[mirror_ubuntu-jammy-kernel.git] / fs / ext4 / readpage.c

// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/ext4/readpage.c
 *
 * Copyright (C) 2002, Linus Torvalds.
 * Copyright (C) 2015, Google, Inc.
 *
 * This was originally taken from fs/mpage.c
 *
 * The ext4_mpage_readpages() function here is intended to
 * replace mpage_readahead() in the general case, not just for
 * encrypted files.  It has some limitations (see below), where it
 * will fall back to read_block_full_page(), but these limitations
 * should only be hit when page_size != block_size.
 *
 * This will allow us to attach a callback function to support ext4
 * encryption.
 *
 * If anything unusual happens, such as:
 *
 * - encountering a page which has buffers
 * - encountering a page which has a non-hole after a hole
 * - encountering a page with non-contiguous blocks
 *
 * then this code just gives up and calls the buffer_head-based read function.
 * It does handle a page which has holes at the end - that is a common case:
 * the end-of-file on blocksize < PAGE_SIZE setups.
 *
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <linux/gfp.h>
#include <linux/bio.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/highmem.h>
#include <linux/prefetch.h>
#include <linux/mpage.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/cleancache.h>

#include "ext4.h"

#define NUM_PREALLOC_POST_READ_CTXS	128

static struct kmem_cache *bio_post_read_ctx_cache;
static mempool_t *bio_post_read_ctx_pool;

/* postprocessing steps for read bios */
enum bio_post_read_step {
	STEP_INITIAL = 0,
	STEP_DECRYPT,
	STEP_VERITY,
	STEP_MAX,
};

struct bio_post_read_ctx {
	struct bio *bio;
	struct work_struct work;
	unsigned int cur_step;
	unsigned int enabled_steps;
};

static void __read_end_io(struct bio *bio)
{
	struct page *page;
	struct bio_vec *bv;
	struct bvec_iter_all iter_all;

	bio_for_each_segment_all(bv, bio, iter_all) {
		page = bv->bv_page;

		/* PG_error was set if any post_read step failed */
		if (bio->bi_status || PageError(page)) {
			ClearPageUptodate(page);
			/* will re-read again later */
			ClearPageError(page);
		} else {
			SetPageUptodate(page);
		}
		unlock_page(page);
	}
	if (bio->bi_private)
		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
	bio_put(bio);
}

static void bio_post_read_processing(struct bio_post_read_ctx *ctx);

static void decrypt_work(struct work_struct *work)
{
	struct bio_post_read_ctx *ctx =
		container_of(work, struct bio_post_read_ctx, work);

	fscrypt_decrypt_bio(ctx->bio);

	bio_post_read_processing(ctx);
}

static void verity_work(struct work_struct *work)
{
	struct bio_post_read_ctx *ctx =
		container_of(work, struct bio_post_read_ctx, work);
	struct bio *bio = ctx->bio;

	/*
	 * fsverity_verify_bio() may call readpages() again, and although verity
	 * will be disabled for that, decryption may still be needed, causing
	 * another bio_post_read_ctx to be allocated.  So to guarantee that
	 * mempool_alloc() never deadlocks we must free the current ctx first.
	 * This is safe because verity is the last post-read step.
	 */
	BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX);
	mempool_free(ctx, bio_post_read_ctx_pool);
	bio->bi_private = NULL;

	fsverity_verify_bio(bio);

	__read_end_io(bio);
}

static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
{
	/*
	 * We use different work queues for decryption and for verity because
	 * verity may require reading metadata pages that need decryption, and
	 * we shouldn't recurse to the same workqueue.
	 */
	switch (++ctx->cur_step) {
	case STEP_DECRYPT:
		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
			INIT_WORK(&ctx->work, decrypt_work);
			fscrypt_enqueue_decrypt_work(&ctx->work);
			return;
		}
		ctx->cur_step++;
		fallthrough;
	case STEP_VERITY:
		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
			INIT_WORK(&ctx->work, verity_work);
			fsverity_enqueue_verify_work(&ctx->work);
			return;
		}
		ctx->cur_step++;
		fallthrough;
	default:
		__read_end_io(ctx->bio);
	}
}

static bool bio_post_read_required(struct bio *bio)
{
	return bio->bi_private && !bio->bi_status;
}

