Re: [libvirt] [libvirt-glib] Add virStorageVolResize()

On 01/26/2012 10:29 PM, Zeeshan Ali (Khattak) wrote: This part forms the public API, This forwards the public API over the wire, this implements things, and this exposes the implementation to the user (which can also be done at the same time as the public api, if it is simple enough). And it's missing tools/virsh.pod for documentation. I think, in the interest of hitting 0.9.10 freeze deadlines, that we want to commit to the API, but that your implementation still has some issues to be worked out. So, what I'm going to do is split this into three patches, then just review _and commit_ the first two, while leaving the implementation for a v2 patch, once you've fixed things to address Dan's comments (such as, if you're going to resize a qcow2 image, you have to do it with qemu-img and not by raw poking in the header of the file; as well as implementing a sparse vs. pre-allocation flag). The rest of this mail is a review of part 1: I think this makes sense. We normally want to resize capacity; which may or may not also increase allocation. We may also want to resize allocation without affecting capacity (basically, turn a thin disk into a full one), but when you throw things like qcow2 in the mix (allocation may be less than capacity when things are sparse, or may be greater than capacity due to the size of the headers managing the disk), I don't think you can ever directly target the allocation parameter. And the presence of flags will let us add flags if we ever change our minds and need to add even more features (such as async operation, where we then send an event when things complete). In what units? virDomainBlockResize used kbytes as the unit, but I think that's not as nice as doing things in raw bytes. Let's go ahead and define some useful flags now, so that we can give further details on the semantics. You don't have to implement them all right away, but I'd rather have things called out in advance. For now, I'm going to document things as having all expansions be all NUL bytes, although we can always add a flag in the future to allow the resize to use unspecified bytes if that can make an operation faster. s/remainining/remaining/ I think this is too strong - downsizing _might_ be reasonable, even though it is generally a form of data loss and thus must not be default, so let's control it by a flag. Allowing a delta might be nice, and that says we should pass a signed value (shouldn't be an issue - if you can show me anyone with a single storage volume with 2^63 bytes, let alone 2^64, I'd be impressed with their setup!). Hmm, I wonder if we also want to support a percentage growth mode (I want my disk to be made 20% bigger than it currently is, no matter its current size); but that seems difficult to do without a floating point parameter; so at this point, I'm inclined to say that the user must call virStorageVolGetInfo, do the percentage growth themselves, then call the API. Even though I'm proposing making capacity signed, we can do some sanity checking on it to avoid negative values without a request to shrink. In addition to Dan's comment about TAB, I also like to sort these lines. Skipping to the only other file I'd like in patch 1: I'll go ahead and add flag support. Long line. Disk manufacturers would have us use multiples of 1000 rather than 1024 in parsing numbers; but at least you are consistent with the rest of virsh. This should be false, so that... this error message gives the right return value. Missing translation marks. Here's the delta I'm proposing; I'll repost this as a formal patch when I finish reviewing part 2. diff --git i/include/libvirt/libvirt.h.in w/include/libvirt/libvirt.h.in index b169592..d26cbbd 100644 --- i/include/libvirt/libvirt.h.in +++ w/include/libvirt/libvirt.h.in @@ -2386,8 +2386,14 @@ char * virStorageVolGetXMLDesc (virStorageVolPtr pool, char * virStorageVolGetPath (virStorageVolPtr vol); +typedef enum { + VIR_STORAGE_VOL_RESIZE_ALLOCATE = 1 << 0, /* force allocation of new size */ + VIR_STORAGE_VOL_RESIZE_DELTA = 1 << 1, /* size is relative to current */ + VIR_STORAGE_VOL_RESIZE_SHRINK = 1 << 2, /* allow decrease in capacity */ +} virStorageVolResizeFlags; + int virStorageVolResize (virStorageVolPtr vol, - unsigned long long capacity, + long long capacity, unsigned int flags); diff --git i/src/driver.h w/src/driver.h index c850926..485b578 100644 --- i/src/driver.h +++ w/src/driver.h @@ -1263,7 +1263,7 @@ typedef int unsigned int flags); typedef int (*virDrvStorageVolResize) (virStorageVolPtr vol, - unsigned long long capacity, + long long capacity, unsigned int flags); typedef int diff --git i/src/libvirt.c w/src/libvirt.c index 44865e8..540d74a 100644 --- i/src/libvirt.c +++ w/src/libvirt.c @@ -12930,23 +12930,39 @@ error: /** * virStorageVolResize: * @vol: pointer to storage volume - * @capacity: new capacity - * @flags: extra flags; not used yet, so callers should always pass 0 - * - * Changes the capacity of the storage volume @vol to @capacity. The new - * capacity must not exceed the sum of current capacity of the volume and - * remainining free space of its parent pool. Also the new capacity must - * be greater than or equal to current allocation of the volume. + * @capacity: new capacity, in bytes + * @flags: bitwise-OR of virStorageVolResizeFlags + * + * Changes the capacity of the storage volume @vol to @capacity. The + * operation will fail if the new capacity requires allocation that would + * exceed the remaining free space in the parent pool. The contents of + * the new capacity will appear as all zero bytes. + * + * Normally, the operation will attempt to affect capacity with a minimum + * impact on allocation (that is, the default operation favors a sparse + * resize). If @flags contains VIR_STORAGE_VOL_RESIZE_ALLOCATE, then the + * operation will ensure that allocation is sufficient for the new + * capacity; this may make the operation take noticeably longer. + * + * Normally, the operation treats @capacity as the new size in bytes; + * but if @flags contains VIR_STORAGE_RESIZE_DELTA, then @capacity + * represents the size difference to add to the current size. It is + * up to the storage pool implementation whether unaligned requests are + * rounded up to the next valid boundary, or rejected. + * + * Normally, this operation should only be used to enlarge capacity; + * but if @flags contains VIR_STORAGE_RESIZE_SHRINK, it is possible to + * attempt a reduction in capacity even though it might cause data loss. * * Returns 0 on success, or -1 on error. */ int virStorageVolResize(virStorageVolPtr vol, - unsigned long long capacity, + long long capacity, unsigned int flags) { virConnectPtr conn; - VIR_DEBUG("vol=%p", vol); + VIR_DEBUG("vol=%p capacity=%lld flags=%x", vol, capacity, flags); virResetLastError(); @@ -12963,6 +12979,16 @@ virStorageVolResize(virStorageVolPtr vol, goto error; } + /* Negative capacity is valid only with both delta and shrink; + * zero capacity is valid with either delta or shrink. */ + if ((capacity < 0 && !(flags & VIR_STORAGE_VOL_RESIZE_DELTA) && + !(flags & VIR_STORAGE_VOL_RESIZE_SHRINK)) || + (capacity == 0 && !((flags & VIR_STORAGE_VOL_RESIZE_DELTA) || + (flags & VIR_STORAGE_VOL_RESIZE_SHRINK)))) { + virLibStorageVolError(VIR_ERR_INVALID_ARG, __FUNCTION__); + goto error; + } + if (conn->storageDriver && conn->storageDriver->volResize) { int ret; ret = conn->storageDriver->volResize(vol, capacity, flags); diff --git i/src/libvirt_public.syms w/src/libvirt_public.syms index 67c113e..8bdb24b 100644 --- i/src/libvirt_public.syms +++ w/src/libvirt_public.syms @@ -519,8 +519,8 @@ LIBVIRT_0.9.9 { LIBVIRT_0.9.10 { global: virDomainShutdownFlags; + virStorageVolResize; virStorageVolWipePattern; - virStorageVolResize; } LIBVIRT_0.9.9; # .... define new API here using predicted next version number .... diff --git i/tools/virsh.c w/tools/virsh.c index 7f3a55c..634c0f8 100644 --- i/tools/virsh.c +++ w/tools/virsh.c @@ -11284,14 +11284,20 @@ cmdVolInfo(vshControl *ctl, const vshCmd *cmd) */ static const vshCmdInfo info_vol_resize[] = { {"help", N_("resize a vol")}, - {"desc", N_("Resizes a storage vol.")