Support reading zstd-compressed initrds #920
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This was referenced Jul 14, 2022
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lucab
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Jul 15, 2022
jlebon
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Jul 15, 2022
| // the magic number of another frame, and decide whether we're done. The | ||
| // raw decoder always stops at frame boundaries, so this is reliable. If | ||
| // done, return Ok(0) and allow the caller to decide what it wants to do | ||
| // about trailing data. |
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Have you considered opening a PR upstream to support this in the higher-level API?
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Hmm. In zstd there are two parts to EOF detection: noticing we're at the end of a frame and checking whether another frame is coming. Upstream could do the first part, but I don't think the second part can be done robustly without something like PeekReader, which the upstream API can't require. And it seems awkward to provide a high-level API that requires the caller to manually read ahead and check magic numbers. Allowing trailing data is a pretty obscure requirement, really, so sticking to the low-level API seems fine.
This adds a library dependency on libzstd, since we're not having the zstd crate statically link it.
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Minor updates for comments and to avoid hardcoding the magic numbers. |
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bgilbert
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On my system, relative to gzip -9, it roughly halves decompression time at boot while also reducing initrd size. RHCOS 8 can't inherit this because the RHEL 8 kernel doesn't enable CONFIG_RD_ZSTD. This requires coreos-installer to support decoding zstd (for `coreos-installer pxe customize`), which is coreos/coreos-installer#920. For coreos/fedora-coreos-tracker#1247.
HuijingHei
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Oct 10, 2023
On my system, relative to gzip -9, it roughly halves decompression time at boot while also reducing initrd size. RHCOS 8 can't inherit this because the RHEL 8 kernel doesn't enable CONFIG_RD_ZSTD. This requires coreos-installer to support decoding zstd (for `coreos-installer pxe customize`), which is coreos/coreos-installer#920. For coreos/fedora-coreos-tracker#1247.
HuijingHei
pushed a commit
to HuijingHei/fedora-coreos-config
that referenced
this pull request
Oct 10, 2023
On my system, relative to gzip -9, it roughly halves decompression time at boot while also reducing initrd size. RHCOS 8 can't inherit this because the RHEL 8 kernel doesn't enable CONFIG_RD_ZSTD. This requires coreos-installer to support decoding zstd (for `coreos-installer pxe customize`), which is coreos/coreos-installer#920. For coreos/fedora-coreos-tracker#1247.
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