WebSVN – HelenOS – Diff – /branches/dynload/uspace/srv/fs/fat/fat_idx.c



 
    /** Sorted list of intervals of freed indices. */
    link_t      freed_head;
} unused_t;
 
/** Futex protecting the list of unused structures. */
static futex_t unused_futex = FUTEX_INITIALIZER;
 
/** List of unused structures. */
static LIST_INITIALIZE(unused_head);
 
/** Futex protecting the up_hash and ui_hash.
 *
 * The locking strategy assumes that there will be at most one fibril for each
 * dev_handle.  Therefore it will be sufficient to hold the futex for shorter
 * times (i.e. only during hash table operations as opposed to holding it the
 * whole time between an unsuccessful find and the following insert). Should the
 * assumption break, the locking strategy for this futex will have to be
 * reconsidered.
 */
static futex_t used_futex = FUTEX_INITIALIZER;
 
/**
 * Global hash table of all used fat_idx_t structures.
 * The index structures are hashed by the dev_handle, parent node's first
 * cluster and index within the parent directory.
 */

{
    link_t *l;
    unused_t *u;
   
    assert(index);
    futex_down(&unused_futex);
    for (l = unused_head.next; l != &unused_head; l = l->next) {
        u = list_get_instance(l, unused_t, link);
        if (u->dev_handle == dev_handle)
            goto hit;
    }
    futex_up(&unused_futex);
   
    /* dev_handle not found */
    return false;  
 
hit:
    if (list_empty(&u->freed_head)) {

             * There are no freed indices, allocate one directly
             * from the counter.
             */
            *index = u->next++;
            --u->remaining;
            futex_up(&unused_futex);
            return true;
        }
    } else {
        /* There are some freed indices which we can reuse. */
        freed_t *f = list_get_instance(u->freed_head.next, freed_t,

        if (f->first++ == f->last) {
            /* Destroy the interval. */
            list_remove(&f->link);
            free(f);
        }
        futex_up(&unused_futex);
        return true;
    }
    /*
     * We ran out of indices, which is extremely unlikely with FAT16, but
     * theoretically still possible (e.g. too many open unlinked nodes or
     * too many zero-sized nodes).
     */
    futex_up(&unused_futex);
    return false;
}
 
/** If possible, coalesce two intervals of freed indices. */
static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)

static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
{
    link_t *l;
    unused_t *u;
 
    futex_down(&unused_futex);
    for (l = unused_head.next; l != &unused_head; l = l->next) {
        u = list_get_instance(l, unused_t, link);
        if (u->dev_handle == dev_handle)
            goto hit;
    }
    futex_up(&unused_futex);
 
    /* should not happen */
    assert(0);
 
hit:
    if (u->next == index + 1) {
        /* The index can be returned directly to the counter. */
        u->next--;
        u->remaining++;
 
    } else {
        /*
         * The index must be returned either to an existing freed
         * interval or a new interval must be created.
         */

            if (f->first == index + 1) {
                f->first--;
                if (lnk->prev != &u->freed_head)
                    try_coalesce_intervals(lnk->prev, lnk,
                        lnk);
                futex_up(&unused_futex);
                return;
            }
            if (f->last == index - 1) {
                f->last++;
                if (lnk->next != &u->freed_head)
                    try_coalesce_intervals(lnk, lnk->next,
                        lnk);
                futex_up(&unused_futex);
                return;
            }
            if (index > f->first) {
                n = malloc(sizeof(freed_t));
                /* TODO: sleep until allocation succeeds */
                assert(n);
                link_initialize(&n->link);
                n->first = index;
                n->last = index;
                list_insert_before(&n->link, lnk);
                futex_up(&unused_futex);
                return;
            }
 
        }
        /* The index will form the last interval. */

        link_initialize(&n->link);
        n->first = index;
        n->last = index;
        list_append(&n->link, &u->freed_head);
    }
    futex_up(&unused_futex);
}
 
fat_idx_t *
fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
{

        [UPH_DH_KEY] = dev_handle,
        [UPH_PFC_KEY] = pfc,
        [UPH_PDI_KEY] = pdi,
    };
 
    futex_down(&used_futex);
    l = hash_table_find(&up_hash, pkey);
    futex_up(&used_futex);
    if (l) {
        fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
    } else {
        fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
        if (!fidx) {

        fidx->dev_handle = dev_handle;
        fidx->pfc = pfc;
        fidx->pdi = pdi;
        fidx->nodep = NULL;
 
        futex_down(&used_futex);
        hash_table_insert(&up_hash, pkey, &fidx->uph_link);
        hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
        futex_up(&used_futex);
    }
 
    return fidx;
}
 

    unsigned long ikey[] = {
        [UIH_DH_KEY] = dev_handle,
        [UIH_INDEX_KEY] = index,
    };
 
    futex_down(&used_futex);
    l = hash_table_find(&ui_hash, ikey);
    futex_up(&used_futex);
    if (l) {
        fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
    }
 
    return fidx;

