| /* |
| * 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_CACHE_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" |
| |
| /* |
| * Call ext4_decrypt on every single page, reusing the encryption |
| * context. |
| */ |
| static void completion_pages(struct work_struct *work) |
| { |
| #ifdef CONFIG_EXT4_FS_ENCRYPTION |
| struct ext4_crypto_ctx *ctx = |
| container_of(work, struct ext4_crypto_ctx, r.work); |
| struct bio *bio = ctx->r.bio; |
| struct bio_vec *bv; |
| int i; |
| |
| bio_for_each_segment_all(bv, bio, i) { |
| struct page *page = bv->bv_page; |
| |
| int ret = ext4_decrypt(page); |
| if (ret) { |
| WARN_ON_ONCE(1); |
| SetPageError(page); |
| } else |
| SetPageUptodate(page); |
| unlock_page(page); |
| } |
| ext4_release_crypto_ctx(ctx); |
| bio_put(bio); |
| #else |
| BUG(); |
| #endif |
| } |
| |
| 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)) { |
| struct ext4_crypto_ctx *ctx = bio->bi_private; |
| |
| if (bio->bi_error) { |
| ext4_release_crypto_ctx(ctx); |
| } else { |
| INIT_WORK(&ctx->r.work, completion_pages); |
| ctx->r.bio = bio; |
| queue_work(ext4_read_workqueue, &ctx->r.work); |
| return; |
| } |
| } |
| bio_for_each_segment_all(bv, bio, i) { |
| struct page *page = bv->bv_page; |
| |
| if (!bio->bi_error) { |
| 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) |
| { |
| struct bio *bio = NULL; |
| unsigned page_idx; |
| 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 (page_idx = 0; nr_pages; page_idx++, 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, |
| mapping_gfp_constraint(mapping, GFP_KERNEL))) |
| 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(READ, bio); |
| bio = NULL; |
| } |
| if (bio == NULL) { |
| struct ext4_crypto_ctx *ctx = NULL; |
| |
| if (ext4_encrypted_inode(inode) && |
| S_ISREG(inode->i_mode)) { |
| ctx = ext4_get_crypto_ctx(inode); |
| 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) |
| ext4_release_crypto_ctx(ctx); |
| goto set_error_page; |
| } |
| bio->bi_bdev = bdev; |
| bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); |
| bio->bi_end_io = mpage_end_io; |
| bio->bi_private = ctx; |
| } |
| |
| 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(READ, bio); |
| bio = NULL; |
| } else |
| last_block_in_bio = blocks[blocks_per_page - 1]; |
| goto next_page; |
| confused: |
| if (bio) { |
| submit_bio(READ, 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(READ, bio); |
| return 0; |
| } |