| Message ID | 1386079072-5035-1-git-send-email-mreitz@redhat.com |
|---|---|
| State | New |
| Headers | show |
Am 03.12.2013 um 14:57 hat Max Reitz geschrieben: > Leaving the backing file open although it is not needed anymore can > cause problems if it is opened through a block driver which allows > exclusive access only and if the create function of the block driver > used for the top image (the one being created) tries to close and reopen > the image file (which will include opening the backing file a second > time). > > In particular, this will happen with a backing file opened through > qemu-nbd and using qcow2 as the top image file format (which reopens the > image to flush it to disk). > > In addition, the BlockDriverState in bdrv_img_create() is used for the > backing file only; it should therefore be made local to the respective > block. > > Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
On Tue, Dec 03, 2013 at 02:57:52PM +0100, Max Reitz wrote: > Leaving the backing file open although it is not needed anymore can > cause problems if it is opened through a block driver which allows > exclusive access only and if the create function of the block driver > used for the top image (the one being created) tries to close and reopen > the image file (which will include opening the backing file a second > time). > > In particular, this will happen with a backing file opened through > qemu-nbd and using qcow2 as the top image file format (which reopens the > image to flush it to disk). > > In addition, the BlockDriverState in bdrv_img_create() is used for the > backing file only; it should therefore be made local to the respective > block. > > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > v3: > - Reverted the revert in v2 and limited the BlockDriverState once again > to the scope its used in (addressing Xia's comment); added a missing > bdrv_unref() in contrast to v1 (addressing Kevin's comment to v1) > > v2: > - Minimizing the changes prevents introducing a leak of the > BlockDriverState in case of an error in bdrv_open() (thanks, Kevin). > --- > block.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) Thanks, applied to my block tree: https://github.com/stefanha/qemu/commits/block Stefan
diff --git a/block.c b/block.c index 382ea71..0468765 100644 --- a/block.c +++ b/block.c @@ -4504,7 +4504,6 @@ void bdrv_img_create(const char *filename, const char *fmt, { QEMUOptionParameter *param = NULL, *create_options = NULL; QEMUOptionParameter *backing_fmt, *backing_file, *size; - BlockDriverState *bs = NULL; BlockDriver *drv, *proto_drv; BlockDriver *backing_drv = NULL; Error *local_err = NULL; @@ -4583,6 +4582,7 @@ void bdrv_img_create(const char *filename, const char *fmt, size = get_option_parameter(param, BLOCK_OPT_SIZE); if (size && size->value.n == -1) { if (backing_file && backing_file->value.s) { + BlockDriverState *bs; uint64_t size; char buf[32]; int back_flags; @@ -4601,6 +4601,7 @@ void bdrv_img_create(const char *filename, const char *fmt, error_get_pretty(local_err)); error_free(local_err); local_err = NULL; + bdrv_unref(bs); goto out; } bdrv_get_geometry(bs, &size); @@ -4608,6 +4609,8 @@ void bdrv_img_create(const char *filename, const char *fmt, snprintf(buf, sizeof(buf), "%" PRId64, size); set_option_parameter(param, BLOCK_OPT_SIZE, buf); + + bdrv_unref(bs); } else { error_setg(errp, "Image creation needs a size parameter"); goto out; @@ -4638,9 +4641,6 @@ out: free_option_parameters(create_options); free_option_parameters(param); - if (bs) { - bdrv_unref(bs); - } if (error_is_set(&local_err)) { error_propagate(errp, local_err); }
Leaving the backing file open although it is not needed anymore can cause problems if it is opened through a block driver which allows exclusive access only and if the create function of the block driver used for the top image (the one being created) tries to close and reopen the image file (which will include opening the backing file a second time). In particular, this will happen with a backing file opened through qemu-nbd and using qcow2 as the top image file format (which reopens the image to flush it to disk). In addition, the BlockDriverState in bdrv_img_create() is used for the backing file only; it should therefore be made local to the respective block. Signed-off-by: Max Reitz <mreitz@redhat.com> --- v3: - Reverted the revert in v2 and limited the BlockDriverState once again to the scope its used in (addressing Xia's comment); added a missing bdrv_unref() in contrast to v1 (addressing Kevin's comment to v1) v2: - Minimizing the changes prevents introducing a leak of the BlockDriverState in case of an error in bdrv_open() (thanks, Kevin). --- block.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)