Re: [PATCH 3/5] perf dso: Use stored fd error instead of stale errno in file_read() and file_size()

[sashiko-bot@kernel.org]

> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> file_read() and file_size() use ret = -errno when
> dso__data(dso)->fd is negative after try_to_open_dso() fails.  By this
> point errno has been through mutex_lock(), nsinfo__mountns_enter(), and
> multiple open() attempts inside try_to_open_dso() — it no longer
> reflects the actual open failure.  If errno happens to be 0, ret = 0
> looks like EOF rather than an error, and file_size() callers like
> dso__data_size() would then report a zero-sized file instead of
> failing.
> 
> dso__data(dso)->fd is always negative on failure — -errno from
> __open_dso() when no filename could be built (e.g. -EINVAL, -ENOENT),
> or -1 when do_open() itself failed — and never 0, so use it directly
> instead of reading the stale global errno.
> 
> No assert() or comment is needed after the assignment: the enclosing
> if (dso__data(dso)->fd < 0) already guarantees ret < 0
> [Namhyung Kim review].
> 
> Fixes: 33bdedcea2d7 ("perf tools: Protect dso cache fd with a mutex")
> Reported-by: sashiko-bot <sashiko-bot@kernel.org>
> Reviewed-by: Ian Rogers <irogers@google.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260813151148.23169-1-acme@kernel.org?part=3