file_direct.c
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/*
* Copyright (c) 2013
* Phillip Lougher <phillip@squashfs.org.uk>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*/
#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);
/* Read separately compressed datablock directly into page cache */
int squashfs_readpage_block(struct page *target_page, u64 block, int bsize)
{
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_CACHE_SHIFT;
int mask = (1 << (msblk->block_log - PAGE_CACHE_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(sizeof(void *) * pages, 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]);
page_cache_release(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);
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;
/* Last page may have trailing bytes not filled */
bytes = res % PAGE_CACHE_SIZE;
if (bytes) {
pageaddr = kmap_atomic(page[pages - 1]);
memset(pageaddr + bytes, 0, PAGE_CACHE_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)
page_cache_release(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]);
page_cache_release(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)
{
struct inode *i = target_page->mapping->host;
struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
block, bsize);
int bytes = buffer->length, res = buffer->error, n, offset = 0;
void *pageaddr;
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_CACHE_SIZE, offset += PAGE_CACHE_SIZE) {
int avail = min_t(int, bytes, PAGE_CACHE_SIZE);
if (page[n] == NULL)
continue;
pageaddr = kmap_atomic(page[n]);
squashfs_copy_data(pageaddr, buffer, offset, avail);
memset(pageaddr + avail, 0, PAGE_CACHE_SIZE - avail);
kunmap_atomic(pageaddr);
flush_dcache_page(page[n]);
SetPageUptodate(page[n]);
unlock_page(page[n]);
if (page[n] != target_page)
page_cache_release(page[n]);
}
out:
squashfs_cache_put(buffer);
return res;
}