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a=rsa-sha256; c=relaxed/relaxed; d=pankajraghav.com; s=MBO0001; t=1715871740; 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=WxNAEyW9ggRd+sEfela/enfZjPtD+w15s4sCnmMcAME=; b=o7RyCWrgTggNBmoO3IGUfYqLO6BZRxxScT26H5+As2pU3NVo+pQT/GHYEQUIjtpNlNEHJA fWDQuVcDQie2arLUzDbZKnj3gUnWiGXphVcTqTb02eXTT2wFEzFmP3ivkCQi//nvQyuQdS aizIQkT9OuyBBX6hd1phh5L7w7gpHLbPLRurQVTpr3vxzslPEQB2gIdn87cql+fLA+ZE3+ +7SN8ru4NNTXE8MkXE2lwCpTQF/HKOlx91tX5Hc1U9TxgQ+hOq4/WYfPzVWwRRFPX53K3m PmQEh31fMQpGg3t89QINzdUQ29WDq5GXl+t2RSPkdWK3k4XFZRmHmkZpDi7OkQ== Date: Thu, 16 May 2024 15:02:06 +0000 From: "Pankaj Raghav (Samsung)" To: Matthew Wilcox Cc: david@fromorbit.com, djwong@kernel.org, hch@lst.de, Keith Busch , mcgrof@kernel.org, akpm@linux-foundation.org, brauner@kernel.org, chandan.babu@oracle.com, gost.dev@samsung.com, hare@suse.de, john.g.garry@oracle.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, p.raghav@samsung.com, ritesh.list@gmail.com, ziy@nvidia.com Subject: Re: [RFC] iomap: use huge zero folio in iomap_dio_zero Message-ID: <20240516150206.d64eezbj3waieef5@quentin> References: <20240503095353.3798063-8-mcgrof@kernel.org> <20240507145811.52987-1-kernel@pankajraghav.com> <20240515155943.2uaa23nvddmgtkul@quentin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 78D94160024 X-Stat-Signature: jrynow6tzixd6bsrt9o4yxa4nkh4zo9u X-HE-Tag: 1715871744-523314 X-HE-Meta: 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 hXo7vV9Q EOv/KoqLqIaOgSH7ZQyNWou1Xo9JXsvX78HBHpen8sZBtM2HSRuY1wVuIs/VrXCLmgJ+niw8oO8WnIwzoy+6FxhtGwLz1iajLohkfXSopDo0HPqVTGggArwNAOQnXXE3Gk8MnfnkgS8s/0pU2BCs91TOl3EPslL2/p9+aVB1k4zKxl/L9jE2UQph9j0MKHEbjLuHjP4jADLW70MU2JilnAFQTsfUKt1emwzNRXrxPPTsVwInIiMPCxzWAEn+aj87luzSOKtoP62RNabqZFFiWjRAv0j9/xXLGbuGhkVgprJl0O3ar4O6b6xoqMw== 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 Wed, May 15, 2024 at 07:03:20PM +0100, Matthew Wilcox wrote: > On Wed, May 15, 2024 at 03:59:43PM +0000, Pankaj Raghav (Samsung) wrote: > > static int __init iomap_init(void) > > { > > + void *addr = kzalloc(16 * PAGE_SIZE, GFP_KERNEL); > > Don't use XFS coding style outside XFS. > > kzalloc() does not guarantee page alignment much less alignment to > a folio. It happens to work today, but that is an implementation > artefact. > > > + > > + if (!addr) > > + return -ENOMEM; > > + > > + zero_fsb_folio = virt_to_folio(addr); > > We also don't guarantee that calling kzalloc() gives you a virtual > address that can be converted to a folio. You need to allocate a folio > to be sure that you get a folio. > > Of course, you don't actually need a folio. You don't need any of the > folio metadata and can just use raw pages. > > > + /* > > + * The zero folio used is 64k. > > + */ > > + WARN_ON_ONCE(len > (16 * PAGE_SIZE)); > > PAGE_SIZE is not necessarily 4KiB. > > > + bio = iomap_dio_alloc_bio(iter, dio, BIO_MAX_VECS, > > + REQ_OP_WRITE | REQ_SYNC | REQ_IDLE); > > The point was that we now only need one biovec, not MAX. > Thanks for the comments. I think it all makes sense: diff --git a/fs/internal.h b/fs/internal.h index 7ca738904e34..e152b77a77e4 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -35,6 +35,14 @@ static inline void bdev_cache_init(void) int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len, get_block_t *get_block, const struct iomap *iomap); +/* + * iomap/buffered-io.c + */ + +#define ZERO_FSB_SIZE (65536) +#define ZERO_FSB_ORDER (get_order(ZERO_FSB_SIZE)) +extern struct page *zero_fs_block; + /* * char_dev.c */ diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 4e8e41c8b3c0..36d2f7edd310 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -42,6 +42,7 @@ struct iomap_folio_state { }; static struct bio_set iomap_ioend_bioset; +struct page *zero_fs_block; static inline bool ifs_is_fully_uptodate(struct folio *folio, struct iomap_folio_state *ifs) @@ -1985,8 +1986,13 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc, } EXPORT_SYMBOL_GPL(iomap_writepages); + static int __init iomap_init(void) { + zero_fs_block = alloc_pages(GFP_KERNEL | __GFP_ZERO, ZERO_FSB_ORDER); + if (!zero_fs_block) + return -ENOMEM; + return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE), offsetof(struct iomap_ioend, io_bio), BIOSET_NEED_BVECS); diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index f3b43d223a46..50c2bca8a347 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -236,17 +236,22 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, loff_t pos, unsigned len) { struct inode *inode = file_inode(dio->iocb->ki_filp); - struct page *page = ZERO_PAGE(0); struct bio *bio; + /* + * Max block size supported is 64k + */ + WARN_ON_ONCE(len > ZERO_FSB_SIZE); + bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE); fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, GFP_KERNEL); + bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos); bio->bi_private = dio; bio->bi_end_io = iomap_dio_bio_end_io; - __bio_add_page(bio, page, len, 0); + __bio_add_page(bio, zero_fs_block, len, 0); iomap_dio_submit_bio(iter, dio, bio, pos); }