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[Qemu-devel] [PATCH v2 6/6] scsi-block: always use SG_IO for MMC devices
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH v2 6/6] scsi-block: always use SG_IO for MMC devices |
Date: |
Mon, 14 Nov 2011 10:40:30 +0100 |
CD burning messes up the state of the host page cache and host block
device. Just pass all operations down to the device, even though that
might have slightly worse performance. Everything else just is not
reliable in combination with burning.
Reported-by: Thomas Schmitt <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/scsi-disk.c | 16 ++++++++++++++--
1 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index c2a3864..9b172b4 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1731,8 +1731,20 @@ static SCSIRequest *scsi_block_new_request(SCSIDevice
*d, uint32_t tag,
case WRITE_VERIFY_10:
case WRITE_VERIFY_12:
case WRITE_VERIFY_16:
- return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun,
- hba_private);
+ /* MMC writing cannot be done via pread/pwrite, because it sometimes
+ * involves writing beyond the maximum LBA or to negative LBA
(lead-in).
+ * And once you do these writes, reading from the block device is
+ * unreliable, too. It is even possible that reads deliver random data
+ * from the host page cache (this is probably a Linux bug).
+ *
+ * We might use scsi_disk_reqops as long as no writing commands are
+ * seen, but performance usually isn't paramount on optical media. So,
+ * just make scsi-block operate the same as scsi-generic for them.
+ */
+ if (s->qdev.type != TYPE_ROM) {
+ return scsi_req_alloc(&scsi_disk_reqops, &s->qdev, tag, lun,
+ hba_private);
+ }
}
return scsi_req_alloc(&scsi_generic_req_ops, &s->qdev, tag, lun,
--
1.7.7.1
- [Qemu-devel] [PATCH v2 0/6] scsi/atapi: MMC fixes, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 1/6] atapi: kill MODE SENSE(6), fix MODE SENSE(10), Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 4/6] scsi: remove block descriptors from CDs, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 3/6] scsi: fix parsing of allocation length field, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 2/6] scsi: update list of commands, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 5/6] scsi: pass down REQUEST SENSE to the device when there is no stored sense, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 6/6] scsi-block: always use SG_IO for MMC devices,
Paolo Bonzini <=
- [Qemu-devel] [PATCH v2 0/6] scsi/atapi: MMC fixes, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 1/6] atapi: kill MODE SENSE(6), fix MODE SENSE(10), Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 2/6] scsi: update list of commands, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 4/6] scsi: remove block descriptors from CDs, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 5/6] scsi: pass down REQUEST SENSE to the device when there is no stored sense, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 3/6] scsi: fix parsing of allocation length field, Paolo Bonzini, 2011/11/14
- [Qemu-devel] [PATCH v2 6/6] scsi-block: always use SG_IO for MMC devices, Paolo Bonzini, 2011/11/14
- Re: [Qemu-devel] [PATCH v2 0/6] scsi/atapi: MMC fixes, Kevin Wolf, 2011/11/18