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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rdXbE-00000007VwD-3yPS; Fri, 23 Feb 2024 15:36:33 +0000 Date: Fri, 23 Feb 2024 15:36:32 +0000 From: Matthew Wilcox To: Tetsuo Handa Cc: Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org, npiggin@gmail.com Subject: Re: [PATCH v2 03/17] mm: Add folio_end_read() Message-ID: References: <20231004165317.1061855-1-willy@infradead.org> <20231004165317.1061855-4-willy@infradead.org> <564df866-e874-400e-aff3-54d75295187b@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <564df866-e874-400e-aff3-54d75295187b@I-love.SAKURA.ne.jp> X-Rspamd-Queue-Id: F1AA81C0023 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: qex6g5t1e6g6ej6fmba3rd8ofos67bnn X-HE-Tag: 1708702599-484246 X-HE-Meta: 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 o29ScXLY zHevotHB9u+PjYTfiOJgj/aiAgFaetjDU5RSqpwM/nwn0RANmM8U1GL2nkgXgW1lEEAKjytJDSCBSY4tuxmQE/UoAiz0sot8yaGshmFtfZkkPn3cZblm/YzuxmBFheijVxcQ760TTPW410FV8d46xPixFeEAc715ltu2KcPzokVXDiF8ZbB4twLcg5g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Feb 24, 2024 at 12:26:41AM +0900, Tetsuo Handa wrote: > During a bisection of a different problem, I noticed that > commit 0b237047d5a7 ("mm: add folio_end_read()") added folio_end_read() as > > ---------------------------------------- > +void folio_end_read(struct folio *folio, bool success) > +{ > + if (likely(success)) > + folio_mark_uptodate(folio); > + folio_unlock(folio); > +} > ---------------------------------------- > > but commit f8174a118122 ("ext4: use folio_end_read()") for unknown reason > removed folio_clear_uptodate() call when bio->bi_status != 0. > > ---------------------------------------- > - bio_for_each_folio_all(fi, bio) { > - struct folio *folio = fi.folio; > - > - if (bio->bi_status) > - folio_clear_uptodate(folio); > - else > - folio_mark_uptodate(folio); > - folio_unlock(folio); > - } > + bio_for_each_folio_all(fi, bio) > + folio_end_read(fi.folio, bio->bi_status == 0); > ---------------------------------------- > > Why > > else > folio_clear_uptodate(folio); > > part is missing in folio_end_read() ? Because the folio already has its uptodate flag clear. We don't re-read folios which have the uptodate flag set. This was always dead code. Now we assert it's true in folio_end_read(): VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);