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authorVishal Verma <vishal.l.verma@intel.com>2017-08-30 19:36:03 -0600
committerDan Williams <dan.j.williams@intel.com>2017-08-31 15:05:10 -0700
commitd9b83c7569536e3255992491737d9f895640ea18 (patch)
tree050059ad7332979b9c2be55702b4df1310503fbb /tools/testing/nvdimm
parentlibnvdimm: fix potential deadlock while clearing errors (diff)
downloadlinux-dev-d9b83c7569536e3255992491737d9f895640ea18.tar.xz
linux-dev-d9b83c7569536e3255992491737d9f895640ea18.zip
libnvdimm, btt: rework error clearing
Clearing errors or badblocks during a BTT write requires sending an ACPI DSM, which means potentially sleeping. Since a BTT IO happens in atomic context (preemption disabled, spinlocks may be held), we cannot perform error clearing in the course of an IO. Due to this error clearing for BTT IOs has hitherto been disabled. In this patch we move error clearing out of the atomic section, and thus re-enable error clearing with BTTs. When we are about to add a block to the free list, we check if it was previously marked as an error, and if it was, we add it to the freelist, but also set a flag that says error clearing will be required. We then drop the lane (ending the atomic context), and send a zero buffer so that the error can be cleared. The error flag in the free list is protected by the nd 'lane', and is set only be a thread while it holds that lane. When the error is cleared, the flag is cleared, but while holding a mutex for that freelist index. When writing, we check for two things - 1/ If the freelist mutex is held or if the error flag is set. If so, this is an error block that is being (or about to be) cleared. 2/ If the block is a known badblock based on nsio->bb The second check is required because the BTT map error flag for a map entry only gets set when an error LBA is read. If we write to a new location that may not have the map error flag set, but still might be in the region's badblock list, we can trigger an EIO on the write, which is undesirable and completely avoidable. Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Toshi Kani <toshi.kani@hpe.com> Cc: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'tools/testing/nvdimm')
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