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I didn't verify that this is > the case for f2fs. Generally you can deduce this as well through > testing, I'd say the following cases would be interesting to test: > > 1) Normal DONTCACHE buffered read > 2) Overwrite DONTCACHE buffered write > 3) Append DONTCACHE buffered write > > Test those with DEBUG_ATOMIC_SLEEP set in your config, and it that > doesn't complain, that's a great start. > > For the above test cases as well, verify that page cache doesn't grow as > IO is performed. A bit is fine for things like meta data, but generally > you want to see it remain basically flat in terms of page cache usage. > > Maybe this is all fine, like I said I didn't verify. Just mentioning it > for completeness sake. Hi, Jens Thanks for your suggestion. As I mentioned earlier in [1], in f2fs, the regular buffered write path invokes folio_end_writeback from a softirq context. Therefore, it seems that f2fs may not be suitable for DONTCACHE I/O writes. I’d like to ask a question: why is DONTCACHE I/O write restricted to non-interrupt context only? Is it because dropping the page might be too time-consuming to be done safely in interrupt context? This might be a naive question, but I’d really appreciate your clarification. Thanks in advance. [1] https://lore.kernel.org/all/137c0a07-ea0a-48fa-acc4-3e0ec63681f4@vivo.com/ >