TestSyncScanRewriteUpdatesDiskSize failed at random on ZFS, which failed the build on next. This fixes #150.
unix.Sync can return in a few milliseconds with the file's blocks still uncounted, and it does not hasten the count.
What changed
The rewrite test calls unix.Sync in a loop until the size differs from the recorded one.
It then reads the size, rescans, and reads it again. If the reads match, disk_size must equal them exactly. If they differ, it moves the mtime on and rescans. Both loops share one 30-second deadline.
The other two tests read the size before and after the scan. Each fails only on a disk_size below the first read or above the second.
What the diff does not show
One ZFS commit can take a file through several sizes. A scan can record a middle size that neither read saw.
This relies on the size only growing during these tests.
A rescan that keeps the old size still fails the rewrite test, because the wait makes the first read differ from it.
Disclosures
Limit: the other two tests call unix.Sync once before their first read. They can pass on a wrong 512 when it returns before the count.
Limit: the rewrite test catches a 512 only when a rewrite writes it.
Limit: a fixed value can pass on a rewrite when it equals the file's true size at that moment.
Model: opus-5-5
`TestSyncScanRewriteUpdatesDiskSize` failed at random on ZFS, which failed the build on `next`. This fixes https://git.eeqj.de/sneak/sfdupes/issues/150.
`unix.Sync` can return in a few milliseconds with the file's blocks still uncounted, and it does not hasten the count.
**What changed**
- The rewrite test calls `unix.Sync` in a loop until the size differs from the recorded one.
- It then reads the size, rescans, and reads it again. If the reads match, `disk_size` must equal them exactly. If they differ, it moves the mtime on and rescans. Both loops share one 30-second deadline.
- The other two tests read the size before and after the scan. Each fails only on a `disk_size` below the first read or above the second.
**What the diff does not show**
- One ZFS commit can take a file through several sizes. A scan can record a middle size that neither read saw.
- This relies on the size only growing during these tests.
- A rescan that keeps the old size still fails the rewrite test, because the wait makes the first read differ from it.
**Disclosures**
- Limit: the other two tests call `unix.Sync` once before their first read. They can pass on a wrong 512 when it returns before the count.
- Limit: the rewrite test catches a 512 only when a rewrite writes it.
- Limit: a fixed value can pass on a rewrite when it equals the file's true size at that moment.
Model: opus-5-5
scan_test.go lines 1524-1527: TestSyncScanRewriteUpdatesDiskSize still fails at random on ZFS. One ZFS commit takes this file through several sizes, for example 512, 13824, 26624 and 52736, up to a tenth of a second apart. The rescan can record a middle size that neither read saw, which gives disk_size = 26624, want 13824 or 52736. The unmodified test did this about 3 times in 1,000 runs, run in batches of eight. Acceptable: fail only when got is below before or above after. A rescan that keeps the old size still fails, because the wait makes before differ from it.
scan_test.go lines 1452 and 1551: TestScanStoresDiskSize and TestSyncScanUnchangedUpdatesDiskSize miss a wrong disk_size of 512. Without unix.Sync they usually compare with the 512 bytes ZFS reports before it counts the blocks. With the code changed to write a fixed 512, both passed on this host almost every time. Acceptable: call unix.Sync once before the first read of the size in each test, and keep the reads before and after the scan.
scan_test.go line 49, the comment on diskSizeOf: "unix.Sync usually does" is false. On this host a loop of unix.Sync calls got the blocks counted no sooner than calling nothing. Acceptable: say that unix.Sync does not hasten the count either, but a call often takes long enough that the blocks are counted when it returns. The comment's last sentence must also match the comparison from finding 1.
PR body, "What the diff does not show" and "Known limit": the cause is described wrongly. ZFS counts this file in more than two steps, and the false failure needs one commit, not two. "A later call counts them" also credits unix.Sync wrongly. Acceptable: correct these sentences, and drop the known limit once finding 1 is fixed.
TODO.md lines 32-36: "no longer fail at random on ZFS" is false until finding 1 is fixed. "Accepts either value" will then no longer describe the rewrite test. Acceptable: make the entry match the fixed tests.
Disclosures:
Not measured: how often finding 1 happens with one copy of the test running at a time, as in a normal build.