/*
 * I/O completion handler for multipage BIOs.
 *
 * The mpage code never puts partial pages into a BIO (except for end-of-file).
 * If a page does not map to a contiguous run of blocks then it simply falls
 * back to block_read_full_page().
 *
 * Why is this?  If a page's completion depends on a number of different BIOs
 * which can complete in any order (or at the same time) then determining the
 * status of that page is hard.  See end_buffer_async_read() for the details.
 * There is no point in duplicating all that complexity.
 */
static void mpage_end_io(struct bio *bio)
{
	if (bio_post_read_required(bio)) {
		struct bio_post_read_ctx *ctx = bio->bi_private;

		ctx->cur_step = STEP_INITIAL;
		bio_post_read_processing(ctx);
		return;
	}
	__read_end_io(bio);
}

static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
{
	return fsverity_active(inode) &&
	       idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
}

static void ext4_set_bio_post_read_ctx(struct bio *bio,
				       const struct inode *inode,
				       pgoff_t first_idx)
{
	unsigned int post_read_steps = 0;

	if (fscrypt_inode_uses_fs_layer_crypto(inode))
		post_read_steps |= 1 << STEP_DECRYPT;

	if (ext4_need_verity(inode, first_idx))
		post_read_steps |= 1 << STEP_VERITY;

	if (post_read_steps) {
		/* Due to the mempool, this never fails. */
		struct bio_post_read_ctx *ctx =
			mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);

		ctx->bio = bio;
		ctx->enabled_steps = post_read_steps;
		bio->bi_private = ctx;
	}
}

static inline loff_t ext4_readpage_limit(struct inode *inode)
{
	if (IS_ENABLED(CONFIG_FS_VERITY) &&
	    (IS_VERITY(inode) || ext4_verity_in_progress(inode)))
		return inode->i_sb->s_maxbytes;

	return i_size_read(inode);
}

int ext4_mpage_readpages(struct inode *inode,
		struct readahead_control *rac, struct page *page)
{
	struct bio *bio = NULL;
	sector_t last_block_in_bio = 0;

	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
	const unsigned blocksize = 1 << blkbits;
	sector_t next_block;
	sector_t block_in_file;
	sector_t last_block;
	sector_t last_block_in_file;
	sector_t blocks[MAX_BUF_PER_PAGE];
	unsigned page_block;
	struct block_device *bdev = inode->i_sb->s_bdev;
	int length;
	unsigned relative_block = 0;
	struct ext4_map_blocks map;
	unsigned int nr_pages = rac ? readahead_count(rac) : 1;

	map.m_pblk = 0;
	map.m_lblk = 0;
	map.m_len = 0;
	map.m_flags = 0;

	for (; nr_pages; nr_pages--) {
		int fully_mapped = 1;
		unsigned first_hole = blocks_per_page;

		if (rac) {
			page = readahead_page(rac);
			prefetchw(&page->flags);
		}

		if (page_has_buffers(page))
			goto confused;

		block_in_file = next_block =
			(sector_t)page->index << (PAGE_SHIFT - blkbits);
		last_block = block_in_file + nr_pages * blocks_per_page;
		last_block_in_file = (ext4_readpage_limit(inode) +
				      blocksize - 1) >> blkbits;
		if (last_block > last_block_in_file)
			last_block = last_block_in_file;
		page_block = 0;

		/*
		 * Map blocks using the previous result first.
		 */
		if ((map.m_flags & EXT4_MAP_MAPPED) &&
		    block_in_file > map.m_lblk &&
		    block_in_file < (map.m_lblk + map.m_len)) {
			unsigned map_offset = block_in_file - map.m_lblk;
			unsigned last = map.m_len - map_offset;

			for (relative_block = 0; ; relative_block++) {
				if (relative_block == last) {
					/* needed? */
					map.m_flags &= ~EXT4_MAP_MAPPED;
					break;
				}
				if (page_block == blocks_per_page)
					break;
				blocks[page_block] = map.m_pblk + map_offset +
					relative_block;
				page_block++;
				block_in_file++;
			}
		}

