busybox/e2fsprogs/ext2fs/icount.c
2006-11-27 16:49:31 +00:00

468 lines
11 KiB
C

/* vi: set sw=4 ts=4: */
/*
* icount.c --- an efficient inode count abstraction
*
* Copyright (C) 1997 Theodore Ts'o.
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
*/
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <stdio.h>
#include "ext2_fs.h"
#include "ext2fs.h"
/*
* The data storage strategy used by icount relies on the observation
* that most inode counts are either zero (for non-allocated inodes),
* one (for most files), and only a few that are two or more
* (directories and files that are linked to more than one directory).
*
* Also, e2fsck tends to load the icount data sequentially.
*
* So, we use an inode bitmap to indicate which inodes have a count of
* one, and then use a sorted list to store the counts for inodes
* which are greater than one.
*
* We also use an optional bitmap to indicate which inodes are already
* in the sorted list, to speed up the use of this abstraction by
* e2fsck's pass 2. Pass 2 increments inode counts as it finds them,
* so this extra bitmap avoids searching the sorted list to see if a
* particular inode is on the sorted list already.
*/
struct ext2_icount_el {
ext2_ino_t ino;
__u16 count;
};
struct ext2_icount {
errcode_t magic;
ext2fs_inode_bitmap single;
ext2fs_inode_bitmap multiple;
ext2_ino_t count;
ext2_ino_t size;
ext2_ino_t num_inodes;
ext2_ino_t cursor;
struct ext2_icount_el *list;
};
void ext2fs_free_icount(ext2_icount_t icount)
{
if (!icount)
return;
icount->magic = 0;
ext2fs_free_mem(&icount->list);
ext2fs_free_inode_bitmap(icount->single);
ext2fs_free_inode_bitmap(icount->multiple);
ext2fs_free_mem(&icount);
}
errcode_t ext2fs_create_icount2(ext2_filsys fs, int flags, unsigned int size,
ext2_icount_t hint, ext2_icount_t *ret)
{
ext2_icount_t icount;
errcode_t retval;
size_t bytes;
ext2_ino_t i;
if (hint) {
EXT2_CHECK_MAGIC(hint, EXT2_ET_MAGIC_ICOUNT);
if (hint->size > size)
size = (size_t) hint->size;
}
retval = ext2fs_get_mem(sizeof(struct ext2_icount), &icount);
if (retval)
return retval;
memset(icount, 0, sizeof(struct ext2_icount));
retval = ext2fs_allocate_inode_bitmap(fs, 0,
&icount->single);
if (retval)
goto errout;
if (flags & EXT2_ICOUNT_OPT_INCREMENT) {
retval = ext2fs_allocate_inode_bitmap(fs, 0,
&icount->multiple);
if (retval)
goto errout;
} else
icount->multiple = 0;
if (size) {
icount->size = size;
} else {
/*
* Figure out how many special case inode counts we will
* have. We know we will need one for each directory;
* we also need to reserve some extra room for file links
*/
retval = ext2fs_get_num_dirs(fs, &icount->size);
if (retval)
goto errout;
icount->size += fs->super->s_inodes_count / 50;
}
bytes = (size_t) (icount->size * sizeof(struct ext2_icount_el));
retval = ext2fs_get_mem(bytes, &icount->list);
if (retval)
goto errout;
memset(icount->list, 0, bytes);
icount->magic = EXT2_ET_MAGIC_ICOUNT;
icount->count = 0;
icount->cursor = 0;
icount->num_inodes = fs->super->s_inodes_count;
/*
* Populate the sorted list with those entries which were
* found in the hint icount (since those are ones which will
* likely need to be in the sorted list this time around).
*/
if (hint) {
for (i=0; i < hint->count; i++)
icount->list[i].ino = hint->list[i].ino;
icount->count = hint->count;
}
*ret = icount;
return 0;
errout:
ext2fs_free_icount(icount);
return retval;
}
errcode_t ext2fs_create_icount(ext2_filsys fs, int flags,
unsigned int size,
ext2_icount_t *ret)
{
return ext2fs_create_icount2(fs, flags, size, 0, ret);
}
/*
* insert_icount_el() --- Insert a new entry into the sorted list at a
* specified position.