Rev 2927	Rev 2948
Line 66...	Line 66...
66		66
67	/** Sorted list of intervals of freed indices. */	67	/** Sorted list of intervals of freed indices. */
68	link_t freed_head;	68	link_t freed_head;
69	} unused_t;	69	} unused_t;
70		70
-		71	/** Futex protecting the list of unused structures. */
-		72	static futex_t unused_futex = FUTEX_INITIALIZER;
-		73
-		74	/** List of unused structures. */
71	static LIST_INITIALIZE(unused_head);	75	static LIST_INITIALIZE(unused_head);
72		76
-		77	/** Futex protecting the up_hash and ui_hash.
-		78	*
-		79	* The locking strategy assumes that there will be at most one fibril for each
-		80	* dev_handle. Therefore it will be sufficient to hold the futex for shorter
-		81	* times (i.e. only during hash table operations as opposed to holding it the
-		82	* whole time between an unsuccessful find and the following insert). Should the
-		83	* assumption break, the locking strategy for this futex will have to be
-		84	* reconsidered.
-		85	*/
-		86	static futex_t used_futex = FUTEX_INITIALIZER;
-		87
73	/**	88	/**
74	* Global hash table of all used fat_idx_t structures.	89	* Global hash table of all used fat_idx_t structures.
75	* The index structures are hashed by the dev_handle, parent node's first	90	* The index structures are hashed by the dev_handle, parent node's first
76	* cluster and index within the parent directory.	91	* cluster and index within the parent directory.
77	*/	92	*/
Line 185...	Line 200...
185	{	200	{
186	link_t *l;	201	link_t *l;
187	unused_t *u;	202	unused_t *u;
188		203
189	assert(index);	204	assert(index);
-		205	futex_down(&unused_futex);
190	for (l = unused_head.next; l != &unused_head; l = l->next) {	206	for (l = unused_head.next; l != &unused_head; l = l->next) {
191	u = list_get_instance(l, unused_t, link);	207	u = list_get_instance(l, unused_t, link);
192	if (u->dev_handle == dev_handle)	208	if (u->dev_handle == dev_handle)
193	goto hit;	209	goto hit;
194	}	210	}
-		211	futex_up(&unused_futex);
195		212
196	/* dev_handle not found */	213	/* dev_handle not found */
197	return false;	214	return false;
198		215
199	hit:	216	hit:
200	if (list_empty(&u->freed_head)) {	217	if (list_empty(&u->freed_head)) {
Line 203...	Line 220...
203	* There are no freed indices, allocate one directly	220	* There are no freed indices, allocate one directly
204	* from the counter.	221	* from the counter.
205	*/	222	*/
206	*index = u->next++;	223	*index = u->next++;
207	--u->remaining;	224	--u->remaining;
-		225	futex_up(&unused_futex);
208	return true;	226	return true;
209	}	227	}
210	} else {	228	} else {
211	/* There are some freed indices which we can reuse. */	229	/* There are some freed indices which we can reuse. */
212	freed_t *f = list_get_instance(u->freed_head.next, freed_t,	230	freed_t *f = list_get_instance(u->freed_head.next, freed_t,
Line 215...	Line 233...
215	if (f->first++ == f->last) {	233	if (f->first++ == f->last) {
216	/* Destroy the interval. */	234	/* Destroy the interval. */
217	list_remove(&f->link);	235	list_remove(&f->link);
218	free(f);	236	free(f);
219	}	237	}
-		238	futex_up(&unused_futex);
220	return true;	239	return true;
221	}	240	}
222	/*	241	/*
223	* We ran out of indices, which is extremely unlikely with FAT16, but	242	* We ran out of indices, which is extremely unlikely with FAT16, but
224	* theoretically still possible (e.g. too many open unlinked nodes or	243	* theoretically still possible (e.g. too many open unlinked nodes or
225	* too many zero-sized nodes).	244	* too many zero-sized nodes).
226	*/	245	*/
-		246	futex_up(&unused_futex);
227	return false;	247	return false;
228	}	248	}
229		249
230	/** If possible, coalesce two intervals of freed indices. */	250	/** If possible, coalesce two intervals of freed indices. */
231	static void try_coalesce_intervals(link_t l, link_t r, link_t *cur)	251	static void try_coalesce_intervals(link_t l, link_t r, link_t *cur)
Line 250...	Line 270...
250	static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)	270	static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
251	{	271	{
252	link_t *l;	272	link_t *l;
253	unused_t *u;	273	unused_t *u;
254		274
-		275	futex_down(&unused_futex);
255	for (l = unused_head.next; l != &unused_head; l = l->next) {	276	for (l = unused_head.next; l != &unused_head; l = l->next) {
256	u = list_get_instance(l, unused_t, link);	277	u = list_get_instance(l, unused_t, link);
257	if (u->dev_handle == dev_handle)	278	if (u->dev_handle == dev_handle)
258	goto hit;	279	goto hit;
259	}	280	}
