Add bdrv_find_image(), bdrv_find_base(), and bdrv_delete_intermediate(). bdrv_find_image(): given a filename and a BDS, find the image in the chain that matches the passed filename.
bdrv_find_base(): given a BDS, find the base image (parent-most image) bdrv_delete_intermediate(): Given 3 BDS (active, top, base), delete images above base up to and including top, and set base to be the parent of top's child node. Signed-off-by: Jeff Cody <jc...@redhat.com> --- block.c | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- block.h | 4 ++ 2 files changed, 139 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 522acd1..a3c8d33 100644 --- a/block.c +++ b/block.c @@ -1408,7 +1408,7 @@ int bdrv_commit(BlockDriverState *bs) if (!drv) return -ENOMEDIUM; - + if (!bs->backing_hd) { return -ENOTSUP; } @@ -1661,6 +1661,110 @@ int bdrv_change_backing_file(BlockDriverState *bs, return ret; } +typedef struct BlkIntermediateStates { + BlockDriverState *bs; + QSIMPLEQ_ENTRY(BlkIntermediateStates) entry; +} BlkIntermediateStates; + + +/* deletes images above 'base' up to and including 'top', and sets the image + * above 'top' to have base as its backing file. + */ +int bdrv_delete_intermediate(BlockDriverState *active, BlockDriverState *top, + BlockDriverState *base) +{ + BlockDriverState *intermediate; + BlockDriverState *base_bs = NULL; + BlockDriverState *new_top_bs = NULL; + BlkIntermediateStates *intermediate_state, *next; + int ret = -1; + + QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete; + QSIMPLEQ_INIT(&states_to_delete); + + if (!top->drv || !base->drv) { + goto exit; + } + + /* special case of top->backing_hd already pointing to base - nothing + * to do, no intermediate images + */ + if (top->backing_hd == base) { + ret = 0; + goto exit; + } + + /* if the active bs layer is the same as the new top, then there + * is no image above the top, so it is also the new_top (and we must + * not delete it below, either) + */ + if (active == top) { + new_top_bs = active; + } else { + intermediate = active; + while (intermediate->backing_hd) { + if (intermediate->backing_hd == top) { + new_top_bs = intermediate; + break; + } + intermediate = intermediate->backing_hd; + } + } + + if (new_top_bs == NULL) { + /* we could not find the image above 'top', this is an error */ + goto exit; + } + + /* if the active and top image passed in are the same, then we + * can't delete the active, so we start one below + */ + intermediate = (active == top) ? active->backing_hd : top; + + /* now we will go down through the list, and add each BDS we find + * into our deletion queue, until we hit the 'base' + */ + while (intermediate) { + intermediate_state = g_malloc0(sizeof(BlkIntermediateStates)); + intermediate_state->bs = intermediate; + QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry); + + if (intermediate->backing_hd == base) { + base_bs = intermediate->backing_hd; + break; + } + intermediate = intermediate->backing_hd; + } + if (base_bs == NULL) { + /* something went wrong, we did not end at the base. safely + * unravel everything, and exit with error */ + goto exit; + } + + /* success - we can delete the intermediate states, and link top->base */ + ret = bdrv_change_backing_file(new_top_bs, base_bs->filename, + base_bs->drv ? base_bs->drv->format_name : ""); + if (ret) { + goto exit; + } + new_top_bs->backing_hd = base_bs; + + + QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) { + /* so that bdrv_close() does not recursively close the chain */ + intermediate_state->bs->backing_hd = NULL; + bdrv_delete(intermediate_state->bs); + } + ret = 0; + +exit: + QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) { + g_free(intermediate_state); + } + return ret; +} + + static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset, size_t size) { @@ -3128,6 +3232,36 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs, return NULL; } +BlockDriverState *bdrv_find_image(BlockDriverState *bs, + const char *filename) +{ + if (!bs || !bs->drv) { + return NULL; + } + + if (strcmp(bs->filename, filename) == 0) { + return bs; + } else { + return bdrv_find_image(bs->backing_hd, filename); + } +} + +BlockDriverState *bdrv_find_base(BlockDriverState *bs) +{ + BlockDriverState *curr_bs = NULL; + + if (!bs) { + return NULL; + } + + curr_bs = bs; + + while (curr_bs->backing_hd) { + curr_bs = curr_bs->backing_hd; + } + return curr_bs; +} + #define NB_SUFFIXES 4 char *get_human_readable_size(char *buf, int buf_size, int64_t size) diff --git a/block.h b/block.h index 25e0230..70fa53c 100644 --- a/block.h +++ b/block.h @@ -183,6 +183,10 @@ int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file, const char *backing_fmt); void bdrv_register(BlockDriver *bdrv); int bdrv_change_hostcache(BlockDriverState *bs, bool enable_host_cache); +BlockDriverState *bdrv_find_image(BlockDriverState *bs, const char *filename); +BlockDriverState *bdrv_find_base(BlockDriverState *bs); +int bdrv_delete_intermediate(BlockDriverState *active, BlockDriverState *top, + BlockDriverState *base); typedef struct BdrvCheckResult { -- 1.7.10.4