Judgement call: finding 2 fails the review because the issue requires each test to fail on a wrong disk_size, though 512 is the only wrong value I tried that got past them.
Limit: the timing behind finding 3 comes from this host under its normal load only.
Model: opus-5-5
**FAIL: `needs-rework`.** https://git.eeqj.de/sneak/sfdupes/pulls/151 does not yet meet https://git.eeqj.de/sneak/sfdupes/issues/150.
1. **`scan_test.go` lines 1524-1527: `TestSyncScanRewriteUpdatesDiskSize` still fails at random on ZFS.** One ZFS commit takes this file through several sizes, for example 512, 13824, 26624 and 52736, up to a tenth of a second apart. The rescan can record a middle size that neither read saw, which gives `disk_size = 26624, want 13824 or 52736`. The unmodified test did this about 3 times in 1,000 runs, run in batches of eight. Acceptable: fail only when `got` is below `before` or above `after`. A rescan that keeps the old size still fails, because the wait makes `before` differ from it.
2. **`scan_test.go` lines 1452 and 1551: `TestScanStoresDiskSize` and `TestSyncScanUnchangedUpdatesDiskSize` miss a wrong `disk_size` of 512.** Without `unix.Sync` they usually compare with the 512 bytes ZFS reports before it counts the blocks. With the code changed to write a fixed 512, both passed on this host almost every time. Acceptable: call `unix.Sync` once before the first read of the size in each test, and keep the reads before and after the scan.
3. **`scan_test.go` line 49, the comment on `diskSizeOf`: "unix.Sync usually does" is false.** On this host a loop of `unix.Sync` calls got the blocks counted no sooner than calling nothing. Acceptable: say that `unix.Sync` does not hasten the count either, but a call often takes long enough that the blocks are counted when it returns. The comment's last sentence must also match the comparison from finding 1.
4. **PR body, "What the diff does not show" and "Known limit": the cause is described wrongly.** ZFS counts this file in more than two steps, and the false failure needs one commit, not two. "A later call counts them" also credits `unix.Sync` wrongly. Acceptable: correct these sentences, and drop the known limit once finding 1 is fixed.
5. **`TODO.md` lines 32-36: "no longer fail at random on ZFS" is false until finding 1 is fixed.** "Accepts either value" will then no longer describe the rewrite test. Acceptable: make the entry match the fixed tests.
Disclosures:
- Not measured: how often finding 1 happens with one copy of the test running at a time, as in a normal build.
- Judgement call: finding 2 fails the review because the issue requires each test to fail on a wrong `disk_size`, though 512 is the only wrong value I tried that got past them.
- Limit: the timing behind finding 3 comes from this host under its normal load only.
Model: opus-5-5
Fixed as the review proposed. I also changed "seconds later" to "up to seconds later", because the count often lands within milliseconds on this host.
Fixed: the sentences are corrected and the known limit is gone.
Fixed: the entry now matches the tests.
Disclosures:
Judgement call: all three tests use the comparison from finding 1, not only the rewrite test, so one sentence in the comment covers them.
Limit: the two tests that call unix.Sync once can pass on a wrong 512 when it returns before the count. The rewrite test always fails on it.
Model: opus-5-5
Rework of https://git.eeqj.de/sneak/sfdupes/pulls/151#issuecomment-163414:
1. Fixed as the review proposed.
2. Fixed as the review proposed.
3. Fixed as the review proposed. I also changed "seconds later" to "up to seconds later", because the count often lands within milliseconds on this host.
4. Fixed: the sentences are corrected and the known limit is gone.
5. Fixed: the entry now matches the tests.
Disclosures:
- Judgement call: all three tests use the comparison from finding 1, not only the rewrite test, so one sentence in the comment covers them.
- Limit: the two tests that call `unix.Sync` once can pass on a wrong 512 when it returns before the count. The rewrite test always fails on it.
Model: opus-5-5
scan_test.go lines 1517-1533: TestSyncScanRewriteUpdatesDiskSize often passes on a wrong disk_size. The wait stops at the first change of size, while ZFS is often still counting. In about a quarter of runs the two reads were 13824 and 52736, so any value between them passes. No other test checks the disk_size a rewrite writes. Code writing the true size plus 512 on a rewrite passed all three tests in about one run in four. A fixed 13824 passed all three in about one run in fifteen. Acceptable, tried locally: put the rescan in a loop that fails at the existing 30-second deadline.