		/*
		 * Then do more ext4_map_blocks() calls until we are
		 * done with this page.
		 */
		while (page_block < blocks_per_page) {
			if (block_in_file < last_block) {
				map.m_lblk = block_in_file;
				map.m_len = last_block - block_in_file;

				if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
				set_error_page:
					SetPageError(page);
					zero_user_segment(page, 0,
							  PAGE_SIZE);
					unlock_page(page);
					goto next_page;
				}
			}
			if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
				fully_mapped = 0;
				if (first_hole == blocks_per_page)
					first_hole = page_block;
				page_block++;
				block_in_file++;
				continue;
			}
			if (first_hole != blocks_per_page)
				goto confused;		/* hole -> non-hole */

			/* Contiguous blocks? */
			if (page_block && blocks[page_block-1] != map.m_pblk-1)
				goto confused;
			for (relative_block = 0; ; relative_block++) {
				if (relative_block == map.m_len) {
					/* needed? */
					map.m_flags &= ~EXT4_MAP_MAPPED;
					break;
				} else if (page_block == blocks_per_page)
					break;
				blocks[page_block] = map.m_pblk+relative_block;
				page_block++;
				block_in_file++;
			}
		}
		if (first_hole != blocks_per_page) {
			zero_user_segment(page, first_hole << blkbits,
					  PAGE_SIZE);
			if (first_hole == 0) {
				if (ext4_need_verity(inode, page->index) &&
				    !fsverity_verify_page(page))
					goto set_error_page;
				SetPageUptodate(page);
				unlock_page(page);
				goto next_page;
			}
		} else if (fully_mapped) {
			SetPageMappedToDisk(page);
		}
		if (fully_mapped && blocks_per_page == 1 &&
		    !PageUptodate(page) && cleancache_get_page(page) == 0) {
			SetPageUptodate(page);
			goto confused;
		}

		/*
		 * This page will go to BIO.  Do we need to send this
		 * BIO off first?
		 */
		if (bio && (last_block_in_bio != blocks[0] - 1 ||
			    !fscrypt_mergeable_bio(bio, inode, next_block))) {
		submit_and_realloc:
			submit_bio(bio);
			bio = NULL;
		}
		if (bio == NULL) {
			/*
			 * bio_alloc will _always_ be able to allocate a bio if
			 * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
			 */
			bio = bio_alloc(GFP_KERNEL, bio_max_segs(nr_pages));
			fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
						  GFP_KERNEL);
			ext4_set_bio_post_read_ctx(bio, inode, page->index);
			bio_set_dev(bio, bdev);
			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
			bio->bi_end_io = mpage_end_io;
			bio_set_op_attrs(bio, REQ_OP_READ,
						rac ? REQ_RAHEAD : 0);
		}

		length = first_hole << blkbits;
		if (bio_add_page(bio, page, length, 0) < length)
			goto submit_and_realloc;

		if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
		     (relative_block == map.m_len)) ||
		    (first_hole != blocks_per_page)) {
			submit_bio(bio);
			bio = NULL;
		} else
			last_block_in_bio = blocks[blocks_per_page - 1];
		goto next_page;
	confused:
		if (bio) {
			submit_bio(bio);
			bio = NULL;
		}
		if (!PageUptodate(page))
			block_read_full_page(page, ext4_get_block);
		else
			unlock_page(page);
	next_page:
		if (rac)
			put_page(page);
	}
	if (bio)
		submit_bio(bio);
	return 0;
}

int __init ext4_init_post_read_processing(void)
{
	bio_post_read_ctx_cache =
		kmem_cache_create("ext4_bio_post_read_ctx",
				  sizeof(struct bio_post_read_ctx), 0, 0, NULL);
	if (!bio_post_read_ctx_cache)
		goto fail;
	bio_post_read_ctx_pool =
		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
					 bio_post_read_ctx_cache);
	if (!bio_post_read_ctx_pool)
		goto fail_free_cache;
	return 0;

fail_free_cache:
	kmem_cache_destroy(bio_post_read_ctx_cache);
fail:
	return -ENOMEM;
}

