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If you have a block device which supports DAX, you can make a filesystem
-on it as usual. When mounting it, use the -o dax option manually
-or add 'dax' to the options in /etc/fstab.
+on it as usual. The DAX code currently only supports files with a block
+size equal to your kernel's PAGE_SIZE, so you may need to specify a block
+size when creating the filesystem. When mounting it, use the "-o dax"
+option on the command line or add 'dax' to the options in /etc/fstab.
Implementation Tips for Block Driver Writers
- implementing the direct_IO address space operation, and calling
dax_do_io() instead of blockdev_direct_IO() if S_DAX is set
- implementing an mmap file operation for DAX files which sets the
- VM_MIXEDMAP flag on the VMA, and setting the vm_ops to include handlers
- for fault and page_mkwrite (which should probably call dax_fault() and
- dax_mkwrite(), passing the appropriate get_block() callback)
+ VM_MIXEDMAP and VM_HUGEPAGE flags on the VMA, and setting the vm_ops to
+ include handlers for fault, pmd_fault and page_mkwrite (which should
+ probably call dax_fault(), dax_pmd_fault() and dax_mkwrite(), passing the
+ appropriate get_block() callback)
- calling dax_truncate_page() instead of block_truncate_page() for DAX files
- calling dax_zero_page_range() instead of zero_user() for DAX files
- ensuring that there is sufficient locking between reads, writes,