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block: introduce bdrv_swap, implement bdrv_append on top of it

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The new function can be made a bit nicer than bdrv_append.  It swaps the
whole contents, and then swaps back (using the usual t=a;a=b;b=t idiom)
the fields that need to stay on top.  Thus, it does not need explicit
bdrv_detach_dev, bdrv_iostatus_disable, etc.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-06-14 16:55:02 +02:00 committed by Kevin Wolf
parent a9fc4408e3
commit 4ddc07cac2
2 changed files with 109 additions and 94 deletions
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202
block.c
View File

@ -971,6 +971,107 @@ static void bdrv_rebind(BlockDriverState *bs)
}
}
static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
BlockDriverState *bs_src)
{
/* move some fields that need to stay attached to the device */
bs_dest->open_flags = bs_src->open_flags;
/* dev info */
bs_dest->dev_ops = bs_src->dev_ops;
bs_dest->dev_opaque = bs_src->dev_opaque;
bs_dest->dev = bs_src->dev;
bs_dest->buffer_alignment = bs_src->buffer_alignment;
bs_dest->copy_on_read = bs_src->copy_on_read;
bs_dest->enable_write_cache = bs_src->enable_write_cache;
/* i/o timing parameters */
bs_dest->slice_time = bs_src->slice_time;
bs_dest->slice_start = bs_src->slice_start;
bs_dest->slice_end = bs_src->slice_end;
bs_dest->io_limits = bs_src->io_limits;
bs_dest->io_base = bs_src->io_base;
bs_dest->throttled_reqs = bs_src->throttled_reqs;
bs_dest->block_timer = bs_src->block_timer;
bs_dest->io_limits_enabled = bs_src->io_limits_enabled;
/* geometry */
bs_dest->cyls = bs_src->cyls;
bs_dest->heads = bs_src->heads;
bs_dest->secs = bs_src->secs;
bs_dest->translation = bs_src->translation;
/* r/w error */
bs_dest->on_read_error = bs_src->on_read_error;
bs_dest->on_write_error = bs_src->on_write_error;
/* i/o status */
bs_dest->iostatus_enabled = bs_src->iostatus_enabled;
bs_dest->iostatus = bs_src->iostatus;
/* dirty bitmap */
bs_dest->dirty_count = bs_src->dirty_count;
bs_dest->dirty_bitmap = bs_src->dirty_bitmap;
/* job */
bs_dest->in_use = bs_src->in_use;
bs_dest->job = bs_src->job;
/* keep the same entry in bdrv_states */
pstrcpy(bs_dest->device_name, sizeof(bs_dest->device_name),
bs_src->device_name);
bs_dest->list = bs_src->list;
}
/*
* Swap bs contents for two image chains while they are live,
* while keeping required fields on the BlockDriverState that is
* actually attached to a device.
*
* This will modify the BlockDriverState fields, and swap contents
* between bs_new and bs_old. Both bs_new and bs_old are modified.
*
* bs_new is required to be anonymous.
*
* This function does not create any image files.
*/
void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old)
{
BlockDriverState tmp;
/* bs_new must be anonymous and shouldn't have anything fancy enabled */
assert(bs_new->device_name[0] == '\0');
assert(bs_new->dirty_bitmap == NULL);
assert(bs_new->job == NULL);
assert(bs_new->dev == NULL);
assert(bs_new->in_use == 0);
assert(bs_new->io_limits_enabled == false);
assert(bs_new->block_timer == NULL);
tmp = *bs_new;
*bs_new = *bs_old;
*bs_old = tmp;
/* there are some fields that should not be swapped, move them back */
bdrv_move_feature_fields(&tmp, bs_old);
bdrv_move_feature_fields(bs_old, bs_new);
bdrv_move_feature_fields(bs_new, &tmp);
/* bs_new shouldn't be in bdrv_states even after the swap! */
assert(bs_new->device_name[0] == '\0');
/* Check a few fields that should remain attached to the device */
assert(bs_new->dev == NULL);
assert(bs_new->job == NULL);
assert(bs_new->in_use == 0);
assert(bs_new->io_limits_enabled == false);
assert(bs_new->block_timer == NULL);
bdrv_rebind(bs_new);
bdrv_rebind(bs_old);
}
/*
* Add new bs contents at the top of an image chain while the chain is
