// SPDX-License-Identifier: GPL-2.0-only /* * Copyright (c) 2013 * Phillip Lougher <phillip@squashfs.org.uk> */ #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 "squashfs_fs.h" #include "squashfs_fs_sb.h" #include "squashfs_fs_i.h" #include "squashfs.h" #include "page_actor.h" static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, int pages, struct page **page, int bytes); /* Read separately compressed datablock directly into page cache */ int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, int expected) { struct inode *inode = target_page->mapping->host; struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; int file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT; int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1; int start_index = target_page->index & ~mask; int end_index = start_index | mask; int i, n, pages, missing_pages, bytes, res = -ENOMEM; struct page **page; struct squashfs_page_actor *actor; void *pageaddr; if (end_index > file_end) end_index = file_end; pages = end_index - start_index + 1; page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL); if (page == NULL) return res; /* * Create a "page actor" which will kmap and kunmap the * page cache pages appropriately within the decompressor */ actor = squashfs_page_actor_init_special(page, pages, 0); if (actor == NULL) goto out; /* Try to grab all the pages covered by the Squashfs block */ for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) { page[i] = (n == target_page->index) ? target_page : grab_cache_page_nowait(target_page->mapping, n); if (page[i] == NULL) { missing_pages++; continue; } if (PageUptodate(page[i])) { unlock_page(page[i]); put_page(page[i]); page[i] = NULL; missing_pages++; } } if (missing_pages) { /* * Couldn't get one or more pages, this page has either * been VM reclaimed, but others are still in the page cache * and uptodate, or we're racing with another thread in * squashfs_readpage also trying to grab them. Fall back to * using an intermediate buffer. */ res = squashfs_read_cache(target_page, block, bsize, pages, page, expected); if (res < 0) goto mark_errored; goto out; } /* Decompress directly into the page cache buffers */ res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor); if (res < 0) goto mark_errored; if (res != expected) { res = -EIO; goto mark_errored; } /* Last page may have trailing bytes not filled */ bytes = res % PAGE_SIZE; if (bytes) { pageaddr = kmap_atomic(page[pages - 1]); memset(pageaddr + bytes, 0, PAGE_SIZE - bytes); kunmap_atomic(pageaddr); } /* Mark pages as uptodate, unlock and release */ for (i = 0; i < pages; i++) { flush_dcache_page(page[i]); SetPageUptodate(page[i]); unlock_page(page[i]); if (page[i] != target_page) put_page(page[i]); } kfree(actor); kfree(page); return 0; mark_errored: /* Decompression failed, mark pages as errored. Target_page is * dealt with by the caller */ for (i = 0; i < pages; i++) { if (page[i] == NULL || page[i] == target_page) continue; flush_dcache_page(page[i]); SetPageError(page[i]); unlock_page(page[i]); put_page(page[i]); } out: kfree(actor); kfree(page); return res; } static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, int pages, struct page **page, int bytes) { struct inode *i = target_page->mapping->host; struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb, block, bsize); int res = buffer->error, n, offset = 0; if (res) { ERROR("Unable to read page, block %llx, size %x\n", block, bsize); goto out; } for (n = 0; n < pages && bytes > 0; n++, bytes -= PAGE_SIZE, offset += PAGE_SIZE) { int avail = min_t(int, bytes, PAGE_SIZE); if (page[n] == NULL) continue; squashfs_fill_page(page[n], buffer, offset, avail); unlock_page(page[n]); if (page[n] != target_page) put_page(page[n]); } out: squashfs_cache_put(buffer); return res; }