block: Use bdrv_refresh_filename() to pull

Before this patch, bdrv_refresh_filename() is used in a pushing manner:
Whenever the BDS graph is modified, the parents of the modified edges
are supposed to be updated (recursively upwards).  However, that is
nonviable, considering that we want child changes not to concern
parents.

Also, in the long run we want a pull model anyway: Here, we would have a
bdrv_filename() function which returns a BDS's filename, freshly
constructed.

This patch is an intermediate step.  It adds bdrv_refresh_filename()
calls before every place a BDS.filename value is used.  The only
exceptions are protocol drivers that use their own filename, which
clearly would not profit from refreshing that filename before.

Also, bdrv_get_encrypted_filename() is removed along the way (as a user
of BDS.filename), since it is completely unused.

In turn, all of the calls to bdrv_refresh_filename() before this patch
are removed, because we no longer have to call this function on graph
changes.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190201192935.18394-2-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/blockdev.c b/blockdev.c
index 8714ad2702..7e6bf9955c 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1627,6 +1627,7 @@ static void external_snapshot_prepare(BlkActionState *common,
                 error_setg_errno(errp, -size, "bdrv_getlength failed");
                 goto out;
             }
+            bdrv_refresh_filename(state->old_bs);
             bdrv_img_create(new_image_file, format,
                             state->old_bs->filename,
                             state->old_bs->drv->format_name,
@@ -3230,6 +3231,7 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
             goto out;
         }
         assert(bdrv_get_aio_context(base_bs) == aio_context);
+        bdrv_refresh_filename(base_bs);
         base_name = base_bs->filename;
     }
 
@@ -3349,6 +3351,10 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
             goto out;
         }
     } else if (has_top && top) {
+        /* This strcmp() is just a shortcut, there is no need to
+         * refresh @bs's filename.  If it mismatches,
+         * bdrv_find_backing_image() will do the refresh and may still
+         * return @bs. */
         if (strcmp(bs->filename, top) != 0) {
             top_bs = bdrv_find_backing_image(bs, top);
         }
@@ -3509,6 +3515,7 @@ static BlockJob *do_drive_backup(DriveBackup *backup, JobTxn *txn,
     if (backup->mode != NEW_IMAGE_MODE_EXISTING) {
         assert(backup->format);
         if (source) {
+            bdrv_refresh_filename(source);
             bdrv_img_create(backup->target, backup->format, source->filename,
                             source->drv->format_name, NULL,
                             size, flags, false, &local_err);
@@ -3889,6 +3896,7 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
             break;
         case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
             /* create new image with backing file */
+            bdrv_refresh_filename(source);
             bdrv_img_create(arg->target, format,
                             source->filename,
                             source->drv->format_name,