fs/ext4/readpage.c - linux - Git at Google

 // 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 intent is the ext4_mpage_readpages() function here is intended
  * to replace mpage_readpages() 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"

 static inline bool ext4_bio_encrypted(struct bio *bio)
 {
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 	return unlikely(bio->bi_private != NULL);
 #else
 	return false;
 #endif
 }

 /*
  * 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)
 {
 	struct bio_vec *bv;
 	int i;

 	if (ext4_bio_encrypted(bio)) {
 		if (bio->bi_status) {
 			fscrypt_release_ctx(bio->bi_private);
 		} else {
 			fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
 			return;
 		}
 	}
 	bio_for_each_segment_all(bv, bio, i) {
 		struct page *page = bv->bv_page;

 		if (!bio->bi_status) {
 			SetPageUptodate(page);
 		} else {
 			ClearPageUptodate(page);
 			SetPageError(page);
 		}
 		unlock_page(page);
 	}

 	bio_put(bio);
 }

 int ext4_mpage_readpages(struct address_space *mapping,
 			 struct list_head *pages, struct page *page,
 			 unsigned nr_pages, bool is_readahead)
 {
 	struct bio *bio = NULL;
 	sector_t last_block_in_bio = 0;

 	struct inode *inode = mapping->host;
 	const unsigned blkbits = inode->i_blkbits;
 	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
 	const unsigned blocksize = 1 << blkbits;
 	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;

 	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;

 		prefetchw(&page->flags);
 		if (pages) {
 			page = list_entry(pages->prev, struct page, lru);
 			list_del(&page->lru);
 			if (add_to_page_cache_lru(page, mapping, page->index,
 				  readahead_gfp_mask(mapping)))
 				goto next_page;
 		}

 		if (page_has_buffers(page))
 			goto confused;

 		block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
 		last_block = block_in_file + nr_pages * blocks_per_page;
 		last_block_in_file = (i_size_read(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) {
 				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)) {
 		submit_and_realloc:
 			submit_bio(bio);
 			bio = NULL;
 		}
 		if (bio == NULL) {
 			struct fscrypt_ctx *ctx = NULL;

 			if (ext4_encrypted_inode(inode) &&
 			    S_ISREG(inode->i_mode)) {
 				ctx = fscrypt_get_ctx(inode, GFP_NOFS);
 				if (IS_ERR(ctx))
 					goto set_error_page;
 			}
 			bio = bio_alloc(GFP_KERNEL,
 				min_t(int, nr_pages, BIO_MAX_PAGES));
 			if (!bio) {
 				if (ctx)
 					fscrypt_release_ctx(ctx);
 				goto set_error_page;
 			}
 			bio_set_dev(bio, bdev);
 			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
 			bio->bi_end_io = mpage_end_io;
 			bio->bi_private = ctx;
 			bio_set_op_attrs(bio, REQ_OP_READ,
 						is_readahead ? 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 (pages)
 			put_page(page);
 	}
 	BUG_ON(pages && !list_empty(pages));
 	if (bio)
 		submit_bio(bio);
 	return 0;
 }
	// 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 intent is the ext4_mpage_readpages() function here is intended
	* to replace mpage_readpages() 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"

	static inline bool ext4_bio_encrypted(struct bio *bio)
	{
	#ifdef CONFIG_EXT4_FS_ENCRYPTION
	return unlikely(bio->bi_private != NULL);
	#else
	return false;
	#endif
	}

	/*
	* 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)
	{
	struct bio_vec *bv;
	int i;

	if (ext4_bio_encrypted(bio)) {
	if (bio->bi_status) {
	fscrypt_release_ctx(bio->bi_private);
	} else {
	fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
	return;
	}
	}
	bio_for_each_segment_all(bv, bio, i) {
	struct page *page = bv->bv_page;

	if (!bio->bi_status) {
	SetPageUptodate(page);
	} else {
	ClearPageUptodate(page);
	SetPageError(page);
	}
	unlock_page(page);
	}

	bio_put(bio);
	}

	int ext4_mpage_readpages(struct address_space *mapping,
	struct list_head pages, struct page page,
	unsigned nr_pages, bool is_readahead)
	{
	struct bio *bio = NULL;
	sector_t last_block_in_bio = 0;

	struct inode *inode = mapping->host;
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
	const unsigned blocksize = 1 << blkbits;
	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;

	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;

	prefetchw(&page->flags);
	if (pages) {
	page = list_entry(pages->prev, struct page, lru);
	list_del(&page->lru);
	if (add_to_page_cache_lru(page, mapping, page->index,
	readahead_gfp_mask(mapping)))
	goto next_page;
	}

	if (page_has_buffers(page))
	goto confused;

	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
	last_block = block_in_file + nr_pages * blocks_per_page;
	last_block_in_file = (i_size_read(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) {
	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)) {
	submit_and_realloc:
	submit_bio(bio);
	bio = NULL;
	}
	if (bio == NULL) {
	struct fscrypt_ctx *ctx = NULL;

	if (ext4_encrypted_inode(inode) &&
	S_ISREG(inode->i_mode)) {
	ctx = fscrypt_get_ctx(inode, GFP_NOFS);
	if (IS_ERR(ctx))
	goto set_error_page;
	}
	bio = bio_alloc(GFP_KERNEL,
	min_t(int, nr_pages, BIO_MAX_PAGES));
	if (!bio) {
	if (ctx)
	fscrypt_release_ctx(ctx);
	goto set_error_page;
	}
	bio_set_dev(bio, bdev);
	bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
	bio->bi_end_io = mpage_end_io;
	bio->bi_private = ctx;
	bio_set_op_attrs(bio, REQ_OP_READ,
	is_readahead ? 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 (pages)
	put_page(page);
	}
	BUG_ON(pages && !list_empty(pages));
	if (bio)
	submit_bio(bio);
	return 0;
	}