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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uD1FE-00000000YR8-2Zfv; Thu, 08 May 2025 13:25:00 +0000 Date: Thu, 8 May 2025 14:25:00 +0100 From: Matthew Wilcox To: Christoph Hellwig Cc: Andrew Morton , Ryusuke Konishi , Hugh Dickins , Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Baolin Wang , linux-nilfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/7] mm: stop passing a writeback_control structure to shmem_writeout Message-ID: References: <20250508054938.15894-1-hch@lst.de> <20250508054938.15894-3-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250508054938.15894-3-hch@lst.de> X-Rspam-User: X-Rspamd-Queue-Id: 4BD3E40004 X-Rspamd-Server: rspam04 X-Stat-Signature: g3hr46qhmqhrnc6b9kuaau5onkm38858 X-HE-Tag: 1746710705-69783 X-HE-Meta: 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 ypcSfHBM 9MNQg1VrLxzKf5ycsyA7yx/Q/mibhzNM81uuZuIwE6TjDQ2crU2AX4m1hFRki+0Pl7atA2Ewrp4Ytbd0yZtx6TsfxIFZaP8E7cCWe4T9pdH/xefWV+5KHsiT3X0nj44zzcAxpNIEjcf2c4cNey5dWWOK4VdpXXjH35xmMGtDncISZlUt9o1f/OHglArrwpvXt3rB0PR6Me8ebjNp1/JeJUtAkDe0+H60AVtZfOJudJG5sE+Ly8i2UrWnZlQ6t5yAo2v7oCYoGSKwpyE92gh+7oBSNf5C6XCGL9VRxp4M0drF82MbwqHkd7ARecGXZcxCNHIByrFPHWQ0VxPjsk8ktGQfpTzyxcos8+mw8 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 Thu, May 08, 2025 at 07:47:44AM +0200, Christoph Hellwig wrote: > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c > @@ -318,7 +318,7 @@ void __shmem_writeback(size_t size, struct address_space *mapping) > if (folio_mapped(folio)) > folio_redirty_for_writepage(&wbc, folio); > else > - error = shmem_writeout(folio, &wbc); > + error = shmem_writeout(folio, NULL, NULL); > } > } This got me to look at why we need to keep wbc in __shmem_writeback(). We only have it because folio_redirty_for_writepage() needs it. And folio_redirty_for_writepage() only needs it because it updates pages_skipped. I'm not quite sure if we can simply call filemap_dirty_folio() here or whether mapping_can_writeback() is true for shmem and we need to do all the other things -- in which case we could just change that one line to if (wbc) wbc->pages_skipped += nr; and then pass NULL to folio_redirty_for_writepage() and delete the wbc on the stack.