| Message ID | 1520849818-6915-5-git-send-email-anton.nefedov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon 12 Mar 2018 11:16:53 AM CET, 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 must return -ENOTSUP if allocation cannot > be done efficiently. > This has to be made sure of by both > - the drivers that support the flag > - and the common block layer (so it will not fall back to any slowpath > (like writing zero buffers) in case the driver does not support > the flag). > > Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> > Reviewed-by: Eric Blake <eblake@redhat.com> > Reviewed-by: Alberto Garcia <berto@igalia.com> Hmm... this is not the patch that I reviewed, please remove the R-b lines when you submit a modified patch. > + /* 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. > + * Must be used together with BDRV_REQ_ZERO_WRITE. I guess it's understandable from the context but it's not immediately obvious that you can set BDRV_REQ_ZERO_WRITE but not this one. Perhaps it could be rephrased as something like "If this is set then BDRV_REQ_ZERO_WRITE must also be set". > + * Contradictory to BDRV_REQ_MAY_UNMAP so the two must not be used together. Or simply "This flag cannot be set together with BDRV_REQ_MAY_UNMAP". > + */ > + BDRV_REQ_ALLOCATE = 0x40, Berto
On 16/3/2018 2:01 PM, Alberto Garcia wrote: > On Mon 12 Mar 2018 11:16:53 AM CET, 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 must return -ENOTSUP if allocation cannot >> be done efficiently. >> This has to be made sure of by both >> - the drivers that support the flag >> - and the common block layer (so it will not fall back to any slowpath >> (like writing zero buffers) in case the driver does not support >> the flag). >> >> Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> >> Reviewed-by: Eric Blake <eblake@redhat.com> >> Reviewed-by: Alberto Garcia <berto@igalia.com> > > Hmm... this is not the patch that I reviewed, please remove the R-b > lines when you submit a modified patch. > Oops. sorry >> + /* 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. >> + * Must be used together with BDRV_REQ_ZERO_WRITE. > > I guess it's understandable from the context but it's not immediately > obvious that you can set BDRV_REQ_ZERO_WRITE but not this one. > > Perhaps it could be rephrased as something like "If this is set then > BDRV_REQ_ZERO_WRITE must also be set". > Sound much better, fixed >> + * Contradictory to BDRV_REQ_MAY_UNMAP so the two must not be used together. > > Or simply "This flag cannot be set together with BDRV_REQ_MAY_UNMAP". > Done >> + */ >> + BDRV_REQ_ALLOCATE = 0x40, > > Berto >
diff --git a/include/block/block.h b/include/block/block.h index 8b6db95..9747632 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -53,9 +53,15 @@ 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. + * Must be used together with BDRV_REQ_ZERO_WRITE. + * Contradictory to BDRV_REQ_MAY_UNMAP so the two must not be used together. + */ + 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 64a5700..9495e35 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -648,7 +648,7 @@ 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 2b09c65..c4f2a07 100644 --- a/block/io.c +++ b/block/io.c @@ -1418,7 +1418,7 @@ 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; @@ -1511,7 +1511,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_pwrite_zeroes && qemu_iovec_is_zero(qiov)) { flags |= BDRV_REQ_ZERO_WRITE; - if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) { + if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP && + !(flags & BDRV_REQ_ALLOCATE)) + { flags |= BDRV_REQ_MAY_UNMAP; } } @@ -1587,6 +1589,9 @@ 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, @@ -1672,6 +1677,9 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, bool use_local_qiov = false; int ret; + assert(!((flags & BDRV_REQ_ALLOCATE) && (flags & BDRV_REQ_MAY_UNMAP))); + assert(!((flags & BDRV_REQ_ALLOCATE) && !(flags & BDRV_REQ_ZERO_WRITE))); + trace_bdrv_co_pwritev(child->bs, offset, bytes, flags); if (!bs->drv) { @@ -1816,6 +1824,12 @@ int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset, { trace_bdrv_co_pwrite_zeroes(child->bs, offset, bytes, flags); + 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 must return -ENOTSUP if allocation cannot be done efficiently. This has to be made sure of by both - the drivers that support the flag - and the common block layer (so it will not fall back to any slowpath (like writing zero buffers) in case the driver does not support the flag). Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> --- include/block/block.h | 8 +++++++- include/block/block_int.h | 2 +- block/io.c | 18 ++++++++++++++++-- 3 files changed, 24 insertions(+), 4 deletions(-)