void ext4_exit_post_read_processing(void)
{
	mempool_destroy(bio_post_read_ctx_pool);
	kmem_cache_destroy(bio_post_read_ctx_cache);
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
f64e02fe TT	2	/*
	3	* linux/fs/ext4/readpage.c
	4	*
	5	* Copyright (C) 2002, Linus Torvalds.
	6	* Copyright (C) 2015, Google, Inc.
	7	*
	8	* This was originally taken from fs/mpage.c
	9	*
6311f91f MWO	10	* The ext4_mpage_readpages() function here is intended to
6311f91f MWO	11	* replace mpage_readahead() in the general case, not just for
f64e02fe TT	12	* encrypted files. It has some limitations (see below), where it
	13	* will fall back to read_block_full_page(), but these limitations
	14	* should only be hit when page_size != block_size.
	15	*
	16	* This will allow us to attach a callback function to support ext4
	17	* encryption.
	18	*
	19	* If anything unusual happens, such as:
	20	*
	21	* - encountering a page which has buffers
	22	* - encountering a page which has a non-hole after a hole
	23	* - encountering a page with non-contiguous blocks
	24	*
	25	* then this code just gives up and calls the buffer_head-based read function.
	26	* It does handle a page which has holes at the end - that is a common case:
ea1754a0	27	* the end-of-file on blocksize < PAGE_SIZE setups.
f64e02fe TT	28	*
	29	*/
	30
	31	#include <linux/kernel.h>
	32	#include <linux/export.h>
	33	#include <linux/mm.h>
	34	#include <linux/kdev_t.h>
	35	#include <linux/gfp.h>
	36	#include <linux/bio.h>
	37	#include <linux/fs.h>
	38	#include <linux/buffer_head.h>
	39	#include <linux/blkdev.h>
	40	#include <linux/highmem.h>
	41	#include <linux/prefetch.h>
	42	#include <linux/mpage.h>
	43	#include <linux/writeback.h>
	44	#include <linux/backing-dev.h>
	45	#include <linux/pagevec.h>
	46	#include <linux/cleancache.h>
	47
	48	#include "ext4.h"
	49
22cfe4b4 EB	50	#define NUM_PREALLOC_POST_READ_CTXS 128
	51
	52	static struct kmem_cache *bio_post_read_ctx_cache;
	53	static mempool_t *bio_post_read_ctx_pool;
	54
	55	/* postprocessing steps for read bios */
	56	enum bio_post_read_step {
	57	STEP_INITIAL = 0,
	58	STEP_DECRYPT,
	59	STEP_VERITY,
68e45330	60	STEP_MAX,
22cfe4b4 EB	61	};
	62
	63	struct bio_post_read_ctx {
	64	struct bio *bio;
	65	struct work_struct work;
	66	unsigned int cur_step;
	67	unsigned int enabled_steps;
	68	};
	69
	70	static void __read_end_io(struct bio *bio)
c9c7429c	71	{
22cfe4b4 EB	72	struct page *page;
	73	struct bio_vec *bv;
	74	struct bvec_iter_all iter_all;
	75
	76	bio_for_each_segment_all(bv, bio, iter_all) {
	77	page = bv->bv_page;
	78
	79	/* PG_error was set if any post_read step failed */
	80	if (bio->bi_status \|\| PageError(page)) {
	81	ClearPageUptodate(page);
	82	/* will re-read again later */
	83	ClearPageError(page);
	84	} else {
	85	SetPageUptodate(page);
	86	}
	87	unlock_page(page);
	88	}
	89	if (bio->bi_private)
	90	mempool_free(bio->bi_private, bio_post_read_ctx_pool);
	91	bio_put(bio);
	92	}
	93
	94	static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
	95
	96	static void decrypt_work(struct work_struct *work)
	97	{
	98	struct bio_post_read_ctx *ctx =
	99	container_of(work, struct bio_post_read_ctx, work);
	100
	101	fscrypt_decrypt_bio(ctx->bio);
	102
	103	bio_post_read_processing(ctx);
	104	}
	105
	106	static void verity_work(struct work_struct *work)
	107	{
	108	struct bio_post_read_ctx *ctx =
	109	container_of(work, struct bio_post_read_ctx, work);
68e45330	110	struct bio *bio = ctx->bio;
22cfe4b4	111
68e45330 EB	112	/*