*/
static struct ext2_icount_el *insert_icount_el(ext2_icount_t icount,
ext2_ino_t ino, int pos)
{
struct ext2_icount_el *el;
errcode_t retval;
ext2_ino_t new_size = 0;
int num;
if (icount->count >= icount->size) {
if (icount->count) {
new_size = icount->list[(unsigned)icount->count-1].ino;
new_size = (ext2_ino_t) (icount->count *
((float) icount->num_inodes / new_size));
}
if (new_size < (icount->size + 100))
new_size = icount->size + 100;
retval = ext2fs_resize_mem((size_t) icount->size *
sizeof(struct ext2_icount_el),
(size_t) new_size *
sizeof(struct ext2_icount_el),
&icount->list);
if (retval)
return 0;
icount->size = new_size;
}
num = (int) icount->count - pos;
if (num < 0)
return 0; /* should never happen */
if (num) {
memmove(&icount->list[pos+1], &icount->list[pos],
sizeof(struct ext2_icount_el) * num);
}
icount->count++;
el = &icount->list[pos];
el->count = 0;
el->ino = ino;
return el;
}
/*
* get_icount_el() --- given an inode number, try to find icount
* information in the sorted list. If the create flag is set,
* and we can't find an entry, create one in the sorted list.
*/
static struct ext2_icount_el *get_icount_el(ext2_icount_t icount,
ext2_ino_t ino, int create)
{
float range;
int low, high, mid;
ext2_ino_t lowval, highval;
if (!icount || !icount->list)
return 0;
if (create && ((icount->count == 0) ||
(ino > icount->list[(unsigned)icount->count-1].ino))) {
return insert_icount_el(icount, ino, (unsigned) icount->count);
}
if (icount->count == 0)
return 0;
if (icount->cursor >= icount->count)
icount->cursor = 0;
if (ino == icount->list[icount->cursor].ino)
return &icount->list[icount->cursor++];
low = 0;
high = (int) icount->count-1;
while (low <= high) {
if (low == high)
mid = low;
else {
/* Interpolate for efficiency */
lowval = icount->list[low].ino;
highval = icount->list[high].ino;
if (ino < lowval)
range = 0;
else if (ino > highval)
range = 1;
else
range = ((float) (ino - lowval)) /
(highval - lowval);
mid = low + ((int) (range * (high-low)));
}
if (ino == icount->list[mid].ino) {
icount->cursor = mid+1;
return &icount->list[mid];
}
if (ino < icount->list[mid].ino)
high = mid-1;
else
low = mid+1;
}
/*
* If we need to create a new entry, it should be right at
* low (where high will be left at low-1).
*/
if (create)
return insert_icount_el(icount, ino, low);
return 0;
}
errcode_t ext2fs_icount_validate(ext2_icount_t icount, FILE *out)
{
errcode_t ret = 0;
unsigned int i;
const char *bad = "bad icount";
EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
if (icount->count > icount->size) {
fprintf(out, "%s: count > size\n", bad);
return EXT2_ET_INVALID_ARGUMENT;
}
for (i=1; i < icount->count; i++) {
if (icount->list[i-1].ino >= icount->list[i].ino) {
fprintf(out, "%s: list[%d].ino=%u, list[%d].ino=%u\n",
bad, i-1, icount->list[i-1].ino,
i, icount->list[i].ino);
ret = EXT2_ET_INVALID_ARGUMENT;
}
}
return ret;
}
errcode_t ext2fs_icount_fetch(ext2_icount_t icount, ext2_ino_t ino, __u16 *ret)
{
struct ext2_icount_el *el;
EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
if (!ino || (ino > icount->num_inodes))
return EXT2_ET_INVALID_ARGUMENT;
if (ext2fs_test_inode_bitmap(icount->single, ino)) {
*ret = 1;
return 0;
}
if (icount->multiple &&
!ext2fs_test_inode_bitmap(icount->multiple, ino)) {
*ret = 0;
return 0;
}
el = get_icount_el(icount, ino, 0);
if (!el) {
*ret = 0;
return 0;
}
*ret = el->count;
return 0;
}
errcode_t ext2fs_icount_increment(ext2_icount_t icount, ext2_ino_t ino,
__u16 *ret)
{
struct ext2_icount_el *el;
EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
if (!ino || (ino > icount->num_inodes))
return EXT2_ET_INVALID_ARGUMENT;
if (ext2fs_test_inode_bitmap(icount->single, ino)) {
/*
* If the existing count is 1, then we know there is
* no entry in the list.
