[linux-block.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 "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;

		if (bio->bi_status)
			ClearPageUptodate(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);
	struct bio *bio = ctx->bio;

	if (fscrypt_decrypt_bio(bio))
		bio_post_read_processing(ctx);
	else
		__read_end_io(bio);
}

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 readahead() 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_folio().
 *
 * 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);
		}

		/*
		 * 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(bdev, bio_max_segs(nr_pages),
					REQ_OP_READ, GFP_KERNEL);
			fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
						  GFP_KERNEL);
			ext4_set_bio_post_read_ctx(bio, inode, page->index);
			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
			bio->bi_end_io = mpage_end_io;
			if (rac)
				bio->bi_opf |= REQ_RAHEAD;
		}

		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_folio(page_folio(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(bio_post_read_ctx, SLAB_RECLAIM_ACCOUNT);

	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>
f64e02fe TT	46
	47	#include "ext4.h"
	48
22cfe4b4 EB	49	#define NUM_PREALLOC_POST_READ_CTXS 128
	50
	51	static struct kmem_cache *bio_post_read_ctx_cache;
	52	static mempool_t *bio_post_read_ctx_pool;
	53
	54	/* postprocessing steps for read bios */
	55	enum bio_post_read_step {
	56	STEP_INITIAL = 0,
	57	STEP_DECRYPT,
	58	STEP_VERITY,
68e45330	59	STEP_MAX,
22cfe4b4 EB	60	};
	61
	62	struct bio_post_read_ctx {
	63	struct bio *bio;
	64	struct work_struct work;
	65	unsigned int cur_step;
	66	unsigned int enabled_steps;
	67	};
	68
	69	static void __read_end_io(struct bio *bio)
c9c7429c	70	{
22cfe4b4 EB	71	struct page *page;
	72	struct bio_vec *bv;
	73	struct bvec_iter_all iter_all;
	74
	75	bio_for_each_segment_all(bv, bio, iter_all) {
	76	page = bv->bv_page;
	77
98dc08ba	78	if (bio->bi_status)
22cfe4b4	79	ClearPageUptodate(page);
98dc08ba	80	else
22cfe4b4	81	SetPageUptodate(page);
22cfe4b4 EB	82	unlock_page(page);
	83	}
	84	if (bio->bi_private)
	85	mempool_free(bio->bi_private, bio_post_read_ctx_pool);
	86	bio_put(bio);
	87	}
	88
	89	static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
	90
	91	static void decrypt_work(struct work_struct *work)
	92	{
	93	struct bio_post_read_ctx *ctx =
	94	container_of(work, struct bio_post_read_ctx, work);
14db0b3c	95	struct bio *bio = ctx->bio;
22cfe4b4	96
14db0b3c EB	97	if (fscrypt_decrypt_bio(bio))
	98	bio_post_read_processing(ctx);
	99	else
	100	__read_end_io(bio);
22cfe4b4 EB	101	}
	102
	103	static void verity_work(struct work_struct *work)
	104	{
	105	struct bio_post_read_ctx *ctx =
	106	container_of(work, struct bio_post_read_ctx, work);
68e45330	107	struct bio *bio = ctx->bio;
22cfe4b4	108
68e45330	109	/*
704528d8	110	* fsverity_verify_bio() may call readahead() again, and although verity
68e45330 EB	111	* will be disabled for that, decryption may still be needed, causing
	112	* another bio_post_read_ctx to be allocated. So to guarantee that
	113	* mempool_alloc() never deadlocks we must free the current ctx first.
	114	* This is safe because verity is the last post-read step.
	115	*/
	116	BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX);
	117	mempool_free(ctx, bio_post_read_ctx_pool);
	118	bio->bi_private = NULL;
	119
	120	fsverity_verify_bio(bio);
	121
	122	__read_end_io(bio);
22cfe4b4 EB	123	}
	124
	125	static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
	126	{
	127	/*
	128	* We use different work queues for decryption and for verity because
	129	* verity may require reading metadata pages that need decryption, and
	130	* we shouldn't recurse to the same workqueue.
