ea_refcount.c revision 65f0aab98b20b5994a726ab90d355248bcddfffd 
1/*
2 * ea_refcount.c
3 *
4 * Copyright (C) 2001 Theodore Ts'o.  This file may be
5 * redistributed under the terms of the GNU Public License.
6 */
7
8#if HAVE_UNISTD_H
9#include <unistd.h>
10#endif
11#include <string.h>
12#include <stdio.h>
13
14#ifdef TEST_PROGRAM
15#undef ENABLE_NLS
16#endif
17#include "e2fsck.h"
18
19/*
20 * The strategy we use for keeping track of EA refcounts is as
21 * follows.  We keep a sorted array of first EA blocks and its
22 * reference counts.  Once the refcount has dropped to zero, it is
23 * removed from the array to save memory space.  Once the EA block is
24 * checked, its bit is set in the block_ea_map bitmap.
25 */
26struct ea_refcount_el {
27	blk_t	ea_blk;
28	int	ea_count;
29};
30
31struct ea_refcount {
32	blk_t		count;
33	blk_t		size;
34	blk_t		cursor;
35	struct ea_refcount_el	*list;
36};
37
38void ea_refcount_free(ext2_refcount_t refcount)
39{
40	if (!refcount)
41		return;
42
43	if (refcount->list)
44		ext2fs_free_mem(&refcount->list);
45	ext2fs_free_mem(&refcount);
46}
47
48errcode_t ea_refcount_create(int size, ext2_refcount_t *ret)
49{
50	ext2_refcount_t	refcount;
51	errcode_t	retval;
52	size_t		bytes;
53
54	retval = ext2fs_get_mem(sizeof(struct ea_refcount), &refcount);
55	if (retval)
56		return retval;
57	memset(refcount, 0, sizeof(struct ea_refcount));
58
59	if (!size)
60		size = 500;
61	refcount->size = size;
62	bytes = (size_t) (size * sizeof(struct ea_refcount_el));
63#ifdef DEBUG
64	printf("Refcount allocated %d entries, %d bytes.\n",
65	       refcount->size, bytes);
66#endif
67	retval = ext2fs_get_mem(bytes, &refcount->list);
68	if (retval)
69		goto errout;
70	memset(refcount->list, 0, bytes);
71
72	refcount->count = 0;
73	refcount->cursor = 0;
74
75	*ret = refcount;
76	return 0;
77
78errout:
79	ea_refcount_free(refcount);
80	return(retval);
81}
82
83/*
84 * collapse_refcount() --- go through the refcount array, and get rid
85 * of any count == zero entries
86 */
87static void refcount_collapse(ext2_refcount_t refcount)
88{
89	unsigned int	i, j;
90	struct ea_refcount_el	*list;
91
92	list = refcount->list;
93	for (i = 0, j = 0; i < refcount->count; i++) {
94		if (list[i].ea_count) {
95			if (i != j)
96				list[j] = list[i];
97			j++;
98		}
99	}
100#if defined(DEBUG) || defined(TEST_PROGRAM)
101	printf("Refcount_collapse: size was %d, now %d\n",
102	       refcount->count, j);
103#endif
104	refcount->count = j;
105}
106
107
108/*
109 * insert_refcount_el() --- Insert a new entry into the sorted list at a
110 * 	specified position.
111 */
112static struct ea_refcount_el *insert_refcount_el(ext2_refcount_t refcount,
113						 blk_t blk, int pos)
114{
115	struct ea_refcount_el 	*el;
116	errcode_t		retval;
117	blk_t			new_size = 0;
118	int			num;
119
120	if (refcount->count >= refcount->size) {
121		new_size = refcount->size + 100;
122#ifdef DEBUG
123		printf("Reallocating refcount %d entries...\n", new_size);
124#endif
125		retval = ext2fs_resize_mem((size_t) refcount->size *
126					   sizeof(struct ea_refcount_el),
127					   (size_t) new_size *
128					   sizeof(struct ea_refcount_el),
129					   &refcount->list);
130		if (retval)
131			return 0;
132		refcount->size = new_size;
133	}
134	num = (int) refcount->count - pos;
135	if (num < 0)
136		return 0;	/* should never happen */
137	if (num) {
138		memmove(&refcount->list[pos+1], &refcount->list[pos],
139			sizeof(struct ea_refcount_el) * num);
140	}
141	refcount->count++;
142	el = &refcount->list[pos];
143	el->ea_count = 0;
144	el->ea_blk = blk;
145	return el;
146}
147
148
149/*
150 * get_refcount_el() --- given an block number, try to find refcount
151 * 	information in the sorted list.  If the create flag is set,
152 * 	and we can't find an entry, create one in the sorted list.