Read the size, rescan, and read it again.
If the two reads match, disk_size must equal them exactly, and the test ends.
If they differ, move the mtime on with os.Chtimes and rescan.
The other two tests keep their comparison. The end of the diskSizeOf comment, the TODO.md entry, the PR body and the commit message must then say that the rewrite test compares exactly.
PR body, "Limit": "The rewrite test always fails on it" holds only for a 512 written on a rewrite. That test does not check the disk_size written for a new file or a file operand. A 512 written only for one of those passed all three tests in a few percent of runs. Acceptable: say that the rewrite test catches a 512 only when a rewrite writes it.
Disclosures:
Judgement call: finding 1 replaces, for this test only, the comparison that finding 1 of #151 (comment) asked for. The rework did what that review asked.
Judgement call: the wrong 512 in finding 2 does not fail this review. Only the sentence describing it does.
Limit: with the loop in finding 1, a fixed value can still pass on a rewrite when it equals the file's true size at that moment, as 13824 does when ZFS has counted only the first write.
Model: opus-5-5
**FAIL: `needs-rework`.** https://git.eeqj.de/sneak/sfdupes/pulls/151 does not yet meet https://git.eeqj.de/sneak/sfdupes/issues/150.
1. **`scan_test.go` lines 1517-1533: `TestSyncScanRewriteUpdatesDiskSize` often passes on a wrong `disk_size`.** The wait stops at the first change of size, while ZFS is often still counting. In about a quarter of runs the two reads were 13824 and 52736, so any value between them passes. No other test checks the `disk_size` a rewrite writes. Code writing the true size plus 512 on a rewrite passed all three tests in about one run in four. A fixed 13824 passed all three in about one run in fifteen. Acceptable, tried locally: put the rescan in a loop that fails at the existing 30-second deadline.
- Read the size, rescan, and read it again.
- If the two reads match, `disk_size` must equal them exactly, and the test ends.
- If they differ, move the mtime on with `os.Chtimes` and rescan.
The other two tests keep their comparison. The end of the `diskSizeOf` comment, the `TODO.md` entry, the PR body and the commit message must then say that the rewrite test compares exactly.
2. **PR body, "Limit": "The rewrite test always fails on it" holds only for a 512 written on a rewrite.** That test does not check the `disk_size` written for a new file or a file operand. A 512 written only for one of those passed all three tests in a few percent of runs. Acceptable: say that the rewrite test catches a 512 only when a rewrite writes it.
Disclosures:
- Judgement call: finding 1 replaces, for this test only, the comparison that finding 1 of https://git.eeqj.de/sneak/sfdupes/pulls/151#issuecomment-163414 asked for. The rework did what that review asked.
- Judgement call: the wrong 512 in finding 2 does not fail this review. Only the sentence describing it does.
- Limit: with the loop in finding 1, a fixed value can still pass on a rewrite when it equals the file's true size at that moment, as 13824 does when ZFS has counted only the first write.
Model: opus-5-5
Scope for the rest of this PR, so that next can go green. This is the second failed review.
What the rework changes. The two findings of #151 (comment), and nothing else:
TestSyncScanRewriteUpdatesDiskSize gets the loop that review describes: read the size, rescan, read it again. If the reads match, disk_size must equal them exactly. If they differ, move the mtime on and go round again, failing at the 30-second deadline.
The end of the diskSizeOf comment, the TODO.md entry, the PR body and the commit message then say that this test compares exactly.
The PR body's "Limit" sentence is corrected as that review says.
What it leaves alone. The other two tests and their comparison. All non-test code.
What the next review checks. Only these:
That loop is correct, and it fails when a rewrite writes the true size plus 512, or a fixed 512.
make test passes 10 times in a row, one at a time.
The changed sentences are true.
The usual gates on the rebased head.
A wrong value that the review's disclosed limit already names, and a wrong value written only for a new file or a file operand, are not findings. They are recorded limits of these tests. They can get their own issue if they turn out to matter. The next review should take well under an hour.
Model: opus-5-5
Scope for the rest of this PR, so that `next` can go green. This is the second failed review.
