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[Qemu-devel] [PULL 5/8] block/mirror: fix and improve do_sync_target_wri
From: |
John Snow |
Subject: |
[Qemu-devel] [PULL 5/8] block/mirror: fix and improve do_sync_target_write |
Date: |
Tue, 15 Jan 2019 20:01:03 -0500 |
From: Vladimir Sementsov-Ogievskiy <address@hidden>
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 <address@hidden>
Signed-off-by: John Snow <address@hidden>
---
block/mirror.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index f0b211a9c8..24ede6fdaa 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);
}
--
2.17.2
- [Qemu-devel] [PULL 0/8] Bitmaps patches, John Snow, 2019/01/15
- [Qemu-devel] [PULL 5/8] block/mirror: fix and improve do_sync_target_write,
John Snow <=
- [Qemu-devel] [PULL 1/8] dirty-bitmap: improve bdrv_dirty_bitmap_next_zero, John Snow, 2019/01/15
- [Qemu-devel] [PULL 2/8] tests: add tests for hbitmap_next_zero with specified end parameter, John Snow, 2019/01/15
- [Qemu-devel] [PULL 4/8] tests: add tests for hbitmap_next_dirty_area, John Snow, 2019/01/15
- [Qemu-devel] [PULL 6/8] Revert "block/dirty-bitmap: Add bdrv_dirty_iter_next_area", John Snow, 2019/01/15
- [Qemu-devel] [PULL 3/8] dirty-bitmap: add bdrv_dirty_bitmap_next_dirty_area, John Snow, 2019/01/15
- [Qemu-devel] [PULL 7/8] Revert "test-hbitmap: Add non-advancing iter_next tests", John Snow, 2019/01/15
- [Qemu-devel] [PULL 8/8] Revert "hbitmap: Add @advance param to hbitmap_iter_next()", John Snow, 2019/01/15
- Re: [Qemu-devel] [PULL 0/8] Bitmaps patches, Peter Maydell, 2019/01/17
- Re: [Qemu-devel] [PULL 0/8] Bitmaps patches, no-reply, 2019/01/21