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Message-Id: <E1KqrTW-0001xU-NY@dylan>
Date: Fri, 17 Oct 2008 16:42:50 +0100
From: Phillip Lougher <phillip@...gher.demon.co.uk>
To: akpm@...ux-foundation.org, linux-embedded@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
tim.bird@...sony.com
Subject: Subject: [PATCH 05/16] Squashfs: Symlink file operations
Signed-off-by: Phillip Lougher <phillip@...gher.demon.co.uk>
---
fs/squashfs/symlink.c | 119 +++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 119 insertions(+), 0 deletions(-)
diff --git a/fs/squashfs/symlink.c b/fs/squashfs/symlink.c
new file mode 100644
index 0000000..c6d8b1a
--- /dev/null
+++ b/fs/squashfs/symlink.c
@@ -0,0 +1,119 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ * Phillip Lougher <phillip@...gher.demon.co.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * symlink.c
+ */
+
+/*
+ * This file implements code to handle symbolic links.
+ *
+ * The data contents of symbolic links are stored inside the symbolic
+ * link inode within the inode table. This allows the normally small symbolic
+ * link to be compressed as part of the inode table, achieving much greater
+ * compression than if the symbolic link was compressed individually.
+ */
+
+#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/zlib.h>
+#include <linux/squashfs_fs.h>
+#include <linux/squashfs_fs_sb.h>
+#include <linux/squashfs_fs_i.h>
+
+#include "squashfs.h"
+
+static int squashfs_symlink_readpage(struct file *file, struct page *page)
+{
+ struct inode *inode = page->mapping->host;
+ struct super_block *s = inode->i_sb;
+ struct squashfs_sb_info *msblk = s->s_fs_info;
+ int index = page->index << PAGE_CACHE_SHIFT;
+ long long block = SQUASHFS_I(inode)->start_block;
+ int offset = SQUASHFS_I(inode)->offset;
+ int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
+ int avail, bytes;
+ void *pageaddr;
+ struct squashfs_cache_entry *entry;
+
+ TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
+ "%llx, offset %x\n", page->index, block, offset);
+
+ /*
+ * Skip index bytes into symlink metadata.
+ */
+ if (index) {
+ bytes = squashfs_read_metadata(s, NULL, block, offset, index,
+ &block, &offset);
+ if (bytes == 0) {
+ ERROR("Unable to read symlink [%llx:%x]\n",
+ SQUASHFS_I(inode)->start_block,
+ SQUASHFS_I(inode)->offset);
+ goto error_out;
+ }
+ }
+
+ /*
+ * Read length bytes from symlink metadata. Squashfs_read_metadata
+ * is not used here because it can sleep and we want to use
+ * kmap_atomic to map the page. Instead call the underlying
+ * squashfs_cache_get routine. As length bytes may overlap metadata
+ * blocks, we may need to call squashfs_cache_get multiple times.
+ */
+ for (bytes = 0; bytes < length; offset = 0, bytes += avail) {
+ entry = squashfs_cache_get(s, msblk->block_cache, block, 0);
+ avail = min(entry->length - offset, length - bytes);
+
+ if (entry->error) {
+ ERROR("Unable to read symlink [%llx:%x]\n",
+ SQUASHFS_I(inode)->start_block,
+ SQUASHFS_I(inode)->offset);
+ squashfs_cache_put(msblk->block_cache, entry);
+ goto error_out;
+ }
+
+ pageaddr = kmap_atomic(page, KM_USER0);
+ memcpy(pageaddr + bytes, entry->data + offset, avail);
+ if (avail == length - bytes)
+ memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
+ else
+ block = entry->next_index;
+ kunmap_atomic(pageaddr, KM_USER0);
+ squashfs_cache_put(msblk->block_cache, entry);
+ }
+
+ flush_dcache_page(page);
+ SetPageUptodate(page);
+ unlock_page(page);
+ return 0;
+
+error_out:
+ SetPageError(page);
+ unlock_page(page);
+ return 0;
+}
+
+
+const struct address_space_operations squashfs_symlink_aops = {
+ .readpage = squashfs_symlink_readpage
+};
--
1.5.2.5
--
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