| Message ID | 1380029714-5239-9-git-send-email-pl@kamp.de |
|---|---|
| State | New |
| Headers | show |
On 09/24/2013 07:35 AM, Peter Lieven wrote: > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > block.c | 37 ++++++++++++++++++++++++++++++++++++- > 1 file changed, 36 insertions(+), 1 deletion(-) > Reviewed-by: Eric Blake <eblake@redhat.com>
On Tue, Sep 24, 2013 at 03:35:02PM +0200, Peter Lieven wrote: > @@ -4245,7 +4250,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, > } > > if (bs->drv->bdrv_co_discard) { > - return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors); > + int max_discard = bs->bl.max_discard ? > + bs->bl.max_discard : MAX_DISCARD_DEFAULT; > + > + while (nb_sectors > 0) { > + int ret; > + int num = nb_sectors; > + > + /* align request */ > + if (bs->bl.discard_alignment && > + num >= bs->bl.discard_alignment && > + sector_num % bs->bl.discard_alignment) { > + if (num > bs->bl.discard_alignment) { > + num = bs->bl.discard_alignment; > + } > + num -= sector_num % bs->bl.discard_alignment; > + } Is it always possible to discard at arbitrary sector offsets?
Am 07.10.2013 um 10:29 schrieb Stefan Hajnoczi <stefanha@gmail.com>: > On Tue, Sep 24, 2013 at 03:35:02PM +0200, Peter Lieven wrote: >> @@ -4245,7 +4250,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, >> } >> >> if (bs->drv->bdrv_co_discard) { >> - return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors); >> + int max_discard = bs->bl.max_discard ? >> + bs->bl.max_discard : MAX_DISCARD_DEFAULT; >> + >> + while (nb_sectors > 0) { >> + int ret; >> + int num = nb_sectors; >> + >> + /* align request */ >> + if (bs->bl.discard_alignment && >> + num >= bs->bl.discard_alignment && >> + sector_num % bs->bl.discard_alignment) { >> + if (num > bs->bl.discard_alignment) { >> + num = bs->bl.discard_alignment; >> + } >> + num -= sector_num % bs->bl.discard_alignment; >> + } > > Is it always possible to discard at arbitrary sector offsets? It should be. This just makes sure that the unaligned part of a request gets executed first (eventually resulting in an -ENOTSUP) and consecutive calls are aligned. For example. The alignment is 1MB (2048 sectors) and max_discard its 2048 sectors as well.. Lets say you want to discard 4096 sectors starting at offset 1024. Then there will be 3 calls 1) discard at 1024, len 1024 2) discard at 2048, len 2048 3) discard at 4096, len 1024. Peter
diff --git a/block.c b/block.c index 580570a..784e545 100644 --- a/block.c +++ b/block.c @@ -4224,6 +4224,11 @@ static void coroutine_fn bdrv_discard_co_entry(void *opaque) rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num, rwco->nb_sectors); } +/* if no limit is specified in the BlockLimits use a default + * of 32768 512-byte sectors (16 MiB) per request. + */ +#define MAX_DISCARD_DEFAULT 32768 + int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors) { @@ -4245,7 +4250,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, } if (bs->drv->bdrv_co_discard) { - return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors); + int max_discard = bs->bl.max_discard ? + bs->bl.max_discard : MAX_DISCARD_DEFAULT; + + while (nb_sectors > 0) { + int ret; + int num = nb_sectors; + + /* align request */ + if (bs->bl.discard_alignment && + num >= bs->bl.discard_alignment && + sector_num % bs->bl.discard_alignment) { + if (num > bs->bl.discard_alignment) { + num = bs->bl.discard_alignment; + } + num -= sector_num % bs->bl.discard_alignment; + } + + /* limit request size */ + if (num > max_discard) { + num = max_discard; + } + + ret = bs->drv->bdrv_co_discard(bs, sector_num, num); + if (ret) { + return ret; + } + + sector_num += num; + nb_sectors -= num; + } + return 0; } else if (bs->drv->bdrv_aio_discard) { BlockDriverAIOCB *acb; CoroutineIOCompletion co = {
Signed-off-by: Peter Lieven <pl@kamp.de> --- block.c | 37 ++++++++++++++++++++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-)