| Message ID | 1501597152-25342-4-git-send-email-anton.nefedov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/01/2017 09:19 AM, Anton Nefedov wrote: > The flag is supposed to indicate that the region of the disk image has > to be sufficiently allocated so it reads as zeroes. The call with the flag > set has to return -ENOTSUP if allocation cannot be done efficiently > (i.e. without falling back to writing actual buffers) > > Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> > --- > include/block/block.h | 6 +++++- > include/block/block_int.h | 2 +- > block/io.c | 20 +++++++++++++++++--- > 3 files changed, 23 insertions(+), 5 deletions(-) Reviewed-by: Eric Blake <eblake@redhat.com> You might want the commit message to be a bit more verbose... > > diff --git a/include/block/block.h b/include/block/block.h > index 7fe0125..828da67 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -65,9 +65,13 @@ typedef enum { > BDRV_REQ_NO_SERIALISING = 0x8, > BDRV_REQ_FUA = 0x10, > BDRV_REQ_WRITE_COMPRESSED = 0x20, > + /* The BDRV_REQ_ALLOCATE flag is used to indicate that the driver has to > + * efficiently allocate the space so it reads as zeroes, or return an error. > + */ > + BDRV_REQ_ALLOCATE = 0x40, > > /* Mask of valid flags */ > - BDRV_REQ_MASK = 0x3f, > + BDRV_REQ_MASK = 0x7f, > } BdrvRequestFlags; > > typedef struct BlockSizes { > diff --git a/include/block/block_int.h b/include/block/block_int.h > index 9b94b32..9b64411 100644 > --- a/include/block/block_int.h > +++ b/include/block/block_int.h > @@ -585,7 +585,7 @@ struct BlockDriverState { > /* Flags honored during pwrite (so far: BDRV_REQ_FUA) */ > unsigned int supported_write_flags; > /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA, > - * BDRV_REQ_MAY_UNMAP) */ > + * BDRV_REQ_MAY_UNMAP, BDRV_REQ_ALLOCATE) */ > unsigned int supported_zero_flags; ...in addition to adding the new flag here and documenting its semantics for drivers... > > /* the following member gives a name to every node on the bs graph. */ > diff --git a/block/io.c b/block/io.c > index 375fc66..04d495e 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1245,7 +1245,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, > assert(!bs->supported_zero_flags); > } > > - if (ret == -ENOTSUP) { > + if (ret == -ENOTSUP && !(flags & BDRV_REQ_ALLOCATE)) { > /* Fall back to bounce buffer if write zeroes is unsupported */ > BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE; ...you also made sure that anywhere the flag is in use you avoid a slow fallback... > @@ -1639,6 +1645,14 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset, > { > trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags); > > + assert(!(flags & BDRV_REQ_MAY_UNMAP && flags & BDRV_REQ_ALLOCATE)); > + > + if (flags & BDRV_REQ_ALLOCATE && > + !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE)) > + { > + return -ENOTSUP; ...as well as providing a sane default to make the flag always trigger -ENOTSUP until individual drivers implement something in later patches.
