Kernel SRU request submitted: https://lists.ubuntu.com/archives/kernel-team/2020-January/thread.html#107106 Changing status to In Progress.
** Description changed: - Discription will provided soon.. + SRU Justification: + ------------------ + + [Impact] + + * A severe problem with 'thin provisioning ECKD volumes', introduced + with 19.10's kernel 5.3, was identified. + + * For enhanced space efficient (ese) volumes, errors may occur when + accessing not formatted tracks. + + * In such a case the driver either formats the track on the fly for + write requests or returns zero data for read requests. + + * But if a write request spans multiple tracks, the indication of an + unformatted track can be in wc applied to all tracks. + + * Hence tracks containing data will be handled as empty tracks, resulting in zero data being returned on read, or overwriting + existing data with zero on write. + + [Fix] + + * Backport: + https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860535/+attachment/5323313/+files/0001-s390 + -dasd-disable-ese-support-due-to-possible-data-c.patch + + [Test Case] + + * An s390x LPAR with Eoan / kernel 5.3 and at least one 3390 DASD (ECKD) + disk is needed ('discard' enabled, which is default). + + * Writing arbitrary files (but with known content, e.g. all '1's) to + fill the disk up to a certain level + + * Since all 3390 DASDs (mod-3, 9, 27 or 54 ...) have 56,664 bytes per + track, writing a file (again with simple but known content) with a size + of a multiple of 56,664 bytes on a thin provisioned ECKD DASD device + should provoke the error situation. + + * Check the files for any modifications (partially filled with '0', + cut/truncated, deleted/zero length). + + [Regression Potential] + + * The regression potential is moderate since this is purely s390x + specific, + + * limited to thin provisioned DASD disks on Eoan / kernel 5.3 + + * and just disables the broken feature and reverts things back to a DASD + functionality that is known to work. + + [Other Info] + + * For 19.10 / Eoan no real fix will be provided, but a patch for + disabling this feature completely (this bug/patch). + + * The broken functionality that got introduced in Eoan, got already + partially removed due to problems on z/VM. + + * For 20.04 / Focal a proper fix is in the works that will be made + available as backport to Focal's kernel 5.4. ** Changed in: linux (Ubuntu) Status: New => Triaged ** Changed in: linux (Ubuntu) Status: Triaged => Invalid ** Changed in: linux (Ubuntu Eoan) Status: New => Triaged ** Changed in: ubuntu-z-systems Status: Incomplete => In Progress -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1860535 Title: Disable ECKD Thin Provisioning to prevent data loss Status in Ubuntu on IBM z Systems: In Progress Status in linux package in Ubuntu: Invalid Status in linux source package in Eoan: Triaged Bug description: SRU Justification: ------------------ [Impact] * A severe problem with 'thin provisioning ECKD volumes', introduced with 19.10's kernel 5.3, was identified. * For enhanced space efficient (ese) volumes, errors may occur when accessing not formatted tracks. * In such a case the driver either formats the track on the fly for write requests or returns zero data for read requests. * But if a write request spans multiple tracks, the indication of an unformatted track can be in wc applied to all tracks. * Hence tracks containing data will be handled as empty tracks, resulting in zero data being returned on read, or overwriting existing data with zero on write. [Fix] * Backport: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860535/+attachment/5323313/+files/0001-s390 -dasd-disable-ese-support-due-to-possible-data-c.patch [Test Case] * An s390x LPAR with Eoan / kernel 5.3 and at least one 3390 DASD (ECKD) disk is needed ('discard' enabled, which is default). * Writing arbitrary files (but with known content, e.g. all '1's) to fill the disk up to a certain level * Since all 3390 DASDs (mod-3, 9, 27 or 54 ...) have 56,664 bytes per track, writing a file (again with simple but known content) with a size of a multiple of 56,664 bytes on a thin provisioned ECKD DASD device should provoke the error situation. * Check the files for any modifications (partially filled with '0', cut/truncated, deleted/zero length). [Regression Potential] * The regression potential is moderate since this is purely s390x specific, * limited to thin provisioned DASD disks on Eoan / kernel 5.3 * and just disables the broken feature and reverts things back to a DASD functionality that is known to work. [Other Info] * For 19.10 / Eoan no real fix will be provided, but a patch for disabling this feature completely (this bug/patch). * The broken functionality that got introduced in Eoan, got already partially removed due to problems on z/VM. * For 20.04 / Focal a proper fix is in the works that will be made available as backport to Focal's kernel 5.4. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1860535/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
