Hi, I am running into failures when run filebench on ramdisk(/dev/ram0) with Ext4-DAX. The kernel version is 4.0, and I also verified it occurs on 4.2-rc1. The issue reproduction steps: // Set ramdisk size to 2GB # mkfs.ext4 /dev/ram0 # mount -o dax /dev/ram0 /mnt/ramdisk # filebench filebench> load fileserver filebench> set $dir=/mnt/ramdisk filebench> run 30 And filebench fails in a few seconds like this: 8163: 22.992: Failed to pre-allocate file /mnt/ramdisk/bigfileset/00000001/00000006/00000001/00000024/00000005/00000002/00000006: No such file or directory on line 128 8163: 22.992: Failed to create filesets on line 128 Or like this: 8141: 16.372: Failed to write 51967 bytes on fd 23: Success 8151: 16.372: Failed to write 136735 bytes on fd 18: Success 8148: 16.372: Failed to write 123317 bytes on fd 31: Success 8141: 16.381: filereaderthread-36: flowop wrtfile1-1 failed 8151: 16.381: filereaderthread-46: flowop wrtfile1-1 failed 8148: 16.381: filereaderthread-43: flowop wrtfile1-1 failed 8098: 16.521: Run took 1 seconds... 8098: 16.521: NO VALID RESULTS! Filebench run terminated prematurely on line 65 8098: 16.521: Shutting down processes Sometimes it succeeds, but the chance is low. The failure rate is 80%+. Note: The issues does not occur with normal Ext4. The issues does not occur with Ext4-DAX on pmem driver (from 01org/prd). The only significant difference between brd.c and pmem.c is that brd.c uses alloc_page() and pmem.c reserved memory range and uses ioremap() to get virtual address. I assume that the memcpy operation(copy_from/to_user) directly between user buffer and page by alloc_page() does not work correctly somehow. I wonder if this is a bug? If it is, how to fix it? Thanks. Thanks, Andiry -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>