WebSVN – HelenOS – Diff – /trunk/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);
 
/**
 * Global hash table of all used fat_idx_t structures.
 * The index structures are hashed by the dev_handle, parent node's first

{
    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)
{

Rev 2890	Rev 2944
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
73	/**	77	/**
74	* Global hash table of all used fat_idx_t structures.	78	* Global hash table of all used fat_idx_t structures.
75	* The index structures are hashed by the dev_handle, parent node's first	79	* The index structures are hashed by the dev_handle, parent node's first
Line 185...	Line 189...
185	{	189	{
186	link_t *l;	190	link_t *l;
187	unused_t *u;	191	unused_t *u;
188		192
189	assert(index);	193	assert(index);
-		194	futex_down(&unused_futex);
190	for (l = unused_head.next; l != &unused_head; l = l->next) {	195	for (l = unused_head.next; l != &unused_head; l = l->next) {
191	u = list_get_instance(l, unused_t, link);	196	u = list_get_instance(l, unused_t, link);
192	if (u->dev_handle == dev_handle)	197	if (u->dev_handle == dev_handle)
193	goto hit;	198	goto hit;
194	}	199	}
-		200	futex_up(&unused_futex);
195		201
196	/* dev_handle not found */	202	/* dev_handle not found */
197	return false;	203	return false;
198		204
199	hit:	205	hit:
200	if (list_empty(&u->freed_head)) {	206	if (list_empty(&u->freed_head)) {
Line 203...	Line 209...
203	* There are no freed indices, allocate one directly	209	* There are no freed indices, allocate one directly
204	* from the counter.	210	* from the counter.
205	*/	211	*/
206	*index = u->next++;	212	*index = u->next++;
207	--u->remaining;	213	--u->remaining;
-		214	futex_up(&unused_futex);
208	return true;	215	return true;
209	}	216	}
210	} else {	217	} else {
211	/* There are some freed indices which we can reuse. */	218	/* There are some freed indices which we can reuse. */
212	freed_t *f = list_get_instance(u->freed_head.next, freed_t,	219	freed_t *f = list_get_instance(u->freed_head.next, freed_t,
Line 215...	Line 222...
215	if (f->first++ == f->last) {	222	if (f->first++ == f->last) {
216	/* Destroy the interval. */	223	/* Destroy the interval. */
217	list_remove(&f->link);	224	list_remove(&f->link);
218	free(f);	225	free(f);
219	}	226	}
-		227	futex_up(&unused_futex);
220	return true;	228	return true;
221	}	229	}
222	/*	230	/*
223	* We ran out of indices, which is extremely unlikely with FAT16, but	231	* We ran out of indices, which is extremely unlikely with FAT16, but
224	* theoretically still possible (e.g. too many open unlinked nodes or	232	* theoretically still possible (e.g. too many open unlinked nodes or
225	* too many zero-sized nodes).	233	* too many zero-sized nodes).
226	*/	234	*/
-		235	futex_up(&unused_futex);
227	return false;	236	return false;
228	}	237	}
229		238
230	/** If possible, coalesce two intervals of freed indices. */	239	/** If possible, coalesce two intervals of freed indices. */
231	static void try_coalesce_intervals(link_t l, link_t r, link_t *cur)	240	static void try_coalesce_intervals(link_t l, link_t r, link_t *cur)
Line 250...	Line 259...
250	static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)	259	static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
251	{	260	{
252	link_t *l;	261	link_t *l;
253	unused_t *u;	262	unused_t *u;
254		263
-		264	futex_down(&unused_futex);
255	for (l = unused_head.next; l != &unused_head; l = l->next) {	265	for (l = unused_head.next; l != &unused_head; l = l->next) {
256	u = list_get_instance(l, unused_t, link);	266	u = list_get_instance(l, unused_t, link);
257	if (u->dev_handle == dev_handle)	267	if (u->dev_handle == dev_handle)
258	goto hit;	268	goto hit;
259	}	269	}
-		270	futex_up(&unused_futex);
260		271
261	/* should not happen */	272	/* should not happen */
262	assert(0);	273	assert(0);
263		274
264	hit:	275	hit:
265	if (u->next == index + 1) {	276	if (u->next == index + 1) {
266	/* The index can be returned directly to the counter. */	277	/* The index can be returned directly to the counter. */
267	u->next--;	278	u->next--;
268	u->remaining++;	279	u->remaining++;
269	return;	-
270	} else {	280	} else {
271	/*	281	/*
272	* The index must be returned either to an existing freed	282	* The index must be returned either to an existing freed
273	* interval or a new interval must be created.	283	* interval or a new interval must be created.
274	*/	284	*/
Line 280...	Line 290...
280	if (f->first == index + 1) {	290	if (f->first == index + 1) {
281	f->first--;	291	f->first--;
282	if (lnk->prev != &u->freed_head)	292	if (lnk->prev != &u->freed_head)
283	try_coalesce_intervals(lnk->prev, lnk,	293	try_coalesce_intervals(lnk->prev, lnk,
284	lnk);	294	lnk);
-		295	futex_up(&unused_futex);
285	return;	296	return;
286	}	297	}
287	if (f->last == index - 1) {	298	if (f->last == index - 1) {
288	f->last++;	299	f->last++;
289	if (lnk->next != &u->freed_head)	300	if (lnk->next != &u->freed_head)
290	try_coalesce_intervals(lnk, lnk->next,	301	try_coalesce_intervals(lnk, lnk->next,
291	lnk);	302	lnk);
-		303	futex_up(&unused_futex);
292	return;	304	return;
293	}	305	}
294	if (index > f->first) {	306	if (index > f->first) {
295	n = malloc(sizeof(freed_t));	307	n = malloc(sizeof(freed_t));
296	/* TODO: sleep until allocation succeeds */	308	/* TODO: sleep until allocation succeeds */
297	assert(n);	309	assert(n);
298	link_initialize(&n->link);	310	link_initialize(&n->link);
299	n->first = index;	311	n->first = index;
300	n->last = index;	312	n->last = index;
301	list_insert_before(&n->link, lnk);	313	list_insert_before(&n->link, lnk);
-		314	futex_up(&unused_futex);
302	return;	315	return;
303	}	316	}
304		317
305	}	318	}
306	/* The index will form the last interval. */	319	/* The index will form the last interval. */
Line 310...	Line 323...
310	link_initialize(&n->link);	323	link_initialize(&n->link);
311	n->first = index;	324	n->first = index;
312	n->last = index;	325	n->last = index;
313	list_append(&n->link, &u->freed_head);	326	list_append(&n->link, &u->freed_head);
314	}	327	}
-		328	futex_up(&unused_futex);
315	}	329	}
316		330
317	fat_idx_t *	331	fat_idx_t *
318	fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)	332	fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
319	{	333	{

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(root)/trunk/uspace/srv/fs/fat/fat_idx.c – Rev 2890 → 2944