This series addresses some errors seen when using the loop device directly backed by a block device. The first change plumbs out the correct error message, and the second change prevents the error from occurring in many cases. The errors look like this: [ 90.880875] print_req_error: I/O error, dev loop5, sector 0 The errors occur when trying to do a discard or write zeroes operation on a loop device backed by a block device that does not support discard. Firstly, the error itself is incorrectly reported as I/O error, but is actually EOPNOTSUPP. The first patch plumbs out EOPNOTSUPP to properly report the error. The second patch prevents these errors from occurring by mirroring the discard capabilities of the underlying block device into the loop device. Before this change, discard was always reported as being supported, and the loop device simply turns around and does a discard operation on the backing device. After this change, backing block devices that do support discard will continue to work as before, and continue to get all the benefits of doing that. Backing devices that do not support discard will fail earlier, avoiding hitting the loop device at all and ultimately avoiding this error in the logs. I can also confirm that this fixes test block/003 in the blktests, when running blktests on a loop device backed by a block device. Changes in v3: - Updated tags - Updated commit description Changes in v2: - Unnested error if statement (Bart) Evan Green (2): loop: Report EOPNOTSUPP properly loop: Better discard support for block devices drivers/block/loop.c | 70 ++++++++++++++++++++++++++++++-------------- 1 file changed, 48 insertions(+), 22 deletions(-) -- 2.20.1
