cregit-Linux how code gets into the kernel

Release 4.10 fs/squashfs/namei.c

Directory: fs/squashfs
 * Squashfs - a compressed read only filesystem for Linux
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <>
 * 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
 * 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.
 * namei.c

 * This file implements code to do filename lookup in directories.
 * Like inodes, directories are packed into compressed metadata blocks, stored
 * in a directory table.  Directories are accessed using the start address of
 * the metablock containing the directory and the offset into the
 * decompressed block (<block, offset>).
 * Directories are organised in a slightly complex way, and are not simply
 * a list of file names.  The organisation takes advantage of the
 * fact that (in most cases) the inodes of the files will be in the same
 * compressed metadata block, and therefore, can share the start block.
 * Directories are therefore organised in a two level list, a directory
 * header containing the shared start block value, and a sequence of directory
 * entries, each of which share the shared start block.  A new directory header
 * is written once/if the inode start block changes.  The directory
 * header/directory entry list is repeated as many times as necessary.
 * Directories are sorted, and can contain a directory index to speed up
 * file lookup.  Directory indexes store one entry per metablock, each entry
 * storing the index/filename mapping to the first directory header
 * in each metadata block.  Directories are sorted in alphabetical order,
 * and at lookup the index is scanned linearly looking for the first filename
 * alphabetically larger than the filename being looked up.  At this point the
 * location of the metadata block the filename is in has been found.
 * The general idea of the index is ensure only one metadata block needs to be
 * decompressed to do a lookup irrespective of the length of the directory.
 * This scheme has the advantage that it doesn't require extra memory overhead
 * and doesn't require much extra storage on disk.

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/dcache.h>
#include <linux/xattr.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "xattr.h"

 * Lookup name in the directory index, returning the location of the metadata
 * block containing it, and the directory index this represents.
 * If we get an error reading the index then return the part of the index
 * (if any) we have managed to read - the index isn't essential, just
 * quicker.

static int get_dir_index_using_name(struct super_block *sb, u64 *next_block, int *next_offset, u64 index_start, int index_offset, int i_count, const char *name, int len) { struct squashfs_sb_info *msblk = sb->s_fs_info; int i, length = 0, err; unsigned int size; struct squashfs_dir_index *index; char *str; TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count); index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL); if (index == NULL) { ERROR("Failed to allocate squashfs_dir_index\n"); goto out; } str = &index->name[SQUASHFS_NAME_LEN + 1]; strncpy(str, name, len); str[len] = '\0'; for (i = 0; i < i_count; i++) { err = squashfs_read_metadata(sb, index, &index_start, &index_offset, sizeof(*index)); if (err < 0) break; size = le32_to_cpu(index->size) + 1; if (size > SQUASHFS_NAME_LEN) break; err = squashfs_read_metadata(sb, index->name, &index_start, &index_offset, size); if (err < 0) break; index->name[size] = '\0'; if (strcmp(index->name, str) > 0) break; length = le32_to_cpu(index->index); *next_block = le32_to_cpu(index->start_block) + msblk->directory_table; } *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; kfree(index); out: /* * Return index (f_pos) of the looked up metadata block. Translate * from internal f_pos to external f_pos which is offset by 3 because * we invent "." and ".." entries which are not actually stored in the * directory. */ return length + 3; }


phillip lougherphillip lougher28496.27%150.00%
dan carpenterdan carpenter113.73%150.00%

static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { const unsigned char *name = dentry->; int len = dentry->d_name.len; struct inode *inode = NULL; struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info; struct squashfs_dir_header dirh; struct squashfs_dir_entry *dire; u64 block = squashfs_i(dir)->start + msblk->directory_table; int offset = squashfs_i(dir)->offset; int err, length; unsigned int dir_count, size; TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset); dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL); if (dire == NULL) { ERROR("Failed to allocate squashfs_dir_entry\n"); return ERR_PTR(-ENOMEM); } if (len > SQUASHFS_NAME_LEN) { err = -ENAMETOOLONG; goto failed; } length = get_dir_index_using_name(dir->i_sb, &block, &offset, squashfs_i(dir)->dir_idx_start, squashfs_i(dir)->dir_idx_offset, squashfs_i(dir)->dir_idx_cnt, name, len); while (length < i_size_read(dir)) { /* * Read directory header. */ err = squashfs_read_metadata(dir->i_sb, &dirh, &block, &offset, sizeof(dirh)); if (err < 0) goto read_failure; length += sizeof(dirh); dir_count = le32_to_cpu(dirh.count) + 1; if (dir_count > SQUASHFS_DIR_COUNT) goto data_error; while (dir_count--) { /* * Read directory entry. */ err = squashfs_read_metadata(dir->i_sb, dire, &block, &offset, sizeof(*dire)); if (err < 0) goto read_failure; size = le16_to_cpu(dire->size) + 1; /* size should never be larger than SQUASHFS_NAME_LEN */ if (size > SQUASHFS_NAME_LEN) goto data_error; err = squashfs_read_metadata(dir->i_sb, dire->name, &block, &offset, size); if (err < 0) goto read_failure; length += sizeof(*dire) + size; if (name[0] < dire->name[0]) goto exit_lookup; if (len == size && !strncmp(name, dire->name, len)) { unsigned int blk, off, ino_num; long long ino; blk = le32_to_cpu(dirh.start_block); off = le16_to_cpu(dire->offset); ino_num = le32_to_cpu(dirh.inode_number) + (short) le16_to_cpu(dire->inode_number); ino = SQUASHFS_MKINODE(blk, off); TRACE("calling squashfs_iget for directory " "entry %s, inode %x:%x, %d\n", name, blk, off, ino_num); inode = squashfs_iget(dir->i_sb, ino, ino_num); goto exit_lookup; } } } exit_lookup: kfree(dire); return d_splice_alias(inode, dentry); data_error: err = -EIO; read_failure: ERROR("Unable to read directory block [%llx:%x]\n", squashfs_i(dir)->start + msblk->directory_table, squashfs_i(dir)->offset); failed: kfree(dire); return ERR_PTR(err); }


phillip lougherphillip lougher56099.29%360.00%
al viroal viro30.53%120.00%
ajeet yadavajeet yadav10.18%120.00%

const struct inode_operations squashfs_dir_inode_ops = { .lookup = squashfs_lookup, .listxattr = squashfs_listxattr };

Overall Contributors

phillip lougherphillip lougher89798.36%666.67%
dan carpenterdan carpenter111.21%111.11%
al viroal viro30.33%111.11%
ajeet yadavajeet yadav10.11%111.11%
Directory: fs/squashfs
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