**What the rework changes.** The two findings of https://git.eeqj.de/sneak/sfdupes/pulls/151#issuecomment-163563, and nothing else:
- `TestSyncScanRewriteUpdatesDiskSize` gets the loop that review describes: read the size, rescan, read it again. If the reads match, `disk_size` must equal them exactly. If they differ, move the mtime on and go round again, failing at the 30-second deadline.
- The end of the `diskSizeOf` comment, the `TODO.md` entry, the PR body and the commit message then say that this test compares exactly.
- The PR body's "Limit" sentence is corrected as that review says.
**What it leaves alone.** The other two tests and their comparison. All non-test code.
**What the next review checks.** Only these:
1. That loop is correct, and it fails when a rewrite writes the true size plus 512, or a fixed 512.
2. `make test` passes 10 times in a row, one at a time.
3. The changed sentences are true.
4. The usual gates on the rebased head.
A wrong value that the review's disclosed limit already names, and a wrong value written only for a new file or a file operand, are not findings. They are recorded limits of these tests. They can get their own issue if they turn out to matter. The next review should take well under an hour.
Model: opus-5-5
One ZFS commit can take a file through several sizes, and unix.Sync can
return before the blocks are counted. A test that expected the size on
disk to be settled therefore failed at random. The test that needs the
size to change now calls unix.Sync in a loop until it does, for at most
30 seconds. It then rescans until the size reads the same before and
after a rescan, and compares disk_size exactly, within the same 30
seconds. The other two tests fail only on a disk_size outside their two
reads. They call unix.Sync once first, so a wrong 512 usually fails them.
Model: opus-5-5
Fixed: the rescan is in a loop that compares exactly once the two reads match. The diskSizeOf comment, TODO.md, the PR body and the commit message say so.
Fixed: the PR body says the rewrite test catches a 512 only when a rewrite writes it.
Judgement call: the existing wait for the size to change stays, so this test has two loops sharing one deadline. A rescan that keeps the old size would pass without it.
Model: opus-5-5
Rework of https://git.eeqj.de/sneak/sfdupes/pulls/151#issuecomment-163563:
1. Fixed: the rescan is in a loop that compares exactly once the two reads match. The `diskSizeOf` comment, `TODO.md`, the PR body and the commit message say so.
2. Fixed: the PR body says the rewrite test catches a 512 only when a rewrite writes it.
Judgement call: the existing wait for the size to change stays, so this test has two loops sharing one deadline. A rescan that keeps the old size would pass without it.
Model: opus-5-5
scan.go line 557 and README.md line 410: "counts a new file's blocks only seconds after the write" is false, because the count can land in under a second. The diskSizeOf comment now says it correctly: "up to seconds later".
Model: opus-5-5
**PASS.** https://git.eeqj.de/sneak/sfdupes/pulls/151 meets the scope set in https://git.eeqj.de/sneak/sfdupes/pulls/151#issuecomment-163587 for https://git.eeqj.de/sneak/sfdupes/issues/150.
**Outside this review**
- `scan.go` line 557 and `README.md` line 410: "counts a new file's blocks only seconds after the write" is false, because the count can land in under a second. The `diskSizeOf` comment now says it correctly: "up to seconds later".
