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qcow2: Extract code from get_cluster_offset() (Laurent Vivier)

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Extract code from get_cluster_offset() into new functions:

- seek_l2_table()

Search an l2 offset in the l2_cache table.

- l2_load()

Read the l2 entry from disk

- l2_allocate()

Allocate a new l2 entry.

Some comment fixups from Kevin Wolf

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Kevin Wolf <kwolf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5003 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2008-08-14 18:07:12 +00:00
parent 16b98a97a9
commit 108534b968
1 changed files with 156 additions and 65 deletions
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221
block-qcow2.c
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@ -480,101 +480,191 @@ static int grow_l1_table(BlockDriverState *bs, int min_size)
return -EIO;
}
/* 'allocate' is:
/*
* seek_l2_table
*
* 0 not to allocate.
* seek l2_offset in the l2_cache table
* if not found, return NULL,
* if found,
* increments the l2 cache hit count of the entry,
* if counter overflow, divide by two all counters
* return the pointer to the l2 cache entry
*
* 1 to allocate a normal cluster (for sector indexes 'n_start' to
* 'n_end')
*
* 2 to allocate a compressed cluster of size
* 'compressed_size'. 'compressed_size' must be > 0 and <
* cluster_size
*
* return 0 if not allocated.
*/
static uint64_t *seek_l2_table(BDRVQcowState *s, uint64_t l2_offset)
{
int i, j;
for(i = 0; i < L2_CACHE_SIZE; i++) {
if (l2_offset == s->l2_cache_offsets[i]) {
/* increment the hit count */
if (++s->l2_cache_counts[i] == 0xffffffff) {
for(j = 0; j < L2_CACHE_SIZE; j++) {
s->l2_cache_counts[j] >>= 1;
}
}
return s->l2_cache + (i << s->l2_bits);
}
}
return NULL;
}
/*
* l2_load
*
* Loads a L2 table into memory. If the table is in the cache, the cache
* is used; otherwise the L2 table is loaded from the image file.
*
* Returns a pointer to the L2 table on success, or NULL if the read from
* the image file failed.
*/
static uint64_t *l2_load(BlockDriverState *bs, uint64_t l2_offset)
{
BDRVQcowState *s = bs->opaque;
int min_index;
uint64_t *l2_table;
/* seek if the table for the given offset is in the cache */
l2_table = seek_l2_table(s, l2_offset);
if (l2_table != NULL)
return l2_table;
/* not found: load a new entry in the least used one */
min_index = l2_cache_new_entry(bs);
l2_table = s->l2_cache + (min_index << s->l2_bits);
if (bdrv_pread(s->hd, l2_offset, l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
return NULL;
s->l2_cache_offsets[min_index] = l2_offset;
s->l2_cache_counts[min_index] = 1;
return l2_table;
}
/*
* l2_allocate
*
* Allocate a new l2 entry in the file. If l1_index points to an already
* used entry in the L2 table (i.e. we are doing a copy on write for the L2
* table) copy the contents of the old L2 table into the newly allocated one.
* Otherwise the new table is initialized with zeros.
*
*/
static uint64_t *l2_allocate(BlockDriverState *bs, int l1_index)
{
BDRVQcowState *s = bs->opaque;
int min_index;
uint64_t old_l2_offset, tmp;
uint64_t *l2_table, l2_offset;
old_l2_offset = s->l1_table[l1_index];
/* allocate a new l2 entry */
l2_offset = alloc_clusters(bs, s->l2_size * sizeof(uint64_t));
/* update the L1 entry */
s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
tmp = cpu_to_be64(l2_offset | QCOW_OFLAG_COPIED);
if (bdrv_pwrite(s->hd, s->l1_table_offset + l1_index * sizeof(tmp),
&tmp, sizeof(tmp)) != sizeof(tmp))
return NULL;
/* allocate a new entry in the l2 cache */
min_index = l2_cache_new_entry(bs);
l2_table = s->l2_cache + (min_index << s->l2_bits);
if (old_l2_offset == 0) {
/* if there was no old l2 table, clear the new table */
memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
} else {
/* if there was an old l2 table, read it from the disk */
if (bdrv_pread(s->hd, old_l2_offset,
