Bug 526869

Summary: Add virtio_blk support cache flush (VIRTIO_BLK_F_FLUSH)
Product: [Fedora] Fedora Reporter: Mark McLoughlin <markmc>
Component: kernelAssignee: Justin M. Forbes <jforbes>
Status: CLOSED RAWHIDE QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: high    
Version: rawhideCC: amit.shah, chellwig, dougsland, gansalmon, itamar, kernel-maint, virt-maint
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Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2009-10-06 10:45:45 EDT Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On:    
Bug Blocks: 498969    

Description Mark McLoughlin 2009-10-02 04:23:07 EDT
See discussion in bug #525890

We should backport:

  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=f1b0ef0626

  virtio_blk: add support for cache flush

  Recent qemu has added a VIRTIO_BLK_F_FLUSH flag to advertise that the
  virtual disk has a volatile write cache that needs to be flushed.  In case
  we see this feature implement tell the Linux block layer about the fact
  and use the new VIRTIO_BLK_T_FLUSH to flush the cache when required.  This
  allows for an correct and simple implementation of write barriers.

This mail from Christoph is a good writeup on the background:

  http://www.mail-archive.com/kvm@vger.kernel.org/msg21559.html

We should get this into F-12 GA even if qemu doesn't yet support it in F-12 so that F-12 guest installer kernels have this feature.
Comment 1 Justin M. Forbes 2009-10-06 10:45:45 EDT
This has been added to the F-12 kernel and should be available in the next kernel tagged.