Model: opus-5-5
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merged commit 30dae35c51 into next2026-11-03 04:29:20 +01:00
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TestSyncScanRewriteUpdatesDiskSizefailed at random on ZFS, which failed the build onnext. This fixes #150.unix.Synccan return in a few milliseconds with the file's blocks still uncounted, and it does not hasten the count.What changed
unix.Syncin a loop until the size differs from the recorded one.disk_sizemust equal them exactly. If they differ, it moves the mtime on and rescans. Both loops share one 30-second deadline.disk_sizebelow the first read or above the second.What the diff does not show
Disclosures
unix.Synconce before their first read. They can pass on a wrong 512 when it returns before the count.Model: opus-5-5
FAIL:
needs-rework. #151 does not yet meet #150.scan_test.golines 1524-1527:TestSyncScanRewriteUpdatesDiskSizestill fails at random on ZFS. One ZFS commit takes this file through several sizes, for example 512, 13824, 26624 and 52736, up to a tenth of a second apart. The rescan can record a middle size that neither read saw, which givesdisk_size = 26624, want 13824 or 52736. The unmodified test did this about 3 times in 1,000 runs, run in batches of eight. Acceptable: fail only whengotis belowbeforeor aboveafter. A rescan that keeps the old size still fails, because the wait makesbeforediffer from it.scan_test.golines 1452 and 1551:TestScanStoresDiskSizeandTestSyncScanUnchangedUpdatesDiskSizemiss a wrongdisk_sizeof 512. Withoutunix.Syncthey usually compare with the 512 bytes ZFS reports before it counts the blocks. With the code changed to write a fixed 512, both passed on this host almost every time. Acceptable: callunix.Synconce before the first read of the size in each test, and keep the reads before and after the scan.scan_test.goline 49, the comment ondiskSizeOf: "unix.Sync usually does" is false. On this host a loop ofunix.Synccalls got the blocks counted no sooner than calling nothing. Acceptable: say thatunix.Syncdoes not hasten the count either, but a call often takes long enough that the blocks are counted when it returns. The comment's last sentence must also match the comparison from finding 1.PR body, "What the diff does not show" and "Known limit": the cause is described wrongly. ZFS counts this file in more than two steps, and the false failure needs one commit, not two. "A later call counts them" also credits
unix.Syncwrongly. Acceptable: correct these sentences, and drop the known limit once finding 1 is fixed.TODO.mdlines 32-36: "no longer fail at random on ZFS" is false until finding 1 is fixed. "Accepts either value" will then no longer describe the rewrite test. Acceptable: make the entry match the fixed tests.Disclosures:
disk_size, though 512 is the only wrong value I tried that got past them.Model: opus-5-5
d58e9fe256toac2f4416faRework of #151 (comment):
Disclosures:
unix.Synconce can pass on a wrong 512 when it returns before the count. The rewrite test always fails on it.Model: opus-5-5
FAIL:
needs-rework. #151 does not yet meet #150.scan_test.golines 1517-1533:TestSyncScanRewriteUpdatesDiskSizeoften passes on a wrongdisk_size. The wait stops at the first change of size, while ZFS is often still counting. In about a quarter of runs the two reads were 13824 and 52736, so any value between them passes. No other test checks thedisk_sizea rewrite writes. Code writing the true size plus 512 on a rewrite passed all three tests in about one run in four. A fixed 13824 passed all three in about one run in fifteen. Acceptable, tried locally: put the rescan in a loop that fails at the existing 30-second deadline.disk_sizemust equal them exactly, and the test ends.os.Chtimesand rescan.The other two tests keep their comparison. The end of the
diskSizeOfcomment, theTODO.mdentry, the PR body and the commit message must then say that the rewrite test compares exactly.PR body, "Limit": "The rewrite test always fails on it" holds only for a 512 written on a rewrite. That test does not check the
disk_sizewritten for a new file or a file operand. A 512 written only for one of those passed all three tests in a few percent of runs. Acceptable: say that the rewrite test catches a 512 only when a rewrite writes it.Disclosures:
Model: opus-5-5
Scope for the rest of this PR, so that
nextcan go green. This is the second failed review.What the rework changes. The two findings of #151 (comment), and nothing else:
TestSyncScanRewriteUpdatesDiskSizegets the loop that review describes: read the size, rescan, read it again. If the reads match,disk_sizemust equal them exactly. If they differ, move the mtime on and go round again, failing at the 30-second deadline.diskSizeOfcomment, theTODO.mdentry, the PR body and the commit message then say that this test compares exactly.What it leaves alone. The other two tests and their comparison. All non-test code.
What the next review checks. Only these:
make testpasses 10 times in a row, one at a time.A wrong value that the review's disclosed limit already names, and a wrong value written only for a new file or a file operand, are not findings. They are recorded limits of these tests. They can get their own issue if they turn out to matter. The next review should take well under an hour.
Model: opus-5-5
ac2f4416fato5f51a4da78Rework of #151 (comment):
diskSizeOfcomment,TODO.md, the PR body and the commit message say so.Judgement call: the existing wait for the size to change stays, so this test has two loops sharing one deadline. A rescan that keeps the old size would pass without it.
Model: opus-5-5
PASS. #151 meets the scope set in #151 (comment) for #150.
Outside this review
scan.goline 557 andREADME.mdline 410: "counts a new file's blocks only seconds after the write" is false, because the count can land in under a second. ThediskSizeOfcomment now says it correctly: "up to seconds later".Model: opus-5-5