On Tue, Dec 11, 2012 at 21:37:18 +0800, Osier Yang wrote:
> This introduces a hash table for qemu driver, to store the shared
> disk's info as (@disk_path, {@ref_count, @orig_cdbfilter}). @ref_count
> is the number of domains which shares the disk. @orig_cdbfilter is
> the original cdbfilter setting of the shared disk, it will be used
> to restore the the disk's cdbfilter setting to original value by
> later patches.
>
> * src/qemu/qemu_conf.h: (Add member 'sharedDisks' of type
> virHashTablePtr; New struct qemuSharedDiskEntry;
> Declare helpers qemuAddSharedDisk,
> qemuRemoveSharedDisk)
> * src/qemu/qemu_conf.c (Implement the two helpers)
> * src/qemu/qemu_process.c (Update 'sharedDisks' when domain
> starting and shutdown)
> * src/qemu/qemu_driver.c (Update 'sharedDisks' when attaching
> or detaching disk).
>
> 0 is passed for orig_cdbfilter temporarily, later patches will update
> it.
> ---
> src/qemu/qemu_conf.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++
> src/qemu/qemu_conf.h | 18 +++++++++++++++++
> src/qemu/qemu_driver.c | 17 ++++++++++++++++
> src/qemu/qemu_process.c | 17 +++++++++++++++-
> 4 files changed, 99 insertions(+), 1 deletions(-)
>
> diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
> index 8d380a1..2b21186 100644
> --- a/src/qemu/qemu_conf.c
> +++ b/src/qemu/qemu_conf.c
> @@ -556,3 +556,51 @@ qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
>
> virHashForEach(driver->closeCallbacks, qemuDriverCloseCallbackRun, &data);
> }
> +
> +/* Increase ref count if the entry already exists, otherwise
> + * add a new entry.
> + */
> +int
> +qemuAddSharedDisk(virHashTablePtr sharedDisks,
> + const char *disk_path,
> + int orig_cdbfilter)
> +{
> + qemuSharedDiskEntryPtr entry = NULL;
> +
> + if ((entry = virHashLookup(sharedDisks, disk_path))) {
> + entry->ref++;
> + } else {
> + if (VIR_ALLOC(entry) < 0)
> + return -1;
> +
> + entry->ref = 1;
> + entry->orig_cdbfilter = orig_cdbfilter;
> +
> + if (virHashAddEntry(sharedDisks, disk_path, entry))
> + return -1;
> + }
In addition to Daniel's comments, I think this hash table should contain
device number rather than disk path since /dev is full of symlinks. One
domain may be configured to use /dev/sdg while another one would use
/dev/disk/by-id/..., another one /dev/disk/by-uuid/... and they can all
lead to the same block device. Thus you need to canonicalize disk_path
first, e.g., into major:minor and store that in the hash table.
Jirka
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