Comment 16 for bug 1468897

Updated information. It seems the issue only comes about with USB 3.0 devices. USB 2.0 devices do not get lumped in with multipath upon detection.

dmesg output from inserting a USB 3.0 device and then a USB 3.0 device. Both into USB 3.0 ports:

[ 223.050845] usb 4-4: new SuperSpeed USB device number 3 using xhci_hcd
[ 223.069996] usb 4-4: New USB device found, idVendor=125f, idProduct=312b
[ 223.070000] usb 4-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 223.070004] usb 4-4: Product: ADATA USB Flash Drive
[ 223.070006] usb 4-4: Manufacturer: ADATA
[ 223.070009] usb 4-4: SerialNumber: 0000000000000454
[ 223.070589] usb-storage 4-4:1.0: USB Mass Storage device detected
[ 223.071125] scsi4 : usb-storage 4-4:1.0
[ 224.071718] scsi 4:0:0:0: Direct-Access ADATA USB Flash Drive 1.00 PQ: 0 ANSI: 6
[ 224.073117] sd 4:0:0:0: Attached scsi generic sg32 type 0
[ 224.073458] sd 4:0:0:0: [sdi] 30869504 512-byte logical blocks: (15.8 GB/14.7 GiB)
[ 224.073729] sd 4:0:0:0: [sdi] Write Protect is off
[ 224.073737] sd 4:0:0:0: [sdi] Mode Sense: 23 00 00 00
[ 224.073992] sd 4:0:0:0: [sdi] Write cache: disabled, read cache: disabled, doesn't support DPO or FUA
[ 224.079661] sdi: sdi1
[ 224.080909] sd 4:0:0:0: [sdi] Attached SCSI removable disk
[ 224.675188] usb 3-3: new high-speed USB device number 3 using xhci_hcd
[ 224.810797] usb 3-3: New USB device found, idVendor=13fe, idProduct=3600
[ 224.810802] usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 224.810805] usb 3-3: Product: MKNUFDPR2GB
[ 224.810807] usb 3-3: Manufacturer: MUSHKIN
[ 224.810810] usb 3-3: SerialNumber: 07C10403C8956553
[ 224.811540] usb-storage 3-3:1.0: USB Mass Storage device detected
[ 224.812218] usb-storage 3-3:1.0: Quirks match for vid 13fe pid 3600: 4000
[ 224.812419] scsi5 : usb-storage 3-3:1.0
[ 225.841184] scsi 5:0:0:0: Direct-Access MUSHKIN MKNUFDPR2GB PMAP PQ: 0 ANSI: 0 CCS
[ 225.842314] sd 5:0:0:0: Attached scsi generic sg33 type 0
[ 226.527048] sd 5:0:0:0: [sdj] 3911680 512-byte logical blocks: (2.00 GB/1.86 GiB)
[ 226.527209] sd 5:0:0:0: [sdj] Write Protect is off
[ 226.527213] sd 5:0:0:0: [sdj] Mode Sense: 23 00 00 00
[ 226.527363] sd 5:0:0:0: [sdj] No Caching mode page found
[ 226.527442] sd 5:0:0:0: [sdj] Assuming drive cache: write through
[ 226.560690] sdj: sdj1
[ 226.562590] sd 5:0:0:0: [sdj] Attached SCSI removable disk

lsblk for relevant devices:

sdi 8:128 1 14.7G 0 disk
├─sdi1 8:129 1 14.7G 0 part
└─mpath4 (dm-8) 252:8 0 14.7G 0 mpath
  └─mpath4-part1 (dm-10) 252:10 0 14.7G 0 part
sdj 8:144 1 1.9G 0 disk
└─sdj1 8:145 1 1.9G 0 part