diff options
| author | Denis V. Lunev <den@openvz.org> | 2016-05-25 21:48:45 -0600 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2016-06-08 10:21:08 +0200 |
| commit | 443668ca408cdb7f01e1a70a58518bb100c3e9d1 (patch) | |
| tree | 668a5dad129a866dcba61c066a193f42e5bdabd9 /block | |
| parent | 6ed5546fa7bf12c5b87ef76bafb86e1d77ed6e85 (diff) | |
block: split write_zeroes always
We should split requests even if they are less than write_zeroes_alignment.
For example we can have the following request:
offset 62k
size 4k
write_zeroes_alignment 64k
The original code sent 1 request covering 2 qcow2 clusters, and resulted
in both clusters being allocated. But by splitting the request, we can
cater to the case where one of the two clusters can be zeroed as a
whole, for only 1 cluster allocated after the operation.
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Message-Id: <1463476543-3087-2-git-send-email-den@openvz.org>
[eblake: Avoid exceeding nb_sectors, hoist alignment checks out of
loop, and update testsuite to show that patch works]
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/io.c | 30 |
1 files changed, 17 insertions, 13 deletions
diff --git a/block/io.c b/block/io.c index 6070e773b7..c73be55f86 100644 --- a/block/io.c +++ b/block/io.c @@ -1118,28 +1118,32 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, struct iovec iov = {0}; int ret = 0; bool need_flush = false; + int head = 0; + int tail = 0; int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_write_zeroes, BDRV_REQUEST_MAX_SECTORS); + if (bs->bl.write_zeroes_alignment) { + assert(is_power_of_2(bs->bl.write_zeroes_alignment)); + head = sector_num & (bs->bl.write_zeroes_alignment - 1); + tail = (sector_num + nb_sectors) & (bs->bl.write_zeroes_alignment - 1); + max_write_zeroes &= ~(bs->bl.write_zeroes_alignment - 1); + } while (nb_sectors > 0 && !ret) { int num = nb_sectors; /* Align request. Block drivers can expect the "bulk" of the request - * to be aligned. + * to be aligned, and that unaligned requests do not cross cluster + * boundaries. */ - if (bs->bl.write_zeroes_alignment - && num > bs->bl.write_zeroes_alignment) { - if (sector_num % bs->bl.write_zeroes_alignment != 0) { - /* Make a small request up to the first aligned sector. */ - num = bs->bl.write_zeroes_alignment; - num -= sector_num % bs->bl.write_zeroes_alignment; - } else if ((sector_num + num) % bs->bl.write_zeroes_alignment != 0) { - /* Shorten the request to the last aligned sector. num cannot - * underflow because num > bs->bl.write_zeroes_alignment. - */ - num -= (sector_num + num) % bs->bl.write_zeroes_alignment; - } + if (head) { + /* Make a small request up to the first aligned sector. */ + num = MIN(nb_sectors, bs->bl.write_zeroes_alignment - head); + head = 0; + } else if (tail && num > bs->bl.write_zeroes_alignment) { + /* Shorten the request to the last aligned sector. */ + num -= tail; } /* limit request size */ |