Hi there, I am using DM MPIO for quite a while now and in general it works. Lately I encountered a problem with one of my boxes that is equipped with USB flash drive and is connected to a disk array. Namely, the flash drive has an empty bcdDevice entry, which translates into empty /sys/block/sdXX/device/rev file. As a result, the 'multipath -ll' command trips over this device and bails out without listing any array mpathXX devices. The devices are created in /dev/disk/by-name/ directory, so it's just the userland tool issue. I've built debug version of multipath and found the following: 1. The function sysfs_get_rev() (which is generated from macro declare_sysfs_get_str()) assumes that the rev has to have at least 2 characters. Since in the case of my device this assumption is false, the function returns 1. 2. The caller function is scsi_sysfs_pathinfo() and it returns 1 as well. 3. The caller function is sysfs_pathinfo(), which returns 1 as well. 4. The caller function is pathinfo(), which also returns 1. 5. The caller function is store_pathinfo(). Here the pathinfo is not stored and NULL is returned to the caller. 6. The caller is path_discover() that returns 1. 7. The caller is path_discovery() that returns non-zero result. 8. The caller is configure() that bails out on this result. I have tried to work around this issue by blacklisting the device, but unfortunately the only blacklist check that is done prior to call to store_pathinfo() in the path_discover() is based on the devnode. This means that effectively I cannot use this workaround since with USB device I cannot guarantee that it will always be mapped to the same devnode. I'd like to propose a couple of options for a fix for this issue: 1. Re-implement sysfs_get_rev() in such a way that rev filed minimal length is no longer required. Please see attached a patch that is supposed to take care of this. 2. Re-implement pathinfo() to check whether vendor and/or product are blacklisted. This way non-compliant devices may be blacklisted based on vendor and/or product name. I am not sure, which option is preferable, but I clearly need at least one of them in the product. Your comments are greatly appreciated. Please note that my patch is against v. 0.4.7 of the multipath tool. I realize that upstream may differ significantly, so if option (1) makes sense I'll revalidate with the latest version and submit the patch if necessary. Thanks, Ilya.
Attachment:
multipath-tools-0.4.7-empty-rev.diff
Description: multipath-tools-0.4.7-empty-rev.diff
-- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
