570d4ad51d
which fixes the bad commit 18473467d55a20d643b6c9b3a52de42f705b4d35 that was tracked down via bisecting, and has a Cc for qemu-stable as well. Issue was easy enough to reproduce with a single virtio-block disk using a few runs of dd if=/dev/urandom of=file bs=1M count=1000 Commit cc071629539dc1f303175a7e2d4ab854c0a8b20f upstream. Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
125 lines
4.9 KiB
Diff
125 lines
4.9 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 23 Sep 2021 09:04:36 -0400
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Subject: [PATCH] block: introduce max_hw_iov for use in scsi-generic
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Linux limits the size of iovecs to 1024 (UIO_MAXIOV in the kernel
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sources, IOV_MAX in POSIX). Because of this, on some host adapters
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requests with many iovecs are rejected with -EINVAL by the
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io_submit() or readv()/writev() system calls.
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In fact, the same limit applies to SG_IO as well. To fix both the
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EINVAL and the possible performance issues from using fewer iovecs
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than allowed by Linux (some HBAs have max_segments as low as 128),
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introduce a separate entry in BlockLimits to hold the max_segments
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value from sysfs. This new limit is used only for SG_IO and clamped
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to bs->bl.max_iov anyway, just like max_hw_transfer is clamped to
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bs->bl.max_transfer.
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Reported-by: Halil Pasic <pasic@linux.ibm.com>
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Cc: Hanna Reitz <hreitz@redhat.com>
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Cc: Kevin Wolf <kwolf@redhat.com>
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Cc: qemu-block@nongnu.org
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Cc: qemu-stable@nongnu.org
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Fixes: 18473467d5 ("file-posix: try BLKSECTGET on block devices too, do not round to power of 2", 2021-06-25)
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Message-Id: <20210923130436.1187591-1-pbonzini@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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block/block-backend.c | 6 ++++++
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block/file-posix.c | 2 +-
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block/io.c | 1 +
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hw/scsi/scsi-generic.c | 2 +-
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include/block/block_int.h | 7 +++++++
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include/sysemu/block-backend.h | 1 +
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6 files changed, 17 insertions(+), 2 deletions(-)
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diff --git a/block/block-backend.c b/block/block-backend.c
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index 6140d133e2..ba2b5ebb10 100644
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--- a/block/block-backend.c
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+++ b/block/block-backend.c
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@@ -1986,6 +1986,12 @@ uint32_t blk_get_max_transfer(BlockBackend *blk)
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return ROUND_DOWN(max, blk_get_request_alignment(blk));
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}
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+int blk_get_max_hw_iov(BlockBackend *blk)
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+{
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+ return MIN_NON_ZERO(blk->root->bs->bl.max_hw_iov,
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+ blk->root->bs->bl.max_iov);
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+}
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+
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int blk_get_max_iov(BlockBackend *blk)
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{
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return blk->root->bs->bl.max_iov;
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diff --git a/block/file-posix.c b/block/file-posix.c
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index c62e42743d..53be0bdc1b 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -1273,7 +1273,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
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ret = hdev_get_max_segments(s->fd, &st);
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if (ret > 0) {
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- bs->bl.max_iov = ret;
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+ bs->bl.max_hw_iov = ret;
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}
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}
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}
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diff --git a/block/io.c b/block/io.c
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index 18d345a87a..bb0a254def 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -136,6 +136,7 @@ static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
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dst->min_mem_alignment = MAX(dst->min_mem_alignment,
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src->min_mem_alignment);
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dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
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+ dst->max_hw_iov = MIN_NON_ZERO(dst->max_hw_iov, src->max_hw_iov);
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}
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typedef struct BdrvRefreshLimitsState {
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diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
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index 665baf900e..0306ccc7b1 100644
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--- a/hw/scsi/scsi-generic.c
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+++ b/hw/scsi/scsi-generic.c
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@@ -180,7 +180,7 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s, int len)
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page = r->req.cmd.buf[2];
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if (page == 0xb0) {
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uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk);
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- uint32_t max_iov = blk_get_max_iov(s->conf.blk);
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+ uint32_t max_iov = blk_get_max_hw_iov(s->conf.blk);
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assert(max_transfer);
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max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size)
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diff --git a/include/block/block_int.h b/include/block/block_int.h
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index ffe86068d4..f4c75e8ba9 100644
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--- a/include/block/block_int.h
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+++ b/include/block/block_int.h
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@@ -718,6 +718,13 @@ typedef struct BlockLimits {
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*/
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uint64_t max_hw_transfer;
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+ /* Maximal number of scatter/gather elements allowed by the hardware.
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+ * Applies whenever transfers to the device bypass the kernel I/O
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+ * scheduler, for example with SG_IO. If larger than max_iov
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+ * or if zero, blk_get_max_hw_iov will fall back to max_iov.
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+ */
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+ int max_hw_iov;
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+
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/* memory alignment, in bytes so that no bounce buffer is needed */
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size_t min_mem_alignment;
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diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
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index 29d4fdbf63..82bae55161 100644
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--- a/include/sysemu/block-backend.h
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+++ b/include/sysemu/block-backend.h
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@@ -211,6 +211,7 @@ uint32_t blk_get_request_alignment(BlockBackend *blk);
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uint32_t blk_get_max_transfer(BlockBackend *blk);
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uint64_t blk_get_max_hw_transfer(BlockBackend *blk);
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int blk_get_max_iov(BlockBackend *blk);
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+int blk_get_max_hw_iov(BlockBackend *blk);
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void blk_set_guest_block_size(BlockBackend *blk, int align);
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void *blk_try_blockalign(BlockBackend *blk, size_t size);
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void *blk_blockalign(BlockBackend *blk, size_t size);
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--
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2.30.2
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