*/
el = get_icount_el(icount, ino, 1);
if (!el)
return EXT2_ET_NO_MEMORY;
ext2fs_unmark_inode_bitmap(icount->single, ino);
el->count = 2;
} else if (icount->multiple) {
/*
* The count is either zero or greater than 1; if the
* inode is set in icount->multiple, then there should
* be an entry in the list, so find it using
* get_icount_el().
*/
if (ext2fs_test_inode_bitmap(icount->multiple, ino)) {
el = get_icount_el(icount, ino, 1);
if (!el)
return EXT2_ET_NO_MEMORY;
el->count++;
} else {
/*
* The count was zero; mark the single bitmap
* and return.
*/
zero_count:
ext2fs_mark_inode_bitmap(icount->single, ino);
if (ret)
*ret = 1;
return 0;
}
} else {
/*
* The count is either zero or greater than 1; try to
* find an entry in the list to determine which.
*/
el = get_icount_el(icount, ino, 0);
if (!el) {
/* No entry means the count was zero */
goto zero_count;
}
el = get_icount_el(icount, ino, 1);
if (!el)
return EXT2_ET_NO_MEMORY;
el->count++;
}
if (icount->multiple)
ext2fs_mark_inode_bitmap(icount->multiple, ino);
if (ret)
*ret = el->count;
return 0;
}
errcode_t ext2fs_icount_decrement(ext2_icount_t icount, ext2_ino_t ino,
__u16 *ret)
{
struct ext2_icount_el *el;
if (!ino || (ino > icount->num_inodes))
return EXT2_ET_INVALID_ARGUMENT;
EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
if (ext2fs_test_inode_bitmap(icount->single, ino)) {
ext2fs_unmark_inode_bitmap(icount->single, ino);
if (icount->multiple)
ext2fs_unmark_inode_bitmap(icount->multiple, ino);
else {
el = get_icount_el(icount, ino, 0);
if (el)
el->count = 0;
}
if (ret)
*ret = 0;
return 0;
}
if (icount->multiple &&
!ext2fs_test_inode_bitmap(icount->multiple, ino))
return EXT2_ET_INVALID_ARGUMENT;
el = get_icount_el(icount, ino, 0);
if (!el || el->count == 0)
return EXT2_ET_INVALID_ARGUMENT;
el->count--;
if (el->count == 1)
ext2fs_mark_inode_bitmap(icount->single, ino);
if ((el->count == 0) && icount->multiple)
ext2fs_unmark_inode_bitmap(icount->multiple, ino);
if (ret)
*ret = el->count;
return 0;
}
errcode_t ext2fs_icount_store(ext2_icount_t icount, ext2_ino_t ino,
__u16 count)
{
struct ext2_icount_el *el;
if (!ino || (ino > icount->num_inodes))
return EXT2_ET_INVALID_ARGUMENT;
EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
if (count == 1) {
ext2fs_mark_inode_bitmap(icount->single, ino);
if (icount->multiple)
ext2fs_unmark_inode_bitmap(icount->multiple, ino);
return 0;
}
if (count == 0) {
ext2fs_unmark_inode_bitmap(icount->single, ino);
if (icount->multiple) {
/*
* If the icount->multiple bitmap is enabled,
* we can just clear both bitmaps and we're done
*/
ext2fs_unmark_inode_bitmap(icount->multiple, ino);
} else {
el = get_icount_el(icount, ino, 0);
if (el)
el->count = 0;
}
return 0;
}
/*
* Get the icount element
*/
el = get_icount_el(icount, ino, 1);
if (!el)
return EXT2_ET_NO_MEMORY;
el->count = count;
ext2fs_unmark_inode_bitmap(icount->single, ino);
if (icount->multiple)
ext2fs_mark_inode_bitmap(icount->multiple, ino);
return 0;
}
ext2_ino_t ext2fs_get_icount_size(ext2_icount_t icount)
{
if (!icount || icount->magic != EXT2_ET_MAGIC_ICOUNT)
return 0;
return icount->size;
}