	131	*/
	132	switch (++ctx->cur_step) {
	133	case STEP_DECRYPT:
	134	if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
	135	INIT_WORK(&ctx->work, decrypt_work);
	136	fscrypt_enqueue_decrypt_work(&ctx->work);
	137	return;
	138	}
	139	ctx->cur_step++;
70d7ced2	140	fallthrough;
22cfe4b4 EB	141	case STEP_VERITY:
	142	if (ctx->enabled_steps & (1 << STEP_VERITY)) {
	143	INIT_WORK(&ctx->work, verity_work);
	144	fsverity_enqueue_verify_work(&ctx->work);
	145	return;
	146	}
	147	ctx->cur_step++;
70d7ced2	148	fallthrough;
22cfe4b4 EB	149	default:
	150	__read_end_io(ctx->bio);
	151	}
	152	}
	153
	154	static bool bio_post_read_required(struct bio *bio)
	155	{
	156	return bio->bi_private && !bio->bi_status;
c9c7429c MH	157	}
c9c7429c MH	158
f64e02fe TT	159	/*
	160	* I/O completion handler for multipage BIOs.
	161	*
	162	* The mpage code never puts partial pages into a BIO (except for end-of-file).
	163	* If a page does not map to a contiguous run of blocks then it simply falls
2c69e205	164	* back to block_read_full_folio().
f64e02fe TT	165	*
	166	* Why is this? If a page's completion depends on a number of different BIOs
	167	* which can complete in any order (or at the same time) then determining the
	168	* status of that page is hard. See end_buffer_async_read() for the details.
	169	* There is no point in duplicating all that complexity.
	170	*/
4246a0b6	171	static void mpage_end_io(struct bio *bio)
f64e02fe	172	{
22cfe4b4 EB	173	if (bio_post_read_required(bio)) {
22cfe4b4 EB	174	struct bio_post_read_ctx *ctx = bio->bi_private;
f64e02fe	175
22cfe4b4 EB	176	ctx->cur_step = STEP_INITIAL;
	177	bio_post_read_processing(ctx);
	178	return;
c9c7429c	179	}
22cfe4b4 EB	180	__read_end_io(bio);
22cfe4b4 EB	181	}
f64e02fe	182
22cfe4b4 EB	183	static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
	184	{
	185	return fsverity_active(inode) &&
	186	idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
	187	}
	188
fd5fe253 EB	189	static void ext4_set_bio_post_read_ctx(struct bio *bio,
	190	const struct inode *inode,
	191	pgoff_t first_idx)
22cfe4b4 EB	192	{
22cfe4b4 EB	193	unsigned int post_read_steps = 0;
22cfe4b4	194
4f74d15f	195	if (fscrypt_inode_uses_fs_layer_crypto(inode))
22cfe4b4 EB	196	post_read_steps \|= 1 << STEP_DECRYPT;
	197
	198	if (ext4_need_verity(inode, first_idx))
	199	post_read_steps \|= 1 << STEP_VERITY;
	200
	201	if (post_read_steps) {
fd5fe253 EB	202	/* Due to the mempool, this never fails. */
	203	struct bio_post_read_ctx *ctx =
	204	mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
	205
22cfe4b4 EB	206	ctx->bio = bio;
	207	ctx->enabled_steps = post_read_steps;
	208	bio->bi_private = ctx;
f64e02fe	209	}
22cfe4b4	210	}
f64e02fe	211
22cfe4b4 EB	212	static inline loff_t ext4_readpage_limit(struct inode *inode)
	213	{
	214	if (IS_ENABLED(CONFIG_FS_VERITY) &&
	215	(IS_VERITY(inode) \|\| ext4_verity_in_progress(inode)))
	216	return inode->i_sb->s_maxbytes;
	217
	218	return i_size_read(inode);
f64e02fe TT	219	}
f64e02fe TT	220
a07f624b	221	int ext4_mpage_readpages(struct inode *inode,
6311f91f	222	struct readahead_control rac, struct page page)
f64e02fe TT	223	{
f64e02fe TT	224	struct bio *bio = NULL;
f64e02fe TT	225	sector_t last_block_in_bio = 0;
f64e02fe TT	226
f64e02fe	227	const unsigned blkbits = inode->i_blkbits;
09cbfeaf	228	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
f64e02fe	229	const unsigned blocksize = 1 << blkbits;
4f74d15f	230	sector_t next_block;
f64e02fe TT	231	sector_t block_in_file;
	232	sector_t last_block;
	233	sector_t last_block_in_file;
