* Re: [PATCH 1/1] prealloc: add truncate mode for prealloc filter
2024-04-30 17:05 [PATCH 1/1] prealloc: add truncate mode for prealloc filter Denis V. Lunev via
@ 2024-05-17 16:37 ` Denis V. Lunev
2024-05-28 14:30 ` Denis V. Lunev
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Denis V. Lunev @ 2024-05-17 16:37 UTC (permalink / raw)
To: Denis V. Lunev, qemu-block, qemu-devel
Cc: Alexander Ivanov, Kevin Wolf, Hanna Reitz,
Vladimir Sementsov-Ogievskiy
On 4/30/24 19:05, Denis V. Lunev wrote:
> Preallocate filter allows to implement really interesting setups.
>
> Assume that we have
> * shared block device, f.e. iSCSI LUN, implemented with some HW device
> * clustered LVM on top of it
> * QCOW2 image stored inside LVM volume
>
> This allows very cheap clustered setups with all QCOW2 features intact.
> Currently supported setups using QCOW2 with data_file option are not
> so cool as snapshots are not allowed, QCOW2 should be placed into some
> additional distributed storage and so on.
>
> Though QCOW2 inside LVM volume has a drawback. The image is growing and
> in order to accomodate that image LVM volume is to be resized. This
> could be done externally using ENOSPACE event/condition but this is
> cumbersome.
>
> This patch introduces native implementation for such a setup. We should
> just put prealloc filter in between QCOW2 format and file nodes. In that
> case LVM will be resized at proper moment and that is done effectively
> as resizing is done in chinks.
>
> The patch adds allocation mode for this purpose in order to distinguish
> 'fallocate' for ordinary file system and 'truncate'.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
> block/preallocate.c | 50 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/block/preallocate.c b/block/preallocate.c
> index 4d82125036..6d31627325 100644
> --- a/block/preallocate.c
> +++ b/block/preallocate.c
> @@ -33,10 +33,24 @@
> #include "block/block-io.h"
> #include "block/block_int.h"
>
> +typedef enum PreallocateMode {
> + PREALLOCATE_MODE_FALLOCATE = 0,
> + PREALLOCATE_MODE_TRUNCATE = 1,
> + PREALLOCATE_MODE__MAX = 2,
> +} PreallocateMode;
> +
> +static QEnumLookup prealloc_mode_lookup = {
> + .array = (const char *const[]) {
> + "falloc",
> + "truncate",
> + },
> + .size = PREALLOCATE_MODE__MAX,
> +};
>
> typedef struct PreallocateOpts {
> int64_t prealloc_size;
> int64_t prealloc_align;
> + PreallocateMode prealloc_mode;
> } PreallocateOpts;
>
> typedef struct BDRVPreallocateState {
> @@ -79,6 +93,7 @@ typedef struct BDRVPreallocateState {
>
> #define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
> #define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
> +#define PREALLOCATE_OPT_MODE "mode"
> static QemuOptsList runtime_opts = {
> .name = "preallocate",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -94,7 +109,14 @@ static QemuOptsList runtime_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "how much to preallocate, default 128M",
> },
> - { /* end of list */ }
> + {
> + .name = PREALLOCATE_OPT_MODE,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode on image expansion "
> + "(allowed values: falloc, truncate)",
> + .def_value_str = "falloc",
> + },
> + { /* end of list */ },
> },
> };
>
> @@ -102,6 +124,8 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> BlockDriverState *child_bs, Error **errp)
> {
> QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> + Error *local_err = NULL;
> + char *buf;
>
> if (!qemu_opts_absorb_qdict(opts, options, errp)) {
> return false;
> @@ -112,6 +136,17 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> dest->prealloc_size =
> qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
>
> + buf = qemu_opt_get_del(opts, PREALLOCATE_OPT_MODE);
> + /* prealloc_mode can be downgraded later during allocate_clusters */
