https://bugzilla.kernel.org/show_bug.cgi?id=195233 Bug ID: 195233 Summary: sd: discard_granularity set smaller than minimum_io_size when LBPRZ=1 Product: IO/Storage Version: 2.5 Kernel Version: 4.4.0 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: SCSI Assignee: linux-scsi@xxxxxxxxxxxxxxx Reporter: dbuckley@xxxxxxxxxxx Regression: No Between 3.10 and 4.4 kernels this patch: https://patchwork.kernel.org/patch/6995131/ was merged to ensure discard_granularity is set to logical_block_size when a disk reports LBPRZ=1. In a case where a disk reports LBPRZ=1 with a 512 logical_block_size and 4096 physical_block_size and minimum_io_size, this results in discard_granularity incorrectly being set to 512 which at least in my case results in discard requests being ignored. I believe the easiest fix would be changing: if (sdkp->lbprz) { q->limits.discard_alignment = 0; q->limits.discard_granularity = logical_block_size; } else { to: if (sdkp->lbprz) { q->limits.discard_alignment = 0; q->limits.discard_granularity = max(logical_block_size, minimum_io_size); } else { but any change which results in discard_granularity being set properly would solve this. I have verified that with a 3.10 kernel discard_granularity is set to 4096 and works as expected, but with 4.4 it is set to 512 and does not work. This is a fairly severe bug for my use case, as I rely on discard to free unused blocks from the storage backing LUNs mounted by Linux clients and this effectively makes critical functions like thin-provisioning and snapshots infeasible for 4.x clients. I have only tested this with the Ubuntu-packaged kernels, but the problematic code still is present in the current source. I'm happy to provide any additional information that might be helpful. -- You are receiving this mail because: You are the assignee for the bug.