	234	sector_t blocks[MAX_BUF_PER_PAGE];
	235	unsigned page_block;
	236	struct block_device *bdev = inode->i_sb->s_bdev;
	237	int length;
	238	unsigned relative_block = 0;
	239	struct ext4_map_blocks map;
6311f91f	240	unsigned int nr_pages = rac ? readahead_count(rac) : 1;
f64e02fe TT	241
	242	map.m_pblk = 0;
	243	map.m_lblk = 0;
	244	map.m_len = 0;
	245	map.m_flags = 0;
	246
de9e9181	247	for (; nr_pages; nr_pages--) {
f64e02fe TT	248	int fully_mapped = 1;
	249	unsigned first_hole = blocks_per_page;
	250
6311f91f MWO	251	if (rac) {
6311f91f MWO	252	page = readahead_page(rac);
d454a273	253	prefetchw(&page->flags);
f64e02fe TT	254	}
	255
	256	if (page_has_buffers(page))
	257	goto confused;
	258
4f74d15f EB	259	block_in_file = next_block =
4f74d15f EB	260	(sector_t)page->index << (PAGE_SHIFT - blkbits);
f64e02fe	261	last_block = block_in_file + nr_pages * blocks_per_page;
22cfe4b4 EB	262	last_block_in_file = (ext4_readpage_limit(inode) +
22cfe4b4 EB	263	blocksize - 1) >> blkbits;
f64e02fe TT	264	if (last_block > last_block_in_file)
	265	last_block = last_block_in_file;
	266	page_block = 0;
	267
	268	/*
	269	* Map blocks using the previous result first.
	270	*/
	271	if ((map.m_flags & EXT4_MAP_MAPPED) &&
	272	block_in_file > map.m_lblk &&
	273	block_in_file < (map.m_lblk + map.m_len)) {
	274	unsigned map_offset = block_in_file - map.m_lblk;
	275	unsigned last = map.m_len - map_offset;
	276
	277	for (relative_block = 0; ; relative_block++) {
	278	if (relative_block == last) {
	279	/* needed? */
	280	map.m_flags &= ~EXT4_MAP_MAPPED;
	281	break;
	282	}
	283	if (page_block == blocks_per_page)
	284	break;
	285	blocks[page_block] = map.m_pblk + map_offset +
	286	relative_block;
	287	page_block++;
	288	block_in_file++;
	289	}
	290	}
	291
	292	/*
	293	* Then do more ext4_map_blocks() calls until we are
	294	* done with this page.
	295	*/
	296	while (page_block < blocks_per_page) {
	297	if (block_in_file < last_block) {
	298	map.m_lblk = block_in_file;
	299	map.m_len = last_block - block_in_file;
	300
	301	if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
	302	set_error_page:
	303	SetPageError(page);
	304	zero_user_segment(page, 0,
09cbfeaf	305	PAGE_SIZE);
f64e02fe TT	306	unlock_page(page);
	307	goto next_page;
	308	}
	309	}
	310	if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
	311	fully_mapped = 0;
	312	if (first_hole == blocks_per_page)
	313	first_hole = page_block;
	314	page_block++;
	315	block_in_file++;
	316	continue;
	317	}
	318	if (first_hole != blocks_per_page)
	319	goto confused; /* hole -> non-hole */
	320
	321	/* Contiguous blocks? */
	322	if (page_block && blocks[page_block-1] != map.m_pblk-1)
	323	goto confused;
	324	for (relative_block = 0; ; relative_block++) {
	325	if (relative_block == map.m_len) {
	326	/* needed? */
	327	map.m_flags &= ~EXT4_MAP_MAPPED;
	328	break;
	329	} else if (page_block == blocks_per_page)
	330	break;
	331	blocks[page_block] = map.m_pblk+relative_block;
	332	page_block++;
	333	block_in_file++;
	334	}
	335	}
	336	if (first_hole != blocks_per_page) {
	337	zero_user_segment(page, first_hole << blkbits,
09cbfeaf	338	PAGE_SIZE);
f64e02fe	339	if (first_hole == 0) {
22cfe4b4 EB	340	if (ext4_need_verity(inode, page->index) &&
	341	!fsverity_verify_page(page))
	342	goto set_error_page;
f64e02fe TT	343	SetPageUptodate(page);
	344	unlock_page(page);
	345	goto next_page;
	346	}
	347	} else if (fully_mapped) {
	348	SetPageMappedToDisk(page);
	349	}
f64e02fe TT	350
	351	/*
	352	* This page will go to BIO. Do we need to send this
	353	* BIO off first?
