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Re: [Qemu-devel] [PATCH v2 3/5] block: Allow NULL file for bdrv_get_bloc
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/5] block: Allow NULL file for bdrv_get_block_status() |
Date: |
Thu, 25 May 2017 14:34:44 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, 05/24 15:28, Eric Blake wrote:
> Not all callers care about which BDS owns the mapping for a given
> range of the file. This patch merely simplifies the callers by
> consolidating the logic in the common call point, while guaranteeing
> a non-NULL file to all the driver callbacks, for no semantic change.
>
> However, this will also set the stage for a future cleanup: when a
> caller does not care about which BDS owns an offset, it would be
> nice to allow the driver to optimize things to not have to return
> BDRV_BLOCK_OFFSET_VALID in the first place. In the case of fragmented
> allocation (for example, it's fairly easy to create a qcow2 image
> where consecutive guest addresses are not at consecutive host
> addresses), the current contract requires bdrv_get_block_status()
> to clamp *pnum to the limit where host addresses are no longer
> consecutive, but allowing a NULL file means that *pnum could be
> set to the full length of known-allocated data.
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v2: new patch
Yes. any particular reason why this patch is useful, besides simplifying
callers?
> ---
> block/io.c | 15 +++++++++------
> block/mirror.c | 3 +--
> block/qcow2.c | 4 +---
> qemu-img.c | 10 ++++------
> 4 files changed, 15 insertions(+), 17 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index 8e6c3fe..eea74cb 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -706,7 +706,6 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags
> flags)
> {
> int64_t target_sectors, ret, nb_sectors, sector_num = 0;
> BlockDriverState *bs = child->bs;
> - BlockDriverState *file;
> int n;
>
> target_sectors = bdrv_nb_sectors(bs);
> @@ -719,7 +718,7 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags
> flags)
> if (nb_sectors <= 0) {
> return 0;
> }
> - ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file);
> + ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, NULL);
> if (ret < 0) {
> error_report("error getting block status at sector %" PRId64 ":
> %s",
> sector_num, strerror(-ret));
> @@ -1737,8 +1736,9 @@ typedef struct BdrvCoGetBlockStatusData {
> * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
> * beyond the end of the disk image it will be clamped.
> *
> - * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set,
> 'file'
> - * points to the BDS which the sector range is allocated in.
> + * If returned value is positive, BDRV_BLOCK_OFFSET_VALID bit is set, and
> + * 'file' is non-NULL, then '*file' points to the BDS which the sector range
> + * is allocated in.
Sounds good.
> */
> static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
> int64_t sector_num,
> @@ -1748,7 +1748,11 @@ static int64_t coroutine_fn
> bdrv_co_get_block_status(BlockDriverState *bs,
> int64_t total_sectors;
> int64_t n;
> int64_t ret, ret2;
> + BlockDriverState *tmpfile;
>
> + if (!file) {
> + file = &tmpfile;
> + }
I don't like this hunk. Instead, how about replacing all "*file = ..." with
"tmpfile = ..." and add "if (file) { *file = tmpfile; }" before returning?
