staging: erofs: add raw address_space operations

// SPDX-License-Identifier: GPL-2.0

/*

 * linux/drivers/staging/erofs/data.c

 *

 * Copyright (C) 2017-2018 HUAWEI, Inc.

 *             http://www.huawei.com/

 * Created by Gao Xiang <gaoxiang25@huawei.com>

 *

 * This file is subject to the terms and conditions of the GNU General Public

 * License.  See the file COPYING in the main directory of the Linux

 * distribution for more details.

 */

#include "internal.h"

#include <linux/prefetch.h>

static inline void read_endio(struct bio *bio)

{

	int i;

	struct bio_vec *bvec;

	const blk_status_t err = bio->bi_status;

	bio_for_each_segment_all(bvec, bio, i) {

		struct page *page = bvec->bv_page;

		/* page is already locked */

		BUG_ON(PageUptodate(page));

		if (unlikely(err))

			SetPageError(page);

		else

			SetPageUptodate(page);

		unlock_page(page);

		/* page could be reclaimed now */

	}

	bio_put(bio);

}

static void __submit_bio(struct bio *bio, unsigned op, unsigned op_flags)

{

	bio_set_op_attrs(bio, op, op_flags);

	submit_bio(bio);

}

static struct bio *prepare_bio(struct super_block *sb,

	erofs_blk_t blkaddr, unsigned nr_pages)

{

	struct bio *bio = bio_alloc(GFP_NOIO | __GFP_NOFAIL, nr_pages);

	BUG_ON(bio == NULL);

	bio->bi_end_io = read_endio;

	bio_set_dev(bio, sb->s_bdev);

	bio->bi_iter.bi_sector = blkaddr << LOG_SECTORS_PER_BLOCK;

	return bio;

}

/* prio -- true is used for dir */

struct page *erofs_get_meta_page(struct super_block *sb,

	erofs_blk_t blkaddr, bool prio)

{

	struct inode *bd_inode = sb->s_bdev->bd_inode;

	struct address_space *mapping = bd_inode->i_mapping;

	struct page *page;

repeat:

	page = find_or_create_page(mapping, blkaddr,

	/*

	 * Prefer looping in the allocator rather than here,

	 * at least that code knows what it's doing.

	 */

		mapping_gfp_constraint(mapping, ~__GFP_FS) | __GFP_NOFAIL);

	BUG_ON(!page || !PageLocked(page));

	if (!PageUptodate(page)) {

		struct bio *bio;

		int err;

		bio = prepare_bio(sb, blkaddr, 1);

		err = bio_add_page(bio, page, PAGE_SIZE, 0);

		BUG_ON(err != PAGE_SIZE);

		__submit_bio(bio, REQ_OP_READ,

			REQ_META | (prio ? REQ_PRIO : 0));

		lock_page(page);

		/* the page has been truncated by others? */

		if (unlikely(page->mapping != mapping)) {

			unlock_page(page);

			put_page(page);

			goto repeat;

		}

		/* more likely a read error */

		if (unlikely(!PageUptodate(page))) {

			unlock_page(page);

			put_page(page);

			page = ERR_PTR(-EIO);

		}

	}

	return page;

}

static int erofs_map_blocks_flatmode(struct inode *inode,

	struct erofs_map_blocks *map,

	int flags)

{

	erofs_blk_t nblocks, lastblk;

	u64 offset = map->m_la;

	struct erofs_vnode *vi = EROFS_V(inode);

	BUG_ON(is_inode_layout_compression(inode));

	nblocks = DIV_ROUND_UP(inode->i_size, PAGE_SIZE);

	lastblk = nblocks - is_inode_layout_inline(inode);

	if (unlikely(offset >= inode->i_size)) {

		/* leave out-of-bound access unmapped */

		map->m_flags = 0;

		map->m_plen = 0;

		goto out;

	}

	/* there is no hole in flatmode */

	map->m_flags = EROFS_MAP_MAPPED;

	if (offset < blknr_to_addr(lastblk)) {

		map->m_pa = blknr_to_addr(vi->raw_blkaddr) + map->m_la;

		map->m_plen = blknr_to_addr(lastblk) - offset;

	} else if (is_inode_layout_inline(inode)) {

		/* 2 - inode inline B: inode, [xattrs], inline last blk... */

		struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);

		map->m_pa = iloc(sbi, vi->nid) + vi->inode_isize +

			vi->xattr_isize + erofs_blkoff(map->m_la);

		map->m_plen = inode->i_size - offset;

		/* inline data should locate in one meta block */

		BUG_ON(erofs_blkoff(map->m_pa) + map->m_plen > PAGE_SIZE);

		map->m_flags |= EROFS_MAP_META;

	} else {

		errln("internal error @ nid: %llu (size %llu), m_la 0x%llx",

			vi->nid, inode->i_size, map->m_la);

		BUG();

	}

out:

	map->m_llen = map->m_plen;

	debugln("%s, m_la 0x%llx m_pa %llx m_len %llu",

		__func__, map->m_la, map->m_pa, map->m_plen);

	return 0;

}

int erofs_map_blocks(struct inode *inode,

	struct erofs_map_blocks *map, int flags)

{

	if (unlikely(is_inode_layout_compression(inode)))

		return -ENOTSUPP;

	return erofs_map_blocks_flatmode(inode, map, flags);

}

static inline struct bio *erofs_read_raw_page(

	struct bio *bio,

	struct address_space *mapping,

	struct page *page,

	erofs_off_t *last_block,

	unsigned nblocks,

	bool ra)

