| Message ID | 00c501cda602$583de850$08b9b8f0$@cn.fujitsu.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Oct 09, 2012 at 05:42:01PM +0800, Chen HanXiao wrote: > When we use SCSI generic device as disk image, function lseek > could not get the size of this kind of device. > So try to use SCSI command Read Capacity(10) when lseek failed to get > the size of SCSI generic device. Eww, this is ugly as hell. Why would you even need the size for a raw passthrough device?
Hi > -----Original Message----- > From: Christoph Hellwig [mailto:hch@lst.de] > Sent: Wednesday, October 10, 2012 1:21 AM > To: Chen HanXiao > Cc: qemu-devel@nongnu.org > Subject: Re: [Qemu-devel] [PATCH] Use SCSI command to get size of SG device > > On Tue, Oct 09, 2012 at 05:42:01PM +0800, Chen HanXiao wrote: > > When we use SCSI generic device as disk image, function lseek could > > not get the size of this kind of device. > > So try to use SCSI command Read Capacity(10) when lseek failed to get > > the size of SCSI generic device. > > Eww, this is ugly as hell. Why would you even need the size for a raw > passthrough device? If we want to enable snapshot for SCSI generic device as disk image, the size of SCSI generic device is needed. Function lseek could not get this, SCSI command can finish the job. Only when lseek failed would Read Capacity command be sent. Regards
Il 10/10/2012 04:11, Chen HanXiao ha scritto: >> > >> > On Tue, Oct 09, 2012 at 05:42:01PM +0800, Chen HanXiao wrote: >>> > > When we use SCSI generic device as disk image, function lseek could >>> > > not get the size of this kind of device. >>> > > So try to use SCSI command Read Capacity(10) when lseek failed to get >>> > > the size of SCSI generic device. >> > >> > Eww, this is ugly as hell. Why would you even need the size for a raw >> > passthrough device? > > If we want to enable snapshot for SCSI generic device as disk image, the size > of SCSI generic device is needed. Function lseek could not get this, SCSI > command can finish the job. > Only when lseek failed would Read Capacity command be sent. You need to use scsi-block instead of scsi-generic. However, I don't see how this can work. After the snapshot, the image will be qcow2, not raw, and thus it will not support bdrv_aio_ioctl. Hence any SCSI command (for scsi-generic) or any non-data SCSI command (for scsi-block) will fail. Can you give an example of what exactly you are trying to do? Paolo
> -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo > Bonzini > Sent: Wednesday, October 10, 2012 2:34 PM > To: Chen HanXiao > Cc: 'Christoph Hellwig'; qemu-devel@nongnu.org > Subject: Re: [PATCH] Use SCSI command to get size of SG device > > Il 10/10/2012 04:11, Chen HanXiao ha scritto: > >> > > >> > On Tue, Oct 09, 2012 at 05:42:01PM +0800, Chen HanXiao wrote: > >>> > > When we use SCSI generic device as disk image, function lseek > >>> > > could not get the size of this kind of device. > >>> > > So try to use SCSI command Read Capacity(10) when lseek failed > >>> > > to get the size of SCSI generic device. > >> > > >> > Eww, this is ugly as hell. Why would you even need the size for a > >> > raw passthrough device? > > > > If we want to enable snapshot for SCSI generic device as disk image, > > the size of SCSI generic device is needed. Function lseek could not > > get this, SCSI command can finish the job. > > Only when lseek failed would Read Capacity command be sent. > > You need to use scsi-block instead of scsi-generic. However, I don't see how > this can work. After the snapshot, the image will be qcow2, not raw, and thus > it will not support bdrv_aio_ioctl. Hence any SCSI command (for scsi-generic) > or any non-data SCSI command (for scsi-block) will