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[Qemu-devel] [PATCH 2/5] qcow2: simplify logic in qcow2_co_write_zeroes
From: |
Denis V. Lunev |
Subject: |
[Qemu-devel] [PATCH 2/5] qcow2: simplify logic in qcow2_co_write_zeroes |
Date: |
Tue, 17 May 2016 12:15:40 +0300 |
Unaligned requests will occupy only one cluster. This is true since the
previous commit. Simplify the code taking this consideration into
account.
In other words, the caller is now buggy if it ever passes us an unaligned
request that crosses cluster boundaries (the only requests that can cross
boundaries will be aligned).
There are no other changes so far.
Signed-off-by: Denis V. Lunev <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
CC: Eric Blake <address@hidden>
CC: Kevin Wolf <address@hidden>
---
block/qcow2.c | 23 +++++------------------
1 file changed, 5 insertions(+), 18 deletions(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index 62febfc..9a54bbd 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2436,33 +2436,20 @@ static coroutine_fn int
qcow2_co_write_zeroes(BlockDriverState *bs,
int tail = (sector_num + nb_sectors) % s->cluster_sectors;
if (head != 0 || tail != 0) {
- int64_t cl_end = -1;
+ int64_t cl_start = sector_num - head;
- sector_num -= head;
- nb_sectors += head;
+ assert(cl_start + s->cluster_sectors >= sector_num + nb_sectors);
- if (tail != 0) {
- nb_sectors += s->cluster_sectors - tail;
- }
+ sector_num = cl_start;
+ nb_sectors = s->cluster_sectors;
if (!is_zero_cluster(bs, sector_num)) {
return -ENOTSUP;
}
- if (nb_sectors > s->cluster_sectors) {
- /* Technically the request can cover 2 clusters, f.e. 4k write
- at s->cluster_sectors - 2k offset. One of these cluster can
- be zeroed, one unallocated */
- cl_end = sector_num + nb_sectors - s->cluster_sectors;
- if (!is_zero_cluster(bs, cl_end)) {
- return -ENOTSUP;
- }
- }
-
qemu_co_mutex_lock(&s->lock);
/* We can have new write after previous check */
- if (!is_zero_cluster_top_locked(bs, sector_num) ||
- (cl_end > 0 && !is_zero_cluster_top_locked(bs, cl_end))) {
+ if (!is_zero_cluster_top_locked(bs, sector_num)) {
qemu_co_mutex_unlock(&s->lock);
return -ENOTSUP;
}
--
2.1.4
- [Qemu-devel] [PATCH v2 0/5] qcow2_co_write_zeroes and related improvements, Denis V. Lunev, 2016/05/17
- [Qemu-devel] [PATCH 4/5] qcow2: fix condition in is_zero_cluster, Denis V. Lunev, 2016/05/17
- [Qemu-devel] [PATCH 5/5] qcow2: merge is_zero_cluster helpers into qcow2_co_write_zeroes, Denis V. Lunev, 2016/05/17
- [Qemu-devel] [PATCH 2/5] qcow2: simplify logic in qcow2_co_write_zeroes,
Denis V. Lunev <=
- [Qemu-devel] [PATCH 3/5] qcow2: add tracepoints for qcow2_co_write_zeroes, Denis V. Lunev, 2016/05/17
- [Qemu-devel] [PATCH 1/5] block: split write_zeroes always, Denis V. Lunev, 2016/05/17
- Re: [Qemu-devel] [PATCH v2 0/5] qcow2_co_write_zeroes and related improvements, Kevin Wolf, 2016/05/17