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author | Kent Overstreet <kent.overstreet@linux.dev> | 2024-02-21 22:10:09 -0500 |
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committer | Kent Overstreet <kent.overstreet@linux.dev> | 2024-03-13 21:22:25 -0400 |
commit | eb386617be4bdfe02eb0972874f726e2bfc7a6e7 (patch) | |
tree | 63b70d6b9c2a966be41d8f44d1d86fe6dc692809 /Documentation/filesystems/bcachefs | |
parent | 150194cdcb6b4305be41cd8af7a42dd2d1457ae1 (diff) | |
download | linux-stable-eb386617be4bdfe02eb0972874f726e2bfc7a6e7.tar.gz linux-stable-eb386617be4bdfe02eb0972874f726e2bfc7a6e7.tar.bz2 linux-stable-eb386617be4bdfe02eb0972874f726e2bfc7a6e7.zip |
bcachefs: Errcode tracepoint, documentation
Add a tracepoint for downcasting private errors to standard errors, so
they can be recovered even when not logged; also, add some
documentation.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'Documentation/filesystems/bcachefs')
-rw-r--r-- | Documentation/filesystems/bcachefs/errorcodes.rst | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Documentation/filesystems/bcachefs/errorcodes.rst b/Documentation/filesystems/bcachefs/errorcodes.rst new file mode 100644 index 000000000000..2cccaa0ba7cd --- /dev/null +++ b/Documentation/filesystems/bcachefs/errorcodes.rst @@ -0,0 +1,30 @@ +.. 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. |