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| -rw-r--r-- | fs/squashfs/file.c | 502 |
1 files changed, 502 insertions, 0 deletions
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c new file mode 100644 index 0000000..717767d --- /dev/null +++ b/fs/squashfs/file.c @@ -0,0 +1,502 @@ +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher <phillip@lougher.demon.co.uk> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2, + * or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + * file.c + */ + +/* + * This file contains code for handling regular files. A regular file + * consists of a sequence of contiguous compressed blocks, and/or a + * compressed fragment block (tail-end packed block). The compressed size + * of each datablock is stored in a block list contained within the + * file inode (itself stored in one or more compressed metadata blocks). + * + * To speed up access to datablocks when reading 'large' files (256 Mbytes or + * larger), the code implements an index cache that caches the mapping from + * block index to datablock location on disk. + * + * The index cache allows Squashfs to handle large files (up to 1.75 TiB) while + * retaining a simple and space-efficient block list on disk. The cache + * is split into slots, caching up to eight 224 GiB files (128 KiB blocks). + * Larger files use multiple slots, with 1.75 TiB files using all 8 slots. + * The index cache is designed to be memory efficient, and by default uses + * 16 KiB. + */ + +#include <linux/fs.h> +#include <linux/vfs.h> +#include <linux/kernel.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/pagemap.h> +#include <linux/mutex.h> +#include <linux/zlib.h> + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs_fs_i.h" +#include "squashfs.h" + +/* + * Locate cache slot in range [offset, index] for specified inode. If + * there's more than one return the slot closest to index. + */ +static struct meta_index *locate_meta_index(struct inode *inode, int offset, + int index) +{ + struct meta_index *meta = NULL; + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + int i; + + mutex_lock(&msblk->meta_index_mutex); + + TRACE("locate_meta_index: index %d, offset %d\n", index, offset); + + if (msblk->meta_index == NULL) + goto not_allocated; + + for (i = 0; i < SQUASHFS_META_SLOTS; i++) { + if (msblk->meta_index[i].inode_number == inode->i_ino && + msblk->meta_index[i].offset >= offset && + msblk->meta_index[i].offset <= index && + msblk->meta_index[i].locked == 0) { + TRACE("locate_meta_index: entry %d, offset %d\n", i, + msblk->meta_index[i].offset); + meta = &msblk->meta_index[i]; + offset = meta->offset; + } + } + + if (meta) + meta->locked = 1; + +not_allocated: + mutex_unlock(&msblk->meta_index_mutex); + + return meta; +} + + +/* + * Find and initialise an empty cache slot for index offset. + */ +static struct meta_index *empty_meta_index(struct inode *inode, int offset, + int skip) +{ + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + struct meta_index *meta = NULL; + int i; + + mutex_lock(&msblk->meta_index_mutex); + + TRACE("empty_meta_index: offset %d, skip %d\n", offset, skip); + + if (msblk->meta_index == NULL) { + /* + * First time cache index has been used, allocate and + * initialise. The cache index could be allocated at + * mount time but doing it here means it is allocated only + * if a 'large' file is read. + */ + msblk->meta_index = kcalloc(SQUASHFS_META_SLOTS, + sizeof(*(msblk->meta_index)), GFP_KERNEL); + if (msblk->meta_index == NULL) { + ERROR("Failed to allocate meta_index\n"); + goto failed; + } + for (i = 0; i < SQUASHFS_META_SLOTS; i++) { + msblk->meta_index[i].inode_number = 0; + msblk->meta_index[i].locked = 0; + } + msblk->next_meta_index = 0; + } + + for (i = SQUASHFS_META_SLOTS; i && + msblk->meta_index[msblk->next_meta_index].locked; i--) + msblk->next_meta_index = (msblk->next_meta_index + 1) % + SQUASHFS_META_SLOTS; + + if (i == 0) { + TRACE("empty_meta_index: failed!