1 files changed, 124 insertions, 0 deletions
diff --git a/fs/squashfs/file_direct.c b/fs/squashfs/file_direct.c
new file mode 100644
index 000000000000..2c3e809d6891
--- /dev/null
+++ b/fs/squashfs/file_direct.c
@@ -0,0 +1,124 @@
+// 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"
+
+/* Read separately compressed datablock directly into page cache */
+int squashfs_readpage_block(struct folio *folio, u64 block, int bsize,
+		int expected)
+{
+	struct page *target_page = &folio->page;
+	struct inode *inode = folio->mapping->host;
+	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
+	loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+	int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
+	loff_t start_index = folio->index & ~mask;
+	loff_t end_index = start_index | mask;
+	loff_t index;
+	int i, pages, bytes, res = -ENOMEM;
+	struct page **page, *last_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;
+
+	/* Try to grab all the pages covered by the Squashfs block */
+	for (i = 0, index = start_index; index <= end_index; index++) {
+		page[i] = (index == folio->index) ? target_page :
+			grab_cache_page_nowait(folio->mapping, index);
+
+		if (page[i] == NULL)
+			continue;
+
+		if (PageUptodate(page[i])) {
+			unlock_page(page[i]);
+			put_page(page[i]);
+			continue;
+		}
+
+		i++;
+	}
+
+	pages = i;
+
+	/*
+	 * Create a "page actor" which will kmap and kunmap the
+	 * page cache pages appropriately within the decompressor
+	 */
+	actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
+						start_index << PAGE_SHIFT);
+	if (actor == NULL)
+		goto out;
+
+	/* Decompress directly into the page cache buffers */
+	res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
+
+	last_page = squashfs_page_actor_free(actor);
+
+	if (res < 0)
+		goto mark_errored;
+
+	if (res != expected || IS_ERR(last_page)) {
+		res = -EIO;
+		goto mark_errored;
+	}
+
+	/* Last page (if present) may have trailing bytes not filled */
+	bytes = res % PAGE_SIZE;
+	if (end_index == file_end && last_page && bytes) {
+		pageaddr = kmap_local_page(last_page);
+		memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
+		kunmap_local(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(page);
+
+	return 0;
+
+mark_errored:
+	/* Decompression failed.  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]);
+		unlock_page(page[i]);
+		put_page(page[i]);
+	}
+
+out:
+	kfree(page);
+	return res;
+}