fail. > That's the issue what I also encountered. Do you mean that it is impossible for us to enable snapshot for scsi-generic? Or patched for qcow2 would solve this? > Can you give an example of what exactly you are trying to do? > I could enable snapshot for scsi-block device, but failed when using scsi-generic with parameter 'snapshot =on'. The first issue is failing to get the size of SG device. So I tried to fix it. Command line: -drive if=none,id=hd,file=/dev/sg2,snapshot=on \ -device virtio-scsi-pci,id=scsi --enable-kvm \ -device scsi-generic,drive=hd,id=vd1 > Paolo Regards
Il 10/10/2012 10:33, Chen HanXiao ha scritto: >> You need to use scsi-block instead of scsi-generic. However, I don't see >> how this can work. After the snapshot, the image will be qcow2, not raw, and >> thus it will not support bdrv_aio_ioctl. Hence any SCSI command (for >> scsi-generic) or any non-data SCSI command (for scsi-block) will fail. > > That's the issue what I also encountered. > Do you mean that it is impossible for us to enable snapshot for > scsi-generic? It's impossible, and rightly so: the user could anyway bypass the snapshotting and write to the disk (WRITE SAME for example). Not just snapshot=on, which fails because it is early enough that the disk fails to initialize. Live snapshots also ought to be blocked, it is a bug that they are not. Paolo
diff --git a/block/raw-posix.c b/block/raw-posix.c index 28d439f..0be7db8 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -53,6 +53,7 @@ #include <linux/cdrom.h> #include <linux/fd.h> #include <linux/fs.h> +#include <scsi/sg.h> #endif #ifdef CONFIG_FIEMAP #include <linux/fiemap.h> @@ -147,6 +148,7 @@ typedef struct BDRVRawReopenState { } BDRVRawReopenState; static int fd_open(BlockDriverState *bs); +static int64_t raw_getlength_ioctl(int fd); static int64_t raw_getlength(BlockDriverState *bs); #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) @@ -653,13 +655,53 @@ static int64_t raw_getlength(BlockDriverState *bs) { BDRVRawState *s = bs->opaque; int ret; - + int64_t len; + ret = fd_open(bs); if (ret < 0) { return ret; } - return lseek(s->fd, 0, SEEK_END); + len = lseek(s->fd, 0, SEEK_END); + if ( len >= 0) { + return len; + } else { + len = raw_getlength_ioctl(s->fd); + return len; + } +} + +/* Use SCSI Read Capacity(10) Command to get length */ +static int64_t raw_getlength_ioctl(int fd) +{ + unsigned char CDB[10] = + {0x25, 0, 0, 0, 0, 0, 0, 0, 0, 0}; + unsigned char sense_buffer[32]; + unsigned char resp_buffer[32]; + uint32_t block_size; + uint64_t last_blk_addr; + struct sg_io_hdr io_hdr; + int64_t ret; + + memset(&io_hdr, 0, sizeof(struct sg_io_hdr)); + memset(sense_buffer, 0, sizeof(sense_buffer)); + memset(sense_buffer, 0, sizeof(resp_buffer)); + io_hdr.interface_id = 'S'; + io_hdr.dxfer_direction = SG_DXFER_FROM_DEV; + io_hdr.cmd_len = sizeof(CDB); + io_hdr.cmdp = CDB; + io_hdr.sbp = sense_buffer; + io_hdr.dxferp = resp_buffer; + io_hdr.dxfer_len = sizeof(resp_buffer); + if((ret = ioctl(fd, SG_IO, &io_hdr)) < 0) + return ret; + + last_blk_addr = ((resp_buffer[0] << 24) | (resp_buffer[1] << 16) | + (resp_buffer[2] << 8) | resp_buffer[3]); + block_size = ((resp_buffer[4] << 24) | (resp_buffer[5] << 16) | + (resp_buffer[6] << 8) | resp_buffer[7]); + ret = (int64_t)((last_blk_addr + 1) * block_size); + return ret; } #endif
When we use SCSI generic device as disk image, function lseek could not get the size of this kind of device. So try to use SCSI command Read Capacity(10) when lseek failed to get the size of SCSI generic device. Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com> --- block/raw-posix.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 44 insertions(+), 2 deletions(-)