUID: Hy4aaEyiT72UlcXdzP8KAw== X-CSE-MsgGUID: wg5IyUUZRyCQQOpbDmO1Hg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,195,1725346800"; d="scan'208";a="81437071" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2024 23:39:28 -0700 From: "Huang, Ying" To: Nhat Pham Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, yosryahmed@google.com, hughd@google.com, shakeel.butt@linux.dev, ryan.roberts@arm.com, chrisl@kernel.org, david@redhat.com, kasong@tencent.com, willy@infradead.org, viro@zeniv.linux.org.uk, baohua@kernel.org, chengming.zhou@linux.dev, v-songbaohua@oppo.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] swap: shmem: remove SWAP_MAP_SHMEM In-Reply-To: <20241002012042.2753174-2-nphamcs@gmail.com> (Nhat Pham's message of "Tue, 1 Oct 2024 18:20:42 -0700") References: <20241002012042.2753174-1-nphamcs@gmail.com> <20241002012042.2753174-2-nphamcs@gmail.com> Date: Fri, 11 Oct 2024 14:35:55 +0800 Message-ID: <87cyk79mes.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F2126A0009 X-Stat-Signature: t8yah9xpxowj9dbs8k19fqrowbk6aj8n X-HE-Tag: 1728628770-156400 X-HE-Meta: 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 ugDLoNf3 +ijAhUDDLCKx+XnclG6f9hjQ8ADvHA2k98BvnlOO9obFAAEiLZ9sopCcOM5FblP6fE5lIwQ1Drvnw3Du31E2Z7BTJhXpxXXQaJC88iyWzQvCpRBg1C4eSfx8n+9js9TnrOF+3oqPM8MbVSI+myqe4Mfft4CvggXR/WnVlVkxH8TwT3r19iezPLdVYoJiwQD3/e9yUckNmI5jgn9EcK7Jk13gEu9s4kJ4sZvMTcCn32U76rTE= 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: Nhat Pham writes: [snip] > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 0cded32414a1..9bb94e618914 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1381,12 +1381,6 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *si, > if (usage == SWAP_HAS_CACHE) { > VM_BUG_ON(!has_cache); > has_cache = 0; > - } else if (count == SWAP_MAP_SHMEM) { > - /* > - * Or we could insist on shmem.c using a special > - * swap_shmem_free() and free_shmem_swap_and_cache()... > - */ > - count = 0; > } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { > if (count == COUNT_CONTINUED) { > if (swap_count_continued(si, offset, count)) > @@ -3626,7 +3620,6 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) > > offset = swp_offset(entry); > VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER); > - VM_WARN_ON(usage == 1 && nr > 1); > ci = lock_cluster_or_swap_info(si, offset); > > err = 0; > @@ -3652,6 +3645,13 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) > err = -EEXIST; > } else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) { > err = -EINVAL; > + } else { > + /* > + * The only swap_duplicate_nr() caller that passes nr > 1 is shmem, > + * who never re-duplicates any swap entry it owns. So this should > + * not happen. > + */ > + VM_WARN_ON(nr > 1 && (count & ~COUNT_CONTINUED) == SWAP_MAP_MAX); Why not VM_WARN_ON_ONCE(nr > 1 && count); ? IIUC, count == 0 is always true for shmem swap entry allocation. Then developers who use __swap_duplicate() with nr > 1 without noticing the unsupported feature can get warning during development immediately. "(count & ~COUNT_CONTINUED) == SWAP_MAP_MAX" is hard to be triggered during common swap test. > } > > if (err) > @@ -3686,27 +3686,28 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr) > return err; > } [snip] -- Best Regards, Huang, Ying