> + dest->prealloc_mode = qapi_enum_parse(&prealloc_mode_lookup, buf,
> + PREALLOCATE_MODE_FALLOCATE,
> + &local_err);
> + g_free(buf);
> + if (local_err != NULL) {
> + error_propagate(errp, local_err);
> + return false;
> + }
> +
> qemu_opts_del(opts);
>
> if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
> @@ -335,9 +370,20 @@ handle_write(BlockDriverState *bs, int64_t offset, int64_t bytes,
>
> want_merge_zero = want_merge_zero && (prealloc_start <= offset);
>
> - ret = bdrv_co_pwrite_zeroes(
> + switch (s->opts.prealloc_mode) {
> + case PREALLOCATE_MODE_FALLOCATE:
> + ret = bdrv_co_pwrite_zeroes(
> bs->file, prealloc_start, prealloc_end - prealloc_start,
> BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
> + break;
> + case PREALLOCATE_MODE_TRUNCATE:
> + ret = bdrv_co_truncate(bs->file, prealloc_end, false,
> + PREALLOC_MODE_OFF, 0, NULL);
> + break;
> + default:
> + return false;
> + }
> +
> if (ret < 0) {
> s->file_end = ret;
> return false;
ping
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] prealloc: add truncate mode for prealloc filter
2024-04-30 17:05 [PATCH 1/1] prealloc: add truncate mode for prealloc filter Denis V. Lunev via
2024-05-17 16:37 ` Denis V. Lunev
@ 2024-05-28 14:30 ` Denis V. Lunev
2024-05-29 2:33 ` Wang, Lei
2024-06-25 16:09 ` Vladimir Sementsov-Ogievskiy
3 siblings, 0 replies; 6+ messages in thread
From: Denis V. Lunev @ 2024-05-28 14:30 UTC (permalink / raw)
To: Denis V. Lunev, qemu-block, qemu-devel
Cc: Alexander Ivanov, Kevin Wolf, Hanna Reitz,
Vladimir Sementsov-Ogievskiy
On 4/30/24 19:05, Denis V. Lunev wrote:
> Preallocate filter allows to implement really interesting setups.
>
> Assume that we have
> * shared block device, f.e. iSCSI LUN, implemented with some HW device
> * clustered LVM on top of it
> * QCOW2 image stored inside LVM volume
>
> This allows very cheap clustered setups with all QCOW2 features intact.
> Currently supported setups using QCOW2 with data_file option are not
> so cool as snapshots are not allowed, QCOW2 should be placed into some
> additional distributed storage and so on.
>
> Though QCOW2 inside LVM volume has a drawback. The image is growing and
> in order to accomodate that image LVM volume is to be resized. This
> could be done externally using ENOSPACE event/condition but this is
> cumbersome.
>
> This patch introduces native implementation for such a setup. We should
> just put prealloc filter in between QCOW2 format and file nodes. In that
> case LVM will be resized at proper moment and that is done effectively
> as resizing is done in chinks.
>
> The patch adds allocation mode for this purpose in order to distinguish
> 'fallocate' for ordinary file system and 'truncate'.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
> block/preallocate.c | 50 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/block/preallocate.c b/block/preallocate.c
> index 4d82125036..6d31627325 100644
> --- a/block/preallocate.c
> +++ b/block/preallocate.c
> @@ -33,10 +33,24 @@
> #include "block/block-io.h"
> #include "block/block_int.h"
>
> +typedef enum PreallocateMode {
> + PREALLOCATE_MODE_FALLOCATE = 0,
> + PREALLOCATE_MODE_TRUNCATE = 1,
> + PREALLOCATE_MODE__MAX = 2,
> +} PreallocateMode;
> +
> +static QEnumLookup prealloc_mode_lookup = {
> + .array = (const char *const[]) {
> + "falloc",
> + "truncate",
> + },
> + .size = PREALLOCATE_MODE__MAX,
> +};
>
> typedef struct PreallocateOpts {
> int64_t prealloc_size;
> int64_t prealloc_align;
> + PreallocateMode prealloc_mode;
> } PreallocateOpts;
>
> typedef struct BDRVPreallocateState {
> @@ -79,6 +93,7 @@ typedef struct BDRVPreallocateState {
>
> #define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
> #define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