	113	* fsverity_verify_bio() may call readpages() again, and although verity
	114	* will be disabled for that, decryption may still be needed, causing
	115	* another bio_post_read_ctx to be allocated. So to guarantee that
	116	* mempool_alloc() never deadlocks we must free the current ctx first.
	117	* This is safe because verity is the last post-read step.
	118	*/
	119	BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX);
	120	mempool_free(ctx, bio_post_read_ctx_pool);
	121	bio->bi_private = NULL;
	122
	123	fsverity_verify_bio(bio);
	124
	125	__read_end_io(bio);
22cfe4b4 EB	126	}
	127
	128	static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
	129	{
	130	/*
	131	* We use different work queues for decryption and for verity because
	132	* verity may require reading metadata pages that need decryption, and
	133	* we shouldn't recurse to the same workqueue.
	134	*/
	135	switch (++ctx->cur_step) {
	136	case STEP_DECRYPT:
	137	if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
	138	INIT_WORK(&ctx->work, decrypt_work);
	139	fscrypt_enqueue_decrypt_work(&ctx->work);
	140	return;
	141	}
	142	ctx->cur_step++;
70d7ced2	143	fallthrough;
22cfe4b4 EB	144	case STEP_VERITY:
	145	if (ctx->enabled_steps & (1 << STEP_VERITY)) {
	146	INIT_WORK(&ctx->work, verity_work);
	147	fsverity_enqueue_verify_work(&ctx->work);
	148	return;
	149	}
	150	ctx->cur_step++;
70d7ced2	151	fallthrough;
22cfe4b4 EB	152	default:
	153	__read_end_io(ctx->bio);
	154	}
	155	}
	156
	157	static bool bio_post_read_required(struct bio *bio)
	158	{
	159	return bio->bi_private && !bio->bi_status;
c9c7429c MH	160	}
c9c7429c MH	161
f64e02fe TT	162	/*
	163	* I/O completion handler for multipage BIOs.
	164	*
	165	* The mpage code never puts partial pages into a BIO (except for end-of-file).
	166	* If a page does not map to a contiguous run of blocks then it simply falls
	167	* back to block_read_full_page().
	168	*
	169	* Why is this? If a page's completion depends on a number of different BIOs
	170	* which can complete in any order (or at the same time) then determining the
	171	* status of that page is hard. See end_buffer_async_read() for the details.
	172	* There is no point in duplicating all that complexity.
	173	*/
4246a0b6	174	static void mpage_end_io(struct bio *bio)
f64e02fe	175	{
22cfe4b4 EB	176	if (bio_post_read_required(bio)) {
22cfe4b4 EB	177	struct bio_post_read_ctx *ctx = bio->bi_private;
f64e02fe	178
22cfe4b4 EB	179	ctx->cur_step = STEP_INITIAL;
	180	bio_post_read_processing(ctx);
	181	return;
c9c7429c	182	}
22cfe4b4 EB	183	__read_end_io(bio);
22cfe4b4 EB	184	}
f64e02fe	185
22cfe4b4 EB	186	static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
	187	{
	188	return fsverity_active(inode) &&
	189	idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
	190	}
	191
fd5fe253 EB	192	static void ext4_set_bio_post_read_ctx(struct bio *bio,
	193	const struct inode *inode,
	194	pgoff_t first_idx)
22cfe4b4 EB	195	{
22cfe4b4 EB	196	unsigned int post_read_steps = 0;
22cfe4b4	197
4f74d15f	198	if (fscrypt_inode_uses_fs_layer_crypto(inode))
22cfe4b4 EB	199	post_read_steps \|= 1 << STEP_DECRYPT;
	200
	201	if (ext4_need_verity(inode, first_idx))
	202	post_read_steps \|= 1 << STEP_VERITY;
	203
	204	if (post_read_steps) {
fd5fe253 EB	205	/* Due to the mempool, this never fails. */
	206	struct bio_post_read_ctx *ctx =
	207	mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
	208
22cfe4b4 EB	209	ctx->bio = bio;
	210	ctx->enabled_steps = post_read_steps;
	211	bio->bi_private = ctx;
f64e02fe	212	}
22cfe4b4	213	}