\n"); + goto failed; + } + + TRACE("empty_meta_index: returned meta entry %d, %p\n", + msblk->next_meta_index, + &msblk->meta_index[msblk->next_meta_index]); + + meta = &msblk->meta_index[msblk->next_meta_index]; + msblk->next_meta_index = (msblk->next_meta_index + 1) % + SQUASHFS_META_SLOTS; + + meta->inode_number = inode->i_ino; + meta->offset = offset; + meta->skip = skip; + meta->entries = 0; + meta->locked = 1; + +failed: + mutex_unlock(&msblk->meta_index_mutex); + return meta; +} + + +static void release_meta_index(struct inode *inode, struct meta_index *meta) +{ + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + mutex_lock(&msblk->meta_index_mutex); + meta->locked = 0; + mutex_unlock(&msblk->meta_index_mutex); +} + + +/* + * Read the next n blocks from the block list, starting from + * metadata block <start_block, offset>. + */ +static long long read_indexes(struct super_block *sb, int n, + u64 *start_block, int *offset) +{ + int err, i; + long long block = 0; + __le32 *blist = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL); + + if (blist == NULL) { + ERROR("read_indexes: Failed to allocate block_list\n"); + return -ENOMEM; + } + + while (n) { + int blocks = min_t(int, n, PAGE_CACHE_SIZE >> 2); + + err = squashfs_read_metadata(sb, blist, start_block, + offset, blocks << 2); + if (err < 0) { + ERROR("read_indexes: reading block [%llx:%x]\n", + *start_block, *offset); + goto failure; + } + + for (i = 0; i < blocks; i++) { + int size = le32_to_cpu(blist[i]); + block += SQUASHFS_COMPRESSED_SIZE_BLOCK(size); + } + n -= blocks; + } + + kfree(blist); + return block; + +failure: + kfree(blist); + return err; +} + + +/* + * Each cache index slot has SQUASHFS_META_ENTRIES, each of which + * can cache one index -> datablock/blocklist-block mapping. We wish + * to distribute these over the length of the file, entry[0] maps index x, + * entry[1] maps index x + skip, entry[2] maps index x + 2 * skip, and so on. + * The larger the file, the greater the skip factor. The skip factor is + * limited to the size of the metadata cache (SQUASHFS_CACHED_BLKS) to ensure + * the number of metadata blocks that need to be read fits into the cache. + * If the skip factor is limited in this way then the file will use multiple + * slots. + */ +static inline int calculate_skip(int blocks) +{ + int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) + * SQUASHFS_META_INDEXES); + return min(SQUASHFS_CACHED_BLKS - 1, skip + 1); +} + + +/* + * Search and grow the index cache for the specified inode, returning the + * on-disk locations of the datablock and block list metadata block + * <index_block, index_offset> for index (scaled to nearest cache index). + */ +static int fill_meta_index(struct inode *inode, int index, + u64 *index_block, int *index_offset, u64 *data_block) +{ + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + int skip = calculate_skip(i_size_read(inode) >> msblk->block_log); + int offset = 0; + struct meta_index *meta; + struct meta_entry *meta_entry; + u64 cur_index_block = squashfs_i(inode)->block_list_start; + int cur_offset = squashfs_i(inode)->offset; + u64 cur_data_block = squashfs_i(inode)->start; + int err, i; + + /* + * Scale index to cache index (cache slot entry) + */ + index /= SQUASHFS_META_INDEXES * skip; + + while (offset < index) { + meta = locate_meta_index(inode, offset + 1, index); + + if (meta == NULL) { + meta = empty_meta_index(inode, offset + 1, skip); + if (meta == NULL) + goto all_done; + } else { + offset = index < meta->offset + meta->entries ? index : + meta->offset + meta->entries - 1; + meta_entry = &meta->meta_entry[offset - meta->offset]; + cur_index_block = meta_entry->index_block + + msblk->inode_table; + cur_offset = meta_entry->offset; + cur_data_block = meta_entry->data_block; + TRACE("get_meta_index: offset %d, meta->offset %d, " + "meta->entries %d\n", offset, meta->offset, + meta->entries); + TRACE("get_meta_index: index_block 0x%llx, offset 0x%x" + " data_block 0x%llx\n", cur_index_block, + cur_offset, cur_data_block); + } + + /* + * If necessary grow cache slot by reading block list. Cache + * slot is extended up to index or to the end of the slot, in + * which case further slots will be used. + */ + for (i = meta->offset + meta->entries; i <= index && + i < meta->offset + SQUASHFS_META_ENTRIES; i++) { + int blocks = skip * SQUASHFS_META_INDEXES; + long long res = read_indexes(inode->i_sb, blocks, + &cur_index_block, &cur_offset); + + if (res < 0) { + if (meta->entries == 0) + /* + * Don't leave an empty slot on read + * error allocated to this inode... + */ + meta->inode_number = 0; + err = res; + goto failed; + } + + cur_data_block += res; + meta_entry = &meta->meta_entry[i - meta->offset]; + meta_entry->index_block = cur_index_block - + msblk->inode_table; + meta_entry->offset = cur_offset; + meta_entry->data_block = cur_data_block; + meta->entries++; + offset++; + } + + TRACE("get_meta_index: meta->offset %d, meta->entries %d\n", + meta->offset, meta->entries); + + release_meta_index(inode, meta); + } + +all_done: + *index_block = cur_index_block; + *index_offset = cur_offset; + *data_block = cur_data_block; + + /* + * Scale cache index (cache slot entry) to index + */ + return offset * SQUASHFS_META_INDEXES * skip; + +failed: + release_meta_index(inode, meta); + return