-		281	futex_up(&unused_futex);
260		282
261	/* should not happen */	283	/* should not happen */
262	assert(0);	284	assert(0);
263		285
264	hit:	286	hit:
265	if (u->next == index + 1) {	287	if (u->next == index + 1) {
266	/* The index can be returned directly to the counter. */	288	/* The index can be returned directly to the counter. */
267	u->next--;	289	u->next--;
268	u->remaining++;	290	u->remaining++;
269	return;	-
270	} else {	291	} else {
271	/*	292	/*
272	* The index must be returned either to an existing freed	293	* The index must be returned either to an existing freed
273	* interval or a new interval must be created.	294	* interval or a new interval must be created.
274	*/	295	*/
Line 280...	Line 301...
280	if (f->first == index + 1) {	301	if (f->first == index + 1) {
281	f->first--;	302	f->first--;
282	if (lnk->prev != &u->freed_head)	303	if (lnk->prev != &u->freed_head)
283	try_coalesce_intervals(lnk->prev, lnk,	304	try_coalesce_intervals(lnk->prev, lnk,
284	lnk);	305	lnk);
-		306	futex_up(&unused_futex);
285	return;	307	return;
286	}	308	}
287	if (f->last == index - 1) {	309	if (f->last == index - 1) {
288	f->last++;	310	f->last++;
289	if (lnk->next != &u->freed_head)	311	if (lnk->next != &u->freed_head)
290	try_coalesce_intervals(lnk, lnk->next,	312	try_coalesce_intervals(lnk, lnk->next,
291	lnk);	313	lnk);
-		314	futex_up(&unused_futex);
292	return;	315	return;
293	}	316	}
294	if (index > f->first) {	317	if (index > f->first) {
295	n = malloc(sizeof(freed_t));	318	n = malloc(sizeof(freed_t));
296	/* TODO: sleep until allocation succeeds */	319	/* TODO: sleep until allocation succeeds */
297	assert(n);	320	assert(n);
298	link_initialize(&n->link);	321	link_initialize(&n->link);
299	n->first = index;	322	n->first = index;
300	n->last = index;	323	n->last = index;
301	list_insert_before(&n->link, lnk);	324	list_insert_before(&n->link, lnk);
-		325	futex_up(&unused_futex);
302	return;	326	return;
303	}	327	}
304		328
305	}	329	}
306	/* The index will form the last interval. */	330	/* The index will form the last interval. */
Line 310...	Line 334...
310	link_initialize(&n->link);	334	link_initialize(&n->link);
311	n->first = index;	335	n->first = index;
312	n->last = index;	336	n->last = index;
313	list_append(&n->link, &u->freed_head);	337	list_append(&n->link, &u->freed_head);
314	}	338	}
-		339	futex_up(&unused_futex);
315	}	340	}
316		341
317	fat_idx_t *	342	fat_idx_t *
318	fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)	343	fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
319	{	344	{
Line 323...	Line 348...
323	[UPH_DH_KEY] = dev_handle,	348	[UPH_DH_KEY] = dev_handle,
324	[UPH_PFC_KEY] = pfc,	349	[UPH_PFC_KEY] = pfc,
325	[UPH_PDI_KEY] = pdi,	350	[UPH_PDI_KEY] = pdi,
326	};	351	};
327		352
-		353	futex_down(&used_futex);
328	l = hash_table_find(&up_hash, pkey);	354	l = hash_table_find(&up_hash, pkey);
-		355	futex_up(&used_futex);
329	if (l) {	356	if (l) {
330	fidx = hash_table_get_instance(l, fat_idx_t, uph_link);	357	fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
331	} else {	358	} else {
332	fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));	359	fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
333	if (!fidx) {	360	if (!fidx) {
Line 348...	Line 375...
348	fidx->dev_handle = dev_handle;	375	fidx->dev_handle = dev_handle;
349	fidx->pfc = pfc;	376	fidx->pfc = pfc;
350	fidx->pdi = pdi;	377	fidx->pdi = pdi;
351	fidx->nodep = NULL;	378	fidx->nodep = NULL;
352		379
-		380	futex_down(&used_futex);
353	hash_table_insert(&up_hash, pkey, &fidx->uph_link);	381	hash_table_insert(&up_hash, pkey, &fidx->uph_link);
354	hash_table_insert(&ui_hash, ikey, &fidx->uih_link);	382	hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
-		383	futex_up(&used_futex);
355	}	384	}
356		385
357	return fidx;	386	return fidx;
358	}	387	}
359		388
Line 365...	Line 394...
365	unsigned long ikey[] = {	394	unsigned long ikey[] = {
366	[UIH_DH_KEY] = dev_handle,	395	[UIH_DH_KEY] = dev_handle,
367	[UIH_INDEX_KEY] = index,	396	[UIH_INDEX_KEY] = index,
368	};	397	};
369		398
-		399	futex_down(&used_futex);
370	l = hash_table_find(&ui_hash, ikey);	400	l = hash_table_find(&ui_hash, ikey);
-		401	futex_up(&used_futex);
371	if (l) {	402	if (l) {
372	fidx = hash_table_get_instance(l, fat_idx_t, uih_link);	403	fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
373	}	404	}
374		405
375	return fidx;	406	return fidx;

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(root)/branches/dynload/uspace/srv/fs/fat/fat_idx.c – Rev 2927 → 2948