/*
* Copyright (c) 2008 Jakub Jermar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
*/
/** @addtogroup fs
* @{
*/
/**
* @file fat_idx.c
* @brief Layer for translating FAT entities to VFS node indices.
*/
#include "fat.h"
#include "../../vfs/vfs.h"
#include <errno.h>
#include <string.h>
#include <libadt/hash_table.h>
#include <libadt/list.h>
#include <assert.h>
#include <futex.h>
/** Each instance of this type describes one interval of freed VFS indices. */
typedef struct {
link_t link;
fs_index_t first;
fs_index_t last;
} freed_t;
/**
* Each instance of this type describes state of all VFS indices that
* are currently unused.
*/
typedef struct {
link_t link;
dev_handle_t dev_handle;
/** Next unassigned index. */
fs_index_t next;
/** Number of remaining unassigned indices. */
uint64_t remaining;
/** 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.
*/
static hash_table_t up_hash;
#define UPH_BUCKETS_LOG 12
#define UPH_BUCKETS (1 << UPH_BUCKETS_LOG)
#define UPH_DH_KEY 0
#define UPH_PFC_KEY 1
#define UPH_PDI_KEY 2
static hash_index_t pos_hash(unsigned long key[])
{
dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
unsigned pdi = (unsigned)key[UPH_PDI_KEY];
hash_index_t h;
/*
* The least significant half of all bits are the least significant bits
* of the parent node's first cluster.
*
* The least significant half of the most significant half of all bits
* are the least significant bits of the node's dentry index within the
* parent directory node.
*
* The most significant half of the most significant half of all bits
* are the least significant bits of the device handle.
*/
h = pfc & ((1 << (UPH_BUCKETS_LOG / 2)) - 1);
h |= (pdi & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
(UPH_BUCKETS_LOG / 2);
h |= (dev_handle & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
(3 * (UPH_BUCKETS_LOG / 4));
return h;
}
static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)
{
dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
unsigned pdi = (unsigned)key[UPH_PDI_KEY];
fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uph_link);
return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
(pdi == fidx->pdi);
}
static void pos_remove_callback(link_t *item)
{
/* nothing to do */
}
static hash_table_operations_t uph_ops = {
.hash = pos_hash,
.compare = pos_compare,
.remove_callback = pos_remove_callback,
};
/**
* Global hash table of all used fat_idx_t structures.
* The index structures are hashed by the dev_handle and index.
*/
static hash_table_t ui_hash;
#define UIH_BUCKETS_LOG 12
#define UIH_BUCKETS (1 << UIH_BUCKETS_LOG)
#define UIH_DH_KEY 0
#define UIH_INDEX_KEY 1
static hash_index_t idx_hash(unsigned long key[])
{
dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
hash_index_t h;
h = dev_handle & ((1 << (UIH_BUCKETS_LOG / 2)) - 1);
h |= (index & ((1 << (UIH_BUCKETS_LOG / 2)) - 1)) <<
(UIH_BUCKETS_LOG / 2);
return h;
}
static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)
{
dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uih_link);
return (dev_handle == fidx->dev_handle) && (index == fidx->index);
}
static void idx_remove_callback(link_t *item)
{
/* nothing to do */
}
static hash_table_operations_t uih_ops = {
.hash = idx_hash,
.compare = idx_compare,
.remove_callback = idx_remove_callback,
};
/** Allocate a VFS index which is not currently in use. */
static bool fat_idx_alloc(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);
/* dev_handle not found */
return false;
hit:
if (list_empty(&u->freed_head)) {
if (u->remaining) {
/*
* 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,
link);
*index = f->first;
if (f->first++ == f->last) {
/* Destroy the interval. */
list_remove(&f->link);
}
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)
{
freed_t *fl = list_get_instance(l, freed_t, link);
freed_t *fr = list_get_instance(r, freed_t, link);
if (fl->last + 1 == fr->first) {
if (cur == l) {
fl->last = fr->last;
list_remove(r);
} else {
fr->first = fl->first;
list_remove(l);
}
}
}
/** Free a VFS index, which is no longer in use. */
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 */
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.
*/
link_t *lnk;
freed_t *n;
for (lnk = u->freed_head.next; lnk != &u->freed_head;
lnk = lnk->next) {
freed_t *f = list_get_instance(lnk, freed_t, link);
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) {
/* TODO: sleep until allocation succeeds */
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. */
/* TODO: sleep until allocation succeeds */
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)
{
fat_idx_t *fidx;
link_t *l;
unsigned long pkey[] = {
[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) {
return NULL;
}
if (!fat_idx_alloc(dev_handle, &fidx->index)) {
return NULL;
}
unsigned long ikey[] = {
[UIH_DH_KEY] = dev_handle,
[UIH_INDEX_KEY] = fidx->index,
};
link_initialize(&fidx->uph_link);
link_initialize(&fidx->uih_link);
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;
}
fat_idx_t *
fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)
{
fat_idx_t *fidx = NULL;
link_t *l;
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;
}