Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH v5 8/9] iov_iter, block: Make bio structs pin pages rather than ref'ing if appropriate | Date | Thu, 12 Jan 2023 10:28:41 +0000 |
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Christoph Hellwig <hch@infradead.org> wrote:
> if (cleanup_mode & FOLL_GET) { > WARN_ON_ONCE(bio_test_flag(bio, BIO_PAGE_PINNED)); > bio_set_flag(bio, BIO_PAGE_REFFED); > } > if (cleanup_mode & FOLL_PIN) { > WARN_ON_ONCE(bio_test_flag(bio, BIO_PAGE_REFFED)); > bio_set_flag(bio, BIO_PAGE_PINNED); > }
That won't necessarily work as you might get back cleanup_mode == 0, in which case both flags are cleared - and neither warning will trip on the next addition.
I could change it so that rather than using a pair of flags, it uses a four-state variable (which can be stored in bi_flags): BIO_PAGE_DEFAULT, BIO_PAGE_REFFED, BIO_PAGE_PINNED, BIO_PAGE_NO_CLEANUP, say.
Or I could add an extra flag to say that the setting is locked. Or we could just live with the scenario I outlined possibly happening.
David
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