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![Paolo Bonzini](/assets/img/avatar_default.png)
This makes the driver thread-safe. The CoMutex is dropped temporarily while accessing the data clusters or the backing file. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20170629132749.997-10-pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
143 lines
4.6 KiB
C
143 lines
4.6 KiB
C
/*
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* QEMU Enhanced Disk Format Cluster functions
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*
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* Copyright IBM, Corp. 2010
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "qed.h"
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/**
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* Count the number of contiguous data clusters
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*
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* @s: QED state
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* @table: L2 table
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* @index: First cluster index
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* @n: Maximum number of clusters
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* @offset: Set to first cluster offset
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*
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* This function scans tables for contiguous clusters. A contiguous run of
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* clusters may be allocated, unallocated, or zero.
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*/
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static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,
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QEDTable *table,
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unsigned int index,
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unsigned int n,
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uint64_t *offset)
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{
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unsigned int end = MIN(index + n, s->table_nelems);
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uint64_t last = table->offsets[index];
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unsigned int i;
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*offset = last;
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for (i = index + 1; i < end; i++) {
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if (qed_offset_is_unalloc_cluster(last)) {
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/* Counting unallocated clusters */
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if (!qed_offset_is_unalloc_cluster(table->offsets[i])) {
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break;
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}
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} else if (qed_offset_is_zero_cluster(last)) {
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/* Counting zero clusters */
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if (!qed_offset_is_zero_cluster(table->offsets[i])) {
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break;
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}
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} else {
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/* Counting allocated clusters */
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if (table->offsets[i] != last + s->header.cluster_size) {
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break;
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}
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last = table->offsets[i];
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}
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}
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return i - index;
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}
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/**
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* Find the offset of a data cluster
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*
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* @s: QED state
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* @request: L2 cache entry
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* @pos: Byte position in device
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* @len: Number of bytes (may be shortened on return)
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* @img_offset: Contains offset in the image file on success
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*
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* This function translates a position in the block device to an offset in the
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* image file. The translated offset or unallocated range in the image file is
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* reported back in *img_offset and *len.
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*
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* If the L2 table exists, request->l2_table points to the L2 table cache entry
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* and the caller must free the reference when they are finished. The cache
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* entry is exposed in this way to avoid callers having to read the L2 table
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* again later during request processing. If request->l2_table is non-NULL it
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* will be unreferenced before taking on the new cache entry.
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*
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* On success QED_CLUSTER_FOUND is returned and img_offset/len are a contiguous
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* range in the image file.
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*
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* On failure QED_CLUSTER_L2 or QED_CLUSTER_L1 is returned for missing L2 or L1
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* table offset, respectively. len is number of contiguous unallocated bytes.
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*
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* Called with table_lock held.
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*/
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int coroutine_fn qed_find_cluster(BDRVQEDState *s, QEDRequest *request,
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uint64_t pos, size_t *len,
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uint64_t *img_offset)
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{
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uint64_t l2_offset;
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uint64_t offset = 0;
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unsigned int index;
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unsigned int n;
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int ret;
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/* Limit length to L2 boundary. Requests are broken up at the L2 boundary
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* so that a request acts on one L2 table at a time.
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*/
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*len = MIN(*len, (((pos >> s->l1_shift) + 1) << s->l1_shift) - pos);
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l2_offset = s->l1_table->offsets[qed_l1_index(s, pos)];
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if (qed_offset_is_unalloc_cluster(l2_offset)) {
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*img_offset = 0;
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return QED_CLUSTER_L1;
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}
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if (!qed_check_table_offset(s, l2_offset)) {
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*img_offset = *len = 0;
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return -EINVAL;
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}
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ret = qed_read_l2_table(s, request, l2_offset);
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if (ret) {
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goto out;
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}
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index = qed_l2_index(s, pos);
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n = qed_bytes_to_clusters(s, qed_offset_into_cluster(s, pos) + *len);
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n = qed_count_contiguous_clusters(s, request->l2_table->table,
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index, n, &offset);
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if (qed_offset_is_unalloc_cluster(offset)) {
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ret = QED_CLUSTER_L2;
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} else if (qed_offset_is_zero_cluster(offset)) {
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ret = QED_CLUSTER_ZERO;
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} else if (qed_check_cluster_offset(s, offset)) {
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ret = QED_CLUSTER_FOUND;
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} else {
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ret = -EINVAL;
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}
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*len = MIN(*len,
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n * s->header.cluster_size - qed_offset_into_cluster(s, pos));
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out:
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*img_offset = offset;
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return ret;
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}
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