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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uVCTl-0000000EZN4-26cY; Fri, 27 Jun 2025 17:03:09 +0000 Date: Fri, 27 Jun 2025 18:03:09 +0100 From: Matthew Wilcox To: =?utf-8?B?6ZmI5rab5rab?= Taotao Chen Cc: "tytso@mit.edu" , "hch@infradead.org" , "adilger.kernel@dilger.ca" , "brauner@kernel.org" , "jani.nikula@linux.intel.com" , "rodrigo.vivi@intel.com" , "tursulin@ursulin.net" , "airlied@gmail.com" , "linux-fsdevel@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "linux-block@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "chentao325@qq.com" , "frank.li@vivo.com" Subject: Re: [PATCH v3 4/4] ext4: support uncached buffered I/O Message-ID: References: <20250627110257.1870826-1-chentaotao@didiglobal.com> <20250627110257.1870826-5-chentaotao@didiglobal.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250627110257.1870826-5-chentaotao@didiglobal.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: B7ED240004 X-Stat-Signature: 5bpzdo5tbmn8pd59i7m5kxxsdar5b71y X-Rspam-User: X-HE-Tag: 1751043801-397399 X-HE-Meta: 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 rn5YHkcH WP3VB8UONtRnPPnJkLZwTZynEDqJjYZEi4pvuSVfCJsIj9tf9WpX7GzMJLldUTARzKDqQmpG7Awx1l/Bp3IWImd0LjnQcR3ansp521p0K7q64I4SZlsqrKJCWF394VmkQ1qsc/sihLoVANZOO8tFU5k1QtcyctW64+EJyCFG6vUVpjlqqlQ6x+ldPSIur6wGv1Sgr6Mr2FK6p3/MFipX2TlKQCjulPqjmNMHnVctGrV2GjgJ8stWCiApNEA== 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 Fri, Jun 27, 2025 at 11:03:13AM +0000, 陈涛涛 Taotao Chen wrote: > +++ b/fs/ext4/inode.c > @@ -1270,6 +1270,9 @@ static int ext4_write_begin(const struct kiocb *iocb, > if (unlikely(ret)) > return ret; > > + if (iocb->ki_flags & IOCB_DONTCACHE) > + fgp |= FGP_DONTCACHE; I think this needs to be: if (iocb && iocb->ki_flags & IOCB_DONTCACHE) because it's legit to call write_begin with a NULL argument. The 'file' was always an optional argument, and we should preserve that optionality with this transformation. I wonder if it's worth abstracting some of this boilerplate. Something like: struct folio *write_begin_get_folio(iocb, mapping, index, len) { fgf_t fgflags = FGP_WRITEBEGIN; if (iocb && iocb->ki_flags & IOCB_DONTCACHE) fgflags |= FGP_DONTCACHE; fgflags |= fgf_set_order(len); return __filemap_get_folio(mapping, index, fgflags, mapping_gfp_mask(mapping)); }