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author | Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> | 2019-01-15 18:26:50 -0500 |
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committer | John Snow <jsnow@redhat.com> | 2019-01-15 18:26:50 -0500 |
commit | 1eaf1b0fdf41069b4b3e67eae88da0d781261792 (patch) | |
tree | 076362574f940fad39b153c7c15415d0842f1ac0 /block | |
parent | bb6a0ec10ee3f791835f1479a8a3226f64cb6d75 (diff) | |
download | qemu-1eaf1b0fdf41069b4b3e67eae88da0d781261792.zip qemu-1eaf1b0fdf41069b4b3e67eae88da0d781261792.tar.gz qemu-1eaf1b0fdf41069b4b3e67eae88da0d781261792.tar.bz2 |
block/mirror: fix and improve do_sync_target_write
Use bdrv_dirty_bitmap_next_dirty_area() instead of
bdrv_dirty_iter_next_area(), because of the following problems of
bdrv_dirty_iter_next_area():
1. Using HBitmap iterators we should carefully handle unaligned offset,
as first call to hbitmap_iter_next() may return a value less than
original offset (actually, it will be original offset rounded down to
bitmap granularity). This handling is not done in
do_sync_target_write().
2. bdrv_dirty_iter_next_area() handles unaligned max_offset
incorrectly:
look at the code:
if (max_offset == iter->bitmap->size) {
/* If max_offset points to the image end, round it up by the
* bitmap granularity */
gran_max_offset = ROUND_UP(max_offset, granularity);
} else {
gran_max_offset = max_offset;
}
ret = hbitmap_iter_next(&iter->hbi, false);
if (ret < 0 || ret + granularity > gran_max_offset) {
return false;
}
and assume that max_offset != iter->bitmap->size but still unaligned.
if 0 < ret < max_offset we found dirty area, but the function can
return false in this case (if ret + granularity > max_offset).
3. bdrv_dirty_iter_next_area() uses inefficient loop to find the end of
the dirty area. Let's use more efficient hbitmap_next_zero instead
(bdrv_dirty_bitmap_next_dirty_area() do so)
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/mirror.c | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/block/mirror.c b/block/mirror.c index f0b211a..24ede6f 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -1185,25 +1185,23 @@ do_sync_target_write(MirrorBlockJob *job, MirrorMethod method, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) { - BdrvDirtyBitmapIter *iter; QEMUIOVector target_qiov; - uint64_t dirty_offset; - int dirty_bytes; + uint64_t dirty_offset = offset; + uint64_t dirty_bytes; if (qiov) { qemu_iovec_init(&target_qiov, qiov->niov); } - iter = bdrv_dirty_iter_new(job->dirty_bitmap); - bdrv_set_dirty_iter(iter, offset); - while (true) { bool valid_area; int ret; bdrv_dirty_bitmap_lock(job->dirty_bitmap); - valid_area = bdrv_dirty_iter_next_area(iter, offset + bytes, - &dirty_offset, &dirty_bytes); + dirty_bytes = MIN(offset + bytes - dirty_offset, INT_MAX); + valid_area = bdrv_dirty_bitmap_next_dirty_area(job->dirty_bitmap, + &dirty_offset, + &dirty_bytes); if (!valid_area) { bdrv_dirty_bitmap_unlock(job->dirty_bitmap); break; @@ -1259,9 +1257,10 @@ do_sync_target_write(MirrorBlockJob *job, MirrorMethod method, break; } } + + dirty_offset += dirty_bytes; } - bdrv_dirty_iter_free(iter); if (qiov) { qemu_iovec_destroy(&target_qiov); } |