153 */
154static struct ea_refcount_el *get_refcount_el(ext2_refcount_t refcount,
155					      blk_t blk, int create)
156{
157	float	range;
158	int	low, high, mid;
159	blk_t	lowval, highval;
160
161	if (!refcount || !refcount->list)
162		return 0;
163retry:
164	low = 0;
165	high = (int) refcount->count-1;
166	if (create && ((refcount->count == 0) ||
167		       (blk > refcount->list[high].ea_blk))) {
168		if (refcount->count >= refcount->size)
169			refcount_collapse(refcount);
170
171		return insert_refcount_el(refcount, blk,
172					  (unsigned) refcount->count);
173	}
174	if (refcount->count == 0)
175		return 0;
176
177	if (refcount->cursor >= refcount->count)
178		refcount->cursor = 0;
179	if (blk == refcount->list[refcount->cursor].ea_blk)
180		return &refcount->list[refcount->cursor++];
181#ifdef DEBUG
182	printf("Non-cursor get_refcount_el: %u\n", blk);
183#endif
184	while (low <= high) {
185#if 0
186		mid = (low+high)/2;
187#else
188		if (low == high)
189			mid = low;
190		else {
191			/* Interpolate for efficiency */
192			lowval = refcount->list[low].ea_blk;
193			highval = refcount->list[high].ea_blk;
194
195			if (blk < lowval)
196				range = 0;
197			else if (blk > highval)
198				range = 1;
199			else {
200				range = ((float) (blk - lowval)) /
201					(highval - lowval);
202				if (range > 0.9)
203					range = 0.9;
204				if (range < 0.1)
205					range = 0.1;
206			}
207			mid = low + ((int) (range * (high-low)));
208		}
209#endif
210		if (blk == refcount->list[mid].ea_blk) {
211			refcount->cursor = mid+1;
212			return &refcount->list[mid];
213		}
214		if (blk < refcount->list[mid].ea_blk)
215			high = mid-1;
216		else
217			low = mid+1;
218	}
219	/*
220	 * If we need to create a new entry, it should be right at
221	 * low (where high will be left at low-1).
222	 */
223	if (create) {
224		if (refcount->count >= refcount->size) {
225			refcount_collapse(refcount);
226			if (refcount->count < refcount->size)
227				goto retry;
228		}
229		return insert_refcount_el(refcount, blk, low);
230	}
231	return 0;
232}
233
234errcode_t ea_refcount_fetch(ext2_refcount_t refcount, blk_t blk,
235				int *ret)
236{
237	struct ea_refcount_el	*el;
238
239	el = get_refcount_el(refcount, blk, 0);
240	if (!el) {
241		*ret = 0;
242		return 0;
243	}
244	*ret = el->ea_count;
245	return 0;
246}
247
248errcode_t ea_refcount_increment(ext2_refcount_t refcount, blk_t blk, int *ret)
249{
250	struct ea_refcount_el	*el;
251
252	el = get_refcount_el(refcount, blk, 1);
253	if (!el)
254		return EXT2_ET_NO_MEMORY;
255	el->ea_count++;
256
257	if (ret)
258		*ret = el->ea_count;
259	return 0;
260}
261
262errcode_t ea_refcount_decrement(ext2_refcount_t refcount, blk_t blk, int *ret)
263{
264	struct ea_refcount_el	*el;
265
266	el = get_refcount_el(refcount, blk, 0);
267	if (!el || el->ea_count == 0)
268		return EXT2_ET_INVALID_ARGUMENT;
269
270	el->ea_count--;
271
272	if (ret)
273		*ret = el->ea_count;
274	return 0;
275}
276
277errcode_t ea_refcount_store(ext2_refcount_t refcount, blk_t blk, int count)
278{
279	struct ea_refcount_el	*el;
280
281	/*
282	 * Get the refcount element
283	 */
284	el = get_refcount_el(refcount, blk, count ? 1 : 0);
285	if (!el)
286		return count ? EXT2_ET_NO_MEMORY : 0;
287	el->ea_count = count;
288	return 0;
289}
290
291blk_t ext2fs_get_refcount_size(ext2_refcount_t refcount)
292{
293	if (!refcount)
294		return 0;
295
296	return refcount->size;
297}
298
299void ea_refcount_intr_begin(ext2_refcount_t refcount)
300{
301	refcount->cursor = 0;
302}
303
304
305blk_t ea_refcount_intr_next(ext2_refcount_t refcount,
306				int *ret)
307{
308	struct ea_refcount_el	*list;
309
310	while (1) {
311		if (refcount->cursor >= refcount->count)
312			return 0;
313		list = refcount->list;
314		if (list[refcount->cursor].ea_count) {
315			if (ret)
316				*ret = list[refcount->cursor].ea_count;
317			return list[refcount->cursor++].ea_blk;
318		}
319		refcount->cursor++;
320	}
321}
322
323
324#ifdef TEST_PROGRAM
325
326errcode_t ea_refcount_validate(ext2_refcount_t refcount, FILE *out)
