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[70.62.41.24]) by smtp.gmail.com with ESMTPSA id z16sm1153120ywj.93.2019.10.25.10.16.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Oct 2019 10:16:20 -0700 (PDT) Subject: Re: first it froze, now the (btrfs) root fs won't mount ... To: Christian Pernegger Cc: Qu Wenruo , linux-btrfs References: <4608b644-0fa3-7212-af45-0f4eebfb0be9@gmx.com> <20f660ea-d659-7ad5-a84d-83d8bfa3d019@gmx.com> <0d6683ee-4a2c-f2ab-857b-c7cd44442dce@gmail.com> <043c2d26-a067-fd03-4c98-7ff76b081fed@gmail.com> From: "Austin S. Hemmelgarn" Message-ID: <6d61f5b5-220a-a35e-c6bc-20eaba45e925@gmail.com> Date: Fri, 25 Oct 2019 13:16:17 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2019-10-25 13:05, Christian Pernegger wrote: > P.P.S (sorry): Would using the DUP profile for metadata conceiveably > be an extra line of defence in such cases (assuming the NVMe doesn't > just eat the extra copies outright)? If so, is enabling it after fs > creation safe and should system be DUP as well? Something like: > # btrfs balance start -mconvert=dup [-sconvert=dup -f] $PATH Yes, using the dup profile for metadata should help, provided it's not an issue with the rest of the system (if the metadata gets corrupted in memory, two bad copies will get written out). On-line conversion is perfectly safe, and should not require explicit conversion of the system chunks (converting metadata will do that automatically). > > Lastly ist $PATH just used to identify the fs, or does it act as a > filter? IOW, can I use whatever or should it be run on the real root > of the fs? I think any path on the volume will work, though it's best to use it on an actual mount point so you know concretely what it's running on. Most of the ioctls are pretty forgiving like this, because it's not unusual to only have non-root subvolumes mounted from a volume.