	354	*/
4f74d15f EB	355	if (bio && (last_block_in_bio != blocks[0] - 1 \|\|
4f74d15f EB	356	!fscrypt_mergeable_bio(bio, inode, next_block))) {
f64e02fe	357	submit_and_realloc:
4e49ea4a	358	submit_bio(bio);
f64e02fe TT	359	bio = NULL;
	360	}
	361	if (bio == NULL) {
5500221e GX	362	/*
	363	* bio_alloc will _always_ be able to allocate a bio if
	364	* __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
	365	*/
07888c66 CH	366	bio = bio_alloc(bdev, bio_max_segs(nr_pages),
07888c66 CH	367	REQ_OP_READ, GFP_KERNEL);
4f74d15f EB	368	fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
4f74d15f EB	369	GFP_KERNEL);
fd5fe253	370	ext4_set_bio_post_read_ctx(bio, inode, page->index);
f64e02fe TT	371	bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
f64e02fe TT	372	bio->bi_end_io = mpage_end_io;
07888c66 CH	373	if (rac)
07888c66 CH	374	bio->bi_opf \|= REQ_RAHEAD;
f64e02fe TT	375	}
	376
	377	length = first_hole << blkbits;
	378	if (bio_add_page(bio, page, length, 0) < length)
	379	goto submit_and_realloc;
	380
	381	if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
	382	(relative_block == map.m_len)) \|\|
	383	(first_hole != blocks_per_page)) {
4e49ea4a	384	submit_bio(bio);
f64e02fe TT	385	bio = NULL;
	386	} else
	387	last_block_in_bio = blocks[blocks_per_page - 1];
	388	goto next_page;
	389	confused:
	390	if (bio) {
4e49ea4a	391	submit_bio(bio);
f64e02fe TT	392	bio = NULL;
	393	}
	394	if (!PageUptodate(page))
2c69e205	395	block_read_full_folio(page_folio(page), ext4_get_block);
f64e02fe TT	396	else
	397	unlock_page(page);
	398	next_page:
6311f91f	399	if (rac)
09cbfeaf	400	put_page(page);
f64e02fe	401	}
f64e02fe	402	if (bio)
4e49ea4a	403	submit_bio(bio);
f64e02fe TT	404	return 0;
f64e02fe TT	405	}
22cfe4b4 EB	406
	407	int __init ext4_init_post_read_processing(void)
	408	{
060f7739 JS	409	bio_post_read_ctx_cache = KMEM_CACHE(bio_post_read_ctx, SLAB_RECLAIM_ACCOUNT);
060f7739 JS	410
22cfe4b4 EB	411	if (!bio_post_read_ctx_cache)
	412	goto fail;
	413	bio_post_read_ctx_pool =
	414	mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
	415	bio_post_read_ctx_cache);
	416	if (!bio_post_read_ctx_pool)
	417	goto fail_free_cache;
	418	return 0;
	419
	420	fail_free_cache:
	421	kmem_cache_destroy(bio_post_read_ctx_cache);
	422	fail:
	423	return -ENOMEM;
	424	}
	425
	426	void ext4_exit_post_read_processing(void)
	427	{
	428	mempool_destroy(bio_post_read_ctx_pool);
	429	kmem_cache_destroy(bio_post_read_ctx_cache);
	430	}