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t=1709028402; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=GPizpXQfLZMMYkc4+cJdFUeRkcKBpv3GClb5bK+Zygo=; b=j8N+B2rP1wM2vqfcQ5wXsuK6VWRk3AETdPUfaEKIuzJtLXSdXO5bdkXIamNLmxiB91c1hy gIuslA4/0417HwlXiOU/fq7GpBzCLIV3lITwTvK8CTLO54VdJFocmMQ6aeLbvmzuwk9O9z NZGjEV8r/FP+HlnRpRmWJeiHrpGKy4mVBOhGK+1zvx+7zLPragr4/t/Wevbcxz+Fih80kO k+WTFm8AAfYxrVFMc63ZFxAWd6WVuthoyIzksqNZWDDugScrWqtjaUnK3pciOD3eGgR4NY XfCyKRA3uDcpwd4SG7Ja0wpC/a5s6PEK5ftYa5sr91MdQ+wbe+5pKT3I7MUxZA== Date: Tue, 27 Feb 2024 11:06:37 +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 03/13] filemap: align the index to mapping_min_order in the page cache Message-ID: <37kubwweih4zwvxzvjbhnhxunrafawdqaqggzcw6xayd6vtrfl@dllnk6n53akf> References: <20240226094936.2677493-1-kernel@pankajraghav.com> <20240226094936.2677493-4-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: q7jo5tebfdjqjrrofm7jmbky7xs9ioig X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 3E7C2120009 X-Rspam-User: X-HE-Tag: 1709028406-952480 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 02:40:42PM +0000, Matthew Wilcox wrote: > On Mon, Feb 26, 2024 at 10:49:26AM +0100, Pankaj Raghav (Samsung) wrote: > > From: Luis Chamberlain > > > > Supporting mapping_min_order implies that we guarantee each folio in the > > page cache has at least an order of mapping_min_order. So when adding new > > folios to the page cache we must ensure the index used is aligned to the > > mapping_min_order as the page cache requires the index to be aligned to > > the order of the folio. > > This seems like a remarkably complicated way of achieving: > > diff --git a/mm/filemap.c b/mm/filemap.c > index 5603ced05fb7..36105dad4440 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2427,9 +2427,11 @@ static int filemap_update_page(struct kiocb *iocb, > } > > static int filemap_create_folio(struct file *file, > - struct address_space *mapping, pgoff_t index, > + struct address_space *mapping, loff_t pos, > struct folio_batch *fbatch) > { > + pgoff_t index; > + unsigned int min_order; > struct folio *folio; > int error; > > @@ -2451,6 +2453,8 @@ static int filemap_create_folio(struct file *file, > * well to keep locking rules simple. > */ > filemap_invalidate_lock_shared(mapping); > + min_order = mapping_min_folio_order(mapping); > + index = (pos >> (min_order + PAGE_SHIFT)) << min_order; That is some cool mathfu. I will add a comment here as it might not be that obvious to some people (i.e me). Thanks. > error = filemap_add_folio(mapping, folio, index, > mapping_gfp_constraint(mapping, GFP_KERNEL)); > if (error == -EEXIST) > @@ -2511,8 +2515,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > if (!folio_batch_count(fbatch)) { > if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) > return -EAGAIN; > - err = filemap_create_folio(filp, mapping, > - iocb->ki_pos >> PAGE_SHIFT, fbatch); > + err = filemap_create_folio(filp, mapping, iocb->ki_pos, fbatch); > if (err == AOP_TRUNCATED_PAGE) > goto retry; > return err;