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487f3202fe
Before this PR, an IO error returned from the kernel, e.g., due to a bad
disk, would get bubbled up, all the way to a user-visible query failing.
This is against the IO error handling policy where we have established
and is hence being rectified in this PR.
[[(internal Policy document
link)]](bef44149f7/src/storage/handling_io_and_logical_errors.md (L33-L35))
The practice on the write path seems to be that we call
`maybe_fatal_err()` or `fatal_err()` fairly high up the stack.
That is, regardless of whether std::fs, tokio::fs, or VirtualFile is
used to perform the IO.
For the read path, I choose a centralized approach in this PR by
checking for errors as close to the kernel interface as possible.
I believe this is better for long-term consistency.
To mitigate the problem of missing context if we abort so far down in
the stack, the `on_fatal_io_error` now captures and logs a backtrace.
I grepped the pageserver code base for `fs::read` to convince myself
that all non-VirtualFile reads already handle IO errors according to
policy.
Refs
- fixes https://github.com/neondatabase/neon/issues/10454