Re: [libvirt] [PATCH 01/12] qemu: Add a hash table for the shared disks

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.