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When running multipath on a VM if all available paths go down the driver can schedule large amounts of storvsc_remove_lun work items to the same lun. In response to the failing paths typically storvsc responds by taking host->scan_mutex and issuing a TUR per lun. If there has been heavy IO to the failed device all the failed IOs are returned from the host. A remove lun work item is issued per failed IO. If the outstanding TURs have not been completed in a timely manner the scan_mutex is never released or released too late. Consequently the many remove lun work items are not completed as scsi_remove_device also tries to take host->scan_mutex. This results in dragging the VM down and sometimes completely. This patch only allows one remove lun to be issued to a particular lun while it is an instantiated member of the scsi stack. Signed-off-by: Cathy Avery <cavery@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Long Li <longli@microsoft.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.