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[76.182.20.124]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e6b71200ed0sm667632276.26.2025.03.28.12.39.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Mar 2025 12:39:29 -0700 (PDT) Date: Fri, 28 Mar 2025 15:39:27 -0400 From: Josef Bacik To: David Sterba Cc: David Sterba , linux-btrfs@vger.kernel.org, Qu Wenruo Subject: Re: [GIT PULL] Btrfs updates for 6.15 Message-ID: <20250328193927.GA1393046@perftesting> References: <20250328132751.GA1379678@perftesting> <20250328173644.GG32661@twin.jikos.cz> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250328173644.GG32661@twin.jikos.cz> On Fri, Mar 28, 2025 at 06:36:44PM +0100, David Sterba wrote: > On Fri, Mar 28, 2025 at 09:27:51AM -0400, Josef Bacik wrote: > > On Mon, Mar 24, 2025 at 05:37:51PM +0100, David Sterba wrote: > > > Hi, > > > > > > please pull the following btrfs updates, thanks. > > > > > > User visible changes: > > > > > > - fall back to buffered write if direct io is done on a file that requires > > > checksums > > > > > > > > What? We use this constantly in a bunch of places to avoid page cache overhead, > > it's perfectly legitimate to do DIO to a file that requires checksums. Does the > > vm case mess this up? Absolutely, but that's why we say use NOCOW for that > > case. We've always had this behavior, we've always been clear that if you break > > it you buy it. This is a huge regression for a pretty significant use case. > > The patch has been up for like 2 months and you could have said "don't > because reasons" any time before the pull request. Now we're left with a > revert, or other alternatives making the use cases working. Boris told me about this and I forgot. I took everybody off the CC list because I don't want to revert it, in fact generally speaking I'd love to never have these style of bug reports again. But it is a pretty significant change. Are we ok going forward saying you don't get O_DIRECT unless you want NOCOW? Should we maybe allow for users to indicate they're not dumb and can be trusted to do O_DIRECT properly? I just think this opens us up to a lot more uncomfortable conversations than the other behavior. I personally think this is better, if it's been sitting there for 2 months then hooray we're in agreement. But I'm also worried it'll come back to bite us. Thanks, Josef