From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Date: Mon, 12 Oct 2020 09:19:46 -0700 Subject: [Cluster-devel] [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread() In-Reply-To: <20201012065635.GB2046448@iweiny-DESK2.sc.intel.com> References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-23-ira.weiny@intel.com> <20201009213434.GA839@sol.localdomain> <20201010003954.GW20115@casper.infradead.org> <20201010013036.GD1122@sol.localdomain> <20201012065635.GB2046448@iweiny-DESK2.sc.intel.com> Message-ID: <20201012161946.GA858@sol.localdomain> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Sun, Oct 11, 2020 at 11:56:35PM -0700, Ira Weiny wrote: > > > > And I still don't really understand. After this patchset, there is still code > > nearly identical to the above (doing a temporary mapping just for a memcpy) that > > would still be using kmap_atomic(). > > I don't understand. You mean there would be other call sites calling: > > kmap_atomic() > memcpy() > kunmap_atomic() Yes, there are tons of places that do this. Try 'git grep -A6 kmap_atomic' and look for memcpy(). Hence why I'm asking what will be the "recommended" way to do this... kunmap_thread() or kmap_atomic()? > And since I don't know the call site details if there are kmap_thread() calls > which are better off as kmap_atomic() calls I think it is worth converting > them. But I made the assumption that kmap users would already be calling > kmap_atomic() if they could (because it is more efficient). Not necessarily. In cases where either one is correct, people might not have put much thought into which of kmap() and kmap_atomic() they are using. - Eric