> *file = NULL;
> total_sectors = bdrv_nb_sectors(bs);
> if (total_sectors < 0) {
> @@ -1916,9 +1920,8 @@ int64_t bdrv_get_block_status(BlockDriverState *bs,
> int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors, int *pnum)
> {
> - BlockDriverState *file;
> int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum,
> - &file);
> + NULL);
> if (ret < 0) {
> return ret;
> }
> diff --git a/block/mirror.c b/block/mirror.c
> index e86f8f8..4563ba7 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -392,7 +392,6 @@ static uint64_t coroutine_fn
> mirror_iteration(MirrorBlockJob *s)
> while (nb_chunks > 0 && sector_num < end) {
> int64_t ret;
> int io_sectors, io_sectors_acct;
> - BlockDriverState *file;
> enum MirrorMethod {
> MIRROR_METHOD_COPY,
> MIRROR_METHOD_ZERO,
> @@ -402,7 +401,7 @@ static uint64_t coroutine_fn
> mirror_iteration(MirrorBlockJob *s)
> assert(!(sector_num % sectors_per_chunk));
> ret = bdrv_get_block_status_above(source, NULL, sector_num,
> nb_chunks * sectors_per_chunk,
> - &io_sectors, &file);
> + &io_sectors, NULL);
> if (ret < 0) {
> io_sectors = MIN(nb_chunks * sectors_per_chunk, max_io_sectors);
> } else if (ret & BDRV_BLOCK_DATA) {
> diff --git a/block/qcow2.c b/block/qcow2.c
> index b3ba5da..8e9e29b 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2448,7 +2448,6 @@ static bool is_zero_sectors(BlockDriverState *bs,
> int64_t start,
> uint32_t count)
> {
> int nr;
> - BlockDriverState *file;
> int64_t res;
>
> if (start + count > bs->total_sectors) {
> @@ -2458,8 +2457,7 @@ static bool is_zero_sectors(BlockDriverState *bs,
> int64_t start,
> if (!count) {
> return true;
> }
> - res = bdrv_get_block_status_above(bs, NULL, start, count,
> - &nr, &file);
> + res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL);
> return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count;
> }
>
> diff --git a/qemu-img.c b/qemu-img.c
> index 5aef8ef..cb78696 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1398,7 +1398,6 @@ static int img_compare(int argc, char **argv)
>
> for (;;) {
> int64_t status1, status2;
> - BlockDriverState *file;
>
> nb_sectors = sectors_to_process(total_sectors, sector_num);
> if (nb_sectors <= 0) {
> @@ -1406,7 +1405,7 @@ static int img_compare(int argc, char **argv)
> }
> status1 = bdrv_get_block_status_above(bs1, NULL, sector_num,
> total_sectors1 - sector_num,
> - &pnum1, &file);
> + &pnum1, NULL);
> if (status1 < 0) {
> ret = 3;
> error_report("Sector allocation test failed for %s", filename1);
> @@ -1416,7 +1415,7 @@ static int img_compare(int argc, char **argv)
>
> status2 = bdrv_get_block_status_above(bs2, NULL, sector_num,
> total_sectors2 - sector_num,
> - &pnum2, &file);
> + &pnum2, NULL);
> if (status2 < 0) {
> ret = 3;
> error_report("Sector allocation test failed for %s", filename2);
> @@ -1615,15 +1614,14 @@ static int convert_iteration_sectors(ImgConvertState
> *s, int64_t sector_num)
> n = MIN(s->total_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
>
> if (s->sector_next_status <= sector_num) {
> - BlockDriverState *file;
> if (s->target_has_backing) {
> ret = bdrv_get_block_status(blk_bs(s->src[src_cur]),
> sector_num - src_cur_offset,
> - n, &n, &file);
> + n, &n, NULL);
> } else {
> ret = bdrv_get_block_status_above(blk_bs(s->src[src_cur]), NULL,
> sector_num - src_cur_offset,
> - n, &n, &file);
> + n, &n, NULL);
> }
> if (ret < 0) {
> return ret;
> --
> 2.9.4
>
Otherwise looks good.
Fam
- Re: [Qemu-devel] [PATCH v2 1/5] qemu-io: Don't die on second open, (continued)
- [Qemu-devel] [PATCH v2 2/5] block: Guarantee that *file is set on bdrv_get_block_status(), Eric Blake, 2017/05/24
- [Qemu-devel] [PATCH v2 4/5] block: Simplify use of BDRV_BLOCK_RAW, Eric Blake, 2017/05/24
- [Qemu-devel] [PATCH v2 3/5] block: Allow NULL file for bdrv_get_block_status(), Eric Blake, 2017/05/24
- Re: [Qemu-devel] [PATCH v2 3/5] block: Allow NULL file for bdrv_get_block_status(),
Fam Zheng <=
- [Qemu-devel] [PATCH v2 5/5] blkdebug: Support .bdrv_co_get_block_status, Eric Blake, 2017/05/24
- Re: [Qemu-devel] [PATCH v2 0/5] more blkdebug tweaks, Fam Zheng, 2017/05/25