> +#define PREALLOCATE_OPT_MODE "mode"
> static QemuOptsList runtime_opts = {
> .name = "preallocate",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -94,7 +109,14 @@ static QemuOptsList runtime_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "how much to preallocate, default 128M",
> },
> - { /* end of list */ }
> + {
> + .name = PREALLOCATE_OPT_MODE,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode on image expansion "
> + "(allowed values: falloc, truncate)",
> + .def_value_str = "falloc",
> + },
> + { /* end of list */ },
> },
> };
>
> @@ -102,6 +124,8 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> BlockDriverState *child_bs, Error **errp)
> {
> QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> + Error *local_err = NULL;
> + char *buf;
>
> if (!qemu_opts_absorb_qdict(opts, options, errp)) {
> return false;
> @@ -112,6 +136,17 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> dest->prealloc_size =
> qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
>
> + buf = qemu_opt_get_del(opts, PREALLOCATE_OPT_MODE);
> + /* prealloc_mode can be downgraded later during allocate_clusters */
> + dest->prealloc_mode = qapi_enum_parse(&prealloc_mode_lookup, buf,
> + PREALLOCATE_MODE_FALLOCATE,
> + &local_err);
> + g_free(buf);
> + if (local_err != NULL) {
> + error_propagate(errp, local_err);
> + return false;
> + }
> +
> qemu_opts_del(opts);
>
> if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
> @@ -335,9 +370,20 @@ handle_write(BlockDriverState *bs, int64_t offset, int64_t bytes,
>
> want_merge_zero = want_merge_zero && (prealloc_start <= offset);
>
> - ret = bdrv_co_pwrite_zeroes(
> + switch (s->opts.prealloc_mode) {
> + case PREALLOCATE_MODE_FALLOCATE:
> + ret = bdrv_co_pwrite_zeroes(
> bs->file, prealloc_start, prealloc_end - prealloc_start,
> BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
> + break;
> + case PREALLOCATE_MODE_TRUNCATE:
> + ret = bdrv_co_truncate(bs->file, prealloc_end, false,
> + PREALLOC_MODE_OFF, 0, NULL);
> + break;
> + default:
> + return false;
> + }
> +
> if (ret < 0) {
> s->file_end = ret;
> return false;
ping v2
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] prealloc: add truncate mode for prealloc filter
2024-04-30 17:05 [PATCH 1/1] prealloc: add truncate mode for prealloc filter Denis V. Lunev via
2024-05-17 16:37 ` Denis V. Lunev
2024-05-28 14:30 ` Denis V. Lunev
@ 2024-05-29 2:33 ` Wang, Lei
2024-05-29 8:34 ` Denis V. Lunev
2024-06-25 16:09 ` Vladimir Sementsov-Ogievskiy
3 siblings, 1 reply; 6+ messages in thread
From: Wang, Lei @ 2024-05-29 2:33 UTC (permalink / raw)
To: Denis V. Lunev, qemu-block, qemu-devel
Cc: Alexander Ivanov, Kevin Wolf, Hanna Reitz,
Vladimir Sementsov-Ogievskiy
On 5/1/2024 1:05, Denis V. Lunev via wrote:
> Preallocate filter allows to implement really interesting setups.
>
> Assume that we have
> * shared block device, f.e. iSCSI LUN, implemented with some HW device
> * clustered LVM on top of it
> * QCOW2 image stored inside LVM volume
>
> This allows very cheap clustered setups with all QCOW2 features intact.
> Currently supported setups using QCOW2 with data_file option are not
> so cool as snapshots are not allowed, QCOW2 should be placed into some
> additional distributed storage and so on.
>
> Though QCOW2 inside LVM volume has a drawback. The image is growing and
> in order to accomodate that image LVM volume is to be resized. This
> could be done externally using ENOSPACE event/condition but this is
> cumbersome.
>
> This patch introduces native implementation for such a setup. We should
> just put prealloc filter in between QCOW2 format and file nodes. In that
> case LVM will be resized at proper moment and that is done effectively
> as resizing is done in chinks.
