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bh=CfDncH9SZJfkOzhOAZvW+P0qSEBgSmxkFRXj5ACGhgU=; b=PtD8UcFyy7iY2qmUohVq8BmQ1q8to/u2N55TFbcIsQ2cqKPL1hD/DwpxrgeM4kK1hMZ2YH sMqQYlpYDSvKZI0w3HIC4rxH2NtK1/G/rDvgMgVGoKGquNbKMaVS8TwOslxea33wQ65X0x Z2KLCGuPJpHKkKiSivIPM8KnSOBbOWSHpmFdqsYjJCxdqEiyiogFSiPYLUYmgtj4apqwhi rstSxqpTx2lpgd2gsAxir2QfXmy2jXRRzGJp8Xu6cJckPyB4oITGEK9M47WXJbn8Y00TYy 6j3mF16KRkcJZiS8iQ/0uGOVJGgcLw06ngOSNhNOKXPDwQoR8p6QyKCBpmF7Dw== Date: Tue, 27 Feb 2024 13:09:27 +0100 From: "Pankaj Raghav (Samsung)" To: Matthew Wilcox Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, david@fromorbit.com, chandan.babu@oracle.com, akpm@linux-foundation.org, mcgrof@kernel.org, ziy@nvidia.com, hare@suse.de, djwong@kernel.org, gost.dev@samsung.com, linux-mm@kvack.org, Pankaj Raghav Subject: Re: [PATCH 04/13] filemap: use mapping_min_order while allocating folios Message-ID: References: <20240226094936.2677493-1-kernel@pankajraghav.com> <20240226094936.2677493-5-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: A89DA2001F X-Stat-Signature: ckfa5a9c1ejqbfwpds9sqk69q6jgozfz X-HE-Tag: 1709035778-636484 X-HE-Meta: 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 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: On Mon, Feb 26, 2024 at 02:47:33PM +0000, Matthew Wilcox wrote: > On Mon, Feb 26, 2024 at 10:49:27AM +0100, Pankaj Raghav (Samsung) wrote: > > Add some additional VM_BUG_ON() in page_cache_delete[batch] and > > __filemap_add_folio to catch errors where we delete or add folios that > > has order less than min_order. > > I don't understand why we need these checks in the deletion path. The > add path, yes, absolutely. But the delete path? I think we initially added it to check if some split happened which might mess up the page cache with min order support. But I think it is not super critical anymore because of the changes in the split_folio path. I will remove the checks. > > > @@ -896,6 +900,8 @@ noinline int __filemap_add_folio(struct address_space *mapping, > > } > > } > > > > + VM_BUG_ON_FOLIO(folio_order(folio) < mapping_min_folio_order(mapping), > > + folio); > > But I don't understand why you put it here, while we're holding the > xa_lock. That seems designed to cause maximum disruption. Why not put > it at the beginning of the function with all the other VM_BUG_ON_FOLIO? Yeah. That makes sense as the folio itself is not changing. > > > @@ -1847,6 +1853,9 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, > > fgf_t fgp_flags, gfp_t gfp) > > { > > struct folio *folio; > > + unsigned int min_order = mapping_min_folio_order(mapping); > > + > > + index = mapping_align_start_index(mapping, index); > > I would not do this here. > > > repeat: > > folio = filemap_get_entry(mapping, index); > > @@ -1886,7 +1895,7 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, > > folio_wait_stable(folio); > > no_page: > > if (!folio && (fgp_flags & FGP_CREAT)) { > > - unsigned order = FGF_GET_ORDER(fgp_flags); > > + unsigned int order = max(min_order, FGF_GET_ORDER(fgp_flags)); > > int err; > > Put it here instead. > > > if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping)) > > @@ -1912,8 +1921,13 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, > > gfp_t alloc_gfp = gfp; > > > > err = -ENOMEM; > > + if (order < min_order) > > + order = min_order; > > if (order > 0) > > alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN; > > + > > + VM_BUG_ON(index & ((1UL << order) - 1)); > > Then you don't need this BUG_ON because it's obvious you just did it. > And the one in filemap_add_folio() would catch it anyway. I agree. I will change it in the next revision.