log: correct size output in disk space check

fanquake commented at 12:26 pm on January 15, 2026: member

The output should be the additional space needed, otherwise we are always warning that 810GB will be stored, even when a user is pruning.

For example on machine with ~20GB free disk, pruning to 40GB:

0./build/bin/bitcoind -prune=40000
1...
22026-01-15T11:45:33Z [warning] Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.
3Warning: Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.

This PR:

0./build/bin/bitcoind -prune=40000
1...
22026-01-15T11:41:49Z [warning] Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 39 GB of data will be stored in this directory.
3Warning: Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 39 GB of data will be stored in this directory.

log: correct size output in disk space check

The output should be the additional space needed, otherwise we are
always warning that 810GB will be stored, even when a user is pruning.

For example on machine with ~20GB free disk, pruning to 40GB:
```bash
./build/bin/bitcoind -prune=40000
...
2026-01-15T11:45:33Z [warning] Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.
Warning: Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.
```

This PR:
```bash
./build/bin/bitcoind -prune=40000
...
2026-01-15T11:41:49Z [warning] Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 39 GB of data will be stored in this directory.
Warning: Disk space for "/root/.bitcoin/blocks" may not accommodate the block files. Approximately 39 GB of data will be stored in this directory.
```

2a42d39ea0

DrahtBot added the label Utils/log/libs on Jan 15, 2026

DrahtBot commented at 12:26 pm on January 15, 2026: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34305.

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Type	Reviewers
ACK	l0rinc, willcl-ark, bensig

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Conflicts

Reviewers, this pull request conflicts with the following ones:

#29678 (Bugfix: Correct first-run free space checks by luke-jr)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

in src/init.cpp:1934 in 2a42d39ea0

1930@@ -1931,7 +1931,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
1931                     "Approximately %u GB of data will be stored in this directory."
1932                 ),
1933                 fs::quoted(fs::PathToString(args.GetBlocksDirPath())),
1934-                chainparams.AssumedBlockchainSize()
1935+                (additional_bytes_needed / 1024 / 1024 / 1024)

l0rinc commented at 12:35 pm on January 15, 2026:

Might be worth noting that this will be capped to current blockchain max size: https://github.com/bitcoin/bitcoin/blob/2a42d39ea0de09d6bbd6852107c6c0fd8cc99d48/src/init.cpp#L1925

l0rinc approved

l0rinc commented at 12:39 pm on January 15, 2026: contributor

tested ACK 2a42d39ea0de09d6bbd6852107c6c0fd8cc99d48

With small prune values it shows the pruning value:

0mkdir -p demo && cmake -B build && cmake --build build -j$(nproc) && ./build/bin/bitcoind -datadir=demo -prune=400000
12026-01-15T12:33:14Z [warning] Disk space for "[...]/bitcoin/demo/blocks" may not accommodate the block files. Approximately 390 GB of data will be stored in this directory.

For very big values it shows the current blocksdir size instead:

0mkdir -p demo && cmake -B build && cmake --build build -j$(nproc) && ./build/bin/bitcoind -datadir=demo -prune=4000000
12026-01-15T12:33:45Z [warning] Disk space for "[...]/bitcoin/demo/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.

willcl-ark approved

willcl-ark commented at 1:16 pm on January 15, 2026: member

tACK 2a42d39ea0de09d6bbd6852107c6c0fd8cc99d48

With 520GB free on /tmp I see:

master:

0❯ /run/current-system/sw/bin/bitcoind -daemon=0 -datadir=/tmp/size-warn -prune=600000
1<snip>
22026-01-15T13:16:00Z [warning] Disk space for "/tmp/size-warn/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.
3Warning: Disk space for "/tmp/size-warn/blocks" may not accommodate the block files. Approximately 810 GB of data will be stored in this directory.

PR

0❯ ./build/bin/bitcoind -daemon=0 -datadir=/tmp/size-warn -prune=600000
1<snip>
22026-01-15T13:13:51Z init message: Pruning blockstore…
32026-01-15T13:13:51Z [warning] Disk space for "/tmp/size-warn/blocks" may not accommodate the block files. Approximately 585 GB of data will be stored in this directory.
4Warning: Disk space for "/tmp/size-warn/blocks" may not accommodate the block files. Approximately 585 GB of data will be stored in this directory.

bensig commented at 7:34 pm on January 19, 2026: contributor

ACK 2a42d39ea0de09d6bbd6852107c6c0fd8cc99d48

log: correct size output in disk space check #34305

Code Coverage & Benchmarks

Reviews

Conflicts