>
> The patch adds allocation mode for this purpose in order to distinguish
> 'fallocate' for ordinary file system and 'truncate'.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
> block/preallocate.c | 50 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/block/preallocate.c b/block/preallocate.c
> index 4d82125036..6d31627325 100644
> --- a/block/preallocate.c
> +++ b/block/preallocate.c
> @@ -33,10 +33,24 @@
> #include "block/block-io.h"
> #include "block/block_int.h"
>
> +typedef enum PreallocateMode {
> + PREALLOCATE_MODE_FALLOCATE = 0,
> + PREALLOCATE_MODE_TRUNCATE = 1,
> + PREALLOCATE_MODE__MAX = 2,
> +} PreallocateMode;
> +
> +static QEnumLookup prealloc_mode_lookup = {
> + .array = (const char *const[]) {
> + "falloc",
> + "truncate",
> + },
> + .size = PREALLOCATE_MODE__MAX,
> +};
>
> typedef struct PreallocateOpts {
> int64_t prealloc_size;
> int64_t prealloc_align;
> + PreallocateMode prealloc_mode;
> } PreallocateOpts;
>
> typedef struct BDRVPreallocateState {
> @@ -79,6 +93,7 @@ typedef struct BDRVPreallocateState {
>
> #define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
> #define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
> +#define PREALLOCATE_OPT_MODE "mode"
Why not keeping the names consistent, I mean:
#define PREALLOCATE_OPT_PREALLOC_MODE "prealloc-mode"
> static QemuOptsList runtime_opts = {
> .name = "preallocate",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -94,7 +109,14 @@ static QemuOptsList runtime_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "how much to preallocate, default 128M",
> },
> - { /* end of list */ }
> + {
> + .name = PREALLOCATE_OPT_MODE,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode on image expansion "
> + "(allowed values: falloc, truncate)",
> + .def_value_str = "falloc",
> + },
> + { /* end of list */ },
> },
> };
>
> @@ -102,6 +124,8 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> BlockDriverState *child_bs, Error **errp)
> {
> QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> + Error *local_err = NULL;
> + char *buf;
>
> if (!qemu_opts_absorb_qdict(opts, options, errp)) {
> return false;
> @@ -112,6 +136,17 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> dest->prealloc_size =
> qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
>
> + buf = qemu_opt_get_del(opts, PREALLOCATE_OPT_MODE);
> + /* prealloc_mode can be downgraded later during allocate_clusters */
> + dest->prealloc_mode = qapi_enum_parse(&prealloc_mode_lookup, buf,
> + PREALLOCATE_MODE_FALLOCATE,
> + &local_err);
> + g_free(buf);
> + if (local_err != NULL) {
> + error_propagate(errp, local_err);
> + return false;
> + }
> +
> qemu_opts_del(opts);
>
> if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
> @@ -335,9 +370,20 @@ handle_write(BlockDriverState *bs, int64_t offset, int64_t bytes,
>
> want_merge_zero = want_merge_zero && (prealloc_start <= offset);
>
> - ret = bdrv_co_pwrite_zeroes(
> + switch (s->opts.prealloc_mode) {
> + case PREALLOCATE_MODE_FALLOCATE:
> + ret = bdrv_co_pwrite_zeroes(
> bs->file, prealloc_start, prealloc_end - prealloc_start,
> BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
> + break;
> + case PREALLOCATE_MODE_TRUNCATE:
> + ret = bdrv_co_truncate(bs->file, prealloc_end, false,
> + PREALLOC_MODE_OFF, 0, NULL);
> + break;
> + default:
> + return false;
> + }
> +
> if (ret < 0) {
> s->file_end = ret;
> return false;
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/1] prealloc: add truncate mode for prealloc filter
2024-05-29 2:33 ` Wang, Lei
@ 2024-05-29 8:34 ` Denis V. Lunev
0 siblings, 0 replies; 6+ messages in thread
From: Denis V. Lunev @ 2024-05-29 8:34 UTC (permalink / raw)
To: Wang, Lei, Denis V. Lunev, qemu-block, qemu-devel
Cc: Alexander Ivanov, Kevin Wolf, Hanna Reitz,
Vladimir Sementsov-Ogievskiy
On 5/29/24 04:33, Wang, Lei wrote:
> On 5/1/2024 1:05, Denis V. Lunev via wrote:
>> Preallocate filter allows to implement really interesting setups.
>>
>> Assume that we have
>> * shared block device, f.e. iSCSI LUN, implemented with some HW device
>> * clustered LVM on top of it
>> * QCOW2 image stored inside LVM volume
>>
>> This allows very cheap clustered setups with all QCOW2 features intact.
