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SubjectRe: [PATCH 02/11] filemap: Remove filemap_check_and_keep_errors()
On Mon, Jan 09, 2023 at 08:48:49AM -0500, Jeff Layton wrote:
> On Mon, 2023-01-09 at 05:18 +0000, Matthew Wilcox (Oracle) wrote:
> > Convert both callers to use the "new" errseq infrastructure.
>
> I looked at making this sort of change across the board alongside the
> original wb_err patches, but I backed off at the time.
>
> With the above patch, this function will no longer report a writeback
> error that occurs before the sample. Given that writeback can happen at
> any time, that seemed like it might be an undesirable change, and I
> didn't follow through.
>
> It is true that the existing flag-based code may miss errors too, if
> multiple tasks are test_and_clear'ing the bits, but I think the above is
> even more likely to happen, esp. under memory pressure.
>
> To do this right, we probably need to look at these callers and have
> them track a long-term errseq_t "since" value before they ever dirty the
> pages, and then continually check-and-advance vs. that.
>
> For instance, the main caller of the above function is jbd2. Would it be
> reasonable to add in a new errseq_t value to the jnode for tracking
> errors?

Doesn't b4678df184b3 address this problem? If nobody has seen the
error, we return 0 instead of the current value of wb_err, ensuring
that somebody always sees the error.

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