l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
return NULL;
}
/* write the l2 table to the file */
if (bdrv_pwrite(s->hd, l2_offset,
l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
return NULL;
/* update the l2 cache entry */
s->l2_cache_offsets[min_index] = l2_offset;
s->l2_cache_counts[min_index] = 1;
return l2_table;
}
static uint64_t get_cluster_offset(BlockDriverState *bs,
uint64_t offset, int allocate,
int compressed_size,
int n_start, int n_end)
{
BDRVQcowState *s = bs->opaque;
int min_index, i, j, l1_index, l2_index, ret;
uint64_t l2_offset, *l2_table, cluster_offset, tmp, old_l2_offset;
int l1_index, l2_index, ret;
uint64_t l2_offset, *l2_table, cluster_offset, tmp;
/* seek the the l2 offset in the l1 table */
l1_index = offset >> (s->l2_bits + s->cluster_bits);
if (l1_index >= s->l1_size) {
/* outside l1 table is allowed: we grow the table if needed */
if (!allocate)
return 0;
if (grow_l1_table(bs, l1_index + 1) < 0)
ret = grow_l1_table(bs, l1_index + 1);
if (ret < 0)
return 0;
}
l2_offset = s->l1_table[l1_index];
/* seek the l2 table of the given l2 offset */
if (!l2_offset) {
/* the l2 table doesn't exist */
if (!allocate)
return 0;
l2_allocate:
old_l2_offset = l2_offset;
/* allocate a new l2 entry */
l2_offset = alloc_clusters(bs, s->l2_size * sizeof(uint64_t));
/* update the L1 entry */
s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
tmp = cpu_to_be64(l2_offset | QCOW_OFLAG_COPIED);
if (bdrv_pwrite(s->hd, s->l1_table_offset + l1_index * sizeof(tmp),
&tmp, sizeof(tmp)) != sizeof(tmp))
/* allocate a new l2 table for this offset */
l2_table = l2_allocate(bs, l1_index);
if (l2_table == NULL)
return 0;
min_index = l2_cache_new_entry(bs);
l2_table = s->l2_cache + (min_index << s->l2_bits);
if (old_l2_offset == 0) {
memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;
} else {
/* the l2 table exists */
if (!(l2_offset & QCOW_OFLAG_COPIED) && allocate) {
/* duplicate the l2 table, and free the old table */
free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
l2_table = l2_allocate(bs, l1_index);
if (l2_table == NULL)
return 0;
l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;
} else {
if (bdrv_pread(s->hd, old_l2_offset,
l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
/* load the l2 table in memory */
l2_offset &= ~QCOW_OFLAG_COPIED;
l2_table = l2_load(bs, l2_offset);
if (l2_table == NULL)
return 0;
}
if (bdrv_pwrite(s->hd, l2_offset,
l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
return 0;
} else {
if (!(l2_offset & QCOW_OFLAG_COPIED)) {
if (allocate) {
free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
goto l2_allocate;
}
} else {
l2_offset &= ~QCOW_OFLAG_COPIED;
}
for(i = 0; i < L2_CACHE_SIZE; i++) {
if (l2_offset == s->l2_cache_offsets[i]) {
/* increment the hit count */
if (++s->l2_cache_counts[i] == 0xffffffff) {
for(j = 0; j < L2_CACHE_SIZE; j++) {
s->l2_cache_counts[j] >>= 1;
}
}
l2_table = s->l2_cache + (i << s->l2_bits);
goto found;
}
}
/* not found: load a new entry in the least used one */
min_index = l2_cache_new_entry(bs);
l2_table = s->l2_cache + (min_index << s->l2_bits);
if (bdrv_pread(s->hd, l2_offset, l2_table, s->l2_size * sizeof(uint64_t)) !=
s->l2_size * sizeof(uint64_t))
return 0;
}
s->l2_cache_offsets[min_index] = l2_offset;
s->l2_cache_counts[min_index] = 1;
found:
/* find the cluster offset for the given disk offset */
l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
cluster_offset = be64_to_cpu(l2_table[l2_index]);
if (!cluster_offset) {
/* cluster doesn't exist */
if (!allocate)
return cluster_offset;
return 0;
} else if (!(cluster_offset & QCOW_OFLAG_COPIED)) {
if (!allocate)
return cluster_offset;
@ -592,6 +682,7 @@ static uint64_t get_cluster_offset(BlockDriverState *bs,
cluster_offset &= ~QCOW_OFLAG_COPIED;
return cluster_offset;
}
if (allocate == 1) {
/* allocate a new cluster */
cluster_offset = alloc_clusters(bs, s->cluster_size);