linux/fs/freevxfs/vxfs_lookup.c
jan Blunck ca572727db fs/: do not fallback to default_llseek() when readdir() uses BKL
Do not use the fallback default_llseek() if the readdir operation of the
filesystem still uses the big kernel lock.

Since llseek() modifies
file->f_pos of the directory directly it may need locking to not confuse
readdir which usually uses file->f_pos directly as well

Since the special characteristics of the BKL (unlocked on schedule) are
not necessary in this case, the inode mutex can be used for locking as
provided by generic_file_llseek().  This is only possible since all
filesystems, except reiserfs, either use a directory as a flat file or
with disk address offsets.  Reiserfs on the other hand uses a 32bit hash
off the filename as the offset so generic_file_llseek() can get used as
well since the hash is always smaller than sb->s_maxbytes (= (512 << 32) -
blocksize).

Signed-off-by: Jan Blunck <jblunck@suse.de>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Anders Larsen <al@alarsen.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-27 09:12:56 -07:00

333 lines
8.1 KiB
C

/*
* Copyright (c) 2000-2001 Christoph Hellwig.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL").
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Veritas filesystem driver - lookup and other directory related code.
*/
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include "vxfs.h"
#include "vxfs_dir.h"
#include "vxfs_inode.h"
#include "vxfs_extern.h"
/*
* Number of VxFS blocks per page.
*/
#define VXFS_BLOCK_PER_PAGE(sbp) ((PAGE_CACHE_SIZE / (sbp)->s_blocksize))
static struct dentry * vxfs_lookup(struct inode *, struct dentry *, struct nameidata *);
static int vxfs_readdir(struct file *, void *, filldir_t);
const struct inode_operations vxfs_dir_inode_ops = {
.lookup = vxfs_lookup,
};
const struct file_operations vxfs_dir_operations = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.readdir = vxfs_readdir,
};
static inline u_long
dir_pages(struct inode *inode)
{
return (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
}
static inline u_long
dir_blocks(struct inode *ip)
{
u_long bsize = ip->i_sb->s_blocksize;
return (ip->i_size + bsize - 1) & ~(bsize - 1);
}
/*
* NOTE! unlike strncmp, vxfs_match returns 1 for success, 0 for failure.
*
* len <= VXFS_NAMELEN and de != NULL are guaranteed by caller.
*/
static inline int
vxfs_match(int len, const char * const name, struct vxfs_direct *de)
{
if (len != de->d_namelen)
return 0;
if (!de->d_ino)
return 0;
return !memcmp(name, de->d_name, len);
}
static inline struct vxfs_direct *
vxfs_next_entry(struct vxfs_direct *de)
{
return ((struct vxfs_direct *)((char*)de + de->d_reclen));
}
/**
* vxfs_find_entry - find a mathing directory entry for a dentry
* @ip: directory inode
* @dp: dentry for which we want to find a direct
* @ppp: gets filled with the page the return value sits in
*
* Description:
* vxfs_find_entry finds a &struct vxfs_direct for the VFS directory
* cache entry @dp. @ppp will be filled with the page the return
* value resides in.
*
* Returns:
* The wanted direct on success, else a NULL pointer.
*/
static struct vxfs_direct *
vxfs_find_entry(struct inode *ip, struct dentry *dp, struct page **ppp)
{
u_long npages, page, nblocks, pblocks, block;
u_long bsize = ip->i_sb->s_blocksize;
const char *name = dp->d_name.name;
int namelen = dp->d_name.len;
npages = dir_pages(ip);
nblocks = dir_blocks(ip);
pblocks = VXFS_BLOCK_PER_PAGE(ip->i_sb);
for (page = 0; page < npages; page++) {
caddr_t kaddr;
struct page *pp;
pp = vxfs_get_page(ip->i_mapping, page);
if (IS_ERR(pp))
continue;
kaddr = (caddr_t)page_address(pp);
for (block = 0; block <= nblocks && block <= pblocks; block++) {
caddr_t baddr, limit;
