RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters
Yeah. That will make the work quite simple. After testing, fdatasync is better than fsync. -Original Message- From: Sasha Levin [mailto:levinsasha...@gmail.com] Sent: Sunday, November 20, 2011 2:23 PM To: Lan, Tianyu Cc: Kevin Wolf; penb...@kernel.org; kvm@vger.kernel.org; asias.he...@gmail.com; prasadjoshi...@gmail.com Subject: RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters On Sun, 2011-11-20 at 14:14 +0800, Lan, Tianyu wrote: > OK. Thx. > But fsync is too slow. I try to find a way to sync a range of file. > Are there any solutions to meet my purpose? fdatasync() is as good as it'll get. tbh, maybe we should just consider opening QCOW images with O_SYNC and just get it over with? > Thanks > Tianyu Lan > > -Original Message- > From: Sasha Levin [mailto:levinsasha...@gmail.com] > Sent: Sunday, November 20, 2011 12:27 AM > To: Lan, Tianyu > Cc: Kevin Wolf; penb...@kernel.org; kvm@vger.kernel.org; > asias.he...@gmail.com; prasadjoshi...@gmail.com > Subject: RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for > copy-on-write clusters > > On Sat, 2011-11-19 at 23:30 +0800, Lan, Tianyu wrote: > > How about using the sync_file_range to sync the metadata? > > sync_file_range() is only a hint, it doesn't actually assure anything. > -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters
On Sun, 2011-11-20 at 14:14 +0800, Lan, Tianyu wrote: > OK. Thx. > But fsync is too slow. I try to find a way to sync a range of file. > Are there any solutions to meet my purpose? fdatasync() is as good as it'll get. tbh, maybe we should just consider opening QCOW images with O_SYNC and just get it over with? > Thanks > Tianyu Lan > > -Original Message- > From: Sasha Levin [mailto:levinsasha...@gmail.com] > Sent: Sunday, November 20, 2011 12:27 AM > To: Lan, Tianyu > Cc: Kevin Wolf; penb...@kernel.org; kvm@vger.kernel.org; > asias.he...@gmail.com; prasadjoshi...@gmail.com > Subject: RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for > copy-on-write clusters > > On Sat, 2011-11-19 at 23:30 +0800, Lan, Tianyu wrote: > > How about using the sync_file_range to sync the metadata? > > sync_file_range() is only a hint, it doesn't actually assure anything. > -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters
OK. Thx. But fsync is too slow. I try to find a way to sync a range of file. Are there any solutions to meet my purpose? Thanks Tianyu Lan -Original Message- From: Sasha Levin [mailto:levinsasha...@gmail.com] Sent: Sunday, November 20, 2011 12:27 AM To: Lan, Tianyu Cc: Kevin Wolf; penb...@kernel.org; kvm@vger.kernel.org; asias.he...@gmail.com; prasadjoshi...@gmail.com Subject: RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters On Sat, 2011-11-19 at 23:30 +0800, Lan, Tianyu wrote: > How about using the sync_file_range to sync the metadata? sync_file_range() is only a hint, it doesn't actually assure anything. -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters
On Sat, 2011-11-19 at 23:30 +0800, Lan, Tianyu wrote: > How about using the sync_file_range to sync the metadata? sync_file_range() is only a hint, it doesn't actually assure anything. -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write clusters
How about using the sync_file_range to sync the metadata?
-Original Message-
From: kvm-ow...@vger.kernel.org [mailto:kvm-ow...@vger.kernel.org] On Behalf Of
Lan, Tianyu
Sent: Saturday, November 19, 2011 10:09 AM
To: Kevin Wolf
Cc: penb...@kernel.org; kvm@vger.kernel.org; asias.he...@gmail.com;
levinsasha...@gmail.com; prasadjoshi...@gmail.com
Subject: RE: [RFC v2 PATCH] kvm tools, qcow: Add the support for copy-on-write
clusters
Hi Kevin:
Thanks for your review. The following means that there should be a
fsync after updating
metadata(refcunt block, l1 table and l2 table).
Thanks
Tianyu Lan
-Original Message-
> + /*write l2 table*/
> + l2t->dirty = 1;
> + if (qcow_l2_cache_write(q, l2t) < 0)
> goto free_cache;
You need to make sure that the refcount update is written first (e.g.
with fsync), otherwise you risk corruption when the host crashes in the middle.
>
> - if (cache_table(q, l2t) < 0) {
> - if (ftruncate(q->fd, f_sz) < 0)
> - goto free_cache;
> + /* Update the l1 talble */
> + l1t->l1_table[l1t_idx] = cpu_to_be64(l2t_new_offset
> + | QCOW2_OFLAG_COPIED);
>
> - goto free_cache;
> - }
> + if (pwrite_in_full(q->fd, l1t->l1_table,
> + l1t->table_size * sizeof(u64),
> + header->l1_table_offset) < 0)
> + goto error;
Likewise, the L1 table write must be ordered against the L2 write.
goto error is using the wrong label.
>
> - /* Update the in-core entry */
> - l1t->l1_table[l1t_idx] = cpu_to_be64(l2t_offset);
> + /*cache l2 table*/
> + cache_table(q, l2t);
After so many explicit comments, you can probably guess what's wrong here...
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Re: KVM for the enterprise
On Fri, Nov 18, 2011 at 11:25:38AM -0500, Michael Waite wrote: > Hi, > The Open Virtualization Alliance is going to be having a webinar on > December 8th which is intended to help promote KVM as an enterprise > class hypervisor. I see so much great engineering work going on to > make KVM a really robust technology and we want to help tell this > story to the world-wide audience. Maybe it's time to create a kvm-marketing@whatever list for sneaky marketing BS from people like you instead of spamming development lists like this one? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