>> Currently supported setups using QCOW2 with data_file option are not
>> so cool as snapshots are not allowed, QCOW2 should be placed into some
>> additional distributed storage and so on.
>>
>> Though QCOW2 inside LVM volume has a drawback. The image is growing and
>> in order to accomodate that image LVM volume is to be resized. This
>> could be done externally using ENOSPACE event/condition but this is
>> cumbersome.
>>
>> This patch introduces native implementation for such a setup. We should
>> just put prealloc filter in between QCOW2 format and file nodes. In that
>> case LVM will be resized at proper moment and that is done effectively
>> as resizing is done in chinks.
>>
>> The patch adds allocation mode for this purpose in order to distinguish
>> 'fallocate' for ordinary file system and 'truncate'.
>>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
>> CC: Kevin Wolf <kwolf@redhat.com>
>> CC: Hanna Reitz <hreitz@redhat.com>
>> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>> ---
>> block/preallocate.c | 50 +++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 48 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/preallocate.c b/block/preallocate.c
>> index 4d82125036..6d31627325 100644
>> --- a/block/preallocate.c
>> +++ b/block/preallocate.c
>> @@ -33,10 +33,24 @@
>> #include "block/block-io.h"
>> #include "block/block_int.h"
>>
>> +typedef enum PreallocateMode {
>> + PREALLOCATE_MODE_FALLOCATE = 0,
>> + PREALLOCATE_MODE_TRUNCATE = 1,
>> + PREALLOCATE_MODE__MAX = 2,
>> +} PreallocateMode;
>> +
>> +static QEnumLookup prealloc_mode_lookup = {
>> + .array = (const char *const[]) {
>> + "falloc",
>> + "truncate",
>> + },
>> + .size = PREALLOCATE_MODE__MAX,
>> +};
>>
>> typedef struct PreallocateOpts {
>> int64_t prealloc_size;
>> int64_t prealloc_align;
>> + PreallocateMode prealloc_mode;
>> } PreallocateOpts;
>>
>> typedef struct BDRVPreallocateState {
>> @@ -79,6 +93,7 @@ typedef struct BDRVPreallocateState {
>>
>> #define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
>> #define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
>> +#define PREALLOCATE_OPT_MODE "mode"
> Why not keeping the names consistent, I mean:
>
> #define PREALLOCATE_OPT_PREALLOC_MODE "prealloc-mode"
>
I have had some thoughts on that, like prealloc-mode
name is already used on the generic level, but obviously
I have mistaken.
Sure thing, I'll rename to "prealloc-mode" and in the
same way in the macro on next submission.
Thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/1] prealloc: add truncate mode for prealloc filter
2024-04-30 17:05 [PATCH 1/1] prealloc: add truncate mode for prealloc filter Denis V. Lunev via
` (2 preceding siblings ...)
2024-05-29 2:33 ` Wang, Lei
@ 2024-06-25 16:09 ` Vladimir Sementsov-Ogievskiy
3 siblings, 0 replies; 6+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2024-06-25 16:09 UTC (permalink / raw)
To: Denis V. Lunev, qemu-block, qemu-devel
Cc: Alexander Ivanov, Kevin Wolf, Hanna Reitz
On 30.04.24 20:05, Denis V. Lunev via wrote:
> Preallocate filter allows to implement really interesting setups.
>
> Assume that we have
> * shared block device, f.e. iSCSI LUN, implemented with some HW device
> * clustered LVM on top of it
> * QCOW2 image stored inside LVM volume
>
> This allows very cheap clustered setups with all QCOW2 features intact.
> Currently supported setups using QCOW2 with data_file option are not
> so cool as snapshots are not allowed, QCOW2 should be placed into some
> additional distributed storage and so on.
>
> Though QCOW2 inside LVM volume has a drawback. The image is growing and
> in order to accomodate that image LVM volume is to be resized. This
> could be done externally using ENOSPACE event/condition but this is
> cumbersome.
>
> This patch introduces native implementation for such a setup. We should
> just put prealloc filter in between QCOW2 format and file nodes. In that
> case LVM will be resized at proper moment and that is done effectively
> as resizing is done in chinks.