f64e02fe	214
22cfe4b4 EB	215	static inline loff_t ext4_readpage_limit(struct inode *inode)
	216	{
	217	if (IS_ENABLED(CONFIG_FS_VERITY) &&
	218	(IS_VERITY(inode) \|\| ext4_verity_in_progress(inode)))
	219	return inode->i_sb->s_maxbytes;
	220
	221	return i_size_read(inode);
f64e02fe TT	222	}
f64e02fe TT	223
a07f624b	224	int ext4_mpage_readpages(struct inode *inode,
6311f91f	225	struct readahead_control rac, struct page page)
f64e02fe TT	226	{
f64e02fe TT	227	struct bio *bio = NULL;
f64e02fe TT	228	sector_t last_block_in_bio = 0;
f64e02fe TT	229
f64e02fe	230	const unsigned blkbits = inode->i_blkbits;
09cbfeaf	231	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
f64e02fe	232	const unsigned blocksize = 1 << blkbits;
4f74d15f	233	sector_t next_block;
f64e02fe TT	234	sector_t block_in_file;
	235	sector_t last_block;
	236	sector_t last_block_in_file;
	237	sector_t blocks[MAX_BUF_PER_PAGE];
	238	unsigned page_block;
	239	struct block_device *bdev = inode->i_sb->s_bdev;
	240	int length;
	241	unsigned relative_block = 0;
	242	struct ext4_map_blocks map;
6311f91f	243	unsigned int nr_pages = rac ? readahead_count(rac) : 1;
f64e02fe TT	244
	245	map.m_pblk = 0;
	246	map.m_lblk = 0;
	247	map.m_len = 0;
	248	map.m_flags = 0;
	249
de9e9181	250	for (; nr_pages; nr_pages--) {
f64e02fe TT	251	int fully_mapped = 1;
	252	unsigned first_hole = blocks_per_page;
	253
6311f91f MWO	254	if (rac) {
6311f91f MWO	255	page = readahead_page(rac);
d454a273	256	prefetchw(&page->flags);
f64e02fe TT	257	}
	258
	259	if (page_has_buffers(page))
	260	goto confused;
	261
4f74d15f EB	262	block_in_file = next_block =
4f74d15f EB	263	(sector_t)page->index << (PAGE_SHIFT - blkbits);
f64e02fe	264	last_block = block_in_file + nr_pages * blocks_per_page;
22cfe4b4 EB	265	last_block_in_file = (ext4_readpage_limit(inode) +
22cfe4b4 EB	266	blocksize - 1) >> blkbits;
f64e02fe TT	267	if (last_block > last_block_in_file)
	268	last_block = last_block_in_file;
	269	page_block = 0;
	270
	271	/*
	272	* Map blocks using the previous result first.
	273	*/
	274	if ((map.m_flags & EXT4_MAP_MAPPED) &&
	275	block_in_file > map.m_lblk &&
	276	block_in_file < (map.m_lblk + map.m_len)) {
	277	unsigned map_offset = block_in_file - map.m_lblk;
	278	unsigned last = map.m_len - map_offset;
	279
	280	for (relative_block = 0; ; relative_block++) {
	281	if (relative_block == last) {
	282	/* needed? */
	283	map.m_flags &= ~EXT4_MAP_MAPPED;
	284	break;
	285	}
	286	if (page_block == blocks_per_page)
	287	break;
	288	blocks[page_block] = map.m_pblk + map_offset +
	289	relative_block;
	290	page_block++;
	291	block_in_file++;
	292	}
	293	}
	294
	295	/*
	296	* Then do more ext4_map_blocks() calls until we are
	297	* done with this page.
	298	*/
	299	while (page_block < blocks_per_page) {
	300	if (block_in_file < last_block) {
	301	map.m_lblk = block_in_file;
	302	map.m_len = last_block - block_in_file;
	303
	304	if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
	305	set_error_page:
	306	SetPageError(page);
	307	zero_user_segment(page, 0,
09cbfeaf	308	PAGE_SIZE);
f64e02fe TT	309	unlock_page(page);
	310	goto next_page;
	311	}
	312	}
	313	if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
	314	fully_mapped = 0;
	315	if (first_hole == blocks_per_page)
	316	first_hole = page_block;
	317	page_block++;
	318	block_in_file++;
	319	continue;
	320	}
	321	if (first_hole != blocks_per_page)
	322	goto confused; /* hole -> non-hole */
	323
	324	/* Contiguous blocks? */
	325	if (page_block && blocks[page_block-1] != map.m_pblk-1)