struct vxfs_dirblk *dbp;
struct vxfs_direct *de;
baddr = kaddr + (block * bsize);
limit = baddr + bsize - VXFS_DIRLEN(1);
dbp = (struct vxfs_dirblk *)baddr;
de = (struct vxfs_direct *)(baddr + VXFS_DIRBLKOV(dbp));
for (; (caddr_t)de <= limit; de = vxfs_next_entry(de)) {
if (!de->d_reclen)
break;
if (!de->d_ino)
continue;
if (vxfs_match(namelen, name, de)) {
*ppp = pp;
return (de);
}
}
}
vxfs_put_page(pp);
}
return NULL;
}
/**
* vxfs_inode_by_name - find inode number for dentry
* @dip: directory to search in
* @dp: dentry we seach for
*
* Description:
* vxfs_inode_by_name finds out the inode number of
* the path component described by @dp in @dip.
*
* Returns:
* The wanted inode number on success, else Zero.
*/
static ino_t
vxfs_inode_by_name(struct inode *dip, struct dentry *dp)
{
struct vxfs_direct *de;
struct page *pp;
ino_t ino = 0;
de = vxfs_find_entry(dip, dp, &pp);
if (de) {
ino = de->d_ino;
kunmap(pp);
page_cache_release(pp);
}
return (ino);
}
/**
* vxfs_lookup - lookup pathname component
* @dip: dir in which we lookup
* @dp: dentry we lookup
* @nd: lookup nameidata
*
* Description:
* vxfs_lookup tries to lookup the pathname component described
* by @dp in @dip.
*
* Returns:
* A NULL-pointer on success, else an negative error code encoded
* in the return pointer.
*/
static struct dentry *
vxfs_lookup(struct inode *dip, struct dentry *dp, struct nameidata *nd)
{
struct inode *ip = NULL;
ino_t ino;
if (dp->d_name.len > VXFS_NAMELEN)
return ERR_PTR(-ENAMETOOLONG);
lock_kernel();
ino = vxfs_inode_by_name(dip, dp);
if (ino) {
ip = vxfs_iget(dip->i_sb, ino);
if (IS_ERR(ip)) {
unlock_kernel();
return ERR_CAST(ip);
}
}
unlock_kernel();
d_add(dp, ip);
return NULL;
}
/**
* vxfs_readdir - read a directory
* @fp: the directory to read
* @retp: return buffer
* @filler: filldir callback
*
* Description:
* vxfs_readdir fills @retp with directory entries from @fp
* using the VFS supplied callback @filler.
*
* Returns:
* Zero.
*/
static int
vxfs_readdir(struct file *fp, void *retp, filldir_t filler)
{
struct inode *ip = fp->f_path.dentry->d_inode;
struct super_block *sbp = ip->i_sb;
u_long bsize = sbp->s_blocksize;
u_long page, npages, block, pblocks, nblocks, offset;
loff_t pos;
lock_kernel();
switch ((long)fp->f_pos) {
case 0:
if (filler(retp, ".", 1, fp->f_pos, ip->i_ino, DT_DIR) < 0)
goto out;
fp->f_pos++;
/* fallthrough */
case 1:
if (filler(retp, "..", 2, fp->f_pos, VXFS_INO(ip)->vii_dotdot, DT_DIR) < 0)
goto out;
fp->f_pos++;
/* fallthrough */
}
pos = fp->f_pos - 2;
if (pos > VXFS_DIRROUND(ip->i_size)) {
unlock_kernel();
return 0;
}
npages = dir_pages(ip);
nblocks = dir_blocks(ip);
pblocks = VXFS_BLOCK_PER_PAGE(sbp);
page = pos >> PAGE_CACHE_SHIFT;
offset = pos & ~PAGE_CACHE_MASK;
block = (u_long)(pos >> sbp->s_blocksize_bits) % pblocks;
for (; page < npages; page++, block = 0) {
caddr_t kaddr;
struct page *pp;
pp = vxfs_get_page(ip->i_mapping, page);
if (IS_ERR(pp))
continue;
kaddr = (caddr_t)page_address(pp);
for (; block <= nblocks && block <= pblocks; block++) {
caddr_t baddr, limit;
struct vxfs_dirblk *dbp;
struct vxfs_direct *de;
baddr = kaddr + (block * bsize);
limit = baddr + bsize - VXFS_DIRLEN(1);
dbp = (struct vxfs_dirblk *)baddr;
de = (struct vxfs_direct *)
(offset ?
(kaddr + offset) :
(baddr + VXFS_DIRBLKOV(dbp)));
for (; (caddr_t)de <= limit; de = vxfs_next_entry(de)) {
int over;
if (!de->d_reclen)
break;
if (!de->d_ino)
continue;
offset = (caddr_t)de - kaddr;
over = filler(retp, de->d_name, de->d_namelen,
((page << PAGE_CACHE_SHIFT) | offset) + 2,
de->d_ino, DT_UNKNOWN);
if (over) {
vxfs_put_page(pp);
goto done;
}
}
offset = 0;
}
vxfs_put_page(pp);
offset = 0;
}
done:
fp->f_pos = ((page << PAGE_CACHE_SHIFT) | offset) + 2;
out:
unlock_kernel();
return 0;
}