Test device numbers #2
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Signed-off-by: Lorenzo Fontana <[email protected]>
fntlnz
commented
Oct 28, 2017
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| return nil | ||
| return CopyFile(path, filepath.Join(dest, relPath)) |
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Here I just noted that checking for the error was a bit redundant, if there's was a reason for that just let me know and I'll send without this
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@mrunalp PTAL |
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LGTM. Thanks! |
kolyshkin
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to kolyshkin/fileutils
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May 16, 2020
This subtle bug keeps lurking in because error checking for `Mkdir()`
and `MkdirAll()` is slightly different wrt `EEXIST`/`IsExist`:
- for `Mkdir()`, `IsExist` error should (usually) be ignored
(unless you want to make sure directory was not there before)
as it means "the destination directory was already there";
- for `MkdirAll()`, `IsExist` error should NEVER be ignored.
This commit removes ignoring the IsExist error, as it should not
be ignored.
For more details, a quote from my runc commit 6f82d4b (July 2015):
TL;DR: check for IsExist(err) after a failed MkdirAll() is both
redundant and wrong -- so two reasons to remove it.
Quoting MkdirAll documentation:
> MkdirAll creates a directory named path, along with any necessary
> parents, and returns nil, or else returns an error. If path
> is already a directory, MkdirAll does nothing and returns nil.
This means two things:
1. If a directory to be created already exists, no error is
returned.
2. If the error returned is IsExist (EEXIST), it means there exists
a non-directory with the same name as MkdirAll need to use for
directory. Example: we want to MkdirAll("a/b"), but file "a"
(or "a/b") already exists, so MkdirAll fails.
The above is a theory, based on quoted documentation and my UNIX
knowledge.
3. In practice, though, current MkdirAll implementation [1] returns
ENOTDIR in most of cases described in mrunalp#2, with the exception when
there is a race between MkdirAll and someone else creating the
last component of MkdirAll argument as a file. In this very case
MkdirAll() will indeed return EEXIST.
Because of mrunalp#1, IsExist check after MkdirAll is not needed.
Because of mrunalp#2 and mrunalp#3, ignoring IsExist error is just plain wrong,
as directory we require is not created. It's cleaner to report
the error now.
Note this error is all over the tree, I guess due to copy-paste,
or trying to follow the same usage pattern as for Mkdir(),
or some not quite correct examples on the Internet.
[1] https://github.com/golang/go/blob/f9ed2f75/src/os/path.go
Signed-off-by: Kir Kolyshkin <[email protected]>
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Wrote a test to be sure that calculated major and minor numbers for devices are working as expected when dealing with devices during copy.
Signed-off-by: Lorenzo Fontana [email protected]