err; +} + + +/* + * Get the on-disk location and compressed size of the datablock + * specified by index. Fill_meta_index() does most of the work. + */ +static int read_blocklist(struct inode *inode, int index, u64 *block) +{ + u64 start; + long long blks; + int offset; + __le32 size; + int res = fill_meta_index(inode, index, &start, &offset, block); + + TRACE("read_blocklist: res %d, index %d, start 0x%llx, offset" + " 0x%x, block 0x%llx\n", res, index, start, offset, + *block); + + if (res < 0) + return res; + + /* + * res contains the index of the mapping returned by fill_meta_index(), + * this will likely be less than the desired index (because the + * meta_index cache works at a higher granularity). Read any + * extra block indexes needed. + */ + if (res < index) { + blks = read_indexes(inode->i_sb, index - res, &start, &offset); + if (blks < 0) + return (int) blks; + *block += blks; + } + + /* + * Read length of block specified by index. + */ + res = squashfs_read_metadata(inode->i_sb, &size, &start, &offset, + sizeof(size)); + if (res < 0) + return res; + return le32_to_cpu(size); +} + + +static int squashfs_readpage(struct file *file, struct page *page) +{ + struct inode *inode = page->mapping->host; + struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; + int bytes, i, offset = 0, sparse = 0; + struct squashfs_cache_entry *buffer = NULL; + void *pageaddr; + + int mask = (1 << (msblk->block_log - PAGE_CACHE_SHIFT)) - 1; + int index = page->index >> (msblk->block_log - PAGE_CACHE_SHIFT); + int start_index = page->index & ~mask; + int end_index = start_index | mask; + int file_end = i_size_read(inode) >> msblk->block_log; + + TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n", + page->index, squashfs_i(inode)->start); + + if (page->index >= ((i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> + PAGE_CACHE_SHIFT)) + goto out; + + if (index < file_end || squashfs_i(inode)->fragment_block == + SQUASHFS_INVALID_BLK) { + /* + * Reading a datablock from disk. Need to read block list + * to get location and block size. + */ + u64 block = 0; + int bsize = read_blocklist(inode, index, &block); + if (bsize < 0) + goto error_out; + + if (bsize == 0) { /* hole */ + bytes = index == file_end ? + (i_size_read(inode) & (msblk->block_size - 1)) : + msblk->block_size; + sparse = 1; + } else { + /* + * Read and decompress datablock. + */ + buffer = squashfs_get_datablock(inode->i_sb, + block, bsize); + if (buffer->error) { + ERROR("Unable to read page, block %llx, size %x" + "\n", block, bsize); + squashfs_cache_put(buffer); + goto error_out; + } + bytes = buffer->length; + } + } else { + /* + * Datablock is stored inside a fragment (tail-end packed + * block). + */ + buffer = squashfs_get_fragment(inode->i_sb, + squashfs_i(inode)->fragment_block, + squashfs_i(inode)->fragment_size); + + if (buffer->error) { + ERROR("Unable to read page, block %llx, size %x\n", + squashfs_i(inode)->fragment_block, + squashfs_i(inode)->fragment_size); + squashfs_cache_put(buffer); + goto error_out; + } + bytes = i_size_read(inode) & (msblk->block_size - 1); + offset = squashfs_i(inode)->fragment_offset; + } + + /* + * Loop copying datablock into pages. As the datablock likely covers + * many PAGE_CACHE_SIZE pages (default block size is 128 KiB) explicitly + * grab the pages from the page cache, except for the page that we've + * been called to fill. + */ + for (i = start_index; i <= end_index && bytes > 0; i++, + bytes -= PAGE_CACHE_SIZE, offset += PAGE_CACHE_SIZE) { + struct page *push_page; + int avail = sparse ? 0 : min_t(int, bytes, PAGE_CACHE_SIZE); + + TRACE("bytes %d, i %d, available_bytes %d\n", bytes, i, avail); + + push_page = (i == page->index) ? page : + grab_cache_page_nowait(page->mapping, i); + + if (!push_page) + continue; + + if (PageUptodate(push_page)) + goto skip_page; + + pageaddr = kmap_atomic(push_page, KM_USER0); + squashfs_copy_data(pageaddr, buffer, offset, avail); + memset(pageaddr + avail, 0, PAGE_CACHE_SIZE - avail); + kunmap_atomic(pageaddr, KM_USER0); + flush_dcache_page(push_page); + SetPageUptodate(push_page); +skip_page: + unlock_page(push_page); + if (i != page->index) + page_cache_release(push_page); + } + + if (!sparse) + squashfs_cache_put(buffer); + + return 0; + +error_out: + SetPageError(page); +out: + pageaddr = kmap_atomic(page, KM_USER0); + memset(pageaddr, 0, PAGE_CACHE_SIZE); + kunmap_atomic(pageaddr, KM_USER0); + flush_dcache_page(page); + if (!PageError(page)) + SetPageUptodate(page); + unlock_page(page); + + return 0; +} + + +const struct address_space_operations squashfs_aops = { + .readpage = squashfs_readpage +}; |