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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rRl1j-0000000Eqh2-1y9B; Mon, 22 Jan 2024 03:31:11 +0000 Date: Mon, 22 Jan 2024 03:31:11 +0000 From: Matthew Wilcox To: Haiqiang Gong Cc: linux-kernel@vger.kernel.org, mike.zhang@mediatek.com, Andrew Morton , Matthias Brugger , AngeloGioacchino Del Regno , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Subject: Re: [PATCH] mm/compaction: add check mechanism to avoid cma alloc fail Message-ID: References: <20240122022317.30091-1-Haiqiang.Gong@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240122022317.30091-1-Haiqiang.Gong@mediatek.com> X-Rspamd-Queue-Id: 5AC4010001D X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 69oqnqp8hfyj8mi7yqpy4rk6mhiyh1bi X-HE-Tag: 1705894277-94543 X-HE-Meta: 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 zVZXoanY DZSJp0y1drhjVa96fbs7RVP8oc0nAdL175FGUoWpWFADJFDrJXzehSQoUoEhwmM7p3OoY/MUSR1sn5WbW1JfVr6LP73dJIAP1AO7lHUMG7lmIlP8dc7MwZt9s5RILR17m6zdzn8mH8aM4v79Ux7NaGDXCYjRSVYTPv0erWSVwjgO2A52Vx4D3o0wn+aVhU+1+p2U1MGMdl2okEJ4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 Mon, Jan 22, 2024 at 10:23:17AM +0800, Haiqiang Gong wrote: > cma alloc may fail when we doing cma alloc/free test on kernel 5.10/5.15. > > We found that the next memory cannot be migrated because of the alloc of > fs as next backtrace: > __alloc_pages_nodemask > pagecache_get_page > grow_dev_page > __getblk_gfp > ext4_sb_breadahead_unmovable > __ext4_get_inode_loc > __ext4_iget > ext4_lookup > __lookup_slow > walk_component > path_lookupat > filename_lookup > vfs_statx > This kind of unmovable memory is not placed in the cma buffer when kernel > memory alloc but is migrated in by kcompactd when the kernel migration. > It will cause memory can't be migrate when cma alloc. I don't understand. You say that the memory isn't movable, but then you say that it's migrated in. So it was movable, but it's no longer movable after being moved once? > Add check mechanism in the compaction_alloc() where kcompaced alloc for > memory. Will return NULL and give up this memory migration if the > allocated memory is in the cma buffer and the memory is unmovable. > +static bool forbid_move_to_cma_range(struct folio *src, struct folio *dst) > +{ > + if (folio_mapping(src) && is_in_cma_range(dst)) > + return true; > + > + return false; > +} Why would folio_mapping() be the right way to determine if memory is unmovable? The vast majority of filesystem data is movable.