>
> The patch adds allocation mode for this purpose in order to distinguish
> 'fallocate' for ordinary file system and 'truncate'.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
> block/preallocate.c | 50 +++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/block/preallocate.c b/block/preallocate.c
> index 4d82125036..6d31627325 100644
> --- a/block/preallocate.c
> +++ b/block/preallocate.c
> @@ -33,10 +33,24 @@
> #include "block/block-io.h"
> #include "block/block_int.h"
>
> +typedef enum PreallocateMode {
> + PREALLOCATE_MODE_FALLOCATE = 0,
> + PREALLOCATE_MODE_TRUNCATE = 1,
> + PREALLOCATE_MODE__MAX = 2,
> +} PreallocateMode;
> +
> +static QEnumLookup prealloc_mode_lookup = {
> + .array = (const char *const[]) {
> + "falloc",
> + "truncate",
> + },
> + .size = PREALLOCATE_MODE__MAX,
> +};
I think instead we should update BlockdevOptionsPreallocate options in qapi/block-core.json. Then corresponding enum would be generated.
Example of parsing options, reusing qapi mechanics is in block/copy-before-write.c - cbw_parse_options(). on-cbw-error field is enum.
>
> typedef struct PreallocateOpts {
> int64_t prealloc_size;
> int64_t prealloc_align;
> + PreallocateMode prealloc_mode;
> } PreallocateOpts;
>
> typedef struct BDRVPreallocateState {
> @@ -79,6 +93,7 @@ typedef struct BDRVPreallocateState {
>
> #define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
> #define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
> +#define PREALLOCATE_OPT_MODE "mode"
> static QemuOptsList runtime_opts = {
> .name = "preallocate",
> .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> @@ -94,7 +109,14 @@ static QemuOptsList runtime_opts = {
> .type = QEMU_OPT_SIZE,
> .help = "how much to preallocate, default 128M",
> },
> - { /* end of list */ }
> + {
> + .name = PREALLOCATE_OPT_MODE,
> + .type = QEMU_OPT_STRING,
> + .help = "Preallocation mode on image expansion "
> + "(allowed values: falloc, truncate)",
> + .def_value_str = "falloc",
> + },
> + { /* end of list */ },
> },
> };
>
> @@ -102,6 +124,8 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> BlockDriverState *child_bs, Error **errp)
> {
> QemuOpts *opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> + Error *local_err = NULL;
> + char *buf;
>
> if (!qemu_opts_absorb_qdict(opts, options, errp)) {
> return false;
> @@ -112,6 +136,17 @@ static bool preallocate_absorb_opts(PreallocateOpts *dest, QDict *options,
> dest->prealloc_size =
> qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
>
> + buf = qemu_opt_get_del(opts, PREALLOCATE_OPT_MODE);
> + /* prealloc_mode can be downgraded later during allocate_clusters */
> + dest->prealloc_mode = qapi_enum_parse(&prealloc_mode_lookup, buf,
> + PREALLOCATE_MODE_FALLOCATE,
> + &local_err);
> + g_free(buf);
> + if (local_err != NULL) {
> + error_propagate(errp, local_err);
> + return false;
> + }
> +
> qemu_opts_del(opts);
>
> if (!QEMU_IS_ALIGNED(dest->prealloc_align, BDRV_SECTOR_SIZE)) {
> @@ -335,9 +370,20 @@ handle_write(BlockDriverState *bs, int64_t offset, int64_t bytes,
>
> want_merge_zero = want_merge_zero && (prealloc_start <= offset);
>
> - ret = bdrv_co_pwrite_zeroes(
> + switch (s->opts.prealloc_mode) {
> + case PREALLOCATE_MODE_FALLOCATE:
> + ret = bdrv_co_pwrite_zeroes(
> bs->file, prealloc_start, prealloc_end - prealloc_start,
> BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
> + break;
> + case PREALLOCATE_MODE_TRUNCATE:
> + ret = bdrv_co_truncate(bs->file, prealloc_end, false,
> + PREALLOC_MODE_OFF, 0, NULL);
> + break;
> + default:
> + return false;
> + }
> +
> if (ret < 0) {
> s->file_end = ret;
> return false;
--
Best regards,
Vladimir
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