	326	goto confused;
	327	for (relative_block = 0; ; relative_block++) {
	328	if (relative_block == map.m_len) {
	329	/* needed? */
	330	map.m_flags &= ~EXT4_MAP_MAPPED;
	331	break;
	332	} else if (page_block == blocks_per_page)
	333	break;
	334	blocks[page_block] = map.m_pblk+relative_block;
	335	page_block++;
	336	block_in_file++;
	337	}
	338	}
	339	if (first_hole != blocks_per_page) {
	340	zero_user_segment(page, first_hole << blkbits,
09cbfeaf	341	PAGE_SIZE);
f64e02fe	342	if (first_hole == 0) {
22cfe4b4 EB	343	if (ext4_need_verity(inode, page->index) &&
	344	!fsverity_verify_page(page))
	345	goto set_error_page;
f64e02fe TT	346	SetPageUptodate(page);
	347	unlock_page(page);
	348	goto next_page;
	349	}
	350	} else if (fully_mapped) {
	351	SetPageMappedToDisk(page);
	352	}
	353	if (fully_mapped && blocks_per_page == 1 &&
	354	!PageUptodate(page) && cleancache_get_page(page) == 0) {
	355	SetPageUptodate(page);
	356	goto confused;
	357	}
	358
	359	/*
	360	* This page will go to BIO. Do we need to send this
	361	* BIO off first?
	362	*/
4f74d15f EB	363	if (bio && (last_block_in_bio != blocks[0] - 1 \|\|
4f74d15f EB	364	!fscrypt_mergeable_bio(bio, inode, next_block))) {
f64e02fe	365	submit_and_realloc:
4e49ea4a	366	submit_bio(bio);
f64e02fe TT	367	bio = NULL;
	368	}
	369	if (bio == NULL) {
5500221e GX	370	/*
	371	* bio_alloc will _always_ be able to allocate a bio if
	372	* __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
	373	*/
5f7136db	374	bio = bio_alloc(GFP_KERNEL, bio_max_segs(nr_pages));
4f74d15f EB	375	fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
4f74d15f EB	376	GFP_KERNEL);
fd5fe253	377	ext4_set_bio_post_read_ctx(bio, inode, page->index);
74d46992	378	bio_set_dev(bio, bdev);
f64e02fe TT	379	bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
f64e02fe TT	380	bio->bi_end_io = mpage_end_io;
ac22b46a	381	bio_set_op_attrs(bio, REQ_OP_READ,
6311f91f	382	rac ? REQ_RAHEAD : 0);
f64e02fe TT	383	}
	384
	385	length = first_hole << blkbits;
	386	if (bio_add_page(bio, page, length, 0) < length)
	387	goto submit_and_realloc;
	388
	389	if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
	390	(relative_block == map.m_len)) \|\|
	391	(first_hole != blocks_per_page)) {
4e49ea4a	392	submit_bio(bio);
f64e02fe TT	393	bio = NULL;
	394	} else
	395	last_block_in_bio = blocks[blocks_per_page - 1];
	396	goto next_page;
	397	confused:
	398	if (bio) {
4e49ea4a	399	submit_bio(bio);
f64e02fe TT	400	bio = NULL;
	401	}
	402	if (!PageUptodate(page))
	403	block_read_full_page(page, ext4_get_block);
	404	else
	405	unlock_page(page);
	406	next_page:
6311f91f	407	if (rac)
09cbfeaf	408	put_page(page);
f64e02fe	409	}
f64e02fe	410	if (bio)
4e49ea4a	411	submit_bio(bio);
f64e02fe TT	412	return 0;
f64e02fe TT	413	}
22cfe4b4 EB	414
	415	int __init ext4_init_post_read_processing(void)
	416	{
	417	bio_post_read_ctx_cache =
	418	kmem_cache_create("ext4_bio_post_read_ctx",
	419	sizeof(struct bio_post_read_ctx), 0, 0, NULL);
	420	if (!bio_post_read_ctx_cache)
	421	goto fail;
	422	bio_post_read_ctx_pool =
	423	mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
	424	bio_post_read_ctx_cache);
	425	if (!bio_post_read_ctx_pool)
	426	goto fail_free_cache;
	427	return 0;
	428
	429	fail_free_cache:
	430	kmem_cache_destroy(bio_post_read_ctx_cache);
	431	fail:
	432	return -ENOMEM;
	433	}
	434
	435	void ext4_exit_post_read_processing(void)
	436	{
	437	mempool_destroy(bio_post_read_ctx_pool);
	438	kmem_cache_destroy(bio_post_read_ctx_cache);
	439	}