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[2003:cb:c704:3500:b8a3:191c:eae:cc05]) by smtp.gmail.com with ESMTPSA id v7-20020a05600c444700b003eb0d6f48f3sm15048551wmn.27.2023.03.06.06.01.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Mar 2023 06:01:53 -0800 (PST) Message-ID: <2a3386e7-9b09-f22e-ee39-a37a046d54ec@redhat.com> Date: Mon, 6 Mar 2023 15:01:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH 3/6] shmem: move reclaim check early on writepages() To: Luis Chamberlain , hughd@google.com, akpm@linux-foundation.org, willy@infradead.org, brauner@kernel.org Cc: linux-mm@kvack.org, p.raghav@samsung.com, da.gomez@samsung.com, a.manzanares@samsung.com, dave@stgolabs.net, yosryahmed@google.com, keescook@chromium.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org References: <20230302232758.888157-1-mcgrof@kernel.org> <20230302232758.888157-4-mcgrof@kernel.org> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230302232758.888157-4-mcgrof@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: cmjnmrmmoi1s8fss5mro9q7ixupti7i7 X-Rspam-User: X-Rspamd-Queue-Id: 76CAA40027 X-Rspamd-Server: rspam06 X-HE-Tag: 1678111652-23626 X-HE-Meta: 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 q+7eI7NX 2ICZvbpPgd7hzvP617gD8ChF2Oas6DAW//lqfyTDD6kLMdbheRf9XcZuJEBt1ZnG2EbJmqhyRYo1K1pRWT5vhx/yrQiqHdRXo5vyxaVxNgno8RBgvM3AVviRHfxlwL+bJHRxXY2+Ez3VKuZ5dp3K/BYZWhDywhOx0EUrVWyuYX4/7CVcwaZOClIps8Ld2DWlIfhqHY5m/EZonpFmihiwdCEl/1T/0n2e7t2PiMPrXCiHJpE+TVUkcPs/61AyojlrxTwcbClyFV1c5tKaZZQNwrvsqyXck86gYiiBy+V4SaCA17nDzaz3F3r1Srq5D4Z0M4FtPpkbDs94DAyXe9mUWuyRJba3Ci8xN++xkbakNRAYPE8bYrOQFRORtBa8p+A8/aeUM2K3IFTh9rUT52nl7Ixvubopf2RdIRdpMfFo7EDKNjX4UTy4qgvcM72DWyodUhHYzK8ZaO4QZK6IJcwMi3jMKMaijaCCuIj323MXeSYbSZXE= 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: On 03.03.23 00:27, Luis Chamberlain wrote: > i915_gem requires huge folios to be split when swapping. > However we have check for usage of writepages() to ensure > it used only for swap purposes later. Avoid the splits if > we're not being called for reclaim, even if they should in > theory not happen. > > This makes the conditions easier to follow on shem_writepage(). > > Signed-off-by: Luis Chamberlain > --- > mm/shmem.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 2b9ff585a553..a5a6da51087e 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1340,6 +1340,18 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > swp_entry_t swap; > pgoff_t index; > > + /* > + * Our capabilities prevent regular writeback or sync from ever calling > + * shmem_writepage; but a stacking filesystem might use ->writepage of > + * its underlying filesystem, in which case tmpfs should write out to > + * swap only in response to memory pressure, and not for the writeback > + * threads or sync. > + */ > + if (!wbc->for_reclaim) { if (WARN_ON_ONCE(!wbc->for_reclaim)) > + WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ And drop the comment :) That's what WARN_ON_ONCE is all about. > + goto redirty; > + } > + > /* > * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or > * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages, > @@ -1360,18 +1372,6 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > if (!total_swap_pages) > goto redirty; > > - /* > - * Our capabilities prevent regular writeback or sync from ever calling > - * shmem_writepage; but a stacking filesystem might use ->writepage of > - * its underlying filesystem, in which case tmpfs should write out to > - * swap only in response to memory pressure, and not for the writeback > - * threads or sync. > - */ > - if (!wbc->for_reclaim) { > - WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ > - goto redirty; > - } > - > /* > * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC > * value into swapfile.c, the only way we can correctly account for a LGTM Acked-by: David Hildenbrand -- Thanks, David / dhildenb