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Re: [Qemu-block] [PATCH v2 14/17] block: Switch transfer length bounds t
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-block] [PATCH v2 14/17] block: Switch transfer length bounds to byte-based |
Date: |
Tue, 21 Jun 2016 15:50:15 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 14.06.2016 um 23:30 hat Eric Blake geschrieben:
> Sector-based limits are awkward to think about; in our on-going
> quest to move to byte-based interfaces, convert max_transfer_length
> and opt_transfer_length. Rename them (dropping the _length suffix)
> so that the compiler will help us catch the change in semantics
> across any rebased code, and improve the documentation. Use unsigned
> values, so that we don't have to worry about negative values and
> so that bit-twiddling is easier; however, we are still constrained
> by 2^31 of signed int in most APIs.
>
> Signed-off-by: Eric Blake <address@hidden>
> @@ -1738,8 +1742,8 @@ static void iscsi_refresh_limits(BlockDriverState *bs,
> Error **errp)
> } else {
> bs->bl.pwrite_zeroes_alignment = iscsilun->block_size;
> }
> - bs->bl.opt_transfer_length =
> - sector_limits_lun2qemu(iscsilun->bl.opt_xfer_len, iscsilun);
> + assert(iscsilun->bl.opt_xfer_len < INT_MAX / iscsilun->block_size);
> + bs->bl.opt_transfer = iscsilun->bl.opt_xfer_len * iscsilun->block_size;
> }
iscsilun->bl.opt_xfer_len comes directly from libiscsi, and presumably
from the iscsi server, without being checked or sanitised. I don't think
we can assert a specific range of values for it but must assume that it
can be any uint32_t.
We can return an error for a device with a value that we don't like
(even though using the maximum might be just fine), but crashing qemu is
not an option.
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index aacf132..f2bea85 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -752,7 +752,8 @@ static void raw_refresh_limits(BlockDriverState *bs,
> Error **errp)
> if (S_ISBLK(st.st_mode)) {
> int ret = hdev_get_max_transfer_length(s->fd);
> if (ret >= 0) {
> - bs->bl.max_transfer_length = ret;
> + assert(ret <= BDRV_REQUEST_MAX_SECTORS);
> + bs->bl.max_transfer = ret << BDRV_SECTOR_BITS;
> }
> }
> }
Same thing here.
Kevin
- [Qemu-block] [PATCH v2 15/17] block: Switch discard length bounds to byte-based, (continued)
- [Qemu-block] [PATCH v2 13/17] block: Set default request_alignment during bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-block] [PATCH v2 14/17] block: Switch transfer length bounds to byte-based, Eric Blake, 2016/06/14
- [Qemu-block] [PATCH v2 10/17] qcow2: Set request_alignment during .bdrv_refresh_limits(), Eric Blake, 2016/06/14
- [Qemu-block] [PATCH v2 07/17] block: Give nonzero result to blk_get_max_transfer_length(), Eric Blake, 2016/06/14
- [Qemu-block] [PATCH v2 17/17] block: Move request_alignment into BlockLimit, Eric Blake, 2016/06/14