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dirty-bitmap: Avoid size query failure during truncate

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We've previously fixed several places where we failed to account
for possible errors from bdrv_nb_sectors().  Fix another one by
making bdrv_dirty_bitmap_truncate() take the new size from the
caller instead of querying itself; then adjust the sole caller
bdrv_truncate() to pass the size just determined by a successful
resize, or to reuse the size given to the original truncate
operation when refresh_total_sectors() was not able to confirm the
actual size (the two sizes can potentially differ according to
rounding constraints), thus avoiding sizing the bitmaps to -1.
This also fixes a bug where not all failure paths in
bdrv_truncate() would set errp.

Note that bdrv_truncate() is still a bit awkward.  We may want
to revisit it later and clean up things to better guarantee that
a resize attempt either fails cleanly up front, or cannot fail
after guest-visible changes have been made (if temporary changes
are made, then they need to be cleanly rolled back).  But that
is a task for another day; for now, the goal is the bare minimum
fix to ensure that just bdrv_dirty_bitmap_truncate() cannot fail.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2017-09-25 09:55:11 -05:00 • committed by Kevin Wolf
parent dfe55c3577
commit 1b6cc579de
3 changed files with 15 additions and 9 deletions
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16
block.c
View file

@ -3545,12 +3545,18 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, PreallocMode prealloc,
assert(!(bs->open_flags & BDRV_O_INACTIVE));
ret = drv->bdrv_truncate(bs, offset, prealloc, errp);
if (ret == 0) {
ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
bdrv_dirty_bitmap_truncate(bs);
bdrv_parent_cb_resize(bs);
atomic_inc(&bs->write_gen);
if (ret < 0) {
return ret;
}
ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not refresh total sector count");
} else {
offset = bs->total_sectors * BDRV_SECTOR_SIZE;
}
bdrv_dirty_bitmap_truncate(bs, offset);
bdrv_parent_cb_resize(bs);
atomic_inc(&bs->write_gen);
return ret;
}