* live, while keeping required fields on the top layer.
@ -984,103 +1085,16 @@ static void bdrv_rebind(BlockDriverState *bs)
*/
void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top)
{
BlockDriverState tmp;
/* bs_new must be anonymous */
assert(bs_new->device_name[0] == '\0');
tmp = *bs_new;
/* there are some fields that need to stay on the top layer: */
tmp.open_flags = bs_top->open_flags;
/* dev info */
tmp.dev_ops = bs_top->dev_ops;
tmp.dev_opaque = bs_top->dev_opaque;
tmp.dev = bs_top->dev;
tmp.buffer_alignment = bs_top->buffer_alignment;
tmp.copy_on_read = bs_top->copy_on_read;
tmp.enable_write_cache = bs_top->enable_write_cache;
/* i/o timing parameters */
tmp.slice_time = bs_top->slice_time;
tmp.slice_start = bs_top->slice_start;
tmp.slice_end = bs_top->slice_end;
tmp.io_limits = bs_top->io_limits;
tmp.io_base = bs_top->io_base;
tmp.throttled_reqs = bs_top->throttled_reqs;
tmp.block_timer = bs_top->block_timer;
tmp.io_limits_enabled = bs_top->io_limits_enabled;
/* geometry */
tmp.cyls = bs_top->cyls;
tmp.heads = bs_top->heads;
tmp.secs = bs_top->secs;
tmp.translation = bs_top->translation;
/* r/w error */
tmp.on_read_error = bs_top->on_read_error;
tmp.on_write_error = bs_top->on_write_error;
/* i/o status */
tmp.iostatus_enabled = bs_top->iostatus_enabled;
tmp.iostatus = bs_top->iostatus;
/* dirty bitmap */
tmp.dirty_count = bs_top->dirty_count;
tmp.dirty_bitmap = bs_top->dirty_bitmap;
assert(bs_new->dirty_bitmap == NULL);
/* job */
tmp.in_use = bs_top->in_use;
tmp.job = bs_top->job;
assert(bs_new->job == NULL);
/* keep the same entry in bdrv_states */
pstrcpy(tmp.device_name, sizeof(tmp.device_name), bs_top->device_name);
tmp.list = bs_top->list;
bdrv_swap(bs_new, bs_top);
/* The contents of 'tmp' will become bs_top, as we are
* swapping bs_new and bs_top contents. */
tmp.backing_hd = bs_new;
pstrcpy(tmp.backing_file, sizeof(tmp.backing_file), bs_top->filename);
pstrcpy(tmp.backing_format, sizeof(tmp.backing_format),
bs_top->drv ? bs_top->drv->format_name : "");
/* swap contents of the fixed new bs and the current top */
*bs_new = *bs_top;
*bs_top = tmp;
/* device_name[] was carried over from the old bs_top. bs_new
* shouldn't be in bdrv_states, so we need to make device_name[]
* reflect the anonymity of bs_new
*/
bs_new->device_name[0] = '\0';
/* clear the copied fields in the new backing file */
bdrv_detach_dev(bs_new, bs_new->dev);
bs_new->job = NULL;
bs_new->in_use = 0;
bs_new->dirty_bitmap = NULL;
bs_new->dirty_count = 0;
qemu_co_queue_init(&bs_new->throttled_reqs);
memset(&bs_new->io_base, 0, sizeof(bs_new->io_base));
memset(&bs_new->io_limits, 0, sizeof(bs_new->io_limits));
bdrv_iostatus_disable(bs_new);
/* we don't use bdrv_io_limits_disable() for this, because we don't want
* to affect or delete the block_timer, as it has been moved to bs_top */
bs_new->io_limits_enabled = false;
bs_new->block_timer = NULL;
bs_new->slice_time = 0;
bs_new->slice_start = 0;
bs_new->slice_end = 0;
bdrv_rebind(bs_new);
bdrv_rebind(bs_top);
bs_top->backing_hd = bs_new;
bs_top->open_flags &= ~BDRV_O_NO_BACKING;
pstrcpy(bs_top->backing_file, sizeof(bs_top->backing_file),
bs_new->filename);
pstrcpy(bs_top->backing_format, sizeof(bs_top->backing_format),
bs_new->drv ? bs_new->drv->format_name : "");
}
void bdrv_delete(BlockDriverState *bs)

1
block.h
View File

@ -122,6 +122,7 @@ int bdrv_create(BlockDriver *drv, const char* filename,
int bdrv_create_file(const char* filename, QEMUOptionParameter *options);
BlockDriverState *bdrv_new(const char *device_name);
void bdrv_make_anon(BlockDriverState *bs);
void bdrv_swap(BlockDriverState *bs_new, BlockDriverState *bs_old);
void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top);
void bdrv_delete(BlockDriverState *bs);
int bdrv_parse_cache_flags(const char *mode, int *flags);