Re: scrub backing device
From: ching <hidden>
Date: 2016-05-15 23:56:58
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 it seems to be a kernel config, and the kernel panic cannot be handled by userspace program On May 14, 2016 6:21:33 AM GMT+08:00, Kent Overstreet [off-list ref] wrote:
On Wed, May 11, 2016 at 04:57:48PM -0700, Marc MERLIN wrote:quoted
On Thu, May 12, 2016 at 07:34:26AM +0800, ching wrote:quoted
for examplehttps://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-scrubquoted
btrfs scrub is designed to make sure all the blocks and checksums are consistent. Ching makes a good point that it would be helpful to have a way to access the underlying backing device directly to ensure it is consistent. I think currently you can use dmsetup with an offset to get the real filesystem past the bcache header, mount that read only somewhere and scrub that. Not ideal because scrub will not be able to fix issues that arefixable,quoted
but at least it should report errors.Look at the verify code in drivers/md/bcache/debug.c, there's a CONFIG_BCACHE_DEBUG mode where every time it reads clean cached data it reads the data from the backing device and compares. But for a scrub though you really want to walk all the _cached_ data, so it'd take a bit more code than that.
-----BEGIN PGP SIGNATURE----- Version: APG v1.1.1 iQQ6BAEBCgAkBQJXOQy8HRxjaGluZyA8dG9tLmx1QGFsdW1uaS51c3QuaGs+AAoJ EJh7yMFRxEtkK/cgAN9XBFqqZ7mhctx8IzSKKZx5GrP4xv7Ew7rITiX4J6J2JLqn 5NZUW9rGReRXKj1MaVz0MGFeD/Lnndzf5gRLwD6cwQtPQAydTm6krd0qsld1V4O+ o9plFThE9IjdKRhWoIr6yA11wKN04MmIInucGtjtNITVBx+vut3MHAcDuRxeIG/Y sGmTrA4VbI34agltybanTn7XfnKULFdXOpfmf35dyqyrgShk22+5atcOW4hug112 5sPOpBo2S1jAwVZLKorwh4gIqeII4pFl+sfo5axJ60qLAZNXHwWeOGidmpcXFJMG /NnSsWRmbrJvMlSsRk/hKTHjvkzZ/Ci7ZU9aB+ICkZQgqk58udRLXc990RhKMpvK mKv9SHhltVYls+zoaaITxM6dS5rlIUwk++OhOU0qjjCOu9TI4yGmeBM5YmA29srb hOc5mtwWnjORcWAf7uttfNS1ECxJ0AlYJIRL9rF5FFCvxEugfxd1UQnZXz3qBj6q KDJo5JARiJvx+ayAw8I3cuh49Gc1U7VktUbRn5y/9Pm+Lj483Eb2Mp5kDyyAZTG5 X2baUtmkH0SkNID62ZzpBT7LE29oaw+PQ02czODIRYgAgJfuuCTEiCq0Q6zvRCDr rG6SO6K4W4CsgN3Hm5W5b832vRuGK/pfWj/DaNmK2XJ30XlckQSGXXV92MitHrs+ bF82odaF2qFHQQA8/W3MX1CcaPazyulvZfVMh6n6+K0cehOd3Gb94J/yQSdcRIM6 ynVu/7DJ+Ig9aH/2MvpzH/y6X1UZZEPvhV+CUyQPcXIXfhm5VMbLEKRq8gpZaq24 3+z/Tf2Vcbw4Wa4+GShGssavHljNr7Q2s4D8Nf6Mfn2fLb6tjIciAms//t+ywXnV DbLx34csTWTRWADq/Izsg2qJT5nAJ82HsAoY0Zg16pJHVgqCvg8gQPUnMvd06VK6 VPr9jcFv6yC3nijC/y78hkCcj2KVU4sx02hk4nxPo7mbbj2dJtrzdMW0HhT4iXhW ELIuNnDYbRX7OzkkggDO9092Y+oCuRPyJdkfVp/kxtpHVBaZzI8BPmJHVusEzanx 6IvS4QgPDTVfmYfvyxHqfRL8d5jc7uvws2uwnsM3hEBoOvTq/bAPSdoM/wibsU9f LmxEs2y5tX+AEHsT62o2FT1hc6ilvHzuRdJzNY+MPIsIFTBCPMF0wJFeL77tYYWE 71SUNDrBL8zT/eqeeneqfn1rbgEuDxucKOUuwLz0oYkWYGk0bhYieoWBrqyZGuq8 CKg2KPUB+2KJuS9Y9wXfL93QohzQOLc8RzOwf2oqCio7uVKn+DNyyE0gF66k0WOV HfSvyfdcSb83CnQxXwVtQbEz9jHyUFe0J5Y6CK4= =aTFB -----END PGP SIGNATURE-----