{

	struct inode *inode = mapping->host;

	erofs_off_t current_block = (erofs_off_t)page->index;

	int err;

	BUG_ON(!nblocks);

	if (PageUptodate(page)) {

		err = 0;

		goto has_updated;

	}

	if (cleancache_get_page(page) == 0) {

		err = 0;

		SetPageUptodate(page);

		goto has_updated;

	}

	/* note that for readpage case, bio also equals to NULL */

	if (bio != NULL &&

		/* not continuous */

		*last_block + 1 != current_block) {

submit_bio_retry:

		__submit_bio(bio, REQ_OP_READ, 0);

		bio = NULL;

	}

	if (bio == NULL) {

		struct erofs_map_blocks map = {

			.m_la = blknr_to_addr(current_block),

		};

		err = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);

		if (unlikely(err))

			goto err_out;

		/* zero out the holed page */

		if (unlikely(!(map.m_flags & EROFS_MAP_MAPPED))) {

			zero_user_segment(page, 0, PAGE_SIZE);

			SetPageUptodate(page);

			/* imply err = 0, see erofs_map_blocks */

			goto has_updated;

		}

		/* for RAW access mode, m_plen must be equal to m_llen */

		BUG_ON(map.m_plen != map.m_llen);

		/* deal with inline page */

		if (map.m_flags & EROFS_MAP_META) {

			void *vsrc, *vto;

			struct page *ipage;

			BUG_ON(map.m_plen > PAGE_SIZE);

			ipage = erofs_get_meta_page(inode->i_sb,

				erofs_blknr(map.m_pa), 0);

			if (IS_ERR(ipage)) {

				err = PTR_ERR(ipage);

				goto err_out;

			}

			vsrc = kmap_atomic(ipage);

			vto = kmap_atomic(page);

			memcpy(vto, vsrc + erofs_blkoff(map.m_pa), map.m_plen);

			memset(vto + map.m_plen, 0, PAGE_SIZE - map.m_plen);

			kunmap_atomic(vto);

			kunmap_atomic(vsrc);

			flush_dcache_page(page);

			SetPageUptodate(page);

			/* TODO: could we unlock the page earlier? */

			unlock_page(ipage);

			put_page(ipage);

			/* imply err = 0, see erofs_map_blocks */

			goto has_updated;

		}

		/* pa must be block-aligned for raw reading */

		BUG_ON(erofs_blkoff(map.m_pa) != 0);

		/* max # of continuous pages */

		if (nblocks > DIV_ROUND_UP(map.m_plen, PAGE_SIZE))

			nblocks = DIV_ROUND_UP(map.m_plen, PAGE_SIZE);

		if (nblocks > BIO_MAX_PAGES)

			nblocks = BIO_MAX_PAGES;

		bio = prepare_bio(inode->i_sb, erofs_blknr(map.m_pa), nblocks);

	}

	err = bio_add_page(bio, page, PAGE_SIZE, 0);

	/* out of the extent or bio is full */

	if (err < PAGE_SIZE)

		goto submit_bio_retry;

	*last_block = current_block;

	/* shift in advance in case of it followed by too many gaps */

	if (unlikely(bio->bi_vcnt >= bio->bi_max_vecs)) {

		/* err should reassign to 0 after submitting */

		err = 0;

		goto submit_bio_out;

	}

	return bio;

err_out:

	/* for sync reading, set page error immediately */

	if (!ra) {

		SetPageError(page);

		ClearPageUptodate(page);

	}

has_updated:

	unlock_page(page);

	/* if updated manually, continuous pages has a gap */

	if (bio != NULL)

submit_bio_out:

		__submit_bio(bio, REQ_OP_READ, 0);

	return unlikely(err) ? ERR_PTR(err) : NULL;

}

/*

 * since we dont have write or truncate flows, so no inode

 * locking needs to be held at the moment.

 */

static int erofs_raw_access_readpage(struct file *file, struct page *page)

{

	erofs_off_t last_block;

	struct bio *bio;

	bio = erofs_read_raw_page(NULL, page->mapping,

		page, &last_block, 1, false);

	if (IS_ERR(bio))

		return PTR_ERR(bio);

	BUG_ON(bio != NULL);	/* since we have only one bio -- must be NULL */

	return 0;

}

static int erofs_raw_access_readpages(struct file *filp,

	struct address_space *mapping,

	struct list_head *pages, unsigned nr_pages)

{

	erofs_off_t last_block;

	struct bio *bio = NULL;

	gfp_t gfp = readahead_gfp_mask(mapping);

	for (; nr_pages; --nr_pages) {

		struct page *page = list_entry(pages->prev, struct page, lru);

		prefetchw(&page->flags);

		list_del(&page->lru);

		if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) {

			bio = erofs_read_raw_page(bio, mapping, page,

				&last_block, nr_pages, true);

			/* all the page errors are ignored when readahead */

			if (IS_ERR(bio)) {

				pr_err("%s, readahead error at page %lu of nid %llu\n",

					__func__, page->index,

					EROFS_V(mapping->host)->nid);

				bio = NULL;

			}

		}

		/* pages could still be locked */

		put_page(page);

	}

	BUG_ON(!list_empty(pages));

	/* the rare case (end in gaps) */

	if (unlikely(bio != NULL))

		__submit_bio(bio, REQ_OP_READ, 0);

	return 0;

}

/* for uncompressed (aligned) files and raw access for other files */

const struct address_space_operations erofs_raw_access_aops = {

	.readpage = erofs_raw_access_readpage,

	.readpages = erofs_raw_access_readpages,

};