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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781787914; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZVVVTITUcrw54iAGavqU8F/yKQPskyiHrFhdNlaRoRA=; b=Wk5cJwepVaWclDc134tmdLNIIt95s41cWvJrYH6zIy4ys2oeHlyZ7+w0NB9b0cAJ8AcELU eUnaOoxjpQTxU1qv/GWWlREw+idktXOppM9MTvbCEogXjBhuP2S80k+/hF2h+PTpaQjRjg gaB7eoLWfGLzW9e19m5+4svhARRIjms= From: Kaitao Cheng To: Andrew Morton , Uladzislau Rezki , Dennis Zhou , Tejun Heo , Christoph Lameter , Vlastimil Babka , Pedro Falcato , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kaitao Cheng Subject: [PATCH v4 3/4] mm/percpu: Make cached pages lookup explicit Date: Thu, 18 Jun 2026 21:04:13 +0800 Message-ID: <20260618130414.96383-4-kaitao.cheng@linux.dev> In-Reply-To: <20260618130414.96383-1-kaitao.cheng@linux.dev> References: <20260618130414.96383-1-kaitao.cheng@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2152720019 X-Stat-Signature: 3psmka3h8frim7ddmjwygurnyhsmge36 X-Rspam-User: X-HE-Tag: 1781787915-875964 X-HE-Meta: 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 51H3ceyO ymGo3kK4E+b7cJyAVkKg97kM4nU3wXgzV/J/XwqMF2O/kTAO4nWazMgSG+VVqk21Tyyf7WTFXKf7OHw0OpBaqcVxeCBTw8HQhRIuS4p57nk/j2YuulMkh8MZs05GPThIUZzq2PVSvDDTJNa68dX10R654y110cRs4cHYhBPD4xp48kl3fnf5JI0dY3L5UD91izDvN02GHWobKGMsXPCm+6CRg8aOEzTEefN1h Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Kaitao Cheng pcpu_depopulate_chunk() only needs the temporary pages array that was already allocated by an earlier successful population attempt. Passing GFP_KERNEL to pcpu_get_pages() in this path is misleading because the depopulation path is not expected to allocate the array. Teach pcpu_get_pages() to treat a zero gfp mask as a cached-only lookup and add pcpu_get_pages_cached() for that use case. This keeps allocation on the populate path tied to the caller supplied GFP mask while making the depopulate path's dependency on the cached array explicit. Suggested-by: Dennis Zhou Signed-off-by: Kaitao Cheng --- mm/percpu-vm.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c index ccd03cc152d4..7ed216192fc0 100644 --- a/mm/percpu-vm.c +++ b/mm/percpu-vm.c @@ -21,7 +21,8 @@ static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk, /** * pcpu_get_pages - get temp pages array - * @gfp: allocation flags passed to the underlying allocator + * @gfp: allocation flags passed to the underlying allocator, 0 to only + * return the cached array * * Returns pointer to array of pointers to struct page which can be indexed * with pcpu_page_idx(). Note that there is only one array and accesses @@ -37,11 +38,16 @@ static struct page **pcpu_get_pages(gfp_t gfp) lockdep_assert_held(&pcpu_alloc_mutex); - if (!pages) + if (!pages && gfp) pages = pcpu_mem_zalloc(pages_size, gfp); return pages; } +static struct page **pcpu_get_pages_cached(void) +{ + return pcpu_get_pages(0); +} + /** * pcpu_free_pages - free pages which were allocated for @chunk * @chunk: chunk pages were allocated for @@ -333,7 +339,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, * successful population attempt so the temp pages array must * be available now. */ - pages = pcpu_get_pages(GFP_KERNEL); + pages = pcpu_get_pages_cached(); BUG_ON(!pages); /* unmap and free */ -- 2.50.1 (Apple Git-155)