On Tue 01 Aug 2017 04:19:00 PM CEST, Anton Nefedov wrote: > The flag is supposed to indicate that the region of the disk image has > to be sufficiently allocated so it reads as zeroes. The call with the flag > set has to return -ENOTSUP if allocation cannot be done efficiently > (i.e. without falling back to writing actual buffers) > > Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> Reviewed-by: Alberto Garcia <berto@igalia.com> > + /* allocation request with qiov provided doesn't make much sense */ > + assert(!(qiov && flags & BDRV_REQ_ALLOCATE)); > + assert(!(flags & BDRV_REQ_MAY_UNMAP && flags & BDRV_REQ_ALLOCATE)); > + > + if (flags & BDRV_REQ_ALLOCATE && > + !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE)) I find it more readable with parentheses like this: assert(!(qiov && (flags & BDRV_REQ_ALLOCATE))); assert(!((flags & BDRV_REQ_MAY_UNMAP) && (flags & BDRV_REQ_ALLOCATE))); if ((flags & BDRV_REQ_ALLOCATE) && !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE)) but your code is correct as it is. Berto
diff --git a/include/block/block.h b/include/block/block.h index 7fe0125..828da67 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -65,9 +65,13 @@ typedef enum { BDRV_REQ_NO_SERIALISING = 0x8, BDRV_REQ_FUA = 0x10, BDRV_REQ_WRITE_COMPRESSED = 0x20, + /* The BDRV_REQ_ALLOCATE flag is used to indicate that the driver has to + * efficiently allocate the space so it reads as zeroes, or return an error. + */ + BDRV_REQ_ALLOCATE = 0x40, /* Mask of valid flags */ - BDRV_REQ_MASK = 0x3f, + BDRV_REQ_MASK = 0x7f, } BdrvRequestFlags; typedef struct BlockSizes { diff --git a/include/block/block_int.h b/include/block/block_int.h index 9b94b32..9b64411 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -585,7 +585,7 @@ struct BlockDriverState { /* Flags honored during pwrite (so far: BDRV_REQ_FUA) */ unsigned int supported_write_flags; /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA, - * BDRV_REQ_MAY_UNMAP) */ + * BDRV_REQ_MAY_UNMAP, BDRV_REQ_ALLOCATE) */ unsigned int supported_zero_flags; /* the following member gives a name to every node on the bs graph. */ diff --git a/block/io.c b/block/io.c index 375fc66..04d495e 100644 --- a/block/io.c +++ b/block/io.c @@ -1245,7 +1245,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, assert(!bs->supported_zero_flags); } - if (ret == -ENOTSUP) { + if (ret == -ENOTSUP && !(flags & BDRV_REQ_ALLOCATE)) { /* Fall back to bounce buffer if write zeroes is unsupported */ BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE; @@ -1331,8 +1331,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req); if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF && - !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes && - qemu_iovec_is_zero(qiov)) { + !(flags & BDRV_REQ_ZERO_WRITE) && !(flags & BDRV_REQ_ALLOCATE) && + drv->bdrv_co_pwrite_zeroes && qemu_iovec_is_zero(qiov)) { flags |= BDRV_REQ_ZERO_WRITE; if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) { flags |= BDRV_REQ_MAY_UNMAP; @@ -1410,6 +1410,9 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, assert(flags & BDRV_REQ_ZERO_WRITE); if (head_padding_bytes || tail_padding_bytes) { + if (flags & BDRV_REQ_ALLOCATE) { + return -ENOTSUP; + } buf = qemu_blockalign(bs, align); iov = (struct iovec) { .iov_base = buf, @@ -1508,6 +1511,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, return ret; } + /* allocation request with qiov provided doesn't make much sense */ + assert(!(qiov && flags & BDRV_REQ_ALLOCATE)); + bdrv_inc_in_flight(bs); /* * Align write if necessary by performing a read-modify-write cycle. @@ -1639,6 +1645,14 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset, { trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags); + assert(!(flags & BDRV_REQ_MAY_UNMAP && flags & BDRV_REQ_ALLOCATE)); + + if (flags & BDRV_REQ_ALLOCATE && + !(child->bs->supported_zero_flags & BDRV_REQ_ALLOCATE)) + { + return -ENOTSUP; + } + if (!(child->bs->open_flags & BDRV_O_UNMAP)) { flags &= ~BDRV_REQ_MAY_UNMAP; }
The flag is supposed to indicate that the region of the disk image has to be sufficiently allocated so it reads as zeroes. The call with the flag set has to return -ENOTSUP if allocation cannot be done efficiently (i.e. without falling back to writing actual buffers) Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> --- include/block/block.h | 6 +++++- include/block/block_int.h | 2 +- block/io.c | 20 +++++++++++++++++--- 3 files changed, 23 insertions(+), 5 deletions(-)