}, + {"desc", N_("Resizes a storage volume.")}, {NULL, NULL} }; static const vshCmdOptDef opts_vol_resize[] = { {"vol", VSH_OT_DATA, VSH_OFLAG_REQ, N_("vol name, key or path")}, - {"capacity", VSH_OT_DATA, VSH_OFLAG_REQ, N_("new capacity for the vol with optional k,M,G,T suffix")}, + {"capacity", VSH_OT_DATA, VSH_OFLAG_REQ, + N_("new capacity for the vol with optional k,M,G,T suffix")}, {"pool", VSH_OT_STRING, 0, N_("pool name or uuid")}, + {"allocate", VSH_OT_BOOL, 0, + N_("allocate the new capacity, rather than leaving it sparse")}, + {"delta", VSH_OT_BOOL, 0, + N_("use capacity as a delta to current size, rather than the new size")}, + {"shrink", VSH_OT_BOOL, 0, N_("allow the resize to shrink the volume")}, {NULL, 0, 0, NULL} }; @@ -11301,7 +11307,18 @@ cmdVolResize(vshControl *ctl, const vshCmd *cmd) virStorageVolPtr vol; const char *capacityStr = NULL; unsigned long long capacity = 0; - bool ret = true; + unsigned int flags = 0; + bool ret = false; + bool delta = false; + + if (vshCommandOptBool(cmd, "allocate")) + flags |= VIR_STORAGE_VOL_RESIZE_ALLOCATE; + if (vshCommandOptBool(cmd, "delta")) { + delta = true; + flags |= VIR_STORAGE_VOL_RESIZE_DELTA; + } + if (vshCommandOptBool(cmd, "shrink")) + flags |= VIR_STORAGE_VOL_RESIZE_SHRINK; if (!vshConnectionUsability(ctl, ctl->conn)) return false; @@ -11311,17 +11328,29 @@ cmdVolResize(vshControl *ctl, const vshCmd *cmd) if (vshCommandOptString(cmd, "capacity", &capacityStr) <= 0) goto cleanup; - if (cmdVolSize(capacityStr, &capacity) < 0) { - vshError(ctl, _("Malformed size %s"), capacityStr); - goto cleanup; + if (delta && *capacityStr == '-') { + if (cmdVolSize(capacityStr + 1, &capacity) < 0) { + vshError(ctl, _("Malformed size %s"), capacityStr); + goto cleanup; + } + capacity = -capacity; + } else { + if (cmdVolSize(capacityStr, &capacity) < 0) { + vshError(ctl, _("Malformed size %s"), capacityStr); + goto cleanup; + } } - if (virStorageVolResize(vol, capacity, 0) == 0) { - vshPrint(ctl, "Size of volume '%s' successfully changed to %s\n", + if (virStorageVolResize(vol, capacity, flags) == 0) { + vshPrint(ctl, + delta ? _("Size of volume '%s' successfully changed by %s\n") + : _("Size of volume '%s' successfully changed to %s\n"), virStorageVolGetName(vol), capacityStr); ret = true; } else { - vshError(ctl, "Failed to change size of volume '%s' to %s\n", + vshError(ctl, + delta ? _("Failed to change size of volume '%s' by %s\n") + : _("Failed to change size of volume '%s' to %s\n"), virStorageVolGetName(vol), capacityStr); ret = false; } diff --git i/tools/virsh.pod w/tools/virsh.pod index 8599f66..6622caf 100644 --- i/tools/virsh.pod +++ w/tools/virsh.pod @@ -2012,6 +2012,17 @@ I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool the volume is in. I<vol-name-or-path> is the name or path of the volume to return the volume key for. +=item B<vol-resize> [I<--pool> I<pool-or-uuid>] I<vol-name-or-path> +I<pool-or-uuid> I<capacity> [I<--allocate>] [I<--delta>] [I<--shrink>] + +Resize the capacity of the given volume, in bytes. +I<--pool> I<pool-or-uuid> is the name or UUID of the storage pool the volume +is in. I<vol-name-or-key-or-path> is the name or key or path of the volume +to resize. The new capacity might be sparse unless I<--allocate> is +specified. Normally, I<capacity> is the new size, but if I<--delta> +is present, then it is added to the existing size. Attempts to shrink +the volume will fail unless I<--shrink> is present. + =back =head1 SECRET COMMMANDS -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org