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I don't want no scrubs (for read-only Crucible backends) #1028

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Merged
hawkw merged 2 commits into from
Jan 30, 2026
+12 −2
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I don't want no scrubs (for read-only Crucible backends) #1028

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I don't want no scrubs (for read-only Crucible backends)
hawkw Jan 29, 2026
01be6dc
Use `is_read_only` here too
hawkw Jan 29, 2026
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7 changes: 5 additions & 2 deletions lib/propolis/src/block/crucible.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,10 @@ impl CrucibleBackend {
.map_err(|e| io::Error::from(CrucibleError::from(e)))?;

// Decide if we need to scrub this volume or not.
if volume.has_read_only_parent() {
//
// We should not scrub read-only volumes, as we cannot write back to
// them, due to...you know, being read-only. So just don't do that.
if !opts.is_read_only() && volume.has_read_only_parent() {
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@leftwo leftwo Jan 30, 2026

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I'm not convinced Nexus can construct a read only volume with a read_only_parent, but I suppose nothing stops you from sending propolis a toml directly that contains such a beast. So, it's probably best to just prevent it.

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@hawkw hawkw Jan 30, 2026

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@jmpesp told me it was possible, though I'm not sure if it will currently happen for the way we construct ro disks or not?

let vclone = volume.clone();
tokio::spawn(async move {
let volume_id = vclone.get_uuid().await.unwrap();
Expand Down Expand Up @@ -217,7 +220,7 @@ impl CrucibleBackend {
let info = block::DeviceInfo {
block_size: block_size as u32,
total_size: sectors,
read_only: opts.read_only.unwrap_or(false),
read_only: opts.is_read_only(),
supports_discard: false,
};

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7 changes: 7 additions & 0 deletions lib/propolis/src/block/mod.rs
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Expand Up @@ -275,6 +275,13 @@ pub struct BackendOpts {
pub skip_flush: Option<bool>,
}

impl BackendOpts {
/// Return `true` if and only if this backend is configured to be read-only.
pub fn is_read_only(&self) -> bool {
self.read_only.unwrap_or(false)
}
}

/// Top-level trait for block devices (frontends) to translate guest block IO
/// requests into [Request]s for the attached [Backend]
pub trait Device: Send + Sync + 'static {
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