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