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- .. SPDX-License-Identifier: GPL-2.0
- bcachefs private error codes
- ----------------------------
- In bcachefs, as a hard rule we do not throw or directly use standard error
- codes (-EINVAL, -EBUSY, etc.). Instead, we define private error codes as needed
- in fs/bcachefs/errcode.h.
- This gives us much better error messages and makes debugging much easier. Any
- direct uses of standard error codes you see in the source code are simply old
- code that has yet to be converted - feel free to clean it up!
- Private error codes may subtype another error code, this allows for grouping of
- related errors that should be handled similarly (e.g. transaction restart
- errors), as well as specifying which standard error code should be returned at
- the bcachefs module boundary.
- At the module boundary, we use bch2_err_class() to convert to a standard error
- code; this also emits a trace event so that the original error code be
- recovered even if it wasn't logged.
- Do not reuse error codes! Generally speaking, a private error code should only
- be thrown in one place. That means that when we see it in a log message we can
- see, unambiguously, exactly which file and line number it was returned from.
- Try to give error codes names that are as reasonably descriptive of the error
- as possible. Frequently, the error will be logged at a place far removed from
- where the error was generated; good names for error codes mean much more
- descriptive and useful error messages.
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