linux/fs/squashfs/file_direct.c
Phillip Lougher 6d56540950 Squashfs: fix failure to unlock pages on decompress error
Direct decompression into the page cache.  If we fall back
to using an intermediate buffer (because we cannot grab all the
page cache pages) and we get a decompress fail, we forgot to
release the pages.

Reported-by: Roman Peniaev <r.peniaev@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
2013-11-24 01:02:50 +00:00

177 lines
4.4 KiB
C

/*
* 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;
}