On 2012年12月13日 19:05, Jiri Denemark wrote:
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.
Hum, agreed, this is really good catch which saves us from the potential bug. Thanks. Regards, Osier