mirror of https://github.com/xemu-project/xemu.git
121 lines
2.6 KiB
C
121 lines
2.6 KiB
C
/*
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* QEMU Block backends
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*
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* Copyright (C) 2014 Red Hat, Inc.
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*
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* Authors:
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* Markus Armbruster <armbru@redhat.com>,
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1
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* or later. See the COPYING.LIB file in the top-level directory.
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*/
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#include "sysemu/block-backend.h"
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#include "block/block_int.h"
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struct BlockBackend {
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char *name;
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int refcnt;
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QTAILQ_ENTRY(BlockBackend) link; /* for blk_backends */
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};
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/* All the BlockBackends */
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static QTAILQ_HEAD(, BlockBackend) blk_backends =
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QTAILQ_HEAD_INITIALIZER(blk_backends);
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/*
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* Create a new BlockBackend with @name, with a reference count of one.
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* @name must not be null or empty.
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* Fail if a BlockBackend with this name already exists.
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* Store an error through @errp on failure, unless it's null.
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* Return the new BlockBackend on success, null on failure.
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*/
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BlockBackend *blk_new(const char *name, Error **errp)
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{
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BlockBackend *blk;
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assert(name && name[0]);
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if (blk_by_name(name)) {
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error_setg(errp, "Device with id '%s' already exists", name);
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return NULL;
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}
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blk = g_new0(BlockBackend, 1);
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blk->name = g_strdup(name);
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blk->refcnt = 1;
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QTAILQ_INSERT_TAIL(&blk_backends, blk, link);
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return blk;
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}
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static void blk_delete(BlockBackend *blk)
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{
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assert(!blk->refcnt);
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QTAILQ_REMOVE(&blk_backends, blk, link);
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g_free(blk->name);
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g_free(blk);
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}
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/*
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* Increment @blk's reference count.
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* @blk must not be null.
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*/
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void blk_ref(BlockBackend *blk)
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{
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blk->refcnt++;
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}
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/*
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* Decrement @blk's reference count.
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* If this drops it to zero, destroy @blk.
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* For convenience, do nothing if @blk is null.
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*/
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void blk_unref(BlockBackend *blk)
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{
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if (blk) {
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assert(blk->refcnt > 0);
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if (!--blk->refcnt) {
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blk_delete(blk);
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}
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}
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}
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/*
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* Return the BlockBackend after @blk.
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* If @blk is null, return the first one.
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* Else, return @blk's next sibling, which may be null.
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*
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* To iterate over all BlockBackends, do
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* for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
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* ...
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* }
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*/
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BlockBackend *blk_next(BlockBackend *blk)
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{
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return blk ? QTAILQ_NEXT(blk, link) : QTAILQ_FIRST(&blk_backends);
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}
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/*
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* Return @blk's name, a non-null, non-empty string.
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*/
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const char *blk_name(BlockBackend *blk)
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{
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return blk->name;
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}
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/*
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* Return the BlockBackend with name @name if it exists, else null.
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* @name must not be null.
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*/
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BlockBackend *blk_by_name(const char *name)
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{
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BlockBackend *blk;
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assert(name);
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QTAILQ_FOREACH(blk, &blk_backends, link) {
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if (!strcmp(name, blk->name)) {
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return blk;
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}
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}
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return NULL;
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}
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