We don't need the can_write_zeroes_with_unmap field in BlockDriverInfo, because it is redundant information with supported_zero_flags & BDRV_REQ_MAY_UNMAP. Note that BlockDriverInfo and supported_zero_flags are both per-device settings, rather than global state about the driver as a whole, which means one or both of these bits of information can already be conditional. Let's audit how they were set:
crypto: always setting can_write_ to false is pointless (the struct starts life zero-initialized), no use of supported_ nbd: just recently fixed to set can_write_ if supported_ includes MAY_UNMAP (thus this commit effectively reverts bca80059e and solves the problem mentioned there in a more global way) file-posix, iscsi, qcow2: can_write_ is conditional, while supported_ was unconditional; but passing MAY_UNMAP would fail with ENOTSUP if the condition wasn't met qed: can_write_ is unconditional, but pwrite_zeroes lacks support for MAY_UNMAP and supported_ is not set. Perhaps support can be added later (since it would be similar to qcow2), but for now claiming false is no real loss all other drivers: can_write_ is not set, and supported_ is either unset or a passthrough Simplify the code by moving the conditional into supported_zero_flags for all drivers, then dropping the now-unused BDI field. For callers that relied on bdrv_can_write_zeroes_with_unmap(), we return the same per-device settings for drivers that had conditions (no observable change in behavior there); and can now return true (instead of false) for drivers that support passthrough (for example, the commit driver) which gives those drivers the same fix as nbd just got in bca80059e. For callers that relied on supported_zero_flags, we now have a few more places that can avoid a wasted call to pwrite_zeroes() that will just fail with ENOTSUP. Suggested-by: Paolo Bonzini <pbonz...@redhat.com> Signed-off-by: Eric Blake <ebl...@redhat.com> Message-Id: <20180126193439.20219-1-ebl...@redhat.com> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> --- include/block/block.h | 11 ----------- block.c | 8 +------- block/crypto.c | 1 - block/file-posix.c | 3 +-- block/iscsi.c | 6 ++++-- block/nbd.c | 11 ----------- block/qcow2.c | 3 +-- block/qed.c | 1 - 8 files changed, 7 insertions(+), 37 deletions(-) diff --git a/include/block/block.h b/include/block/block.h index 24ef816960e..19b3ab9cb5e 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -26,17 +26,6 @@ typedef struct BlockDriverInfo { * to the LBPRZ flag in the SCSI logical block provisioning page. */ bool unallocated_blocks_are_zero; - /* - * True if the driver can optimize writing zeroes by unmapping - * sectors. This is equivalent to the BLKDISCARDZEROES ioctl in Linux - * with the difference that in qemu a discard is allowed to silently - * fail. Therefore we have to use bdrv_pwrite_zeroes with the - * BDRV_REQ_MAY_UNMAP flag for an optimized zero write with unmapping. - * After this call the driver has to guarantee that the contents read - * back as zero. It is additionally required that the block device is - * opened with BDRV_O_UNMAP flag for this to work. - */ - bool can_write_zeroes_with_unmap; /* * True if this block driver only supports compressed writes */ diff --git a/block.c b/block.c index f94585b2304..814e5a02da6 100644 --- a/block.c +++ b/block.c @@ -4010,17 +4010,11 @@ bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs) bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs) { - BlockDriverInfo bdi; - if (!(bs->open_flags & BDRV_O_UNMAP)) { return false; } - if (bdrv_get_info(bs, &bdi) == 0) { - return bdi.can_write_zeroes_with_unmap; - } - - return false; + return bs->supported_zero_flags & BDRV_REQ_MAY_UNMAP; } const char *bdrv_get_encrypted_filename(BlockDriverState *bs) diff --git a/block/crypto.c b/block/crypto.c index 70e3691cd84..3df66947c5a 100644 --- a/block/crypto.c +++ b/block/crypto.c @@ -576,7 +576,6 @@ static int block_crypto_get_info_luks(BlockDriverState *bs, } bdi->unallocated_blocks_are_zero = false; - bdi->can_write_zeroes_with_unmap = false; bdi->cluster_size = subbdi.cluster_size; return 0; diff --git a/block/file-posix.c b/block/file-posix.c index dd8d7cbbd21..ca49c1a98ae 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -549,7 +549,6 