9e5b265a58
Since udev will probe block devices it is advisable to hold a lock on the device when modifying its partition table or the superblock of the filesystem (see [1]). osbuild loopback devices do support this via the `lock` option. Set this option for all operation that involve changing block device "metadata" that could potentionally race with udev, such as sfdisk, mkfs, creating a luks2 container and creating LVM2 volume groups and logical volumes. NB: osbuild also has its own device inhibition logic to prevent udev/lvm2 from auto activating devices and in general to limit the interaction between the host and devices used by osbuild. See [2] for more information. NB: this also locks the loopback device in situation where we the it is strickly not the right thing to do, e.g. when creating a fs on a logical voume that is located on a loopback device, since in this case the device we would need to lock is the logical volume. Sadly, LVM/DM devices are exempt from block device locking. But, due to a bug in osbuild < 50, the udev inhibitor does *not* work for loopback devices and therefore we have to use the actual lock to preven LVM device auto-activation via `69-dm-lvm-metad.rules`. The change was implemented by adding a new boolean to `getDevices` indicating if the loopback device should be locked or not. Once we depend on osbuild 50 we can change the logic in `getDevices` to only lock the loopback device if the number of devices is one, i.e. we are working directly on the loopback device. [1] https://systemd.io/BLOCK_DEVICE_LOCKING/ [2] /usr/lib/udev/rules.d/10-osbuild-inhibitor.rules
29 lines
702 B
Go
29 lines
702 B
Go
package osbuild2
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// Expose a file (or part of it) as a device node
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type LoopbackDeviceOptions struct {
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// File to associate with the loopback device
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Filename string `json:"filename"`
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// Start of the data segment
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Start uint64 `json:"start,omitempty"`
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// Size limit of the data segment (in sectors)
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Size uint64 `json:"size,omitempty"`
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// Sector size (in bytes)
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SectorSize *uint64 `json:"sector-size,omitempty"`
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// Lock (bsd lock) the device after opening it
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Lock bool `json:"lock,omitempty"`
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}
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func (LoopbackDeviceOptions) isDeviceOptions() {}
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func NewLoopbackDevice(options *LoopbackDeviceOptions) *Device {
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return &Device{
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Type: "org.osbuild.loopback",
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Options: options,
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}
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}
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