327{
328	errcode_t	ret = 0;
329	int		i;
330	const char *bad = "bad refcount";
331
332	if (refcount->count > refcount->size) {
333		fprintf(out, "%s: count > size\n", bad);
334		return EXT2_ET_INVALID_ARGUMENT;
335	}
336	for (i=1; i < refcount->count; i++) {
337		if (refcount->list[i-1].ea_blk >= refcount->list[i].ea_blk) {
338			fprintf(out, "%s: list[%d].blk=%u, list[%d].blk=%u\n",
339				bad, i-1, refcount->list[i-1].ea_blk,
340				i, refcount->list[i].ea_blk);
341			ret = EXT2_ET_INVALID_ARGUMENT;
342		}
343	}
344	return ret;
345}
346
347#define BCODE_END	0
348#define BCODE_CREATE	1
349#define BCODE_FREE	2
350#define BCODE_STORE	3
351#define BCODE_INCR	4
352#define BCODE_DECR	5
353#define BCODE_FETCH	6
354#define BCODE_VALIDATE	7
355#define BCODE_LIST	8
356#define BCODE_COLLAPSE 9
357
358int bcode_program[] = {
359	BCODE_CREATE, 5,
360	BCODE_STORE, 3, 3,
361	BCODE_STORE, 4, 4,
362	BCODE_STORE, 1, 1,
363	BCODE_STORE, 8, 8,
364	BCODE_STORE, 2, 2,
365	BCODE_STORE, 4, 0,
366	BCODE_STORE, 2, 0,
367	BCODE_STORE, 6, 6,
368	BCODE_VALIDATE,
369	BCODE_STORE, 4, 4,
370	BCODE_STORE, 2, 2,
371	BCODE_FETCH, 1,
372	BCODE_FETCH, 2,
373	BCODE_INCR, 3,
374	BCODE_INCR, 3,
375	BCODE_DECR, 4,
376	BCODE_STORE, 4, 4,
377	BCODE_VALIDATE,
378	BCODE_STORE, 20, 20,
379	BCODE_STORE, 40, 40,
380	BCODE_STORE, 30, 30,
381	BCODE_STORE, 10, 10,
382	BCODE_DECR, 30,
383	BCODE_FETCH, 30,
384	BCODE_DECR, 2,
385	BCODE_DECR, 2,
386	BCODE_COLLAPSE,
387	BCODE_LIST,
388	BCODE_VALIDATE,
389	BCODE_FREE,
390	BCODE_END
391};
392
393int main(int argc, char **argv)
394{
395	int	i = 0;
396	ext2_refcount_t refcount;
397	int		size, arg;
398	blk_t		blk;
399	errcode_t	retval;
400
401	while (1) {
402		switch (bcode_program[i++]) {
403		case BCODE_END:
404			exit(0);
405		case BCODE_CREATE:
406			size = bcode_program[i++];
407			retval = ea_refcount_create(size, &refcount);
408			if (retval) {
409				com_err("ea_refcount_create",
410					retval, "");
411				exit(1);
412			} else
413				printf("Creating refcount with size %d\n",
414				       size);
415			break;
416		case BCODE_FREE:
417			ea_refcount_free(refcount);
418			refcount = 0;
419			printf("Freeing refcount\n");
420			break;
421		case BCODE_STORE:
422			blk = (blk_t) bcode_program[i++];
423			arg = bcode_program[i++];
424			retval = ea_refcount_store(refcount, blk, arg);
425			printf("Storing blk %u with value %d\n", blk, arg);
426			if (retval)
427				com_err("ea_refcount_store", retval, "");
428			break;
429		case BCODE_FETCH:
430			blk = (blk_t) bcode_program[i++];
431			retval = ea_refcount_fetch(refcount, blk, &arg);
432			if (retval)
433				com_err("ea_refcount_fetch", retval, "");
434			else
435				printf("bcode_fetch(%u) returns %d\n",
436				       blk, arg);
437			break;
438		case BCODE_INCR:
439			blk = (blk_t) bcode_program[i++];
440			retval = ea_refcount_increment(refcount, blk,
441							   &arg);
442			if (retval)
443				com_err("ea_refcount_increment", retval,
444					"");
445			else
446				printf("bcode_increment(%u) returns %d\n",
447				       blk, arg);
448			break;
449		case BCODE_DECR:
450			blk = (blk_t) bcode_program[i++];
451			retval = ea_refcount_decrement(refcount, blk,
452							   &arg);
453			if (retval)
454				com_err("ea_refcount_decrement", retval,
455					"while decrementing blk %u", blk);
456			else
457				printf("bcode_decrement(%u) returns %d\n",
458				       blk, arg);
459			break;
460		case BCODE_VALIDATE:
461			retval = ea_refcount_validate(refcount, stderr);
462			if (retval)
463				com_err("ea_refcount_validate",
464					retval, "");
465			else
466				printf("Refcount validation OK.\n");
467			break;
468		case BCODE_LIST:
469			ea_refcount_intr_begin(refcount);
470			while (1) {
471				blk = ea_refcount_intr_next(refcount,
472								&arg);
473				if (!blk)
474					break;
475				printf("\tblk=%u, count=%d\n", blk,
476				       arg);
477			}
478			break;
479		case BCODE_COLLAPSE:
480			refcount_collapse(refcount);
481			break;
482		}
483
484	}
485}
486
487#endif
488