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, s->has_discard = true; s->has_write_zeroes = true; - bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP; if ((bs->open_flags & BDRV_O_NOCACHE) != 0) { s->needs_alignment = true; } @@ -599,6 +598,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } #endif + bs->supported_zero_flags = s->discard_zeroes ? BDRV_REQ_MAY_UNMAP : 0; ret = 0; fail: if (filename && (bdrv_flags & BDRV_O_TEMPORARY)) { @@ -2223,7 +2223,6 @@ static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) BDRVRawState *s = bs->opaque; bdi->unallocated_blocks_are_zero = s->discard_zeroes; - bdi->can_write_zeroes_with_unmap = s->discard_zeroes; return 0; } diff --git a/block/iscsi.c b/block/iscsi.c index 9f99ae5e07b..421983dd6ff 100644 --- a/block/iscsi.c +++ b/block/iscsi.c @@ -1877,7 +1877,6 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags, if (iscsilun->dpofua) { bs->supported_write_flags = BDRV_REQ_FUA; } - bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP; /* Check the write protect flag of the LUN if we want to write */ if (iscsilun->type == TYPE_DISK && (flags & BDRV_O_RDWR) && @@ -1961,6 +1960,10 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags, } } + if (iscsilun->lbprz && iscsilun->lbp.lbpws) { + bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP; + } + out: qemu_opts_del(opts); g_free(initiator_name); @@ -2160,7 +2163,6 @@ static int iscsi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) { IscsiLun *iscsilun = bs->opaque; bdi->unallocated_blocks_are_zero = iscsilun->lbprz; - bdi->can_write_zeroes_with_unmap = iscsilun->lbprz && iscsilun->lbp.lbpws; bdi->cluster_size = iscsilun->cluster_sectors * BDRV_SECTOR_SIZE; return 0; } diff --git a/block/nbd.c b/block/nbd.c index 411eeb42a7d..ef81a9f53ba 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -566,14 +566,6 @@ static void nbd_refresh_filename(BlockDriverState *bs, QDict *options) bs->full_open_options = opts; } -static int nbd_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) -{ - if (bs->supported_zero_flags & BDRV_REQ_MAY_UNMAP) { - bdi->can_write_zeroes_with_unmap = true; - } - return 0; -} - static BlockDriver bdrv_nbd = { .format_name = "nbd", .protocol_name = "nbd", @@ -591,7 +583,6 @@ static BlockDriver bdrv_nbd = { .bdrv_detach_aio_context = nbd_detach_aio_context, .bdrv_attach_aio_context = nbd_attach_aio_context, .bdrv_refresh_filename = nbd_refresh_filename, - .bdrv_get_info = nbd_get_info, }; static BlockDriver bdrv_nbd_tcp = { @@ -611,7 +602,6 @@ static BlockDriver bdrv_nbd_tcp = { .bdrv_detach_aio_context = nbd_detach_aio_context, .bdrv_attach_aio_context = nbd_attach_aio_context, .bdrv_refresh_filename = nbd_refresh_filename, - .bdrv_get_info = nbd_get_info, }; static BlockDriver bdrv_nbd_unix = { @@ -631,7 +621,6 @@ static BlockDriver bdrv_nbd_unix = { .bdrv_detach_aio_context = nbd_detach_aio_context, .bdrv_attach_aio_context = nbd_attach_aio_context, .bdrv_refresh_filename = nbd_refresh_filename, - .bdrv_get_info = nbd_get_info, }; static void bdrv_nbd_init(void) diff --git a/block/qcow2.c b/block/qcow2.c index a64a572785d..801e29fc56e 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1479,7 +1479,7 @@ static int qcow2_do_open(BlockDriverState *bs, QDict *options, int flags, /* Initialise locks */ qemu_co_mutex_init(&s->lock); - bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP; + bs->supported_zero_flags = header.version >= 3 ? BDRV_REQ_MAY_UNMAP : 0; /* Repair image if dirty */ if (!(flags & (BDRV_O_CHECK | BDRV_O_INACTIVE)) && !bs->read_only && @@ -3771,7 +3771,6 @@ static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) { BDRVQcow2State *s = bs->opaque; bdi->unallocated_blocks_are_zero = true; - bdi->can_write_zeroes_with_unmap = (s->qcow_version >= 3); bdi->cluster_size = s->cluster_size; bdi->vm_state_offset = qcow2_vm_state_offset(s); return 0; diff --git a/block/qed.c b/block/qed.c index 205dbf16e35..c6ff3ab015d 100644 --- a/block/qed.c +++ b/block/qed.c @@ -1438,7 +1438,6 @@ static int bdrv_qed_get_info(BlockDriverState *bs, BlockDriverInfo *bdi) bdi->cluster_size = s->header.cluster_size; bdi->is_dirty = s->header.features & QED_F_NEED_CHECK; bdi->unallocated_blocks_are_zero = true; - bdi->can_write_zeroes_with_unmap = true; return 0; } -- 2.14.3